• Volume 43, All articles

Continuous Article Publishing mode

• Molecular simulation study of CO$_2$ adsorption in carbon slit pores at high temperature and pressure conditions

This work contributes to the estimation of new and complementary density data for carbon dioxide (CO$_2$) confined in carbon slit pores at different conditions. Grand canonical Monte Carlo (GCMC) simulations were employed topredict the CO$_2$ adsorption capacities in carbon slit pores of height 20, 31.6, 63.2, 94.85 and 126.5 Å at 673.15 and 873.15 K over a pressure range of 500–4000 kPa, which corresponds to steam reforming of methane process. The bulk densities of CO$_2$ at these temperature and pressure conditions have been estimated via isothermal–isobaric ensemble MC simulations using the Elementary Physical Model. The predicted density shows an excellent agreement with the experimental data. The adsorption capacities of CO$_2$ in all the aforementioned pores at 673.15 and 873.15 K over the pressure range of500–4000 kPa have also been estimated in the presence of wall–fluid interactions, in addition to the fluid–fluid interactions. The study on the thermodynamic phase behaviour of confined CO$_2$ in the presence of wall–fluid interactions showed the existence of vapour–liquid equilibria at high temperature and pressure conditions.

• Diatomite/silver phosphate composite for efficient degradation of organic dyes under solar radiation

In this study, an effort has been made to synthesize diatomite/silver phosphate (DT/AgP) composites and dye degradation test was carried out to evaluate the photocatalytic activity under solar light irradiation. Diatomite–silverphosphate composites with different DT/AgP ratios were prepared by precipitation of Ag$_3$PO$_4$ on diatomite that led to the formation of small Ag$_3$PO$_4$ particles on the diatomite surfaces. UV–visible diffuse reflectance analysis shows that DT/AgP composites can absorb visible wavelength, whereas TiO$_2$ catalyst only work under UV irradiance. Compared to pure AgP, the composite samples show higher specific surface area measured by Brunauer–Emmett–Teller analysis. Dye degradation test under solar light irradiation reveals that the photocatalytic reaction follows a pseudo-first-order rate law and the composite catalyst with DT/AgP ratio 1:0.8 shows better catalytic activity towards both rhodamine B and methyl orange degradation. As reference, a well-known commercial TiO$_2$ (Evonik-P25) was used in dye degradation test. It could be presumed that deposition of silver phosphate clusters (Ag$_3$PO$_4$, AgP) on diatom frustules (diatomite) provided anefficient photocatalyst activated by solar light irradiation.

• Impedance analysis of zirconium-doped lithium manganese oxide

In recent days, portable electronic devices are indispensable to improve the standard of living, which led to the demand for energy storage devices with good performance. Among the storage devices, rechargeable lithium ion batteries play a vital role due to the good electrical conductivity. In this study, impedance and electrical performance were studied for zirconium-doped Li$_4$Mn$_5$O$_{12}$ at different concentrations (0.1, 0.2, 0.3 and 0.4 mol). The structural andmorphological properties of the material were studied by powder X-ray diffractometer spectra and scanning electron microscopy analysis. Morphological properties exhibit the combination of polyhedral and needle-shaped particles, which were in micron size. The Nyquist plot indicates the absence of grain boundary effect and explained the bulk property, i.e., the negative temperature co-efficient of resistance property of the material. Zirconium-doped lithium manganese oxide (0.2 mol) exhibits good electrical property than other concentrations. Maximum conductivity was ($1.4 \times 10^{-5}$ S cm$^{-1}$)observed at 160$^{\circ}$C for the same. These results suggested that 0.2 mol of zirconium will enhance the electrical property of lithium manganese oxide (Li$_4$Mn$_5$O$_{12}$).

• Manifestation of descent symmetry phenomena in tetrahedral structure of M$_4^{2+}$ (M $=$ P, As, Sb) analogues

Manifestation of descent symmetry phenomena induced by pseudo Jahn–Teller interactions is reported for the P$_4$ dicationic tetrahedral structure and its As$_4$ and Sb$_4$ analogues. The symmetry descent phenomena in the dicationic tetrahedral structure for the series is caused by the pseudo Jahn–Teller effect (PJTE) where the unstable (high T$_{\rm d}$ symmetry) configuration distorts to the equilibrium geometry with a lower, C$_2$ symmetry. State averaging six low-lying electronic states via CASSCF(8,8)/cc-pVTZ–(PP) computations determined the adiabatic potential energy surfaces along the distorting normal coordinate. The (E$_{\rm (I)}$ $+$ A$_1$ $+$ E$_{\rm (II)}$) $\otimes$ $e$ for the M$_4^{2+}$ (M $=$ P, As, Sb) series has been formulated accordingly. Subsequently, the coupling constants were estimated by fitting energies obtained from the PJTE equations. Moreover, to understand how removing or adding electrons affects the PJTE in the M$_4^{2+}$ series, electronic configurations were analysed for M$_4^{(0,2+,4+)}$ analogues in which the M$_4^{(0,4+)}$ are stable in their tetrahedral structure.

• Electrochemical studies on wafer-scale synthesized silicon nanowalls for supercapacitor application

Silicon-based supercapacitors are highly essential for the utilization of supercapacitor technology in consumer electronics, owing to their on-chip integration with the well-established complementary metal–oxide–semiconductor-related fabrication technology. In this study, silicon nanowalls were carved on commercially available silicon wafers by using a facile, low-cost and complementary metal–oxide–semiconductor compatible method of metal (silver)-assisted chemical etching. The electron microscopic studies of the carved out silicon nanowalls reveal that they are smooth, single crystalline and vertically aligned to their base silicon wafer. Raman and ATR-FTIR spectroscopy confirmthat the surface of the silicon nanowalls has Si–O–Si bonded structures. Cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) studies were carried out in the organic electrolyte tetraethylammonium tetrafluroborate(NEt$_4$BF$_4$) in propylene carbonate (PC). It is evident from both the CV and GCD studies that the silicon nanowalls exhibit redox peaks arising from the silver-related deep-level trap state in silicon in contact with adsorbed water and also from the oxidation of silicon and its hydrides by the water present in the electrolyte. The presence of silver in silicon nanowalls and water in the electrolyte are considered to be due to the minute amount of silver left over during its removal by HNO$_3$, owing to the bunching of nanowalls and the highly moisture sensitive nature of the electrolyte, respectively. The influenceof such redox peaks on capacitance and cycle life are discussed.

• Characteristics of ionic adsorption on silica nanoparticles and its impact on the long term stability of dye-sensitized solar cells

Quasi-solid electrolytes based on silica nanopowder are well known in literature and these electrolytes are able to match in performance with that of liquid electrolytes. However, contrasting results are observed in literatureregarding stability of dye-sensitized solar cells (DSSCs) with most of the reported articles projecting silica-loaded quasisolid electrolyte-based cells as a stable alternative to liquid electrolyte-based cells, while a few others contradicting thesame. The present study demonstrates the effect of ageing under heat (60$^{\circ}$C) and illumination on the performance of liquid electrolyte and silica-loaded electrolyte-based DSSCs. It has been observed that DSSC based on silica-loaded electrolyte are less stable than DSSC based on liquid electrolyte even though independent study on both electrolytes by thermal analysis shows silica-loaded electrolyte to be more stable than liquid electrolyte. Segregation of silica in electrolyte has been confirmed through cryo-field emission gun-scanning electron microscopy. Zeta potential measurements show that ions are desorbed from the surface of silica on ageing under heat and illumination.

• Synthesis of ZSM-5 zeolites using palygorskite as raw material under solvent-free conditions

Zeolites have extensively been applied in gas adsorption and separation, catalysis, and ion exchange thanks to their numerous interesting features. However, the synthesis of zeolites usually requires solvents, which often lead to water pollution, loss of silicon and aluminium components, and low synthesis efficiency. In this account, ZSM-5 zeolites were synthesized from natural clay palygorskite (PAL) by acid leaching, followed by thermal treatment under solvent-free conditions. The as-obtained ZSM-5 zeolites exhibited high crystallinity and mesoporous structure. The NMR spectra of ZSM-5 zeolites confirmed the presence of aluminium element derived from the acid-treated PAL (APAL) existed in zeolite framework. Thus, PAL was simultaneously employed as silica and aluminium sources for zeolite preparation. The Si/Al molar ratio of ZSM-5 zeolites could be adjusted by adding NaAlO$_2$, but against growth of ZSM-5 zeolites, resulting in formation of analcime. On the other hand, long thermal treatment for 72 h caused the dissolution of ZSM-5 zeolite crystals and formation of analcime. Overall, calcination could enhance the activity of APAL and crystallinity of ZSM-5zeolites, and solvent-free synthesis of zeolites from clay might efficiently reduce the cost of zeolites.

• Key parameters to improve zeolites hierarchization in direct synthesis

In this study, we propose the generation of micro/mesoporous zeolites with ZSM-11 structure by hydrothermal treatment using tetrabutylammonium hydroxide (TBAOH) as micropore structure directing agent and cetyltrimethylammonium bromide (CTAB) as mesotemplate. From many synthesis parameters evaluated (crystallization time, hydrothermal temperature, CTAB content), the type of base employed in the synthesis gel showed notorious influence in the structure, textural properties and morphology of the micro/mesoporous ZSM-11 zeolites. The samples were characterized by different techniques such as X-ray diffraction, nitrogen adsorption and desorption isotherms, Brunauer–Emmett–Teller surface area, scanning electron microscope, ICP-AES and ${}^{27}$Al MAS NMR. The characterization results revealed that the crystallization time, CTAB content and type of base (NaOH, KOH, Ca(OH)$_2$ and NaCO$_3$) played a dominant role in controlling the formation of both microporous and mesoporous structures. The base employed in the synthesis and its concentration showed important effects on the structure and textural properties of the composite materials. It was found that to obtain the best characteristics in terms of crystallinity and textural parameters, NaOH and KOH should be employed.

• Structural, out-gassing and nanomechanical properties of super-hydrophobic transparent silica aerogels developed by ambient pressure drying for space application

Transparent super-hydrophobic monolithic silica aerogels are prepared by the cost-effective ambient pressure drying. The drying of aerogel is performed at various temperatures ranging from 25 to 200$^{\circ}$C. Oxidation states of different silica aerogels are investigated by XPS which shows the presence of both SiO and SiO$_2$ phases. Thermal stability of hydrophobic aerogel is found as $\sim$320$^{\circ}$C investigated by TGA and DSC. The chemical bonds (i.e., $–$CH$_3$) responsible for the hydrophobic (WCA > 170$^{\circ}$) nature of synthesized silica aerogels are identified by FTIR. Further, out-gassingproperties of the silica aerogels have been investigated and they are found in limit for the space application. The highest hardness and Young’s modulus are measured by the nanoindentation technique for the aerogel dried at 120$^{\circ}$C which has higher density, while density decreases for the aerogel dried at 200$^{\circ}$C and the corresponding nanomechanical propertiesare found to be lowest as expected.

• In situ preparation of magnetic molecularly imprinted polymer particles utilizing moulding particles

A novel synthetic method for the preparation of magnetic molecularly imprinted polymer (MMIP) particles is presented. Magnetic moulding particles with supporting framework and large inner space were first prepared by suspensionpolymerization. MMIP particles were synthesized in situ by polymerizing imprinted polymers within the inner space of moulding particles. The resulting MMIP particles possessed high affinity to template molecules and excellent selectivity of similar substrates in terms of their chemical structures. These MMIP particles could be handled easily and separated rapidly under a magnetic field.

• Studies on structural and magnetic properties of NdFeO$_3$ single crystals grown by optical floating zone technique

NdFeO$_3$ single crystals have been grown by optical floating-zone technique using Nd$_2$O$_3$ and Fe$_2$O$_3$ as the source by solid-state reaction method. The crystalline structure of NdFeO$_3$ belongs to orthorhombic symmetry and the presence of a distorted perovskite structure was confirmed by powder X-ray diffraction (XRD) analysis. From the XRDresults, it is visualized that the lattice expansion has been observed in the unit cell parameters which may appear due to interstitial defects in the NdFeO$_3$ matrix. The deficiency of oxygen atoms and the presence of excess Fe ions in NdFeO$_3$ have been confirmed with EDX spectra. The spin-reorientation region ($T=120$ K) exhibits lower coercive field and the hysteresis loops depict enhanced magnetization ($M_{\rm s}$ and $M_{\rm r}$) values of NdFeO$_3$ single crystal. Presence of compensation temperature point at $T_{\rm comp} = 7.5$ K denotes the anti-parallel alignment of rare-earth ions with Fe magnetic moments. At high temperatures, Fe$^{3+}$ magnetic moments show strong antiferromagnetic interactions ensuing in Neel temperature ($T_{\rm N}$)at 690 K.

• First-principles structural, electronic, optical and bonding properties of scandium-based ternary indide system Sc$_5$T$_2$In$_4$ (T$=$Ni, Pd, Pt)

The structural, electronic and optical properties of rare-earth, scandium-based compounds within the family of RE$_5$-T$_2$-In$_4$ (T$=$Ni, Pd, Pt) intermetallics are calculated by using density functional theory-based orthogonalized linear combination of atomic orbitals method. The studied compounds crystallize in orthorhombic structure with space groupPbam (No. 55). The electronic properties exhibit conducting features of all three compounds. Charge transfer and crystal strength analysis were carried out by computing bond order and effective charge. Regarding optical properties thecomplex dielectric function, optical conductivity and electron energy loss function have been assessed. All the three compounds demonstrate optically anisotropic behaviour for energy values up to 7.0 eV and turned towards isotropicnature at higher energy (>7.0 eV). Optical conductivity spectra designate that the compounds are optically active for visible to UV light. Two major peaks are observed in energy loss spectra, at 13.2 and 32.6 eV, which correspond toplasmonic resonance points. The interatomic bonding characteristics between distinct pair of atoms within each compound have also been elaborated in comprehensive manner.

• Electrochemical studies of V$_2$O$_5$/GOx for glucose detection

A component of biosensor was prepared based on vanadium pentoxide xerogel (V$_2$O$_5$) and glucose oxidase (GOx). GOx was immobilized on V2O5 to obtain V$_2$O$_5$/GOx thin film. V$_2$O$_5$/GOx thin film was deposited onto an indiumtin-oxide-coated polyethylene terephthalate film as substrate. The immobilization of the enzyme GOx on V$_2$O$_5$ was crosslinked by covalent bonds. After immobilization of GOx, an increase in total charge was observed. The rugosity factor indicated a 0.125 of electrochemically active surface of V$_2$O$_5$/GOx with low porosity. V$_2$O$_5$/GOx thin film presented a sensibility in different concentrations of glucose as well as a good linear correlation.

• Dielectric and ferroelectric properties evolution of ($1-x$)(Bi$_{0.5}$Na$_{0.5}$TiO$_3$)–$x$K$_{0.5}$Na$_{0.5}$NbO$_3$ piezoceramics

In this work, piezoceramics of ($1-x$)(Bi$_{0.5}$Na$_{0.5}$)TiO$_3$$–x(K_{0.5}Na_{0.5})NbO_3, (1-x)BNT–xKNN, in the compositional range 0.00 ≤ x ≤ 0.07, were prepared by a mechanochemically activated solid-state method. The structural phase formation and microstructural, dielectric, and ferroelectric properties were studied. Although changes, in symmetry of the perovskite structure, were not detected with the composition (i.e., from a perspective of its intrinsic properties), the microstructural evolution was strongly dependent on the content of the KNN phase (i.e., based on its extrinsic properties). Specifically, KNN favoured the formation of a microstructure with cubic grains, typical morphology of the alkalineniobate ceramics. After KNN addition, both the maximum permittivity temperature and the long-range to short-range ordered transition temperature were reduced. Additionally, ferroelectric loops and strain deformation curves also reflect the long-range to short-range order evolution with KNN addition and temperature. • A facile, low temperature spray pyrolysed tungsten oxide (WO_3): an approach to antifouling coating by amalgamating scratch resistant and water repellent properties In this study, a facile spray pyrolysed hydrophobic robust tungsten oxide (WO_3) films were deposited at an annealing temperature of 400^{\circ}C on inexpensive glass substrates, using clear and homogeneous precursor solution containing tungsten hexachloride and 2-methoxyethanol. The 10 and 15 times sprayed films were polycrystalline with the monoclinic crystal structure, uniform with the submicron-sized grain morphology (size \sim320–420 nm), with an average surface roughness ranging from 12 to 17 nm and transparent above 60% in the visible region with a thickness of 380 and 550 nm, respectively. Elemental existence of tungsten and oxygen was recognized on the surface of the films possessing the highest lattice oxygen percentage of 91.1. Increment in the scratch hardness of the films with the number of sprays compared to uncoated glass was identified. The films were hydrophilic in nature (water contact angle <8^{\circ}), converted to hydrophobic (>120^{\circ}) by treating chemically with octadecyltrichlorosilane to form a self-assembled monolayer on the top and the hydrophobicity remained same (\sim120^{\circ}) even after a year. These films with unique and combined properties of scratch hardness and hydrophobicity can serve in the potential application as antifouling coatings. • Enhanced antibacterial activity by silver nanoparticles-doped NiCo_2O_4 nanosheets for the application of antibiotic resistance Antibiotic resistance has increased to dangerous levels across the globe. A growing list of bacterial infections that lead to blood poisoning or foodborne disease now represent a clinical challenge due to the loss of antibiotic efficacy.Studies on the antibacterial performance of Ag nanoparticles and other transitional metal oxides have gained attention as alternative therapeutic strategies. In this study, NiCo_2O_4 and Ag/NiCo_2O_4 composites of different Ag content were synthesized through a simple co-precipitation method and assessed through transmission electron microscopy, X-ray diffraction and scanning electron microscopy. We found that the morphology of NiCo_2O_4 was unaffected by Ag addition. NiCo_2O_4 and Ag/NiCo_2O_4 composites containing different amounts of Ag were of a suitable size (\sim10 nm). The NiCo_2O_4 and Ag/NiCo_2O_4 composites showed potent activity against a range of disease-causing bacteria. Ag/NiCo_2O_4composites with a low Ag content showed only weak antibacterial activity. These data highlight new strategies to overcome antibiotic resistance. • Formation of diamond nanostructures from graphite using 10 W fibre laser The high activation energy required for graphite–diamond transition limits its applicability in novel areas. To exploit fully the multifunctional properties of diamond in diverse fields, there is a necessity to explore more efficient waysfor its synthesis. In this study, we have demonstrated a new approach for nanodiamonds formation by employing a commercially available low power 10 W continuous-wave fibre laser. The laser system is modulated to generate the highpressure high temperature environment necessary for the phase conversion of graphite to diamond. The microsecond pulse duration combined with liquid confinement effect on plasma provide scope for a lower rate of supercooling, which restricts the epitaxial growth of the crystals. The sample is characterized by X-ray powder diffraction, transmission electron microscope and Raman spectroscopy, confirming the presence of different types of nanodiamonds including newly discovered n-diamond. The process offers many important advantages like scalable process, non-catalyst-based eco-friendly and cost-effective synthesis of metastable nanodiamonds. The results demonstrate the effectuality of inexpensive commercial lasers towards attaining the localized extreme environment necessary for direct phase conversion of diamond materials. • Behaviour of Raman B_1 (high) mode and evaluation of crystalline quality in the In_xGa_{1–x}N alloys grown by RF-MBE In_xGa_{1–x}N ternary alloys are very promising for a variety of applications. However, high-quality growth of In_xGa_{1–x}N alloys, particularly in the intermediate In composition range, is very difficult. This study reports on a systematic analysis of the Raman spectra from the In_xGa_{1–x}N alloys grown by radio-frequency molecular beam epitaxy (RF-MBE)for the whole In compositional range, particularly in the intermediate range of In composition. The B_1 (high) mode, which is inherently Raman inactive is observed for the In_xGa_{1–x}N alloys grown by RF-MBE. The behaviour of Raman inactive B_1 (high) mode is studied for the evaluation of In_xGa_{1–x}N quality, which is found to vary with the In composition and thetemperature of growth. The crystallinity of the In_xGa_{1–x}N alloys can be assessed using B_1 (high) mode’s relative signal intensity and full-width at half-maximum, which are well agreed with the reflection high energy electron diffraction and X-ray diffraction analyses. The optimum growth temperature for the In_xGa_{1–x}N alloys grown by RF-MBE in the intermediate range of In composition is also discussed. • Manganese dioxide nanoparticles: synthesis, application and challenges In recent days, manganese oxide nanoparticles (MnO_2 NPs) have intrigued material science researches extensively due to its wide range of applications. They are widely used in energy storage devices (lithium-ion batteries, capacitors), catalysts, adsorbent, sensors and imaging, therapeutic activity, etc. Since they hold a lot of distinguished potentials, a robust protocol for cheap, stable, biocompatible and eco-friendly MnO_2 NPs is necessary. They can be categorized into different phases like \alpha, \beta, \delta and others. Thus, owing to their peculiar character, they could be utilized forvarious purposes depending on the mode of action and applications. Hence, this review has summarized conventional methods, such as hydrothermal, sol–gel, oxidation–reduction used for the generation of MnO_2 NPs. Likewise, morphological characterization by various spectroscopic techniques also outlined. It is found that the particular method of generation of MnO_2 NPs is useful for a specific phase. • Composition-dependent structural, electrical, magnetic and magnetoelectric properties of (1-x)BaTiO_3$$-x$CoFe$_2$O$_4$ particulate composites

Multiferroic composite with the general formula $(1 - x)$BaTiO$_3$$-xCoFe_2O_4 (x = 0.05, 0.15, 0.25, 0.35 and0.45) has been synthesized by a standard solid-state reaction route. Powder X-ray diffraction analysis confirms the existence of ferrite (spinel CoFe_2O_4) and ferroelectric (tetragonal BaTiO_3) biphase without any impurity phases in the sintered composites. Microstructure of the composite displays two different grain sizes and shapes studied from SEM analysis. The composites show both ferroelectric and ferromagnetic ordering: the saturation magnetization (M_{\rm s}) and retentivity (M_{\rm r}) of the composite are improved with the increase in ferrite phase, while leakage current, ferroelectric and dielectric properties of the composites show a drop. Existence of coupling between ferroelectric and ferromagnetic ordering measured through magnetodielectric (MD) and magnetoelectric (ME) studies reveal an increase in % MD and ME coefficients with an increase in ferrite content. An enhanced ME coupling coefficient of 17 mV cm^{-1} Oe^{-1} has been realized at a dc magnetic field of 5 kOe with a ac frequency of 50 Hz in (1 - x)BaTiO_3$$-x$CoFe$_2$O$_4$ ($x = 0.45$) composite.

• Detailed investigation of the optical properties of the (C$_8$H$_{11}$BrN)$_3$BiCl$_6$ compound by UV–visible measurements

The UV–visible studies of the hybrid tris(4-bromo-N,N-dimethylanilinium) hexachlorobismuthate (III) compound [(C$_8$H$_{11}$BrN)$_3$BiCl$_6$], prepared by slow evaporation at room temperature, were investigated in detail from 200–2400 nm. The absorption peaks show the presence of a peak in the UV–C region around $\lambda_{\rm des}=254$ nm which has the property of disinfecting water. The optical bandgap $E_{\rm g}$, determined by both absorbance and reflectance measurements, was estimated to be ($3.390 \pm 0.009$) and ($3.354 \pm 0.009$) eV, respectively. In addition, these measurements approve the direct behaviour of the allowed optical transitions. The low Eurbach energy (128 meV) confirms the high quality of the prepared sample. The dependence on the incident wavelength of the optical constants such as the extinction coefficient $k$ and the refractive index $n$ was discussed. The dispersion parameters $E_0$ and $E_{\rm d}$ of this compound were calculated on the basis of the Wemple–Didomenico model. Furthermore, the dielectric studies show that the dissipation factor $\tan \delta$ has very low value. All the results demonstrate that this compound may be proposed as a good candidate for optical and optoelectronic applications.

• Effect of CuIn$_{1-x}$Al$_x$Se$_2$ (CIAS) thin film thickness and diode annealing temperature on Al/p-CIAS Schottky diode

Al/p-CIAS Schottky diodes were fabricated by depositing aluminium (Al) on different flash evaporated copper–indium–aluminium–diselenide (CIAS) films of varying thickness. Further, all diodes were annealed at 573 K for an hour. The influence of p-CIAS film thickness and the thermal annealing of Al/p-CIAS Schottky diode were investigated by observing current–voltage ($I–V$) and capacitance–voltage ($C–V$) characteristics at room temperature. Various diodeparameters, such as ideality factor ($\eta$), barrier height ($\phi_{\rm bo}$) and series resistance ($R_{\rm s}$) were calculated using Cheung’s and Norde methods. $\phi_{\rm bo}$ found to increase with annealing as well as with increase in the film thickness. However, the value of $\eta$ and $R_{\rm s}$ decreases with annealing and CIAS thickness. The effective density of states ($N_{\rm v}$), acceptor density of states ($N_{\rm A}$) and barrier height have been calculated from $C–V$ measurements. Values obtained from CV analysis were well matched with $I–V$ results. The value of $N_{\rm v}$ decreases and the value of $N_{\rm A}$ increases with the increase in the film thickness. Using $I–V$ and $C–V$ parameters, energy band gap for the prepared Al/p-CIAS diodes has been reconstructed.

• Electrodeposited thick coatings of V$_2$O$_5$ on Ni foam as binder free electrodes for supercapacitors

Thick coatings, up to few microns, of the active material are necessary for the preparation and commercialization of electrode materials for energy storage applications, as thin layers of active material drains out of the currentcollector after a few cycles. Moreover, larger mass loading of the active material is required for high energy density pseudocapacitor applications as more active material involves more redox reactions to store large amount of charge. Thisstudy reports thick electrodeposits of vanadium pentoxide (V$_2$O$_5$) on nickel foam substrate and its evaluation as supercapacitor electrode material. Vanadium pentoxide with thickness of 3–5 $\mu$m were successfully electrodeposited (potentiostatically and galvanostatically) on metallic nickel foam to obtain potentiostatically electrodeposited V$_2$O$_5$ on nickel foam (PE-V$_2$O$_5$Ni) and galvanostatically electrodeposited V$_2$O$_5$ on nickel foam (GE-V$_2$O$_5$Ni), respectively. The PEV$_2$O$_5$Ni electrode with layered morphologies exhibits more charge storage and discharge capability than spherically dense morphologies of GE-V$_2$O$_5$Ni electrodes. The synthesized electrode materials were structurally, morphologically andchemically characterized through X-ray diffractometer, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The PE-V$_2$O$_5$Ni and GE-V$_2$O$_5$Ni exhibited gravimetric capacitance of 657 and 421 F g$^{-1}$ with tremendous stability in the polypropylene carbonate electrolyte.

• Spectroscopic and third-order nonlinear optical properties of organic single-crystal 2-picolinictrichloroacetate: an overview

Organic single crystals of 2-picolinictrichloroacetate (PTCA) have been successfully grown by slow evaporation technique. The structural and optical characterization of the PTCA is analysed experimentally by Fouriertransform infrared and UV–visible spectroscopic technique and theoretical studies, by density functional theory method. The charge transfer interactions leading to nonlinear properties taking place in the molecule have been studied by highest energy occupied molecular orbital and lowest energy unoccupied molecular orbital analysis and natural bond orbital analysis. Open-aperture Z-scan results on evaluating the nonlinear optical properties experimentally, confirm these materials as good optical limiters. In addition, the PTCA exhibits a blue luminescence emission which shows that it is a potential material for OLED device applications.

• Flexible and free-standing MnO$_x$/reduced graphene oxide paper with excellent cycling stability for Li-ion battery anode

In this study, the performance of manganese oxide nanorods/reduced graphene oxide (MnO$_x$/rGO) composite papers as anode for lithium-ion battery is investigated. The self-supporting and flexible composite papers are fabricated via traditional vacuum filtration. The crystal structure, chemical state and morphology are determined by XRD, XPS and SEM, respectively. And the electrochemical performance is measured by means of cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) techniques. It is proved that the MnO$_x$/rGO papers exhibit layer-by-layer structure in which rod-shaped MnO$_x$ is sandwiched among the rGO sheets. As anode for lithium-ion batteries, the capacity of MnO$_x$/rGO paper can be stabilized at 518 mAh g$^{-1}$ for 1500 charge/discharge cycles.

• Synthesis, structural, crystal growth, electrical and mechanical properties of potassium 4-methyl benzene sulphonate

Semi-organic crystal of potassium 4-methyl benzene sulphonate (KOPT) was grown by slow evaporation solution growth technique. Structural parameters of the grown crystal were obtained by single-crystal X-ray diffraction analysis. It reveals that the crystal belongs to monoclinic system and crystallized in noncentrosymmetric space group P2$_1$. The vibrational frequencies of corresponding functional groups in the compound were analysed by Fourier-transform infrared and FT-Raman spectroscopy. ${}^1$H and ${}^{13}$C NMR spectral analyses have been carried out to confirm the molecular structure of the grown crystal. The thermal properties of KOPT were evaluated by thermogravimetric analysis/differential scanning calorimetry measurements. Ultraviolet–Visible spectral studies revealed the cut-off wavelength, transparency and corresponding bandgap (4.5 eV) of KOPT crystal. The dielectric and mechanical characteristics were studied to test the KOPT crystal for nonlinear optical applications.

• Electrochemical and photocatalytic applications of Ce-MOF

We report on the applicability of an easy and general synthesis procedure for the formation of Ce(IV)-MOFs. Cerium-based metal–organic frame (Ce-MOF) was successfully synthesized by a simple, cost-effective and green route. Highly homogeneous topology, nano-sized crystals, stable oxidation states Ce(III) and Ce(IV) at room temperature, significant surface area and thermal stability up to 320$^{\circ}$C are the notable properties achieved by Ce-MOF. Electrontransferability of the cerium electrode was used for the detection of methylene blue (MB) analyte in acidic buffer solution. Also the effect of different pH buffer solutions on electrode response has been studied. Photocatalytic performance of nano-Ce-MOF was studied on the degradation of MB analyte under visible light.

• Density functional study of elastic and thermal properties of cubic mercury-zinc-chalcogenide ternary alloys

First principle calculations of elastic and thermal properties of zinc-blende specimens within Hg$_x$Zn$_{1–x}$S, Hg$_x$Zn$_{1-x}$Se and Hg$_x$Zn$_{1-x}$Te ternary systems are executed. Elastic stiffness constants decrease non-linearly with increasing Hg-concentration in each system. Each cubic sample is mechanically and dynamically stable, elastically anisotropic, compressible against elastic deformation, ductile and fairly plastic. Hardness of specimens in each system reduces with enhancement in Hg-composition. Mixed kind of bonding with dominancy of covalent over ionic in most cases, bond bending over stretching and central type of interatomic bonding forces are calculated. In each system,covalency, Debye temperature and frequency, Debye temperature for acoustic phonon, thermal conductivity and melting temperature of specimens decreases, while Philip ionicity and Gruneisen parameter increases with enhancingHg-concentration.

• Adsorption effect of NO$_2$ on ZnO (100 nm) nanowires, leading towards reduced reverse leakage current and voltage enhancement

Here, we report the adsorption effect of NO$_2$ on ZnO (100 nm) nanowires. We have studied the effect of adsorbed NO$_2$ molecules on ZnO nanowire-based energy harvester for an exposure time of 1, 2, 3, 4, 5 and 6 h in a sealedchamber at 50 ppm which yielded piezoelectric voltage of 543.6 mV, 834.6 mV, 1.071 V, 1.78 V, 1.969 V and 2.835 V, respectively. We have thoroughly investigated the behaviour of ZnO nanowires in the presence of NO$_2$ and observed a maximum output piezoelectric voltage of 2.835 V with a power density 158.2 mW cm$^{-2}$. This is the first time that ZnO based piezoelectric energy harvester is being used for the voltage enhancement in the presence of NO$_2$. We have used vertically integrated nanowire generator (VING) structure. X-ray diffraction pattern revealed the growth orientation ofZnO nanowires were along the $c$-axis from the substrate. ZnO nanowires were grown on indium tin oxide-coated polyethylene terephthalate substrates via a hydrothermal route. Surface morphology has been examined by scanning electron microscopy images and diameter of ZnO nanowires was found to be around 100 nm. Piezoelectric voltage has been generated by the VING by applying minute external force of $\sim$50 nN. Periodic output voltage peaks were being measured by picoscope 5204.

• Analysis of ITO surface modified with aromatic-based self-assembled molecules

This study focuses on characterization and enhancement of indium tin oxide (ITO) surface by using a self-assembled monolayer (SAM) technique. It is generally used to establish a compatible interface and a good chargeinjection from ITO surface. New generation organic semiconductor molecules such as dibenzo[$a,c$]phenazine-11-carboxylic acid, 4-(9$H$-carbazol-9-yl) benzoic acid, 4-(2,5-di-2-thienyl-1$H$-pyrrol-1-yl) benzoic acid, 5-[(diphenyl)amino]isophthalic acid and 5-[(3-methylphenyl)(phenyl)amino]isophthalic acid were coated on ITO. The surface of ITO was characterized by scanning spreading resistance microscopy, Kelvin probe force microscopy, scanning tunnelling microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry techniques to ensure the chemical bonding of SAM materials on it.

• Efficient photocatalytic degradation of crystal violet by using graphene oxide/nickel sulphide nanocomposites

This study aims to develop the graphene oxide-based metal sulphide nanocomposite, which has outstanding photocatalytic properties. The graphene oxide (GO) was prepared by the Hummers method, and GO/nickel sulphide (GO/NiS) nanocomposite was synthesized by the hydrothermal method to evaluate the photocatalytic dye degradation. The synthesized nanocomposites were characterized by X-ray diffraction, Fourier transform infrared, ultraviolet–visible,scanning electron microscopy with energy-dispersive X-ray and transmission electron microscopy techniques. Photocatalytic dye degradation efficiency of GO, NiS and GO/NiS nanocomposites were evaluated by using crystal violet (CV)dye. The GO/NiS nanocomposite exhibited good photocatalytic activity as compared to NiS as well as GO. The optimum condition obtained for the effective photocatalytic degradation of CV is pH $=$ 8.0, crystal violet $=$ $2.0 \times 10^{-5}$ M, nanocomposite $=$ 0.30 g. The rate of degradation of CV with the composite was found to be $2.39\times 10^{-4}$ s$^{-1}$.

• In-situ synthesized carboxymethyl chitosan/poly(vinyl alcohol) bio-nanocomposite hydrogels containing nanoparticles with drug-delivery properties

A drug-delivery approach was developed through effective preparation of bio-nanocomposite hydrogels in situ with ZnO/CuO/Ag nanoparticles being formed within swollen carboxymethyl chitosan (CMCh)/poly(vinyl alcohol) (PVA) hydrogels. Different experimental techniques, including Fourier transform-infrared, X-ray diffraction (XRD), energy-dispersive X-ray (EDX) analysis, and scanning electron microscopy (SEM) were applied to study and compare the prepared hydrogels. XRD and EDX analyses confirmed the formation of nanoparticles in the hydrogel matrix, while SEM micrographs showed that ZnO, CuO and Ag nanoparticles ranged from 36.26 to 76.09 nm, 34.15–71.71 nm and 36.21–78.47 nm within the same matrix, respectively. According to the results, an increased number of nanoparticles resulted from increased ion concentration. At pH 2.1 and pH 7.4, the bio-nanocomposite hydrogels were investigated in terms of the swelling behaviour; in comparison with neat CMCh/PVA hydrogel, they showed a pH-sensitive swelling ratio. As an in-vitro drug release test, the bio-nanocomposite hydrogels were applied to sustained and controlled drugdelivery system that increased with the increase in nanoparticles content that could result in protracted release of the ibuprofen.

• A study on the vibrational frequencies, elastic properties and sound velocities of vanadium spinel oxides AV$_2$O$_4$ (A $=$ Mn, Fe and Zn) short-range non-Coulomb potential theoretical model

Owing to the fact of the AB$_2$O$_4$ spinel oxide’s chemical and thermal stability, and other intriguing properties make them suitable candidate materials for many applications, including chemical looping and catalytic reactions. To do our investigations, a short-range non-Coulomb potential theoretical model is used to calculate the zone-centre, elastic constants, infrared phonon mode frequencies, Raman phonon mode frequencies, velocities of the sound wave along the highly symmetric three crystallographic-axes and Debye temperature of the vanadium spinel oxides AV$_2$O$_4$ (A $=$ Mn, Fe and Zn). The preliminary results of our calculations show that the interaction inthe second neighbour (V–O) is much stronger than the interaction of the first neighbour (A–O). Moreover, from the analysis of the obtained results of elastic constants, the nature of the studied vanadium spinels are found to beductile.

• Impurity mechanism of monocrystalline silicon PERC solar cells stimulated by prelight-induced degradation

Although the monocrystalline silicon (mono-Si)-passivated emitter and rear contact (PERC) solar cells have achieved incredible efficiency, they still can be further improved by hydrogenation. So the hydrogenation was performedto investigate the improvement of large area (>240 cm$^2$) mono-Si PERC solar cells and estimate the significance of previous light-induced degradation (pre-LID) under a high-intensity infrared (HI-IR) LEDs source platform. Then, theresults indicated that the parameters, such as open-circuit voltage ($U_{\rm oc}$) and short-circuit current density ($J_{\rm sc}$) and fill factor (FF), could be better improved after LED hydrogenation with the execution of the pre-LID. The efficiency of mono-Si PERC solar cells with pre-LID increased by $\sim$0.190 $\pm$ 0.005%$_{\rm abs.}$ for 2 min, which was higher than that without pre-LID (0.115 $±$ 0.005%$_{\rm abs.}$). Moreover, the results showed that the efficiency of large area mono-Si PERC solar cells with light-induceddegradation (LID) treatment after LED hydrogenation only existed a slight degradation of about $-$0.253 $\pm$ 0.005%$_{\rm rel.}$. Compared with mono-Si PERC solar cells without pre-LID, the efficiency improvement and LIDmitigation of mono-Si solar cells with pre-LID was faster and more significant by LED hydrogenation, so that the LED hydrogenation time significantly can shorten from 6 to 2 min. Additionally, the possible presence of a boron-oxygen (BO) model was estimated, and this BO model is susceptible to be activated by the injection of external energy, resulting in more BO defects in the process of pre-LID, so that subsequent hydrogenation rate becomes faster.

• Wear and thermal resistance properties of aluminium particulate microcomposites

Wear resistance and thermal stability are not fundamental properties of materials, but their effects are inevitable in applications involving two-body contact because of friction-induced wear and heat. Wear resistance andthermal stability of epoxy containing 10% by weight of 66.34 $\mu$m aluminium particles were examined using mass loss per sliding distance approach and glass transition temperature ($T_{\rm g}$) was used as a parameter for thermal stability. The results obtained revealed a reduction in the wear rate due to addition of aluminium particles. About 62, 58 and 39% reductions at9 N/0.65 m s$^{-1}$; 9 N/1.3 m s$^{-1}$ and 25 N/1.3 m s$^{-1}$, respectively imply that both sliding speed ($v$) and the applied load ($F$) contribute to an increase in the wear rate. A lower coefficient of friction of epoxy aluminium composites signifies lower surface wear rate in comparison with that of the epoxy polymer upon contact with another body in applications. The linear model establishes that $v$ with a $P$ value of 0.0046 has a greater significant influence on the wear resistance of the composite than $F$ with a higher $P$ value (0.0103). By the model, the epoxy aluminium composite under 24.63 N isexpected to experience a wear rate of 0.000537 g m$^{-1}$ which is 1380% lower than that established by the results of the experiment. About 36% increase in $T_{\rm g}$ is observed and 2FI model affirms that there is a gradual increase in $T_{\rm g}$ with heat flow through the sample during the glass transition period. Hence, the 2FI model having adequate precision of 164 > 4 is appropriate to be used for navigating a design phase for thermal stability properties.

• Negative capacitance effect of Cu–TiC thin film deposited by DC magnetron plasma

The quest for low power consumption devices with new functionalities has made the negative capacitance (NC) effect, the most captivating and studied phenomenon. The NC effect is observed in Cu–TiC thin film at a low frequencyrange between 112.9 Hz and 2 kHz. The Cu–TiC thin film was deposited on Si (100) substrate by DC magnetron co-sputtering process and then annealed in a vacuum at different temperatures (100–600$^{\circ}$C). The magnitude ofNC increased from $-$0.016 to $-$27.5 lF after annealing. The NC behaviour is also observed in the forward biased region of the capacitance–voltage ($C–V$) characteristics. The current–voltage ($I–V$) characteristics reveal the decreasing static and dynamic resistance for higher annealed films. An improved electrical conductivity ($27.70 \times 10^3$ to $384.62 \times 10^3$ S m$^{-1}$)is evidenced with decreasing ideality factor (2.01–0.55) in the post-annealed films. The films were found to be polycrystalline from X-ray diffraction patterns with Cu and TiC phases. Raman studies have also confirmed the presence of Cuand TiC vibrational modes in all films. The intensity of C peaks detected at 1359 cm$^{-1}$ (D peak) and at 1590 cm$^{-1}$ (G peak) in the as-deposited film decreased after annealing. The annealing effect reduced the amount of unreacted carbon and contributed to form stoichiometric TiC from non-stoichiometric TiC.

• Effects of annealing processes on the crystallization and magnetic properties of nickel ferrite thin films

Magnetic nickel ferrite (NFO), NiFe$_2$O$_4$, thin films were fabricated using the chemical solution deposition method on (100)-oriented silicon substrates. The effects of an annealing process on the crystallization and magnetic properties of NFO thin films were investigated. Two annealing methods were used, namely layer-by-layer multiple rapidannealing process and single slow-annealing process. The results showed that the appropriate pyrolysis temperatures range from 400 to 500$^{\circ}$C. NFO thin films crystallized well when they were annealed at 750$^{\circ}$C or above. The NFO thin filmsfabricated using the single slow-annealing process (NFO-S) show better crystallinity compared to the films fabricated using the layer-by-layer multiple rapid-annealing process (NFO-R) when the annealing temperatures were low. NFO-R thin films show preferred (400) orientation growth and the relative intensity of the (400) peak raises with the annealing heating rate. Fine magnetic hysteresis loops and good magnetic properties were observed in both NFO-S and NFO-R thin films. A saturation magnetization of 277 emu cm$^{-3}$ was derived for the NFO-S thin films, compared to a 230 emu cm$^{-3}$ for the NFO-R thin films, which is a very high value compared with former reported values for NFO thin films.

• Structural, impedance and electrical evaluation of complex perovskite: Ca(Mn$_{1/3}$Ni$_{1/3}$W$_{1/3}$)O$_3$

A complex perovskite Ca(Mn$_{1/3}$Ni$_{1/3}$W$_{1/3}$)O$_3$, abbreviated as CMNWO, is synthesized by adopting the solid-stateceramic procedure. The X-ray diffraction analysis of CMNWO shows that the present perovskite is acquiring a cubic crystal structure having the cell dimension of $a = 3.8321$ Å. The obtained cell parameter is in good agreement with the theoretical cell parameter obtained from the SPuDS-V2.19.05.14 code. The micrograph describes the uniform grain distribution in the CMNWO sample. The average crystallite size of the sample was found to be 50.98 nm, which was calculated using the Scherrer relation. The dielectric and electrical properties like dielectric constant, dissipation factor, impedance, electrical modulus and conductivity of CMNWO were studied. The activation energies were determined from the AC-conductivity data in the temperature range of 200–350$^{\circ}$C and 360–500$^{\circ}$C. The dielectric spectra with temperature suggest that the present CMNWO is semiconducting in nature and follows the negative temperature coefficient of resistance kind of behaviour.

• Synthesis of novel g-C$_3$N$_4$/KBiFe$_2$O$_5$ composite with enhanced photocatalytic efficiency

Novel graphitic carbon nitride (g-C$_3$N$_4$)/potassium bismuth ferrite (KBiFe$_2$O$_5$) composite photocatalysts were synthesized using facile grinding and calcination method. X-ray diffraction, transmission electron microscopy, scanning electron microscopy and UV–visible diffuse reflectance spectroscopy analysis were carried out to investigate structural,morphological and optical properties of the prepared samples. The photocatalytic properties of the samples were studied by photocatalytic degradation of methylene blue under visible light irradiation. The composite showed enhanced photocatalytic efficiency compared to both pristine g-C$_3$N$_4$ and KBiFe$_2$O$_5$. Out of four composites with different weight percentagesof KBiFe$_2$O$_5$, one with 30 wt% showed the maximum photocatalytic efficiency. Samples with a higher content of KBiFe$_2$O$_5$ showed decreased photocatalytic efficiency indicating 30 wt% as the optimum composition. The increase in the photocatalytic efficiency is mainly due to efficient charge separation of photo-generated electron–hole pairs in the composites.The possible mechanism for the photo-catalysis of g-C$_3$N$_4$/KBiFe$_2$O$_5$ composites was also proposed.

• Efficient surface plasmon propagation on flexible free-standing and PMMA sandwiched graphene at optimized near to far-IR frequencies

Graphene is an important material for the design of flexible and stretchable electronic and optoelectronic devices on account of its high Young’s modulus and generation of highly confined surface plasmons. In this work, we report the near to far-infrared (FIR) input frequencies required to generate the maximum electric field and magnetic field for the efficient propagation of surface plasmons for differently doped, micron-long, free-standing and poly(methyl methacrylate) (PMMA) sandwiched graphene sheets. The effect of the variation of doping of graphene, graphene sheet length and bent angle of the graphene sheet on the propagating electromagnetic field is analysed at the obtained inputexcitation frequencies using finite element method. Low attenuation of 0.034 and 0.234 dB along with relatively high confinement of $\sim$6 and $\sim$13 nm for the surface plasmons are achieved for micron-long, bent, highly doped, freelysuspended and PMMA sandwiched graphene sheets at 193.5 and 190 THz, respectively. The knowledge of these optimized NIR–FIR input excitation frequencies producing maximum electric and magnetic field output at the end ofgraphene sheet is useful for designing compact and efficient graphene-based flexible and wearable devices for medical imaging applications.

• NPAM-assisted rapid synthesis of BiOBr ultrathin hierarchical clusters for efficient photocatalytic degradation of RhB and ciprofloxacin

Nonionic polyacrylamide (NPAM) bismuth bromoxide (BiOBr) ultrathin hierarchical clusters have been prepared by a rapid solvothermal synthesis route. The formation mechanism of the NPAM-BiOBr ultrathin hierarchical clusterswas based on the strong bridging role of NPAM between the bismuthyl nitrate (BiONO$_3$) particles and subsequently results in tight junctions between BiOBr nanosheets. The structure, morphology and optical properties of the prepared samples were characterized by X-ray diffraction, Raman spectra, scanning electron microscopy, diffuse reflectance spectroscopy and photoluminescence. The photocatalytic performance of NPAM-BiOBr was evaluated by the degradation of Rhodamine B (RhB) and ciprofloxacin. The photocatalytic efficiency increased by 2.1 and 2.5 times of NPAM-BiOBr for RhB andciprofloxacin decomposition, respectively. The enhanced photocatalytic activity of NPAM-BiOBr was attributed to the increased light absorption capacity and lower recombination rate of the photo-generated electron and hole pairs.

• Preparation and characterization of Guar gum-based solid biopolymer electrolyte doped with lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) plasticized with glycerol

The Guar gum (GG)–lithium bis(trifluoromethanesulphonyl)imide (LiTFSI)-glycerol-based solid biopolymer electrolyte has been investigated. The polymer electrolytes has been prepared via solution casting technique and characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), 3D-laser profilometry and AC impedance studies. The amorphous nature and complexation has been revealed by XRD and FTIR. TGA reveals that the polymer electrolyte is stable up to 260$^{\circ}$C. The average roughness was measured using 3D-laser profilometry. The ionic conductivity of the electrolyte was studied using impedance analysis. The best optimum ionic conductivity of $2.041 \times 10^{-3}$ S cm$^{-1}$ has been achieved for the film containing 60 wt% GG–40 wt% LiTFSI.

• Facile low-temperature synthesis of W-rich Cu$_{1-x}$Zn$_x$WO$_4$ nanoparticles and the electrochemical performance

This paper reports the facile low-temperature synthesis of Cu$_{1-x}$Zn$_x$WO$_4$ nanoparticles by varying the concentration of Zn using solid-state reaction method. The incorporation of various Zn concentrations can alter the valence band energy and enhance the structural, optical and electrochemical properties. The prepared nanoparticles have a triclinic crystal structure with minimum strain. The variation in zinc concentration is shown by the densely aggregated particles in the SEM image. These nanoparticles exhibit strong absorption in the visible region and the bandgap is found to increase with an increase in Zn concentration. The photocurrent density increases with an increase in the concentration of zinc and found to be a maximum of 8.5 $\mu$A cm$^{-2}$ for $x = 0.4$ due to a lower bandgap of 2.65 eV. Finally, it is observed that an optimum zinc concentration promotes improved photocurrent generation.

• Charge conduction mechanisms and MR behaviour of sol–gel-grown nanostructured La$_{0.6}$Nd$_{0.1}$Sr$_{0.3}$MnO$_3$ manganites

In this communication, structure and charge, conduction mechanisms have been understood for sol–gel grown nanostructured La$_{0.6}$Nd$_{0.1}$Sr$_{0.3}$MnO$_3$ (LNSMO) manganites prepared at different process temperatures under air and oxygen environments. Obtained X-ray diffraction patterns of all the samples were analysed using Rietveld refinements and obtained structural lattice parameters have been discussed in correlation with resistivity behaviour of the samples. Observed low temperature resistivity upturn behaviour has been examined in the context of electron–electron scattering mechanism. Metallic and insulating/semiconducting behaviours of all the nanostructured LNSMO manganites have been understood by using various models and mechanisms. Magnetoresistance isotherms have also been theoretically fitted and separate grain and grain boundary contributions have been studied for LNSMO manganite samples. Allobtained fitting parameters have been discussed in the context of role of applied magnetic field, process temperature and annealing environment.

• Sonochemically synthesized Na$_2$Ti$_6$O$_{13}$ nanorod: an efficient electrode material for Na-ion battery

A simple cost-effective wet synthesis route has been proposed for synthesis of Na$_2$Ti$_6$O$_{13}$, which is an efficient anode material that can be used for 1–3 volt batteries. The material has been synthesized by sonochemical route,which offers two distinct features: (1) energy-savvy (green) synthesis by significantly lowering the final calcination temperature and duration, and (2) formation of uniform and nano-scale particles suitable for battery application. Thesonochemical synthesis was carried out at 20 kHz–500 W by applying sonication for 30 min at 25$^{\circ}$C, using precursors (NaOH:TiO$_2$) in a molar ratio of 6:1 followed by calcination at 750$^{\circ}$C for 1 h in air. This material showed excellent reversible electrochemical performance (up to 93% retention) and offers reversible capacity around 40 mAh g$^{-1}$ acting to be 0.82 V anode for Na-ion battery.

• Enhancement of optical properties of boron-doped SiC thin film: a SiC QD effect

Silicon carbide quantum dots (SiC-QD) embedded inside the SiC thin film deposited on silicon (111) wafer is directly synthesized by modified chemical vapour deposition technique using boron-doped liquid polycarbosilane as aprecursor. Subsequent microscopic characterization of the thin film exhibits the presence of QD, which is theoretically corroborated from the exciton Bohr radius. The film shows interesting visible and near-infra-red photoluminescence atroom temperature with enhanced lifetime. In addition to the lifetime, the quantum efficiency in the visible emission was also enhanced substantially than what was reported previously.

• Fabrication and characterization of three-dimensional porous cornstarch/n-HAp biocomposite scaffold

The aim of this study is to investigate the morphological, functional group, crystallinity and mechanical properties of a three-dimensional porous cornstarch/n-HAp (nano-hydroxyapatite) biocomposite scaffold. In this study,cornstarch/n-HAp scaffolds were fabricated using the solvent casting and particulate leaching technique. The porous cornstarch/n-HAp composites with various cornstarch contents (30, 40, 50, 60, 70, 80 and 90 wt%) were prepared and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometer and compression test. The morphology of the scaffolds possessed macropores (200–600 $\mu$m) and micropores (50–100 $\mu$m) with a high interconnectivity. The porosity of the porous cornstarch/n-HAp scaffolds varied between 53 and 70% with compressive strength and compressive modulus of 2.03 and 8.27 MPa, respectively. The results suggested that highly porous cornstarch/n-HAp scaffold properties with adequate mechanical properties can be obtained for applications in bone tissue engineering.

• Antibactericidal nanoclay-based biomaterial for sustained delivery of tetracycline hydrochloride

Nanoclay-based drug delivery vehicle has acquired immense recognition owing to its unique physico-chemical properties. In this study, tetracycline hydrochloride (TCH) drug was intercalated into the interlayer gallery of montmorillonite (Mt) clay by a cation exchange process. The intercalated nanocomposites were characterized by Fourier transform infraredspectroscopy, X-ray diffraction, energy dispersive X-ray and thermogravimetric study. It was evident from the characterization that TCH drug was successfully intercalated into the interlayer gallery of Mt clay. These clay-based formulations exhibited antibacterial activity against both Gram-positive and Gram-negative bacteria on analyses via zone inhibitionmethods. An in-vitro drug release study was performed in phosphate buffer at physiological temperature and interestingly it exhibited sustained and controlled release of TCH from the nanocomposites, after an initial burst-out effect. Overall, this study showed that these nanocomposite materials have immense potential for use in controlled drug delivery strategies for antibacterial treatment.

• Structural, dielectric and magnetoelectric coupling analysis in SrBi$_2$Nb$_2$O$_9$–CoFe$_2$O$_4$ composites

Ferroelectric–magnetic composites of SrBi$_2$Nb$_2$O$_9$–CoFe$_2$O$_4$ (SBN–CFO) were synthesized via conventional solid state reaction route. The powder X-ray diffraction, Raman spectroscopy and scanning electron microscopy measurements confirm the existence of two chemically separated phases and phase purity in the SBN–CFO composites. Magnetization measurements confirm the enhanced values of the magnetic parameters. The change in the area of theferroelectric P vs. E loops with frequency confirms the enhanced ferroelectric nature of the SBN–CFO composites. The quantified maximum values of magnetoelectric coefficient ($\alpha$) are observed from the $P$ vs. $E$ loop measurements in the influence of applied magnetic field and found to be 4.475 mV cm$^{-1}$ Oe$^{-1}$ at 688 Oe for SBN–0.1CFO and 3.389 mV cm$^{-1}$ Oe$^{-1}$ at 1000 Oe for SBN–0.2CFO composites, respectively. The shifting in the peaks of temperature-dependent dielectric maxima towards the higher temperature side confirms the relaxor behaviour in the SBN–CFO composite samples.

• In-situ annealing and characterization of superhydrophobic electrospun poly(acrylonitrile) ionized nanofibre smart material properties

Poly(acrylonitrile) (PAN) electrospun nanofibres were stabilized at 285$^{\circ}$C in surrounded conditions for 1 h and then carbonized at 900$^{\circ}$C for 1 h in inert nitrogen (N) at 10 psi. The resulting carbonized PAN nanofibre films were fabricated into square pieces and exposed to several classification procedures. Raman spectroscopy analysis was used to stretch approximately 920 cm$^{-1}$ of the designated construction of the G-band of the carbonized nanofibres. Energy dispersive X-ray (EDX) spectroscopy was used to examine the chemical structures and elemental distribution of the carbonized PAN nanofibres. EDX spectroscopy revealed the PAN carbon core at roughly 61%. After annealing, the PAN carbon nanofibres were 89% carbon weight (atomic %), with N and minor quantities of Ni and O. The structure was confirmed by X-ray diffraction for bulk PAN and carbonized PAN nanofibres. Examination of the outcomes may be valuable for improving the use of various smart nanofibre materials in the industry and for water treatment sensor applications.

• Amperometric assay of hydrazine utilizing electro-deposited cobalt hexacyanoferrate nanocrystals on graphene oxide sheets

In-situ electrochemical deposition of cobalt hexacyanoferrate (CoHCF) on graphene oxide (GO) and its application for the electrocatalytic hydrazine determination in real samples are described in this research study. Co$^{2+}$ is immobilized on GO and the resulting material, GO-Co$^{2+}$ is coated on the surface of glassy carbon (GC) electrode. The fabricated electrode (GC/GO-Co$^{2+}$) is subjected to a continuous potential cycling in the range of 0.0–1.0 V which results in the formation of a thin CoHCF film on the surface of GO coated on the GC electrode (abbreviated as GC/GO-CoHCF). The synthesized GO-CoHCF composite material is characterized by Fourier transform infrared and scanning electron microscopy. GC/GO-CoHCF electrode electrocatalytically oxidizes hydrazine at low overpotential (0.63 V) and thisphenomenon is subsequently utilized for the sensitive determination of hydrazine in aqueous solutions. It exhibits a wide linear calibration range (0.1–400 $\mu$M), high sensitivity (0.93 $\mu$A $\mu$M$^{-1}$ cm$^{-2}$) and low limit of detection (17.5 nM) for the determination of hydrazine. Further, this electrode is employed for hydrazine determination in real samples.

• Cubic to pseudo-cubic tetragonal phase transformation with lithium and beryllium doping in CaTiO$_3$ and its impact on electronic and optical properties: a DFT approach

First-principles calculations, with CASTEP code, were employed to study the effect of lithium (Li) and beryllium (Be) doping on structural stability, phase transformation, electronic band structure and optical characteristics ofCaTiO$_3$. The substitution of Ca-atoms with the Li- and Be-atoms changes the lattice parameters and hence unit cell volume and consequently the electronic band structure of CaTiO$_3$ is modified. With 12.5% Li- and Be-doping, weobserved a structural phase transformation from cubic to pseudo-cubic tetragonal structure which is in good agreement with the literature. The impact of structural phase transformation on the electronic band structure has been explained with the help of total, partial and elemental partial density of states. In case of Li-doping, the value of band gap slightly increases from 1.866 to 1.964 eV while the band gap value decreases to 1.614 eV for Be-doping. In both cases of doping, maxima of valence band are shifted from R to Z symmetry point whereas the minima of conduction band remain at G symmetry point. In pure and doped cases, the nature of the band gap remains unaltered, i.e., indirect band gap. From optical response of the doped compounds, we perceive a red shift in the absorption. With Be- and Li-doping, the static refractive index also increased from 2.48 to 2.63 and 4.1, respectively. The change in electronic structure and optical characteristic with Li- and Be-doping would make this compound a suitable candidate for future optoelectronic devices.

• AC conductivity and dielectric relaxation of chitosan/poly(vinyl alcohol) biopolymer polyblend

Polyblend samples of chitosan/poly(vinyl alcohol) (PVA) have been prepared using a casting technique. Scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis measurementsrevealed that chitosan and PVA are compatible with each other. Alternate current (AC) conductivity and dielectric relaxation features of pure and polyblend samples are analysed in the frequency range of 0.1 Hz to 100 kHz covering abroad temperature range from room temperature to 423 K. Variation of AC conductivity, $\rho_{\rm AC}$, of pure and chitosan/PVA polyblend samples is found to be characterized by a plateau region at low frequency and high temperature, and this plateau region increases with increase in temperature. Based on the behaviour of the exponent $s$ $vs$. temperature, AC conductivitydependence on frequency is found to be correlated with overlapping-large polaron tunnelling (OLPT) model. The polyblend samples showed an improvement in their dielectric properties compared to the pure materials. The dielectric constant, $\epsilon '$, of polyblend samples was increased by increasing the content of PVA. The dielectric dispersion was observed in the variation of $\epsilon '$ against frequency for all samples. The high values of $\epsilon '$ for all samples at high temperature and low frequency are attributed to space charge polarization. Also, loss tangent-frequency behaviour of pure chitosan, PVA andall polyblend samples showed two distinguished relaxation peaks with different values of activation energies. The first relaxation peak is termed as interfacial polarization or Maxwell–Wagner–Sillars polarization due to heterogeneity of thepolyblend samples, whereas, the second relaxation peak is termed as $\delta$-relaxation and $\alpha$-relaxation, for pure chitosan and PVA, respectively.

• Opuntia ficus-indica as a durable and eco-friendly corrosion inhibitor on AISI 410 stainless steel in 0.5 M H$_2$SO$_4$

In the dental office, surgical instruments must be sterilized for each patient, following their contamination by saliva and blood. Repeated sterilization cycles cause corrosion. A worn out and corroded instrument may cause toxicity tothe patient. The aim of our study is to improve the corrosion resistance of orthodontic pliers during sterilization using green inhibitors. The behaviour of AISI 410 stainless steel with respect to corrosion was studied in a 0.5 M H$_2$SO$_4$, using cladodes of Opuntia ficus-indica (OFI) as a green inhibitor. Temperature effect on OFI efficacy was studied for different ranges (25, 35 and 45$^{\circ}$C). The study was carried out using the weight loss method, the stationary electrochemical techniques (polarizationcurves), the transients (electrochemical impedance spectroscopy), and the scanning electron microscopy associated with X-ray dispersive energy spectroscopy (SEM–EDX) and atomic force microscopy (AFM) observations. OFI behaves as a mixed inhibitor, with a physisorbed adsorption obeying to Langmuir isotherm and, with an efficacy ranging from 95.12 to 15% (v/v) obtained after 12 h immersion at a temperature of 25$^{\circ}$C. The SEM–EDX and AFM observations confirm the obtained results. In conclusion, OFI improves corrosion resistance of AISI 410 stainless steels in 0.5 M H$_2$SO$_4$ at 25$^{\circ}$C.

• Atomic simulations of melting behaviours for TiAl alloy nanoparticles during heating

Titanium alloys not only have a high strength to weight ratio and good corrosion resistance but also have a higher cost on traditionally metallurgy. In additive manufacturing (AM) process, the thermal stability of alloy particlesduring heating has an important influence on fabricating parts. This article presents atomic simulations to study changes of packing structures and atomic level stresses by using a molecular dynamics (MD) approach within the framework of embedded atom method (EAM). This research provides different evolution patterns of TiAl nanoparticles with different sizes owing to the following facts that the atoms undergo different strain states. In these particles, a large proportion of Al atoms are subjected to tensile or compressive strain, whereas a considerable number of Ti atoms are stretched or compressed only at high temperatures. Back propagation neural network is used to calculate data of specific heat, and the machine learning provides the possibility to determine critical size suitable for the classical Dulong–Petit law under certain thermal conditions.

• Electrochemical characterization of nanosurface-modified screen-printed electrodes by using a source measure unit

In this study, the performance of a source measure unit (SMU) performing cyclic and differential pulse voltammetry analyses, in comparison to potentiostat, is investigated. SMU is a versatile and accurate tool, capable of sourcing and measuring simultaneously and is comparable to the use of a potentiostat for such measurements. Here, two surface-functionalized screen-printed carbon electrodes with two different nanocomposites were utilized to represent theelectrochemical system. The results unveil that the electrochemical behaviour of SMU is qualitatively comparable to that of the potentiostat with more than 97% accuracy; for both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Consequently, SMU is feasible for CV and DPV measurements.

• Synthesis and characterization of gadolinium-doped ceria and barium cerate-based composite electrolyte material for IT-SOFC

A nanocomposite, containing gadolinium-doped ceria (GDC, Ce$_{0.85}$Gd$_{0.15}$O$_{1.925}$) and 10 mol% gadoliniumdopedbarium cerate (BGC, BaCe$_{0.85}$Gd$_{0.15}$O$_{2.925}$), was developed as an electrolyte material for intermediate temperature solid oxide fuel cell. The composite powder was synthesized through an auto-combustion process that yielded the desired phases right after combustion. The powder was characterized using X-ray diffraction, particle size analysis, Brunauer–Emmett–Teller surface area analysis and transmission electron microscopy. The electrical properties of the composite electrolyte were characterized by electrochemical impedance spectroscopy under air as a function of temperature. The effect of second phase on total conductivity and activation energy of the composite material was compared with that of GDC of similar composition. For this, GDC (Ce$_{0.85}$Gd$_{0.15}$O$_{1.925}$) powder was produced using a similar processing technique. The microstructural characterization of GDC and GDC–10BGC composite materials was studied through scanning electron microscopy. The electrochemical properties of planar cell, using GDC–10BGC as electrolyte and employing Ni–(GDC–10BGC) and La$_{0.6}$Sr$_{0.4}$Co$_{0.2}$Fe$_{0.8}$O$_{3-\delta}$-based anode and cathode materials, were investigated.

• Frequency-dependent electrical behaviour of Na$_2$SiO$_3$: a brief report

The present study reports the frequency-dependent electrical properties of sodium silicate (Na$_2$SiO$_3$) (SS) at different temperatures to understand the contribution of grain and grain boundary polarization to its electricalresponse at a lower frequency region. The low-frequency dielectric dispersion and non-Debye-type dielectric relaxation are attributed to polaron hopping that controls the complex impedance of SS. A single semi-circular arc in Nyquistplot indicates a dominance of grain boundary polarization in the relaxation mechanism. The analysis of frequency dependent ac conductivity in the studied temperature regime can be used to define the correlated barrier hoppingmodel.

• A study of the in-vitro bioactivity, dissolution and antibacterial activity of larnite prepared by a novel sol–gel combustion method using sucrose as a fuel

This article presents the preparation and antibacterial activity of larnite bioceramics, an active calcium silicate ceramic material having the molecular formula Ca$_2$SiO$_4$. A stepwise sol–gel combustion approach was used toprepare the single phasic larnite. The synthesis of larnite was carried out with calcium nitrate tetrahydrate as a source of calcium which acts as an oxidizing agent and tetraethyl orthosilicate as a source of silicate which acts as a reducing agent (fuel). The powders thus prepared were calcined at temperatures ranging from 400 to 800$^{\circ}$C. X-ray diffraction analysis was used to study the phase formation and determine the hydroxyapatite (HAP) formation during the bioactivity studies. The synthesized materials were also characterized by Fourier-transform infrared, scanning electron microscopy and energy dispersive X-ray techniques. Elemental ionic concentration of the Ca, P and Si in stimulated body fluid (SBF) solution was analysed by inductively coupled plasma-optical emission spectroscopy. The bone-like apatite formation ability of larnite scaffolds was investigated by immersing it in SBF. It was observed that larnite has the capability to deposit HAP within the early stage of immersion. The antimicrobial activity of the larnite was screened against nine clinical pathogens. The fabricated larnite compound was tested against both Gram-positive bacteria (Staphylococcus aureus and Enterococcus sp.) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, Shigella sp., Proteus mirabilis, Salmonella sp. and Klebsiella pneumoniae) via the agar diffusion method. Theobtained results suggested that the prepared larnite has a high antibacterial property against Gram-negative bacteria because of its thin peptidoglycan layer. From the overall results it is concluded that larnite could be a promising candidate for biomedical applications.

• Preparation of natural dyes from salvia and spathodea for TiO$_2$-based dye-sensitized solar cells (DSSCs) and their electrochemical impedance spectroscopic study under light and dark conditions

In this research investigation, natural dyes have been prepared from salvia and spathodea flowers for dyesensitized solar cells (DSSCs). TiO$_2$ nanosphere-based thin films were prepared using the doctor blade method and the natural dyes were loaded on TiO$_2$ nanospheres. The electrochemical and photoelectrochemical properties were studied using electrochemical impedance spectroscopy and $J–V$ measurement, respectively. This study has been used for device fabrication. The results show that the fabricated dye improves efficiency of solar cells. Electrochemical properties were studied under dark and light conditions and the optical properties of TiO$_2$-based DSSCs were also studied. The efficiency of solar cells increases by using the fabricated natural dyes. As far as the advantage of using natural dyes is concerned, they can be beneficial for future bio-photovoltaic technology.

• Application of $k\cdot p$ method on band structure of GaAs obtained through joint density-functional theory

The structural and electronic properties of zinc-blende GaAs were calculated within the framework of planewave density-functional theory code JDFTx by using Becke 86 in 2D and PBE exchange-correlation functionals from libXC. The standard optimized norm-conserving Vanderbilt pseudopotentials were used to calculate optimized lattice constants, band gap and spin–orbit (SO) split-off parameter. The calculated values of optimized lattice constants and direct band gap are in satisfactory agreement with other published theoretical and experimental findings. By including SO coupling, conduction bands and valence bands were studied under parabolicity to calculate effective masses. The calculated values of effective masses and SO split-off parameter are in satisfactory agreement with most recent findings. This study will be useful for more computational studies related to semiconductor spintronic devices.

• Gallium nitride nanocrystal formation in Si$_3$N$_4$ matrix by ion synthesis

Synthesis of nanoparticles in insulators attracts tremendous attention due to their unique electrical and optical properties. Here, the gallium (Ga) and gallium nitride (GaN) nanoclusters have been synthesized in the silicon nitridematrix by sequential ion implantation (gallium and nitrogen ions) followed by either furnace annealing (FA) or rapid thermal annealing (RTA). The presence of Ga and GaN nanoclusters has been confirmed by Fourier-transform infrared,Raman and X-ray photoelectron spectroscopy. Thereafter, the effect of RTA and FA on the conduction of charge carriers has been studied for the fabricated devices. It is found from the current–voltage measurements that the carrier transport is controlled by the space charge limited current conduction mechanism, and the observed values of parameter $m$ (trap density and the distribution of localized state) for the FA and RTA devices are $\sim$2 and $\sim$4.1, respectively. This reveals that more defects are formed in the RTA device and that FA provides better performance than RTA from the viewpoint ofopto- and nano-electronic applications.

• Preliminary study of linearity response of $\gamma$-irradiated graphene oxide as a novel dosimeter using the Raman spectroscopy

In this experimental study, graphene oxide (GO) nanopowder was prepared and irradiated by the ${}^{60}$Co $\gamma$-rays in different absorbed doses of 0, 10, 30, 50, 80, 100, 120 and 150 kGy at dose rate of 1.62 Gy s$^{-1}$ at room temperature. Field emission scanning electron microscope and high-resolution transmission electron microscopy analyses were used to investigate structural defects in GO material. Then, using Raman spectroscopy, the ratio of $I_{\rm D}/I_{\rm G}$ related to D- and G-bands in the wavenumbers of 1350 and 1586 cm$^{-1}$ was, respectively, measured in terms of absorbed dose to determine the dose–response of GO material. The results showed that the dose–response of $\gamma$-irradiated samples at the dose range of 0–50 kGy was linear. There was a decline in dose–response after 100 kGy due to graphitization of carbon nanostructure material or annealing the defects in the sample. The results of this study showed that the linearity response of $\gamma$-irradiated GO as a novel passive dosimeter is suitable for the dosimetry of $\gamma$-rays at the radiation processing level.

• Stealth cross-linked polymeric nanoparticles for passive drug targeting: a combination of molecular docking and comprehensive in vitro assay

Till date, several studies have reported magnetic drug targeting as well as passive drug delivery. In this study, the passive characteristic of PEGylated carriers with a neutral surface charge rather than chitosan (CS)-based nanoparticles (NPs) with a positive charge was proved using molecular docking. The complete and without flaw stealth CS-coated magnetic NPs (mNPs) loaded with an anticancer drug for intravenous drug delivery were prepared using a modified ionic crosslinking method. The physicochemical properties of the prepared magnetic-CS NPs were characterized in detail. The transmission electron micrographs of NPs showed an uniform particle morphology with an average diameter of smaller than 10 nm. The average IC50 values of the drug in PEGylated NPs for MCF-7 and PC-12 cells were 44 and 72 lM, respectively. The fabricated stealth NPs can increase the cytotoxicity and cell permeability of formulation that may release the entire drug in targeted shape to objective tissues that were firstly proved by molecular docking. This strategy showed a reduction in up taking of mNPs by the reticuloendothelial system, which indeed increases the concentration of therapeutic agent(s) in the target site.

• Effect of thermo-mechanical alloying and ageing in AA2014 aluminium alloys after synthesized using graphite

There is always a necessity to tailor new age materials for use in aircraft and automobile industries, and also in sophisticated fields at which resistance to elevated temperatures is of prime importance. To ensure the stability of high strength levels of conventionally precipitation-hardened aluminium (Al) alloys, thermo-mechanical alloying and ageing treatment (TMAAT) was applied to AA2014 Al alloys. Essentially, AA2014 alloy was thoroughly decorated with fine Aldispersoids and precipitates bymeans of ball-milling and conventional ageing. Hence, using powder metallurgy methodology, powders of AA2014 alloy and graphite were mechanically alloyed (MA) for 7 h in a vertical attritor. The obtained powder mixture was then cold pressed into samples under the pressure of 800 MPa. To decorate the matrix with finely distributed Al$_4$C$_3$ phase particles (dispersoids), samples were systematically annealed (sintered) for a long time in a furnace system operating under a controlled atmosphere of argon at 550$^{\circ}$C. This temperature was found to form a ternary Al–Cu–Mgliquid phase in carbon-blended AA2014 alloy during sintering. However, the Al$_4$C$_3$ phase could not be observed. After subsequent homogenization and water quenching, all samples were age hardened at 150$^{\circ}$C for 46 h. Results confirmed that ordinary AA2014 alloy with Al$_2$Cu precipitates over-aged normally as expected. In contrast, the material treated by MA had reinforcing Al$_4$C$_3$ particles together with Al$_2$Cu precipitates. It was realized that this reinforced material did not soften and still retained its high peak hardness level even during prolonged over-ageing treatment. Consequently, it was apparent that TMAAT improved the strength, and therefore was promising for resistance to high-temperature exposure of the material.

• Formulation of a smart nanocomposite coating with pH-responsive loaded halloysite and investigation of its anticorrosion behaviour

In this research study, halloysite nanotubes (HNTs) were applied as nanocontainers to encapsulate the synthesized 3,4$^{\prime}$-dihydro-3-[2$^{\prime}$-mercaptothiazolidine]indol-2-one (DMI) molecules for corrosion protection of carbon steel in a 3.5% NaCl solution. Fourier transform infrared analysis was used to prove the loading of HNTs with DMI. Poly(ethylene-co-acrylic acid) and branched polyethylenimine polyelectrolyte layers were deposited on the surface of DMI-loaded HNTs by a layer by layer (LbL) method. The LbL deposition technique was verified by a zeta potential test. Release of DMI corrosion inhibitors from HNTs in alkaline pH was verified by using UV–visible spectroscopy results. Electrochemical impedance spectroscopy technique was applied to consider the anticorrosion ability of 1, 2.5 and 5 wt% DMI-loaded HNTs as smart epoxy coatings.

• Studying the change in organic light-emitting diode performance at various vacuum-deposition rates of hole and electron transport layers

The electroluminescence (EL) of classic and thermally activated delayed fluorescence (TADF) organic light emitting diodes (OLEDs) at various vacuum-deposition rates of hole and electron transport layer (HTL and ETL) has beenstudied. The external quantum efficiency (EQE) measurements showed that the best performance devices were those with a high charge carrier balance inside the emitting layer, which was engineered using hole and electron current manipulation as a result of vacuum-deposition rate control. Changing the vacuum-deposition rate of HTL and ETL leads to a change in the maximum EQE (EQE$_{\rm max}$) of the classic and TADF OLEDs without obvious changes in EQE roll-off ratio at high current density. We used a simple analytical model to clarify that the enhanced hole current in HTL at high deposition rates is dominated by high hole mobility attributed to the increased hole hopping rate due to the reduction of the intermolecular separation between horizontally oriented $N,N'$-diphenyl-$N,N'$-bis(1-naphthyl)-1,1$'$-biphenyl-4,4$'$-diamine($\alpha$-NPD) molecules. The increase in the electron current of tris-(8-hydroxyquinoline) aluminium (Alq$_3$) ETL at low deposition rate was ascribed to high electron injection from cathode into ETL by the fabrication and comparison of $J–V$ characteristic of two electron-only devices with a difference at deposition rate of ETL near cathode interface. Finally, we introduced an OLED with novel gradient and barrier structures for the emitting layer in which high injected charge carriers recombined inside added recombination zone to raise radiative recombination and efficiency of the device. Our results demonstrated that EL efficiency of an OLED can be changed by controlling the vacuum-deposition rate of organic layers.

• DFT study of the enhancement of physico-chemical, nonlinear and optoelectronic properties of the 2-cyano-3-[4(diphenylamino) phenyl] acrylic acid molecule by doping with the potassium atom

In this study, the molecule 2-cyano-3-[4(diphenylamino)phenyl] acrylic acid (L0) was doped with a potassium atom at two different positions to obtain LK(1) and LK(2). The three molecules were studied using DFT (B3LYP) and HF methods, with the basic sets 6-31G(d,p) and 6-311G(d,p). From our results, we observed that energy gap at the B3LYP level is smaller in the doped molecules LK(1) (2.842–3.074 eV) and LK(2) (2.758–2.850 eV) compared to the virgin molecule L0 (3.194–3.226 eV). The energy gap value for each molecule is smaller when the 6-31G(d,p) basis set is used. The dipole moment, average polarizability, first-order hyperpolarizability, refractive index, electric susceptibility,dielectric constant increased considerably in the doped molecules, especially in LK(2). These results show that LK(1) and LK(2) are good candidates for applications in nonlinear optical materials and photovoltaic devices compared to L0.

• To develop biodegradable Mg-based metal ceramic composites as bone implant material

Biodegradable materials for orthopaedic implants have gained much attention due to their similar properties to natural bone. Magnesium-based alloys are considered the best biodegradable material for bone substitute materials.However, magnesium alloys have very high corrosion rate. Research has been focused to fabricate and to make their composites to control their corrosion rates in human physiological environment and to develop the ability of formingbone-like apatite layer on their surface. In the present study, Mg–Zn–Mn metal alloys were selected for making their composites with hydroxyapatite (HAp) and bio-glasses. HAp was prepared by the co-precipitation method and bio-glasses(45S5P7) were prepared by the melting and quenching method. Samples from metal–ceramic composites were prepared by the powder metallurgy route in various compositions. Furthermore, samples were characterized for their phases,microstructure, corrosion behaviour, mechanical properties and bioactivity. The composites showed bioactivity in simulated body fluid (SBF) solution and their young’s modulus values were obtained near to the human bone. The degradation properties, as studied in SBF solution, revealed Mg-based alloy composites having approximately 10% bio-active glasses and 10% b-tri-calcium phosphate resulted in the reduction of the corrosion rate.

• tert-Butylamine borane as a reductant in electroless nickel plating for improved etch resistance in the electrolyte

An Ni–B coating was developed on a copper substrate by the direct electroless technique and from a plating bath containing tert-butylamine borane (TBAB). The influence of the electroless plating conditions, using TBAB as a reducing agent on the composition, surface morphology, high-temperature stability and etch resistance in the electrolyte of the coatings, was investigated. The resulting electroless Ni–B plating surfaces were examined and characterized by scanning electron microscopy and X-ray fluorescence spectroscopy for morphology and chemical composition, respectively.Electrochemical characterization by potentiodynamic polarization confirmed that a 0.1 M nickel concentration bath for the Ni–B plating was optimized by a TBAB concentration of 0.03 M, temperature of 60$^{\circ}$C and pH of 8. Under theoptimal bath conditions, the Ni–B electroless plating layer exhibited superior etch resistance in the electrolyte as well as improved stability at high temperature than the Ni–B electroless plating layer prepared using dimethylamine borane.Hence, owing to the remarkable properties of the Ni–B electroless plating layer, this fabrication technique that employs TBAB can be extended to fabricate other Ni–B electroless plating layers.

• Microstructure and optical properties of TiO$_2$- and HA-coated Ti6Al7Nb alloy by sol–gel method

In this study, the combination of titanium dioxide (TiO$_2$) and/or hydroxyapatite (HA) coatings on Ti6Al7Nb titanium alloy to be used as an implant was performed in different solution retention times by the sol–gel dip-coatingmethod and the characterization and optical properties of these coatings were investigated. Two different coatings were made on the substrate, the first group of samples was first coated with TiO$_2$ and then with HA, while the second group of samples was coated with TiO$_2$ alone. Before sol–gel coating, the samples were rinsed in distilled water and dried at 200$^{\circ}$Cfor 2 h. The samples were immersed perpendicular to the coating solution. Thin films were obtained at a draw rate of 2 mm s$^{-1}$. Microstructure investigations of the prepared coatings were examined under optical and scanning electronmicroscopes, while solid-state elemental fractions were determined by energy-dispersive X-ray spectroscopy analysis. Fourier-transform infrared spectroscopy analysis was performed to determine the functional groups placed on the surfaceof the material. The optical properties of the material were determined by UV analysis.

• Design and synthesis of organic dyes with various donor groups: promising dyes for dye-sensitized solar cells

The present work is involved in the computational and experimental studies of organic dyes and their applications as dye-sensitized solar cells (DSSCs). This comprised the study of three hydrazone-based sensitizers ($E$)-2-cyano-$N'$-((2-hydroxynaphthalen-1-yl)methylene)acetohydrazide (CHMA), ($E$)-2-cyano-$N'$-(4-(dimethylamino)benzylidene)acetohydrazide (CDBA), ($E$)-$N'$-(anthracen-9-ylmethylene)-2-cyanoacetohydrazide (AMCH) that have been prepared and confirmed by means of several analytical procedures like Fourier transform infrared, UV–visible and nuclear magnetic resonance techniques to investigate the best possible selection for DSSCs by computational and experimental techniques. The computational methods are applied to optimize the structures of prepared organic dyes via density functional theory (DFT) method at B3LYP/6-311G(p,d) level of theory. The time-dependent DFT (TD-B3LYP/6-311G**) was used with and without solvent to find out the absorption spectra and matched with the experimental data and the electro-optical and reorganization energies of prepared dyes were further investigated. The results revealed that the prepared dyes would be better sensitizers for DSSCs because of small highest-occupied molecular orbital–lowest unoccupied molecular orbital energy gap. Moreover, on the basis of the above results, we fabricated the devices via the doctor blade method to study the photovoltaic performance with the prepared dyes (CHMA, CDBA and AMCH). The dye AMCH exhibited the maximum efficiency with commercial TiO$_2$.

• Study on the synthesis and photocatalysis of Ag$_3$PO$_4$ polyhedral microcrystals

The silver phosphate (Ag$_3$PO$_4$) sample was synthesized using Na$_3$PO$_4$, AgNO$_3$ and PEG-10000 as raw materials by the hydrothermal method. Its different morphologies were obtained by changing temperature and surfactant. And its structures and morphology were characterized by X-ray diffraction and field emission scanning electronmicroscopy. The result of the study indicated that after the heat treatment at 150$^{\circ}$C, the as-obtained Ag$_3$PO$_4$ polyhedral microcrystal’s diameter was about 4 $\mu$m. Meanwhile, it showed that using Ag$_3$PO$_4$ polyhedral microcrystals as photocatalysts, the photocatalytic degradation rate of methylene blue in aqueous solution was close to 98.5% after 25 min ofsunlight.

• Novel plasticizer for acrylonitrile butadiene rubber (NBR) and its effect on physico-mechanical and electrical properties of the vulcanizates

In the manuscript, the quaternization method followed by anion exchange reaction was used to prepare 1-dodecyl-3-methylimidazolium tetrafluoroborate [C12MIM]BF$_4^-$ ionic liquid (IL). The prepared IL was verified throughFourier transform infrared and 1H-nuclear magnetic resonance spectroscopy. The IL, as a novel plasticizer, is incorporated into the acrylonitrile butadiene rubber (NBR) composite with different contents from 1 to 5 phr in comparison with dioctyl phthalate (DOP) as a traditional plasticizer. The IL effect on the rheology, mechanical, electrical properties of the vulcanizates and their resistance to thermal ageing were investigated. The morphology of NBR composites was investigated by a scanning electron microscope. The results show that adding IL to the NBR vulcanizates improves both mechanical and electrical properties of composites more than traditional DOP.

• Investigation of oxidation behaviour of AISI-430 steel interconnects in the presence of Ni–Co–CeO$_2$ composite coating for application of solid oxide fuel cells

AISI 430 stainless steels are used as interconnects in solid oxide fuel cells. One of the problems with these steels is the migration of chromium through the chrome shell and its transfer to the cathode, resulting in contamination andreduction in the efficiency of the fuel cells. To improve the oxidation resistance of these steels, a protective coating layer can be applied on the steel surface. In this investigation, AISI 430 stainless steel was electroplated with nickel, cobalt and cerium oxide. To investigate oxidation behaviour, isothermal oxidation and cyclic oxidation were performed at 800$^{\circ}$C. The coating on the steel surface was studied using scanning electron microscopy and X-ray diffraction. In isothermal and cyclic tests, the coated samples showed less weight gain than the uncoated samples due to the formation of NiFe$_2$O$_4$, CoFe$_2$O$_4$ spinels and NiCr$_2$O$_4$. These spinels prevented the outward diffusion of the chromium, improving the oxidation resistance of the steel substrate. Cyclical oxidation results showed that the coating formed on the steel surface resistedcracking and delamination.

• Enhanced dielectric and thermal performance by fabricating coalesced network of alumina trihydrate/boron nitride in silicone rubber for electrical insulation

Silicone rubber filled with micron-alumina trihydrate (ATH) is a substantially used composite material for high voltage outdoor insulators. This article investigates the effect of nano-boron nitride (BN) addition on the dielectric,thermal stability and thermal conductivity of solely micron-ATH-filled silicone rubber by fabricating coalesced network of particles. Micron-ATH/nano-BN-filled hybrid silicone rubber composites are fabricated with a ratio of 30/0 wt%(ATH30), 29/1 wt% (ATBN1), 27/3 wt% (ATBN3), 25/5 wt% (ATBN5) and 23/7 wt% (ATBN7) using mechanical mixing and water bath sonication techniques. Results suggest that the hybrid batch of silicone rubber composites (ATBN) possess lower permittivity, dielectric loss, enhanced thermal stability and thermal conductivity relative to ATH30. ATBN1 offers low permittivity and dielectric loss values of 3.64 and 0.0086 at 1000 Hz relative to 3.87 and 0.0224 ofATH30, respectively. As far as thermal properties are concerned, ATBN5 emerges as the most promising candidate for electrical insulation with 31 and 200$^ {\circ}$C higher temperatures for 10 and 15% mass loss, whilst it has shown 20% higher thermal conductivity than ATH30.

• Synergy studies on polyurethane–carbon black, multi-walled carbon nanotube-based heterogeneous electroactive shape memory nanocomposite system

This paper describes a multi-filler synergy study that was carried out for multi-walled carbon nanotubes (MWCNTs) and carbon black (CB) filler systems in polyurethane (PU) resin, and the individual contributions of the fillers were evaluated. The hybrid nanocomposite was found resistant to ultraviolet radiation and exhibited a high glass transition temperature enabling it suitable for space applications. The contributions of individual fillers in the hybrid system werecompared with the binary nanocomposites of respective fillers and the advantages of hybrid system are also highlighted. The synthesized hybrid polymer nanocomposite (PU $+$ CB $+$ MWCNT) was found to have superior thermal, electrical and mechanical properties even at a very low content of reinforcements and a percolation threshold of 5% CB and 0.15% MWCNT combination was also observed. Shape memory effect of the hybrid system was evaluated and compared with binary systems. A faster recovery time of 41 s was observed for a combination of 5% CB and 0.25% MWNT against 50 sfor 25% CB alone upon thermal actuation. On electrical actuation, the hybrid nanocomposite system was observed to have a three-fold faster recovery compared to the binary systems of CB alone. The hybrid system proves to be a reliable choice for replacing an expensive single reinforcement system of MWCNTs.

• Antimicrobial and larvicidal activity of zinc-substituted hydroxyapatite

Mosquitoes transmit serious human infections and cause a number of deaths in tropical and subtropical environment countries every year. In the present work the zinc-substituted hydroxyapatite Ca$_{5-x}$Zn$_x$(PO$_4$)$_3$OH ($x = 0,0.05, 0.2$ and $1.0$) was synthesized by two different methods: the hydrothermal method and the sol–gel method. The phase formation, functional group and surface morphology of Zn-HAP were authenticated using X-ray diffraction, Fourier transform infrared and scanning electron microscopy-energy-dispersive X-ray spectroscopy, respectively. The antimicrobial activity of the synthesized compounds was tested against different organisms such as Escherichia coli, Staphylococcus aureus and Candida albicans. Moreover, excellent antimicrobial activity was observed for hydrothermal synthesized (Zn-HAP) compound compared to that of the sol–gel method. The synthesized Zn-HAP nanoparticles were reported for larvicidal activity against the filarial and Japanese encephalitis vector, Culex quinquefasciatus. The hydrothermal-synthesized (1.0 M Zn-HAP) compound exhibited higher larvicidal activity ($93 \pm 6.62$) with minimumlethal concentration LC$_{50}$ (33.74 mg ml$^{-1}$) (to kill 50% of the care for larvae of the relevant species) and LC$_{90}$ (139.92 mg ml$^{-1}$) (to kill 90% of the treated larvae of the respective species) after 24 h, respectively than that of the sol–gel method.

• Morphology, optical, thermal and antimicrobial studies of ibuprofen-based hyperbranched polyester

Herein we report the synthesis of ibuprofen-based hyperbranched polyester ranging from morphological, thermal and fluorescent behaviour. The proposed synthesis of ibuprofen-based hyperbranched polyester was achieved by asimple acid chloride approach. The formation of aromatic ester linkage in the product was confirmed using Fourier transform infrared and nuclear magnetic resonance spectroscopy. The morphology of ibuprofen-based hyperbranchedpolyester was investigated by using the X-ray diffraction, scanning electron microscopy and differential scanning calorimetry (DSC) analyses. The glass transition temperature ($\sim$78$^{\circ}$C) and double melting peaks of ibuprofen-based hyperbranched polyester were observed using DSC. The liquid chromatography-mass spectrometry analysis confirmed the chemical structure and the molecular weight of the ibuprofen-based hyperbranched polyester. The presence of broad absorption peak at 301 nm in UV region indicated the fluorescent property of ibuprofen-based hyperbranched polyester.The antimicrobial tests of ibuprofen-based hyperbranched polyester were carried against Gram-negative organisms such as Escherichia coli MCIM 2065 and Salmonella paratyphi MCIM 2501, Gram-positive organisms such as Bacillus subtilis NCIM 2063 and Staphylococcus aureus NCIM 2079 and fungi such as Aspergillus niger MTCC 1344 and Candida albicans MTCC 3100. The result of agar disc diffusion method showed that the polymer had higher antimicrobial potential towards fungi than bacteria.

• Study of ac conductivity mechanism and impedance spectroscopy in CNT-added Cu$_5$Se$_{75}$Te$_{10}$In$_{10}$ chalcogenide system

This study is devoted to the investigation of electrical properties of multi-walled carbon nanotube (MWCNT)-contaminated Cu-Se-Te-In chalcogenide glassy composite in the temperature range 303–373 K and frequencyinterval from 1 Hz to 1 MHz. The MWCNT/chalcogenide glass was characterized by means of X-ray diffractometer, field emission scanning electron microscope, impedance spectroscopy and electrical measurements. Electrical conductivity was increased by 10–100 times of magnitude by adding 1 and 2 wt% of MWCNT to it, changing the behaviour from insulator to the semiconductor. This rapid change in the electrical conductivity for carbon nanotube-added glasses is due to the highly conducting behaviour of carbon nanotubes. The data observed from dc conductivity measurement in the temperature range 303–373 K suggest that thermally activated hopping is the dominant conduction mechanism betweenlocalized states in band tails, which is explained by Mott’s model. The temperature-dependent relaxation phenomenon has also been examined by a detailed analysis of impedance spectra.

• Recyclable heterogeneous Pd nanoparticles supported on plant polyphenol-modified $\gamma$-Al$_2$O$_3$ for hydrodechlorination of 2,4-dichlorophenols

Heterogeneous Pd catalysts were developed by immobilizing Pd nanoparticles (Pd NPs) onto plant polyphenol (bayberry tannin, BT) decorated $\gamma$-Al$_2$O$_3$. The abundant hydroxyls of plant polyphenols were capable of stabilizing the Pd NPs. Transmission electron microscopy observation confirmed that the Pd NPs with the diameter of $3.75\pm 0.5$ nm were highly dispersed in the catalyst. The as-prepared Al$_2$O$_3$–BT–Pd catalysts were found to be highly active in mild hydrodechlorination (HDC) of 2,4-dichlorophenols (DCPs) using formic acid as a hydrogen source. The 2,4-DCPs were completely dechlorinated in 4 h at 30$^{\circ}$C and under atmospheric pressure. During the catalytic HDC, the stabilizingcapability of BT successfully prevented the leakage and aggregation of Pd NPs, thus ensuring a high cycling stability withstable and high catalytic activity. The Al$_2$O$_3$–BT–Pd catalysts were recycled six times, without obvious loss of activity. In the sixth cycle, the catalytic HDC yield still reached 98.29% under the same reaction conditions, superior to the controlcatalysts, including $\gamma$-Al$_2$O$_3$ supported Pd NPs (Al$_2$O$_3$–Pd) and powdered activated carbon supported Pd NPs (AC–Pd).Furthermore, the Al$_2$O$_3$–BT–Pd also showed high activity in the mild catalytic HDC of 2,4,6-trichlorophenols andchlorobenzene derivatives. Our results demonstrated efficient catalysts to address the environmental issue of chlorophenolpollution.

• Screening of soil fungi in order to biosynthesize AgNPs and evaluation of antibacterial and antibiofilm activities

The biosynthesis of nanoparticles (NPs) has recently attracted a lot of research attention due to its being an eco-friendly and economical method. NPs are formed under normal temperatures and pressures. The shape and size ofNPs can be controlled by choosing a suitable pH and temperature. In this study, 24 strains of fungi isolated from desert soils were screened for AgNP synthesis. The MS17 isolated was chosen as the superior strain capable of rapidlysynthesizing monodisperse AgNPs. The optimum conditions for AgNP synthesis were investigated. AgNPs were characterized by UV–visible spectrophotometry, dynamic light scattering, X-ray diffraction, transmission electron microscopyand Fourier-transform infrared. The NPs produced were found to be in the form of Ag/AgCl with a size range of 5–15 nm. Then, the NPs were capped by proteins and carbohydrates, which play an important role in NP stability. The NPs werecapable of antimicrobial activities against the standard bacterial pathogens, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, Bacillus subtilis ATCC 6633, Staphylococcus aureus ATCC 1431 and the multidrugresistant P. aeruginosa B52 and P. aeruginosa 48.

• Sacrificial sulphonated polystyrene template-assisted synthesis of mesoporous hollow core-shell silica nanoparticles for drug-delivery application

Spherical mesoporous hollow core-shell silica nanoparticles (HCSNs) of size $200 \pm 50$ nm with tunable thickness from 20 to 60 nm are synthesized using a sacrificial sulphonated polystyrene (PS, particle size 160 nm) template. A facile method is adopted for the sulphonation of PS using sulphuric acid, which enhanced the negative charge on the surface of PS as confirmed by zeta potential analysis and Fourier transform infrared radiation analysis. The thickness of the silica shell is tuned by altering the concentration of the silica precursor and is found to increase due to the use of the sulphonated PS template. N$_2$ adsorption/desorption studies reported the variation of specificsurface area of HCSNs from 644.1 to 197.8 m$^ 2$ g$^{-1}$ and average pore size from 1.55 to 3.4 nm. The drug release behaviour of HCSNs with different shell thicknesses is investigated using doxorubicin as the model drug. A delay inthe drug release for $\sim$300 min is successfully achieved by employing HCSNs with enhanced thickness of 60 nm. Application of HCSNs in targeted drug delivery was further supported by the in-vitro cytotoxicity studies carried out on lung adenocarcinoma cells.

• Photoluminescence properties of pure, Fe-doped and surfactant-assisted Fe-doped tin-oxide nanoparticles

A co-precipitation method with water as a distinctive solvent was used for the synthesis of pure, Fe-doped and surfactant-assisted Fe-doped SnO$_2$ nanoparticles (NPs). Furthermore, the NPs were characterized using X-ray diffraction (XRD), Fourier-transform infrared, scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDAX), high-resolution transmission electron microscopy (HRTEM), UV–visible, photoluminescence spectroscopy and spectrofluorometer. XRD patterns showed a tetragonal rutile structure of SnO$_2$ phase without additional peaks and a shift was noted for Fe-doped and surfactant-assisted Fe-doped samples. The crystallite sizes of Fe-doped and surfactant-assisted Fedoped SnO$_2$ NPs were found to decrease from 10.39 to 6.347 nm. Spherical morphology with uniform size was observed in all samples from SEM and HRTEM images. The presence of Sn, O and Fe ions was confirmed by EDAX analysis. The band gap energy of NPs was measured to be 3.487, 3.741, 3.845, 3.783 and 3.552 eV for pure, Fe-doped, cetyltrimethylammonium bromide, sodium dodecyl sulphate and Triton (surfactants) assisted Fe-doped NPs, respectively. An increase in the band gap was observed due to addition of Fe and surfactants. The photocatalytic study confirms that pure SnO$_2$ NPs exhibit a significant photo-degradation of methylene blue dye under sun light. Moreover, the physical properties of SnO$_2$ were modified by Fe-doping and addition of surfactants in comparison with pure SnO$_2$ NPs.

• Significance of artificial neural network analytical models in materials’ performance prediction

In materials science, performance prediction of materials plays an important role in improving the quality of materials as well as preventing serious damage to the environment and threat to public safety. Traditional regression analysismodels in materials science are not yet perfect, limited to capture nonlinearities of data and time-consumption for prediction, and have a poor ability to handle a large amount of data. This leads to a demand for analyses of materials data using novel computer science methods. In recent years, artificial neural networks (ANNs) are increasingly performing as a strong tool to establish the relationships among data and being successfully applied in materials science due to their generalization ability, noise tolerance and fault tolerance. In this paper, some typical ANN applications for predicting various properties (corrosion,structural, tribological and so on) of different materials serving multiple environments (atmosphere, stress, weld and so on) are reviewed. It highlights the significance of ANN in materials-related problems in separate sections arranged by the level of simplicity, ranging from simple ANN models alone to more complicated ANN models along with the hybrid use of other computing and input-ranking methods, and the trend of ANN in the context of materials science with some limitations.

• Effect of nature of polymer as a binder in making photoanode layer and its influence on the efficiency of dye-sensitized solar cells

A simple method has been developed for the preparation of photoanode paste from hydrothermally synthesized nanocomposite, using different nature of polymers viz., synthetic: poly(vinyl alcohol) and polystyrene (PS) andnatural: casein and sodium alginate (NaAlg) as binders. The titanium dioxide (TiO$_2$)/multi-walled carbon nanotube (MWCNT) nanocomposite powder and film were characterized for analysis of their structure, crystallinity and morphologyby X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. Dye-sensitized solar cells (DSSCs) were fabricated using TiO2/MWCNT composite paste made withdifferent binders as photoanode, N719 dye, platinum as photocathode and Idolyte HI-30. The observed results of photocurrent density–voltage characteristics and electrochemical impedance spectroscopy suggested that the nature of the binder used in making photoanode film showed significant influence on the overall characteristics of DSSCs. Among the cells fabricated, the DSSC fabricated using TiO$_2$/MWCNT-PS binder showed highest power conversion efficiency of 3.03%.

• PDMS–ZnO flexible piezoelectric composites for measurement of muscle activity

Measurement of muscle activity is important for muscle health monitoring, biomechanics studies, developing prosthesis, etc. This article describes a flexible piezoelectric composite material as a sensing element for measuring muscle activity. The developed piezoelectric material is a composite of olydimethylsiloxane and zinc oxide, and exists in monolayer and bilayer configurations. To test the piezoelectric properties in bending mode, a composite patch is attached to a cantilever beam setup. Peak sinusoidal voltage generated from the composite material due to the vibrating cantilever is found to be highest (1.5 V) for bilayer configuration with 30 wt% ZnO. For testing in axial mode, the peak output voltage from the material due to an impulse load is maximum (0.9 V) for the monolayer configuration of the composite with 30 wt% ZnO. The sensor consisting of a bilayer composite patch is wrapped around a specific muscle to measure its activity. The change in output voltage from the sensor is measured for increasing load and is then mapped to the corresponding value of elastic modulus of the muscle measured using a durometer. The sensitivity of the muscle activity measurement for biceps brachii and flexor carpi is found to be 3.826 and 1.245 V MPa$^{-1}$, respectively.

• Magnetodielectric effects in three reduced graphene oxide–polymer nanocomposites

Three polymers, poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA) and poly(methyl methacrylate) (PMMA), are used as matrices to synthesize three nanocomposites each with reduced graphene oxide (RGO) fillers (5 wt%). The dielectric properties of these nanocomposites, RGO–PVA, RGO–PAA and RGO–PMMA, are studied in zero magnetic field and in magnetic field ($H$) up to 1.2 T. From these data magnetodielectric effects are obtained as the variation of $\epsilon^{\prime}$ and $\epsilon^{\prime\prime}$—the real and imaginary parts of complex dielectric constant with $H$ at some frequencies. Thus at 100 kHz for the increase of $H$ from zero to 1 T $\epsilon^{\prime}$ decreases by 5% in RGO–PVA and by 4% in RGO–PAA, whereas $\epsilon^{\prime}$ increases by 4% in RGO–PMMA. The observed magnetodielectric effects, though small, are significant. They show both decrease and increase of $\epsilon^{\prime}$ depending on the polymer. This fact is the indicative of the interaction between RGO filler particles and polymer chains.

• Enhanced electrical, mechanical and thermal properties of chemically modified graphene-reinforced polybenzimidazole nanocomposites

Chemically modified graphene-reinforced polybenzimidazole (PBI) nanocomposites were prepared by liquid phase exfoliation of graphene oxide (GO) and reduced graphene oxide (rGO) in methanesulphonic acid (CH$_4$O$_3$S), followed by in-situ polymerization using GO–CH$_4$O$_3$S and rGO–CH$_4$O$_3$S suspensions as reaction media. Various reducing agents were used to produce rGOs and their reducing efficiency was examined to attain highly graphitic structure and excellent electrical conductivity of the resulting rGOs. The results of Raman, Fourier transform infrared and X-rayphotoelectron spectroscopy indicate higher extent of reduction of GO with hydrazine compared to other reducing agents. The PBI nanocomposite containing 10 wt% rGO derived from hydrazine reduction reaction (rGO–H) exhibits the highest dc conductivity of $2.77\times 10^{-3}$ S cm$^{-1}$ at room temperature, which is 11 orders of magnitude higher than pure PBI. Thethermal annealing treatment at 350$^{\circ}$C resulted in a substantial increase in dc conductivity of the PBI/GO nanocomposite, whereas the enhancement of conductivity is much less for the PBI/rGO nanocomposites. Compared to pure PBI, both tensile strength and Young’s modulus enhanced by 3.4 times and 6.9 times, respectively, for the PBI nanocomposites with 10 wt% GO content, which is ascribed to strong interfacial interactions and subsequent effective stress transfer between the PBI matrix and GO. The PBI/rGO nanocomposites exhibited relatively lower tensile strength/modulus compared to the GO-reinforced nanocomposite. The thermal stability of PBI was significantly improved upon the incorporation of both GO and rGO nanosheets, whereas higher thermal stability was achieved for rGO-reinforced nanocomposites.

• Initiatively embedding silver colloids in glass used in silver paste to improve metallization ohmic contact on silicon wafers

One of the decisive factors in realizing ohmic contact of silver (Ag) paste metallization on silicon (Si) wafers is the presence of Ag colloids in the glass phase at the Ag/Si interface. The Ag colloids are formed during the reaction between glass frit and Ag powder in the sintering process of Ag paste; thus, it is difficult to control the quantity of Ag colloids formed. In this study, we attempted to prepare a glass embedded with a large number of Ag colloids first to further improve the quality of ohmic contact of Ag paste metallization. In the PbO–TeO$_2$–SiO$_2$ glass system, a route was found for increasing the solubility of Ag in the glass melt by precipitating the Ce$_{1.88}$Pb$_{2.12}$O$_{6.53}$ crystal, which enabled a molar amount of recrystallized Ag colloids reach a high level of about $1/10$ of oxides in the glass. As a result, the esistivity of the Ag/Si contact can be decreased substantially. The formation mechanism of Ag colloids in glass isrevealed by various characterization and analysis methods, such as X-ray diffraction, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, UV–visible and so on. Furthermore, it was also found that too high content of Ag in the glass melt would destroy the pyramid texture surface structure of Si wafers, which is not conducive to obtain high-quality Ag/Si ohmic contact. For this concern, optimal content of Ag colloids formed in glass is discussed.

• Interaction of modified nucleic bases with graphene and doped graphenes: a DFT study

In order to design biosensors, it is quite necessary to have an insight upon the nature of interaction between the modified nucleic bases (MNBs) and carbonaceous materials. This study is focussed upon the interaction of the various doped graphene models like graphene (GR), aluminium doped graphene (AlG), sulphur doped graphene (SG), nickel doped graphene (NiG), chromium doped graphene (CrG) and germanium doped graphene (GeG) with MNBs (caffeine, hypoxanthine, uric acid and xanthine) by employing the electronic structure calculations and the associated methodology. All the geometries considered in this study (MNBs and graphene models)were initially optimized at M06-2X/6-31$+$G$^{**}$ basis set without any constraints followed by the single point energy calculation at three different and well established methodsusing the Gaussian 09 software package. A detailed comparison of the interaction energy is accomplished in this study. The interaction energy values were further corrected for the basis set superposition error. The theory of atoms in molecules analysis is also performed in detail, which showcases the bond critical points, Laplacian and various other parameters of interest. The variation of frontier molecular orbitals, i.e., highest occupied molecular orbital–lowest unoccupied molecular orbital gap for different models of graphene have been discussed in detail upon the adsorption of MNBs. Among the dopedgraphene models, the graphene model doped with Cr seems to be more suitable for the application of sensors, also it is found that the MNBs interact primarily via $\pi-\pi$ interaction. The results highlight that the CrG can act as a sensor for the detection of MNBs.

• Iron tungstate ceramic nanofibres fabricated using the electrospinning method

Given the importance of tungstate in industry and aiming to introduce new tungstate nanostructure with a modern method, iron tungsten nanofibres were prepared for the first time by sol–gel followed by electrospinning andcalcination. First, poly(vinyl alcohol) (PVA) as a matrix polymer was mixed separately with tungstic acid (H$_2$WO$_4$) and iron(III) nitrate (Fe(NO$_3$)$_3$). The controlled mixing of the two solutions followed by electrospinning led to the fabrication of PVA/tungstic acid/iron(III) nitrate composite nanofibres. Finally, ceramic nanofibres of iron tungstate were obtainedfrom the calcination of polymeric nanofibres under thermal control conditions. The final product was analysed by scanning electron microscopy, energy-dispersive X-ray spectroscope, Fourier transform infrared spectroscopy, X-raydiffraction, vibrating sample magnetometer, Brunauer–Emmett–Teller surface area analysis and Barrett–Joyner–Halenda pore size and volume analysis.

• Enhancement of proton conduction in carboxymethyl cellulose-polyvinyl alcohol employing polyethylene glycol as a plasticizer

The present study deals with the enhancement of proton transport and conduction properties of solid polymer electrolyte (SPE)-based carboxymethyl cellulose (CMC) blended with polyvinyl alcohol (PVA) doped with ammoniumnitrate (NH$_4$NO$_3$) and plasticized with various compositions of polyethylene glycol (PEG). The SPE system was successfully prepared using an economical method, the solution casting technique, and analysed by Fourier transform infrared spectroscopy and electrical impedance spectroscopy. The infrared spectra show that interaction had occurred at O$–$H and COO$^{-}$ from CMC when PEG was added which prevailed the enhancement of ion dissociation. Glass transition measurement highlighted that the interaction between CMC–PVA–NH$_4$NO$_3$ and ethylene carbonate at 8 wt% give the most plasticization effect that achieved the lowest $T_{\rm g}$. The highest conductivity of the SPE system achieved at ambient temperature was $1.70\times 10^{-3}$ S cm$^{-1}$ for a non-plasticized sample, and further enhanced to $3.00 \times 10^{-3}$ S cm$^{-1}$ when 8 wt% PEG was incorporated into the SPE system. The sample with the highest conductivity was found to obey theArrhenius behaviour with a function of temperature. The ionic conductivity of the SPE system was shown to be primarily influenced by a number of ions ($\eta$), ion mobility ($\mu$) and diffusion coefficient ($D$).

• Investigation on single crystal by tartaric acid–barium chloride: growth and characterization of novel NLO materials

The progress of single crystal followed by C$_4$H$_6$O$_6$ (tartaric acid) and BaCl$_2$ (barium chloride) (TABC; third order nonlinear optics semi-organic) was synthesized with slow evaporation method using distilled water at room temperature. TABC single crystal was introduced into various characterizations like X-ray diffraction to determine inter atomic cell parameter values. The samples are crystalline structure of monoclinic, which have space group of P$_2$. The functional groups of the current material are identified using FT-IR spectrum. Optical parameters like transparency, energy bandgap and Urbach energy have been determined using UV–vis–NIR spectrum. The thermal stability of the material was investigated by differential scanning calorimeter analysis. The mechanical property was studied using Vickers microhardness test. The surface morphology of the material was determined by scanning electron microscope technique. The change in dielectric behaviour of TABC with respect to the function of frequency at various temperatures has been keenly absorbed and discussed. The third-order nonlinear optical parameters were measured using Z-scan analyses.

• Terahertz dual-band/broadband metamaterial absorber enabled by SiO$_2$: polyimide and PET dielectric substrates with absorption characteristics

A compact dual-band/broadband polarization in-sensitive terahertz (THz) metamaterial absorber (MMA) is discussed in this article. It consists of a simple planar structure as a unit cell and an optically transparent indium tin oxide(ITO) ground plane, which are separated by a 50 $\mu$m dielectric substrate. We designed three combinations of MMA, which are ITO–SiO$_2$–ITO, ITO–polyimide–ITO and ITO–polyethylene terephthalate (PET)–ITO for the same planar structure. The proposed structure has dual-band absorbance with peak absorptivity of[98% for all three given combinations. By changing the substrate of the structure, the resonant frequency and bandwidth of the absorber structure is varied and by adjusting the design parameters, broadband absorbance is achieved for the same planar structure. The numerical simulation of the absorber shows that the broadband absorptivity is >98% for all three substrates. Polyimide, PET and SiO$_2$ based absorbers are demonstrated with bandwidth of 0.467, 0.527 and 0.6 THz with covered broadband frequency rangeof 0.390–0.857, 0.407–0.934 and 0.433–1.03 THz, respectively. ITO–PET–ITO absorber structures also possess optical transparency. These bandwidths are convenient and compatible with electronic and magnetic sources in the terahertzregion. This study provides applications in THz detection, sensing, bolometric imaging, and stealth and communication systems. All three absorbers have greater absorbance characteristics for transverse electric and transverse magnetic polarizations. The proposed structure is working well for wide angles of incident and polarization angles wave up to 90$^{\circ}$.

• Facile fabrication of CeO$_2$ nanomaterials by hydrothermal methods and their photocatalytic and hydrophobic properties

CeO$_2$ nanomaterialswere synthesized by a simple hydrothermal method, and their photocatalytic and hydrophobic propertieswere systematically investigated. CeO$_2$ nanomaterials displayed excellent photocatalytic properties, and under UV light irradiation, 98.5% Rhodamine B was degenerated by CeO$_2$ nanomaterials grown on Ni foam. After chemical modificationwith 1H, 1H, 2H, 2H-perfluorodecyl-triethoxysilane (PFDTES), CeO$_2$ nanomaterials showed good hydrophobic properties and water contact angles were in the range of 124−135$^{\circ}$. The hydrophobic property of the CeO$_2$ nanomaterials contributed to the self-assembled membrane also with hydrophobic properties on the surface of the treated CeO$_2$ nanomaterialswith PFDTES. Therefore, the study not only presents a facile method to fabricate CeO$_2$ nanomaterials, but also demonstrates the promising applications of CeO$_2$ in the treatment of waste water and self-cleaning of building materials.

• Diffuse spectra model of photoluminescence in carbon quantum dots

The attractive aspect of excitation related to fluorescence nature in carbon quantum dots (CQD) has guided to several assumptions correlated with clusters size distribution, shapes as well as presence of different emissive states. Inthis study, a dimer–excimer model of photoluminescence (PL) in CQD describing discrete multiple electronic states for the excitation-dependent emission is described. The functional dependence of the characteristic width of the diffusespectra of PL on the size of a quantum dots are calculated. The effective width of PL spectrum can be tuned from 0.1 to 1 eV.

• Highly efficient perylene-based polymer photocatalyst/biocatalyst systems for L-glutamate production under solar light

The selective production of fine chemicals using inexpensive solar light continues to be a challenge. As a means to achieve this we report herein the synthesis and development of a perylene-based solar-light-driven photocatalyst(PDA–DAA) obtained by the covalent bonding of perylene tetracarboxylic dianhydride (PDA) with a 2,6-diaminoanthraquinone (DAA) molecule. The photocatalyst/biocatalyst coupled system developed using PDA–DAA as a photocatalyst functions in a highly efficient manner, leading to high NADH regeneration (80.12%), followed by its consumption in exclusive production of L-glutamate (94.16%) from a-ketoglutarate. The present research highlights the development and application of the PDA–DAA photocatalyst for direct formation of L-glutamate under solar light.

• Electrical, thermal and elastic properties of methylammonium lead bromide single crystal

We report temperature-dependent dielectric permittivity, thermal conductivity and mechanical resonances of as-grown hybrid perovskite single crystal CH$_3$NH$_3$PbBr$_3$. Structural phase transitions are analysed using new experimental techniques, where thermal conductivity by steady-state process and elastic modulai by ultra-resonance spectroscopy is carried out through [100] and [110] directions, respectively. Performing thermal conductivity measurement on small-sized samples usually pose a significant challenge due to its dimensional limit. Following the steady-state technique, we measured the thermal conductivity of around 1 W m$^{-1}$ K$^{-1}$ in the temperature range 100–300 K on $2 \times 2$ mm$^2$ size crystal. This is found to be comparable with I$^{+3}$ anion-based hybrid perovskites as reported by Pisoni et al 2014 J. Phys. Chem. Lett. 5 2488. Room temperature electrical resistivity and dielectric permittivity of order 10$^9$ and 10$^2$, respectively, shows sharp transitions while approaching 150 K, which strongly supports first-order structural transition. Thermally activated resistivity behaviour above 280 K follows $1/T$ dependence, yielding activation energy of 0.2 eV. Softening of elastic moduli on approaching the phase transition is analysed from resonant ultrasound spectroscopy measurement. Square of the resonance frequency is found to diverge below 236 K, which inhibits any further experimental determination of elastic moduli at low temperature.

• Investigation of multiferroic behaviour at room temperature in Bi-induced orthoferrite: combined experimental and first principles studies

Perovskite oxides are an important and exciting class of materials owing to the structural diversity with remarkable magnetic, optical and electronic behaviours. Here, a single-phase multiferroic orthoferrite, Y$_{0.74}$Bi$_{0.25}$FeO$_{2.97}$ (YBFO), has been synthesized by a conventional solid-state method. The crystal structure was refined using the Rietveld refinement method from powder X-ray diffraction data, and confirms an orthorhombic structure with the Pnma space group. The Curie-Weiss fitting to the magnetic susceptibility shows that the $\theta$-value is $–$926 K and $\mu_{\rm eff} = 5.59$ $\mu_{\rm B}$, exhibiting canted antiferromagnetism. Room temperature magnetic and ferroelectric hysteresis loops verify the presence of magnetic as well as ferroelectric ordering in the material with a remnant polarization ($P_{\rm r}$) of 0.27 $\mu$C cm$^{–2}$ and electric coercivity ($E_{\rm c}$) of 15 kV cm$^{–1}$. Temperature-dependent $P–E$ loops and pyrocurrent response confirm the inherent multiferroic nature of the material. The UV–visible study indicates a semiconductor nature with the bandgap of 1.86 eV. Density-functional theory calculations support the observed experimental behaviour and it signified the role of Bisubstitution. Even a very less concentration of Bi-doping can form an exciting room temperature multiferroic material.

• A sensitive voltammetric sensor based on silver nanoparticles/carbon nitride nanotubes@graphene quantum dots/a novel organic liquid: determination of triclosan in wastewater

A new sensor approach based on silver nanoparticles (AgNPs)/carbon nitride nanotubes (C$_3$N$_4$NTs)@graphene quantum dots (GQDs)/5-nitro-2-(3-hydroxy-4-methoxybenzylidenamino)-thiazole (ILs) was presented fortriclosan (TCS) detection in wastewater samples. X-ray diffraction method, scanning electron microscope, electrochemical impedance spectroscopy, transmission electron microscope and cyclic voltammetry methods were used for all nanomaterials’ characterizations. The linearity range and the detection limit (LOD) were found as $1.0 \times 10^{-11}$ to $1.0 \times 10^{-8}$ M and $2.0 \times 10^{-12}$ M, respectively. The nanocomposite-modified electrode was used for wastewater sample analysis in the presence of different agents.

• Ovalbumin-stabilized concentrated emulsion gels

In this paper, ovalbumin is used as the sole emulsifier to produce stable concentrated oil (oil phase $=$ 70 wt%) in water emulsion near ovalbumin isoelectric point. The emulsions display excellent stability against flocculation andcoalescence at ovalbumin concentration ranging from 0.6 to 1 wt%. The oil–water interfacial tension decreases in the presence of ovalbumin, indicating the adsorption of ovalbumin at the interface. Although the increase in ovalbumin from0.1 to 1 wt% does not significantly influence the equilibrium interfacial tension, the surface mean diameter of the emulsion droplets decreases as the concentration increases from 0.1 to 1 wt%. These emulsions exhibit solid gel-likebehaviour. At low ovalbumin concentrations ($0.1–0.4$ wt%), emulsions undergo a phase separation after 24 h. We hypothesize that emulsions with higher ovalbumin content contain oil droplets with multilayer adsorbed films. The stericstabilization due to adsorbed multilayers and the ability of rigid interfacial films to withstand external droplet pressures upon contact contributes to emulsion stability.

• Facile one-step fabrication of super-repellent nanoporous anodic alumina using a non-fluorinated approach

Inspired by lotus-effect, superhydrophobicity has attracted considerable interest in various areas such as selfcleaning, antifouling and liquid transportation, and so on. Superhydrophobic surfaces can be prepared mostly by altering the surface with creating micro/nanoscale structures or with chemically modifying by materials of low surface energy. In this study, the electrochemically fabricated nanoporous alumina is deposited with poly(dimethylsiloxane) via a one-step thermal treatment to achieve ultra-water repellent or superhydrophobic surfaces. Nanoporous anodic alumina substrates with varying pore diameters were used for the poly(dimethylsiloxane) deposition, and their morphological characterization is carried out using the field emission scanning electron microscope. Energy-dispersive X-ray spectroscopy, Fourier transforminfrared spectroscopy inferred the chemical composition, while contact angle measurements using a commercial contact angle measurement system is exploited to probe the water spreading behaviour on the fabricated substrates. The substrates also exhibit high repellence behaviour towards ethylene glycol. The superhydrophobic behaviour of the fabricated substrates is investigated while the substrate is immersed in organic solvents like decane, hexane and toluene. In addition, the super repellence behaviour of the substrates against the corrosive chemicals such as aqua regia and saturated sodium hydroxideis investigated and the substrate was found to retain its super repellence behaviour against corrosive solutions. Further, the self-cleaning properties and antifouling behaviour of the fabricated substrates were also demonstrated.

• Sulphonated polysilsesquioxane–polyimide composite membranes: proton exchange membrane properties

This study reports the preparation of a –COOH-containing sulphonated copolymer (SPI-COOH-70) and its composite membranes. The composite membranes (SPI/SS-X) were prepared by using the solution casting route byadding different weight percentages of 3-(trihydroxysilyl) propane-1-sulphonic acid into SPI-COOH-70 solution. The proton exchange membrane properties such as morphology, ion-exchange capacity, water uptake and proton conductivity of the prepared composite membranes were studied as a function of sulphopropylated polysilsesquioxane (SiOPS) filler and temperature. All the SPI/SS-X composite membranes showed high-thermal stability and chemical stability, which are attributed to the presence of polar phosphine oxide and the wholly aromatic nature of the copolymers. The homogeneous distribution of the SiOPS nanoparticles in the polymer matrix observed from the scanning electronmicroscopy and atomic force microscopy images are attributed to the formation of covalent bonds between the –OH and –COOH groups of SiOPS and SPI-COOH-70, respectively. The composite membranes with 10 wt% SiOPSexhibited much higher proton conductivity (205 mS cm$^{-1}$), which is much higher than that of the pristine copolymer membrane (114 mS cm$^{-1}$) under similar experimental conditions. The improvement in proton conductivity is attributed to the presence of pendant sulphonic acid groups in the nanofiller, which provides a better proton transport pathway in the composite membranes.

• Static and dynamic behaviour of aqueous drops on thin lubricating fluid-coated slippery (LCS) surfaces

Inspired by Nepenthes pitcher plants, lubricating fluid infused slippery (LIS) surfaces have recently gained tremendous attention from various research groups. We, alternatively, present lubricating fluid-coated slippery (LCS) surfaces based on smooth solid surfaces. The biggest advantage of LCS surfaces over LIS surfaces is that solid surfaces need not be rough or porous. We discuss that the surface energy of the underlying solid surfaces plays the most important role in preparing the LCS surfaces. Lubricating fluid-coated hydrophilic surfaces result in sinking aqueous drops due to the instability of the thin lubricating film. Additionally, stable and floating aqueous drops are observed on similar hydrophobic surfaces. We also observed that the presence of surface roughness enhances the stability and performance of LCS surfaces. Later we discuss various characteristics of LCS surfaces and its effects on the static and dynamic behaviour of aqueous drops on LCS surfaces.

• Polyurethane–POSS hybrid materials: by solution blending and in-situ polymerization processes

Polyhedral oligomeric silsesquioxane (POSS) is a nanostructured softmaterial that tremendously influences the properties of polymers. This paper delineates the preparation of polyurethane–POSS hybrid materials by physical blendingand in-situ polymerization, and studies their properties. In the physical blending method, a polyurethane (BDO–PU) was prepared by using polycaprolactone diol (PCL-diol) as a soft segment, 4,4$^{\prime}$-methylenebis(phenyl isocyanate) (MDI) as a diisocyanate and 1,4-butanediol (BDO) as a chain extender. The PU–POSS hybrid material (BDO–PU/POSS) was then prepared by the dispersion of POSS (octahydroxy POSS) molecules in the synthesized BDO–PU matrix by the solution mixing method. In the in-situ polymerization method, POSS–PU and POSS–BDO–PU hybrid materials were prepared using POSS and the combination of POSS and BDO as a crosslinker or a chain extender. The formation of PU and PU–POSS hybrid materials was confirmed by Fourier transform infrared and differential scanning calorimetry analyses. The introduction of octahydroxy POSS molecules into the PU matrix resulted in a reduction of glass transition temperature ($T_g$). However, POSS–PU hybrid materials prepared by the in-situ polymerization method had significantly less $T_g$ compared to the hybrid materials prepared by the solution or physical blending method. The incorporation of POSS molecules by using the in-situ polymerization process resulted in an increase in the surface hydrophobicity (water contact angle, WCA $=$ 125$^{\circ}$) compared to the same prepared by using the solution blending process (WCA $=$ 106$^{\circ}$). Moreover, the WCA values of all hybrid materials (WCA = 106–125$^{\circ}$) are much higher than those of the pristine BDO–PU (WCA = 84$^{\circ}$). The higher WCA value of the hybrid materials is due to the combined effect of the hydrophobic nature of POSS molecules as well as the increased surface roughness, as evidenced by the AFM 3D images. The hybrid materials prepared by the in-situ polymerizationmethod exhibited improved mechanical and thermal properties compared to those prepared by the solution blending method.

• Effect of grafting density on local dynamics in functionalized polymer-grafted nanoparticle systems

Functionalized polymer-grafted nanoparticles (PGNs) form bonds when their coronas overlap. The extent of bond formation between PGNs depends on both the number of grafted arms (grafting density) and the strength of bonds.Using computer simulations, based on a multicomponent model, we examine the role of grafting density in local dynamics of the PGNs. The simulation results show that grafting density has a significant effect on local dynamics in such systems. In particular, we show that force–extension curves characterizing local responses, to constant strain rate pulling, of simple two- and three-particle systems depend on grafting density. Furthermore, by employing oscillatory deformation simulations we show that the local elastic and viscous responses of PGN systems can be nonlinear even at small strain amplitudes. We characterize the nonlinear response using Chebyshev polynomials of the first kind and determine the elastic and viscous Chebyshev coefficients for a simple three-particle model system subjected to oscillatory shear.

• Wide thermal range, exclusive occurrence of technically significant chiral nematic phase: synthesis and mesomorphism of cholesterol-based non-symmetric dimers

Fifteen newnon-symmetric chiral dimers belonging to three different series have been synthesized and evaluated for their mesomorphic properties. They are formed by interlinking cholesterolwith salicylaldimine (SAN) cores (with reverse imine groups) via an $\omega$-oxyalkanoyloxy spacer. Within a series, the length of the terminal $n$-alkoxy tails has been varied for a fixed even-parity spacer. Three even-parity spacers such as 4-oxybutanoyloxy, 6-oxyhexanoyloxy and 8-oxyoctanoyloxy have been used to join two cores, whereas the terminal tails such as $n$-butyloxy, $n$-hexyloxy, $n$-octyloxy, $n$-decyloxy and $n$-dodecyloxy chains have been attached to the SAN core. Microscopic and calorimetric experimental results show that all the dimers behave identically exhibiting the chiral nematic (${\rm N}^*$) phase solely, which was authenticated by powder X-ray diffraction studies carried out on some selected samples. In the vast majority of the cases, this phase is thermodynamicallystable, and while cooling, it exists over a wide thermal range covering room temperature (RT) due to supercooling. This finding is notable given the fact that the ${\rm N}^*$ phase possesses technologically significant optical properties. At RT, the ${\rm N}^*$ phase displayed one of the iridescent colours characteristically caused by interference and diffraction of the reflected and scattered light. A comparative study reveals that the lengths of both the terminal chain and central spacer influence the clearing temperature of the dimers, and also the temperature range of the ${\rm N}^*$ phase. The selective reflection measurements revealed that the pitch of the ${\rm N}^*$ phase is either temperature sensitive or temperature insensitive. Temperature-dependentcircular dichroism (CD) spectra were recorded for the planar texture of the ${\rm N}^*$ phase formed by a dimer, as a representative case. The presence of an intense negative CD band suggests the left-handed screw sense of the ${\rm N}^*$ phase helix.

• Metal mesh-based transparent electrodes as high-performance EMI shields

Electromagnetic interference (EMI) shields in the form of coatings and films are useful for blocking radiations in various household and industrial settings. Being transparent and flexible would enhance their utility domain. In this study, we have fabricated transparent and flexible EMI shields made of metal meshes produced using the crack templating method pioneered in the laboratory. A Cu metal mesh with polyethylene terephthalate (PET) sheet as its substrate exhibited a visible transmittance of $\sim$85% and a sheet resistance of $\sim$0.83 $\Omega$ per square. The shielding efficiency was tested over a wide spectral range of the K$_{\rm u}$ band (12–18 GHz), relevant to communication electronics. The Cu mesh/PET film showed a remarkably high value for total EMI shielding (SE$_{\rm T}$) with the average value being $\sim$41 dB. The film could be laminated using a commonly available method, thus protecting exposure of the mesh to the environment. The laminated film is multifunctional, and this aspect was demonstrated by fabricating a large area (3.5 $\times$ 2.2 cm$^ 2$) Joule heater for defrosting and defogging applications.

• Hydrophobic recovery of cross-linked polydimethylsiloxane films and its consequence in soft nano patterning

Cross-linked polydimethylsiloxane (PDMS) films and surfaces obtained by thermal cross-linking of commercially available Sylgard 184 are widely utilized in many areas of science, due to superior thermal stability, low dielectric constant, transparency and biocompatibility. Cross-linked PDMS surfaces are weakly hydrophobic and several experiments, particularly the ones that utilize capillary-driven microscale flow require the modulation of the surface wettability. A well-known strategy to achieve the same is by exposing the Sylgard 184 surface to UV/ozone (UVO) treatment at room temperature. Depending on the duration of exposure, the wettability drops from hydrophobic to a nearcompletewetting (water contact angle $\sim$10$^{\circ}$), due to the formation of a surface oxide layer. However, under normal atmospheric conditions, these surfaces recover their hydrophobicity over a period of time due to diffusive migration of the uncrosslinked oligomers to the surface, and formation of a hydrophobic dimethyl silicone layer. We explore the hydrophobic recovery process as a function of cross-linker concentration and UVO exposure time and show how a partially or fully recovered PDMS stamp may influence subsequent nanopatterning, including the possible creation of features with different morphology using a single stamp.

• Kinetics of domain growth in Ising systems with bond disorder at regularly selected sites

We study the structure, phase behaviour and growth laws in Ising ferromagnets and binary mixtures with bond disorder introduced at regularly selected sites for a critical quench. The results presented here are from extensive Monte Carlo simulations on two-dimensional Ising systems. Domain growth in a ferromagnet is modelled by using nonconserved spinflip (Glauber) kinetics, and phase separation in a binary (AB) mixture is modelled by conserved spin-exchange (Kawasaki) kinetics. In both cases, we observed that the domain growth law is consistent with the respective power-law growth with thevariable growth exponent that depends on the number of disordered sites. The nonconserved Ising system follows dynamical scaling for all the number of disordered sites studied here; however, a small deviation is noticed for $r\to 0$ at a large number of disordered sites. Whereas, for the conserved case, dynamical scaling deviates from the master curve after a reasonable number of disordered lattice sites; we notice the formation of lamellar evolution morphology at a higher number of disordered sites at later times.

• Direct imaging of rippled structures of lipid–cholesterol membranes using cryo-SEM and AFM

Cholesterol is a major component of many eukaryotic cellmembranes and hence its effect on the structure of lipid membranes is of considerable interest. One major role of cholesterol is to stabilize the biologically relevant fluid phase over the crystalline gel phase. The suppression of the gel phase occurs above a threshold concentration of cholesterol. There have been reports on the formation of modulated phases at lower cholesterol concentrations, characterized by one-dimensional periodic rippling of the membranes. However, some of these structures have not been investigated in much detail. We have probed the structure of the gel phase of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membranes containing cholesterol using two direct-imaging techniques, cryogenic-scanning electron microscopy (cryo-SEM) and atomic force microscopy (AFM). In addition to confirming the results of earlier studies, we found evidence for the formation of two novel modulated structures in DPPC–cholesterol membranes.We also report the first direct observation of the cholesterol-induced modulated phase of DPPC membranes using AFM, which had so far been observed only using X-ray scattering.

• Formation of self-propelling clusters starting from randomly dispersed Brownian particles

We present a simple chemical strategy for the formation of a self-propelling cluster via the process of capture and assembly of passive colloids on the surface of a chemically active colloid. The two species of colloids that are isotropic and Brownian otherwise interact to form propelling clusters.With the help of coarse-grained numerical simulations,we show that a chemically active colloid can induce diffusiophoretic motility to nearby chemically inert colloids towards itself. This propulsion and then self-assembly can then lead to the formation of active clusters. We observe the formation of propelling dimers, trimers, tetramers, etc. depending on the chemical activity and size of the colloids.

• Influence of particle size on the thermoresponsive and rheological properties of aqueous poly($N$-isopropylacrylamide) colloidal suspensions

Thermoresponsive poly($N$-isopropylacrylamide) (PNIPAM) particles of different sizes are synthesized by varying the concentration of sodium dodecyl sulphate (SDS) in a one-pot method. The sizes, size polydispersities and thethermoresponsivity of the PNIPAM particles are characterized by using dynamic light scattering and scanning electron microscopy. It is observed that the sizes of these particles decrease with increase in SDS concentration. Swelling ratios ofPNIPAM particles measured from the thermoresponsive curves are observed to increase with decrease in particle size. This observation is understood by minimizing the Helmholtz free energy of the system with respect to the swelling ratio of the particles. Finally, the dynamics of these particles in jammed aqueous suspensions are investigated by performing rheological measurements.

• Molecular dynamics simulations of a stacked $\pi$-conjugated soft material: binding energy and preferential geometry for self-assembly

Understanding intermolecular interactions among supramolecular self-assembled organization and identifying the molecular structure relevant to the self-assembly are crucial for designing materials with desired functionalities. Interactions of aromatic rings in a peptide–perylenediimide conjugate (P-1) are investigated using dispersion-corrected density functional theory. The binding energies of fully optimized dimeric P-1 are calculated to identify the most stable conformation of the dimer. We show that the dispersion correction terms have significant contributions to the total energies of the dimers. The combined results from electronic structure calculations and molecular dynamics simulations demonstrate that the stacked dimer with negative inter-planar angle with clock-wise rotation has stronger binding energy than the dimer with positive inter-planar angle. The excess stability of the dimer with clock-wise rotation is attributed to the intra- and inter-molecular π–π stacking of the side aromatic rings of the dimer facilitated by formation of less number of hydrogenbonds. The stacked P-1 dimer with negative inter-planar angle and stronger binding energy is identified as the building block of a super structure with left-handed helical arrangements. Our calculations will build the first step towards understanding the molecular origin of the stability of a specific super structure of P-1 over the other, as obtained in the experiment relevant to material science and technology.

• Solvo-selective imprinting of a thin polymer blend film for creating multi-length scale patterns

Controlling and spatial ordering of the phase separation in ultra-thin polymer-blend films is a viable approach to create complex surface structures with unique properties. This study reports a facile solvo-selective patterning techniquein a phase-separated polymer blend thin film comprising of immiscible polymers polystyrene (PS) and poly(methylmethacrylate) (PMMA). The pattern replication was achieved using capillary force lithography by imprinting the blendfilms with cross-linked polydimethylsiloxane stamp with grating patterns. The replication was done in the presence of 1-chloropentane or acetic acid vapours, which are selective solvents for PS and PMMA, respectively. This engenderedcapillary flow of only one phase while the domains of the second phase remain rigid. Depending on the initial as-cast morphology of the film which is a function of the relative proportion of PS and PMMA, a variety of structures wereobtained by combining the phase-separated domains with the structure imposed by the stamp. This method can be considered as a simple, one-step technique for creating hierarchical patterns that are likely to find applications inmodulating properties of soft surfaces.

• Paths to lowering critical point in a two-dimensional order–disorder transition by Au nanoparticle ‘decoration’

Effect of mixing dodecanethiol-capped Au nanoparticles (AuNPs) on the critical point of the liquid ordered ($L_{\rm o}$) to liquid disordered ($L_{\rm d}$) phase transition of myristic acid (MyA) Langmuir monolayer has been studied through quantitative evaluation of the two-dimensional patterns of AuNP clusters created through de-mixing and observed through Brewster angle microscopy. The critical temperature ($T_{\rm c}$), marked by the emergence of a Bethe lattice-like (BLL) pattern of ‘fingers’ and ‘arms’, was brought down from 38$^{\circ}$C in pristine MyA monolayers to 28 and 10$^{\circ}$C for 20 and 40% w/w AuNP concentrations. Analysis of the BLL at the length scales of these ‘fingers’ and ‘arms’ showed that the lowering of $T_{\rm c}$ follows two different paths for the two concentrations, through a repulsive force for the lower and an attractive force for the higher concentration at the ‘fingers’ length scale, while at the scale of ‘arms’ the force between NPs is always repulsive. Based on the observations that the repulsive force operates at larger interparticle separation and the attractive one acts at smaller separations, we tentatively assign the first to be a dipolar repulsion and the second to be lipophilic force of quantummechanical origin.We have also indicated qualitatively how this realignment of forces between nanoparticles can affect the lipophilic force between the hydrocarbon chains of the NP capping and those chains in the monolayer.

• Recent advances in block copolymer-based supramolecules containing semiconducting molecules

The block copolymer with functional small molecules formed via non-covalent interactions has tremendous appeal in various fields of applications. When the functional small molecules were attached to one of the blocks of the block copolymer, it can produce hierarchical structures with built-in functionality. This technique enables for the generation of controlled nanostructures in the solid-state, and also creates nanoporous templates by selective dissolution of smallmolecules. In this featured paper, we review the recent trends of block copolymer-based supramolecules in the self-assembly process of organic semiconductors and nano-particles within the block copolymer domains in bulk and thin films.

• Colloidal hydrodynamics using a quasi-steady algorithm in lattice Boltzmann method

Hydrodynamics can play an important role in determining the behaviour of colloidal particles in many softmatter systems. Analytical solutions for fluid dynamics are limited and incorporating the particle dynamics in numerical methods is challenging, since grid points belonging to fluid and solid phases are exchanged during the simulations. As a solution, here, we introduce a quasi-steady method to simulate dynamics of particles within the frame work of lattice Boltzmann method. This method not only carries the advantages of lattice Boltzmann, namely the simple and straight forward algorithm ofprogramming and the simplicity in imposing the boundary conditions, but it also avoids the complications associated with exchange of particle and fluid nodes. Exploiting the smallness of Reynold’s number associated with colloidal hydrodynamics, the proposed algorithm works in an instantaneous frame of reference and particle velocities are then calculated by imposing additional constraints of force and torque acting on the particle. We illustrate the method using the classic examples of settling particles and a system of recent interest-dynamics of active particles, both in the presence of a wall. Therefore, weexpect the proposed method to be suitable and useful in variety of soft and active matter systems.

• Phase transitions of liquid crystal confined in electrospun polymer nanofibres

Phase behaviour as well as phase transitions of 4$^{\prime}$-pentyl-4-biphenylcarbonitrile (5CB) liquid crystal (LC) confined in an amorphous polymer matrix of electrospun nanofibres were investigated. The nanofibres were fabricated from simple monoaxial electrospinning using 5CB/polymer mixtures as well as coaxial electrospinning, where the polymer solution and neat 5CB constituted the shell- and core-forming fluids, respectively. The 5CB was found to be miscible with polystyrene (PS) and poly(4-vinyl pyridine) (P4VP). This was evident from the sharp drop in the glass transition temperature ($T_{\rm g}$) of PS and P4VP in their mixtures with 5CB. Hence, the phase transitions of 5CB were completely suppressed in its mixture with PS and P4VP in electrospun nanofibres as ascertained from DSC and polarized optical microscopy measurements. However, the electrospun nanofibres composed of poly(vinyl pyrrolidone) (PVP) and 5CB showed phase-separated morphology. The phase-separated morphology was unambiguously characterized using SEM andTEM measurements. Furthermore, the phase separation resulted in 5CB exhibiting its liquid crystalline characteristics. However, the radial constraint of the nanofibres led to the formation of small-sized 5CB domains with limited spatialconnectivity, which resulted in deviation from the known phase-transition characteristics of 5CB. It was also observed that the inherent orientation of the nanofibres favours the nematic to crystalline transition in the blend nanofibres. The present study gives new insight and understanding about phase behaviour of LC in electrospun polymer fibre and has technological relevance for the design of LC-based flexible fibrous components with tunable optical, thermal and dielectric properties.

• Highly sensitive electrochemical sensing of neurotransmitter dopamine from scalable UV irradiation-based nitrogen-doped reduced graphene oxide-modified electrode

Present study develops a facile, low-temperature and cost-effective route for the synthesis of nitrogen-doped reduced graphene oxide (N-rGO). The synthesized N-rGO was characterized using X-ray diffraction (XRD), micro-Ramanand Fourier transform infrared (FTIR) spectroscopies. An electrochemical sensor using N-rGO-modified glassy carbon electrode (GCE) was fabricated for the determination of dopamine (DA), a neurotransmitter. Because the electrochemical determination and quantification of DA play a significant role inmedical diagnosis, such as making soft material-based hydrogelfor wound healing. Cyclic voltammetry (CV), amperometry, differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS)-based standard techniques were used to evaluate and establish the optimum electrochemical sensing performance, detection limit, steadiness and reliability of N-rGO/GCE sensing system to the DA detection. The DPV measurements resemble a wide linear range from 100 to 3000 $\mu$M and demonstrated a limit of detection (LOD) of 57 nM. It is evidently proved that N-rGO/GCE has great potential to be a preferable electrochemical sensing system for DAdetection.

• Manipulation of the exciton diffusion length of conjugated polymer nanoparticles: role of electron and hole scavenger molecules

Exciton generation, migration and dissociation are key fundamental processes that dictate the efficiency of optoelectronic devices. Here, we investigate exciton diffusion process of conjugated polymer nanoparticles (PNPs) in the presence of electron and hole scavenger molecules using time-resolved spectroscopy. We found that the exciton diffusion length of hole transporting PNPs, decreases in the presence of hole scavenger molecule and it increases in the presence of electron scavenger molecule. Analysis reveals that the diffusivity of excitons can be controlled by changing the nature of scavenger molecules. Such fundamental study is important for developing devices where lower and higher exciton diffusivities are required depending on the requirement of application mode.

• Evaporation-driven self-assembly in the mixtures of micro and nanoparticles

We report experimental studies on the self-assembly of silica microspheres and Laponite nanoplatelets (NPs) in evaporating sessile droplets and in thin films, respectively. A ring-like stain of the silica microspheres with positionalorder is observed after the evaporation of sessile droplets due to the coffee-ring effect. This effect is suppressed in the binary mixtures of silica microspheres and Laponite NPs. A depletion zone has been observed in the mixtures during the sessile droplet evaporation, the width of which can be tuned by varying the compositions. We demonstrate a simple method for preparing core–shell particles by evaporating thin films of binary mixtures in which the Laponite NPs self-assemble to form a crystalline shell on the amorphous silica microspheres.We present a possible orientation of the Laponite NPs in the shell.

• Design of cationic amphiphiles for generating self-assembled soft nanostructures, micelles and hydrogels

Design of amphiphiles to develop robust self-assembled soft nanomaterials, such as micelles and hydrogels is an interesting subject. A series of cationic amphiphilic compounds were synthesized comprising 1-ethoxy (3-pentadecyl)benzene as the hydrophobic tail. The second carbon of ethoxy was linked to quaternary head groups (trimethyl ammonium bromide (PEA), triethyl ammonium bromide (PETE), pyridinium bromide (PEPy), N-methyl morpholino bromide (PENM), N-methyl piperidine bromide (PENP)). Inclusion of benzene ring leads to a significant decrease in critical micellar concentration (CMC) as compared to other cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB). Interestingly, at higher concentration, these cationic amphiphiles were forming soft hydrogels with critical gelation concentration (CGC) from 3 to 10% (w/v). The small-angle X-ray scattering (SAXS) analysis of xerogel revealed the formation of self-assembled lamellar patterns of molecules. Further, the morphology of xerogels were also seen under a scanning electron microscope (SEM) which correlates with SAXS data. The SAXS and SEM data confirms the formation of worm-like micellar structures and entangle themselves to form a hydrogel. The cytotoxicity assay was done on HDFA, HeLa and HEK cell lines, haemolysis assay showed better haemocompatibility than CTAB. The synthesized surfactants exhibited up to 3-fold higher solubilization capability against hydrophobic molecules than CTAB.

• 3D printing of semicrystalline polypropylene: towards eliminating warpage of printed objects

Fused filament fabrication (FFF) is an extrusion-based 3D printing technique for thermoplastic polymers. In this technique, molten polymer is extruded through a print nozzle and is laid down layer by layer to build up the printed object.Currently, FFF is used primarily to print amorphous or low-crystallinity polymers, such as acrylonitrile butadiene styrene copolymer (ABS) or polylactic acid (PLA). Printing of semicrystalline polymers, such as polyethylene or polypropyleneremains particularly challenging. During FFF of semicrystalline polymers, large thermomechanical stresses are generated when the polymer solidifies on cooling. These stresses result in warpage of the printed part. Here, we analyse the factors that influence stresses generated during FFF 3D printing of a commercial semicrystalline polymer, isotactic polypropylene. We investigate the effect of height of the printed object on part warpage, as well the effect of infilling during printing. We demonstrate that the stresses generated during FFF can be substantially decreased by incorporation of a ‘brim’, viz. a thin layer at the base of the printed object, and by adhering the brim to the print substrate using common polyvinyl acetate based glue. We systematically investigate the effect of the brim size on the warpage of the printed object. We support ourexperimental findings with finite element method (FEM) simulations that explain the mechanism of stress buildup during printing. The trend in stresses calculated in the FEM simulations parallel the warpage measured in the experiments. Thus,this work represents an important methodological advance towards warpage-free FFF printing of semicrystalline polymers.

• Intensified dewetting of polystyrene thin film under water-solvent mixture: role of solvent composition

Intensified dewetting of ultra thin polystyrene (PS) films induced by immersing in a homogeneous mixture of good solvent and water was previously reported to push the limits of dewetting to the sub-100 nm scale. Here, we systematically analyse the role of dewetting mixture composition, i.e. solvent to water ratio, on the length scales of instability. The effect of the solvent concentration in the dewetting mixture on the instability wavelength ($\lambda$) and droplet diameter ($d$) are determined. The instability wavelength ($\lambda$) for 50 nm thick PS film was found to be decreasing from nearly 17 to 7 $\mu$m as the solvent concentration is decreased from 95 to 35% in the dewetting mixture. This is significantly smaller than the instability wavelength in air, which is nearly 50 $\mu$m for the same PS film. The solubility of PS in the dewetting mixture is also examined and the mechanism of observed variation in the length scale is proposed.

• Electrohydrodynamic instability: effect of rheological characteristics on the morphological evolution of liquid crystal–polymer interface

Electrohydrodynamic instability, in a polymer–air or polymer–polymer bilayer settings, gives rise to the formation of the orderedmicropillars or microwells at the initial planar interface. It is well known that the complex interplay amongthe controlling parameters, such as the intensity of the electrostatic field, film thickness, interfacial tension and dielectric constants of the layers determine the morphology of the interface. In this report, for the first time, experimentally it is shown that rheological property of the lower polymer layer [here, polydimethylsiloxane (PDMS)] has a significant influence on the morphological evolution.We probe the kinetic time scale of the evolution by inducing fast destabilization of the interface due to the high dielectric contrast between two layers (liquid crystal–PDMS) and reduced interfacial tension. At this time scale,it was demonstrated that micropillars are formed for thin viscoelastic ‘soft’ PDMS film, whereas microwells were observed for viscoelastic ‘hard’ film in similar settings. A transition from micropillar to microwell was observed for viscoelastic ‘soft’ film when the thickness of the film increased from $\sim$4 to 11 $\mu$m. Based on this observation, by controlling the rheological properties, different patterns were developed from similar templated PDMS substrates.

• The fascinating world of Soft Materials

• Enhanced performance of Fe-doped manganese oxide films as supercapacitor electrodes

This paper reports enhancement in the specific capacitance of iron-doped manganese oxide (MnO$_2$) films, potentiostatically deposited on stainless-steel substrates. The properties of deposited films were investigated through cyclicvoltammetry and galvanostatic charge/discharge characteristics. The specific capacitance, as determined through cyclic voltammetry and galvanostatic charge/discharge characteristics, respectively, was found to be 248.79 and 277.5 F g$^{−1}$ for undoped films, whereas it exhibited an increase with doping and was found to be 449.61 and 487.5 F g$^{−1}$, respectively, corresponding to a dopant concentration of 4 atomic percentage. The electrochemical impedance data were fitted with a modified Randles equivalent circuit to find series resistance, charge-transfer resistance, double-layer capacitance and iondiffusion. According to electrochemical impedance spectroscopy, the enhancement of ion diffusion was found to be the major cause for enhancement in capacitive performance of the films.

• Role of Ba(O$_2$)$_{1-x}$O$_x$ species in improvement of selective oxidation activity of CoO$_x$/CeO$_{2-y}$

A series of Ba-doped CoO$_x$/CeO$_{2-y}$ catalysts was prepared by co-precipitation followed by the deposition–precipitation method. The catalysts were investigated for selective oxidation (selox) of benzyl alcohol (B-ol) using tertiarybutyl hydroperoxide (TBHP) without solvent and activity was compared with Co$_{0.5}$/Ce$_{0.5}$. The Ba loading has been optimized with time and temperature for selox reaction. The catalyst was characterized by various surface and bulk characterization techniques. The characterization study indicates that the synergistic interaction between Ba and CoCe could form more oxygen vacancies and peroxide species responsible for the activation of B-ol and TBHP. The formation of Ba(O$_2$)$_{1-x}$O$_x$ oxide (peroxide) was observed and could be responsible for the activation of B-ol. The optimum Ba doping enhances selectivity and yields benzaldehyde. However, the increase in Ba concentration on CoO$_x$/CeO$_{2-y}$ could lead to the over-oxidation of B-ol to by-products.

• Studies on polyoxyethylene octyl phenyl ether supported thorium(IV) phosphates: a new cation exchange material

A new surfactant supported cation exchanger and adsorbent named, polyoxyethylene octyl phenyl ether supported thorium(IV) phosphate (TX-100ThP) has been reported along with its synthesis, physico-chemical characterization such as scanning electron microscopy, X-ray diffraction, thermogravimetric analysis–differential thermal analysis and Fourier transform infra-red study. Following the characterization, the formed product has been tested for its efficiency in ion exchange chemistry and in analytical chemistry. For the testing, adsorption of alkaline earths—Mg$^{2+}$, Ca$^{2+}$, Sr$^{2+}$ and Ba$^{2+}$ and transition metal ions such as Fe$^{3+}$, Mn$^{2+}$, Ni$^{2+}$, Cd$^{2+}$, Co$^{2+}$, Cu$^{2+}$, Hg$^{2+}$ and Pb$^{2+}$ have been explored in different acidic media and the results revealed the selectivity of synthesized material towards Hg$^{2+}$ ions. On that basis, the material has been used to treat the binary laboratory-made samples, exploring the environmental importance of the cation exchanger in material science.

• Studies on thermal stability and life estimation of epoxy adhesive by thermogravimetric analysis for high-temperature applications

Structural epoxy adhesive was investigated for its thermal stability and degradation behaviour in a thermooxidative environment by thermogravimetry analysis (TGA). Non-isothermal TGA was performed at temperatures between30 and 600$^{\circ}$C utilizing different heating rates. The ageing characteristics of material were determined by an accelerated ageing study using isothermal TGA at different temperatures for 5% threshold conversion. The activation energies from both non-isothermal TGA and isothermal TGA were estimated and the activation energy values for 5% degradation from both the methods were in good agreement. The epoxy adhesive with titanium dioxide as filler showed a shelf life exceeding 13 years at ambient conditions (27$^{\circ}$C). Additionally, the lap shear strength of the adhesive joint was also tested after treating thesamples at 70$^{\circ}$C with 90% relative humidity to evaluate the hydrothermal effect on adhesive joint.

• Rapid fabrication of Cu$_2$ZnSnS$_4$:CdS graded interfaces via spray coating

Cu$_2$ZnSnS$_4$ (CZTS) is a non-toxic and cheap photovoltaic absorber material, however, many challenges still remain for the successful fabrication of these devices. In this study, CZTS was deposited with CdS, a commonlyused buffer layer, using different spray coating procedures (i.e., two-step, single-step and graded deposition techniques), to demonstrate a facile and rapid fabrication technique of creating CZTS:CdS photovoltaic devices. Scanning electron microscopy (SEM) was used to determine the morphology of the deposited films, showing that the two-step, single-step and the graded deposition with 2 s of overlap time produced clear and defined layers. However, when the overlap time exceeded 4 s the layer became less defined, thicker and less dense, resulting in failed photovoltaic devices. This was attributed to the additional source of air during the deposition period, resulting in air being trapped by the deposited precursor, which therefore forms more foam-like functional layers. X-ray diffraction (XRD) analysis reflected this change in morphology, with graded samples above 4 s displaying no obvious CZTS peaks, suggesting an ineffective decomposition route. Depositions using a two-step, single-step and the gradeddeposition technique with 2 s of overlap time were shown to form functional photovoltaic devices, with a 2 s graded overlap performing three times better than the ungraded samples, resulting in an improved power conversion efficiencyof 0.41%. It is important to highlight that the device prepared with a 2 s graded interface significantly increased the current peak performance of CZTS photovoltaic devices deposited using xanthate precursors.

• A novel carbon/germanium conic structure: theoretical study using density functional theory

Complete optimization without geometry constraints and calculation of electronic properties of novel conic molecules such as C$_n$H$_n$Ge$_n$H$_n$ and C$_n$Ge$_n$H$_n$, with $n = 3−8$, was carried out with density functional theory using B3LYP and PBE1PBE functionals with 6-31$+$G(d, p) and cc-pVTZ basis sets. Calculations of formation energy showed stable and peculiar geometric and electronic properties. All carbon and germanium atoms for C$_n$H$_n$Ge$_n$H$_n$ compounds, which are sp$^3$-hybridized, were located in the same plane. This finding contradicts the notions of hybridization known to date. For these new molecular compounds, quantum descriptors such as electrochemical potential ($\mu$), chemical hardness ($\eta$), electrophilicity index ($\omega$), dipole moment, energy gap and the shape of the molecular orbital have been calculated in additionto nucleus independent chemical shifts, polarizability and harmonic oscillator model of aromaticity which are important tools for determining the aromaticity of the studied compounds. Thus, the aim of the work is, on the one hand, to propose new stable molecular structures formed of carbon and germanium atoms, and on the other hand, to challenge our understanding of hybridization and aromaticity notion.

• Modelling experimental parameters for fabrication of nanofibres using Taguchi optimization by an electrospinning machine

In this research study, a photo-electrospinning device was designed and manufactured to produce nanofibres (NFs) by using an optical polymerizationmethod. For this purpose, an electrospinning machine was designed and optimized. Various parameters such as voltage, speed of collector and distance were investigated on the uniformity and diameter ofpolycaprolactone fibres. Therefore, a Taguchi experimental design was used to optimize the diameter of the fibres. Nine experiments were conducted using scanning electron microscopy to study the surface morphology of the obtained fibres. The best conditions for producing NFs include: voltage$=$15 V, speed of collector$=$600 rpm and distance$=$20 cm.

• Photoinduced synthesis of variable-sized magnetite nanoparticles and their photodegradation for orange II

Magnetite (Fe$_3$O$_4$) nanoparticles with different particle sizes (9.9–29.1 nm) were prepared by using the aerial oxidation method under light irradiation with various wavelengths at room temperature. The photocatalytic degradation of orange II using Fe$_3$O$_4$ nanoparticles as photocatalysts was evaluated. Experimental results showed that the particle sizes of Fe$_3$O$_4$ nanocrystals decreased gradually with the decreasing wavelengths of light irradiation. With the decrease in the size of the samples, the Fe$_3$O$_4$ nanoparticles exhibited a large surface area and high adsorption. Furthermore, the smallparticle-sized Fe$_3$O$_4$ sample could cause an appropriate red shift of the spectra and promote the decomposition of H$_2$O$_2$, and produce high-content ${}^{\bullet}$OH radicals, which lead to an improvement of photodegradation efficiency of orange II.

• Colorimetric molecular receptors for the sensing of acetate, fluoride and mercury based on Schiff’s bases

The real-time monitoring of biologically relevant anions and mercuric ion concentration in aqueous and physiological media and its quantitative determination across a large concentration range are of vital importance inenvironmental, health-care issues, industrial and scientific fields. Anion-like fluoride and acetate play an important role in a wide range of chemical and biological systems. This study reports the synthesis of a series of new molecular receptors based on Schiff’s bases by adopting a green strategy. The adopted procedures were simple and less complicated. A new simple colorimetric receptor based on salicylaldehyde Schiff’s bases sharing $–$OH and C$=$N moieties as anion binding sites have been successfully synthesized through one-step synthesis, and the sensing studies revealed that the receptors synthesized were found to be an elegant solution to the colorimetric sensing of the anions, especially acetate and fluoride.

• Landau mean-field model with the cubic term for the $\alpha–\beta$ transition in quartz

Thermodynamic quantities are calculated as a function of temperature by using Landau mean-field model for the $\alpha–\beta$ transition in quartz. By expanding the Gibbs free energy in terms of the order parameter ($Q$) with the cubic term ($Q_3$), the temperature dependence of the relevant thermodynamic quantities are predicted using the heat capacity ($C_{\rm P}$), which is fitted to the experimental data from the literature for the $\alpha–\beta$ transition in quartz. Our results indicate that the Landau mean-field model is adequate to describe the first-order $\alpha–\beta$ transition in quartz.

• Effect of annealing temperature on the structural, dielectric and electric properties of Ni$_{0.7}$Cd$_{0.3}$Fe$_2$O$_4$ ferrites

A composition of Ni$_{0.7}$Cd$_{0.3}$Fe$_2$O$_4$ (NCF) ferrite nanoparticles was synthesized by a sol–gel auto-combustion technique. The particles in powder form were annealed at 550 and 700$^{\circ}$C to study the structural, dielectric and electric properties of NCF by using X-ray diffraction (XRD), field emission scanning electron microscopy, impedance and modulusspectroscopy. XRD patterns confirmed the single phase cubic spinel structure of the sample. The average crystallite size of NCF was found to be 17 nm at 550$^{\circ}$C and 31 nm at 700$^{\circ}$C, respectively. The variation in complex dielectric constant, loss tangent and impedance along with the modulus properties of NCF with frequencies was observed at room temperature becauseof their size and annealing temperature. Notably, dielectric dispersion of the materials was observed at low frequencies because of Maxwell–Wagner interfacial polarization. The impedance and modulus spectroscopy were used to investigate the electric properties of the materials, which revealed the increase in grain and grain boundary resistance with annealing temperature. A non-Debye type of relaxation in the materials was evidenced through the Cole–Cole study of impedance and modulus spectra.

• Electroplated Co$_3$O$_4$ selective coatings for high-temperature solar thermal applications

This communication presents the optical characterization of Co$_3$O$_4$ films electroplated on Cu- and Ni-coated Cu substrates. Co$_3$O$_4$ films were successfully deposited by using the electrochemical deposition method with cobalt acetate tetrahydrate as a cobalt precursor followed by annealing at 350$^{\circ}$C. The as-prepared films were characterized using X-raydiffraction, UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and stagnation temperature test.The characterization shows the presence of only the cubic spinal Co$_3$O$_4$ phase in all films. The morphological analysis revealed the generation of unique fish-shaped Co$_3$O$_4$ particles with uniform size distribution for the films obtained on the Ni-coated Cu substrate. The Cu substrate with and without nickel plating used for deposition has shown a profound effect on the optical characteristics of films. The solar absorbance as high as 0.96 and thermal emittance as low as 0.02 were obtained for the films deposited on the Ni-coated Cu substrate. The highest value of the figure of merit ($F_1$) of $\sim$0.34 and extrapolated stagnation temperature of $\sim$362$^{\circ}$C were realized for films having better optical characteristics. The results obtained indicate very good potential of the deposited films for solar thermal applications.

• 3D interconnected graphene aerogels/carbon foam networks with balanced performance in specific surface area and electrical conductivity for supercapacitors

To balance the performance in specific surface area and electrical conductivity, ordered sheets of graphene aerogels were induced into porous carbon foam for supercapacitors with enhanced specific capacitance. Systematic investigations into morphology, structure and electrochemical properties confirmed that the introduction of graphene aerogels can effectively make specific surface area to increase, however, the declined resistance is neither due to electrolyte diffusion nor charge transfer, which gave rise to the improvement of electrochemical performance by 55.3% with a great specific capacitance of 210.5 F g$^{−1}$ at the current density of 0.5 A g$^{−1}$ compared to that of carbon foam.

• Local structure analysis of $B$O$_6$ ($B = {\rm Fe, Cu}$) octahedron correlated with the magnetic properties of Cu-doped Ba$_{0.5}$Sr$_{0.5}$FeO$_{3–\delta}$

Perovskite-based Ba$_{0.5}$Sr$_{0.5}$Fe$_{1–x}$Cu$_x$O$_{3–\delta}$ (BSFCO-$x$, $x = 0–0.2$) was synthesized by sol–gel self-combustionmethod. The crystallinity was evaluated through X-ray diffraction, besides further local structure analysis, using X-ray absorption spectroscopy (XAS) showed a cubic symmetry for $x = 0.05$; 0.10, which was tetragonal at higher values, $x =0.15; 0.20$. XAS analysis predicted the oxidation state (OS) of Cu to be a mixture of 3$+$ and 2$+$, while Fe includes 3$+$ and 4$+$. Conversely, the OS of Fe and Cu in the octahedron site influence the number of an unpair electron that determine the magnetic properties of perovskite. In addition, the magnetization for Ba$_{0.5}$Sr$_{0.5}$FeO$_{3–\delta}$ is 0.172 emu g$^{-1}$, originating from the ferromagnetic ordering Fe$^{3+}$($t_{2g}^3 e_g^2$)–O(2p)–Fe$^{4+}$($t_{2g}^3 e_g^1$) interaction. This effect increase, due to the presence of oxygen vacancy in BSFCO-0.05, which weakens the $d–p$ interaction of Fe-O, while the generation of higher Cu doping to increase the amount of Fe$^{4+}$ leads to a decline in Cu$^{3+}$. Therefore, Cu doping is confirmed to play a role in the paramagnetic–ferromagnetic transition.

• Efficient electrocatalytic activity for oxygen reduction reaction by phosphorus-doped graphene using supercritical fluid processing

Oxygen reduction reaction (ORR) plays a vital role in various fields, such as combustion, corrosion and fuel cell applications. Herein, we report the production of phosphorus-doped reduced graphene oxide (P-RGO) using triphenylphosphine as a phosphorus source and graphene oxide in supercritical fluid method. The ratio of phosphorus source and graphene oxide has been varied to obtain optimum P-doping. P-RGO materials are characterized through X-raydiffractometer, Raman, field emission scanning electron microscopy and X-ray photoelectron spectroscopy techniques. The electrocatalytic activity of P-RGO materials are studied using linear sweep voltammetry and their ORR performanceare evaluated using linear sweep voltammetry-rotating ring disk electrode studies in 0.1 M KOH electrolyte. Among the three different P-RGO materials, RGO with phosphorus doping (2:1) delivered the best ORR performance (0.75 A mg$^{-1}$) compared to commercial HiSPEC Pt/C (0.12 A mg$^{-1}$) catalyst. The enhanced ORR activity could be ascribed to the existence of surface-active phosphorous sites over the RGO sheet surface.

• Effect of addition of a mixed filler of CoCl$_2$ and LiBr into PEMA and its morphological, thermal and electrical properties

Poly ethyl methacrylate (PEMA) films doped with various concentrations of a mixed filler (CoCl$_2$ and LiBr) were prepared by using the casting method and their morphological, thermal and electrical properties were investigated.Scanning electron microscopy showed partial compatibility between the PEMA and the mixed filler. Differential scanning calorimetry was shown to increase their thermal stability with an increase in the concentration of the mixed filler in thefilms. The electrical properties were investigated using DC electrical conductivity ($\rho$), which showed an improvement in electrical conductivity after addition of the mixed filler.

• Effect of WO$_3$ nanoparticle doping on the physical properties of PVC polymer

Poly(vinyl chloride)/tungsten oxide (PVC/WO$_3$) nanocomposite films were synthesized with different ratio of WO$_3$ content (0, 0.05, 0.1, 0.2 and 0.3 wt%). The sol–gel method was used to prepare WO$_3$ nanoparticles (NPs). X-ray diffraction and scanning electron microscope techniques confirmed that the WO$_3$ NPs were successfully dispersed in a PVC matrix with a single-phase structure. Characteristic absorption bands were observed in infrared spectra for pure PVC and nanocomposites. The morphology of WO$_3$ was observed using transmission electron microscope. The optical energy band gaps ($E_{\rm opt}$; direct and indirect) were estimated by using Tauc’s formula. It was found that the direct band gap energies decreased from 5.15 to 4.53 eV and the indirect bands decreased from 4.8 to 4.1 eV as WO$_3$ doping increased, while the Urbach energy ($E_{\rm u}$) increased as WO$_3$ content increased. It was found that the steepness parameter decreased, which confirms the formation of localized states in the band gap and increasing disorder in PVC polymer samples. The dielectric constant ($\epsilon'$) of the PVC/WO$_3$ nanocomposite films decreased as frequency increased. At a low frequency region, the loss factor ($\epsilon''$) has a high value and then sharply decreased as frequency increased, reaching a frequency independent region at high frequency values. The obtained data are very useful for using the investigated samples (PVC/WO$_3$) as the cores of high frequency transformers with very low dielectric loss.

• Microstructure and wear behaviour of graphene–Si$_3$N$_4$ binary particle-reinforced aluminium hybrid composites

In this study, Si$_3$N$_4$ and graphene-reinforced aluminium matrix composites (AMCs) with various contents (Si$_3$N$_4$: 1, 3, 6, 9 wt%; graphene: 0.1, 0.3, 0.5 wt%) were produced by the powder metallurgy method. The phase and microstructure analyses of the composites were performed by X-ray diffractometry and scanning electron microscopy, respectively. To investigate the tribological behaviour of Al–Si$_3$N$_4$ and Al–Si$_3$N$_4$–graphene composites, pin-on-disc experiments were conducted with different loads ($F = 10$, 20 and 30 N) at a constant sliding speed (200 rpm). Thus, the effects of Si$_3$N$_4$ and graphene contents on microstructure, Vickers hardness, apparent density, porosity, wear rate and friction coefficient of AMCs were investigated. Test results reveal that the highest Vickers hardness ($66 \pm 1$ HV), the lowest porosity (5.6%), wear rate ($3.1 \times 10^{−5}$ mm$^3$ N$^{−1}$ m$^{−1}$) and friction coefficient (0.13) were obtained for Al–9Si$_3$N$_4$–0.1 graphene. After attaining 0.1% graphene content, agglomeration was detected from the microstructure images of Si$_3$N$_4$–graphene reinforced AMCs. It was concluded that Si$_3$N$_4$ had an outstanding wear resistance and graphene was a good solid lubricantfor AMCs.

• Preparation and thermophysical properties of graphene oxide–silver hybrid nanofluids

Ethylene glycol (EG)-based hybrid nanofluids containing graphene oxide–silver nanosheets (GO–Ag) were simply prepared without using any surfactant. The graphene oxide–silver composites were characterized using X-raydiffraction analysis, transmission electron microscope, infrared and UV–visible spectroscopy. The stability of GO–Ag nanofluids was estimated by UV–visible spectroscopy. The GO–Ag/EG hybrid nanofluids has good stability withoutsignificant sedimentation for 60 days. A few thermophysical properties of GO–Ag/EG nanofluids with 0.1, 0.2 and 0.3 wt% nanosheets were analysed experimentally at different temperatures ranging from 20 to 50$^{\circ}$C.

• Effect of reaction temperature on the structural and electronic properties of stannic oxide nanostructures

Different nanostructured materials are having important roles in optoelectronics, gas sensing and photocatalytic applications due to their high surface to volume ratio. In this study, stannic oxide (SnO$_2$) nanostructures are prepared by hydrothermal method under optimal conditions at different temperatures (160, 180 and 200$^{\circ}$C) using surfactant cetyltrimethyl ammonium bromide. X-ray diffraction studies reveal rutile tetragonal structures of SnO$_2$ nanostructures, showing that average crystallite size is less than 10 nm. Field emission scanning electron microscope imaging reveals the morphological analysis of SnO$_2$ nanostructures fabricated at different reaction temperatures (160, 180 and 200$^{\circ}$C). Energy dispersive X-ray spectroscopy confirmed the elemental analysis of SnO$_2$ nanostructures. FTIR spectrum is recorded to confirm the presence of various functional and vibrational groups in the prepared SnO2 nanostructures. Optical properties of these nanostructures are analysed by UV–vis absorption studies. Bandgap of prepared SnO$_2$ decreased with increasing reaction temperature. Two-probe setup along with Keithley source metre is used for analysis of electricalproperties of SnO$_2$ nanostructures.

• Strategy for enhancing the hydrogen evolution reaction properties of MoS$_2$ by utilizing the ordered mesoporous carbon as support and modification with nickel

Surface modification of electrocatalyst suitable for yielding reduced over potential with improved exchange current density at the interface is highly desired for hydrogen evolution reaction (HER). Herein, the present report demonstratesthe HER performance of ordered mesoporous carbon (OMC)-supported nickel-modified MoS$_2$ electrocatalysts [NiMoS($x$)–OMC] synthesized by hydrothermal route. Inherent activity of pristine MoS$_2$ was improved by two vital surface strategies utilizing OMC as the support matrix for the dispersed growth of active catalyst and surpassing the active sites formation via augmentation of various concentrations of nickel. Crystalline phase, heterostructure vibrations, morphological orientationand electrocatalytic property of the prepared catalysts are comprehensively studied using different spectroscopic methods. Linear sweep voltammetric analysis suggests that the HER from the pristine MoS2 could be amplified by introducing OMC as support matrix. Synergistic enrichment of Ni (3 and 5 wt%) on MoS$_2$–OMC matrix enables both the lowest onset potential (180 and 185 mV) and Tafel slope values (103 and 100 mV per decade), with retained stability promising for further optimization and scalability.

• Adsorption of H$_2$, N$_2$, CO, H$_2$S, NH$_3$, SO$_2$ and CH$_4$ on Li-functionalized graphitic carbon nitride investigated by density functional theory

The interaction of small gas molecules as H$_2$, N$_2$, CO, H$_2$S, NH$_3$, SO$_2$ and CH$_4$ on Li-functionalized graphitic carbon nitride was investigated by using the density functional theory, to explore their gas adsorption properties. The calculated $E_{\rm ads}$ values of all gas molecules on [Li g-C$_3$N$_4$]$^+$ show that these gas molecules present favourable interaction with the lithium atom coordinated on the sheet. NH$_3$ and SO$_2$ molecules present strong interactions, with $E_{\rm ads}$ values of $-$18.60 and $-$9.50 kcal mol$^{-1}$. The natural bond orbital analysis indicates that donor orbitals belong to the lone pairs of oxygen, nitrogen, sulphur and carbon atoms from SO$_2$, N$_2$, NH$_3$, H$_2$S, CO molecules, and acceptor orbitals (LP$^*$) from the lithium atom. Computational studies suggest that H$_2$, N$_2$, CO, H$_2$S, NH$_3$, SO$_2$ and CH$_4$ molecules on [Li g-C$_3$N$_4$]$^+$ present physisorption.

• Modified high-density polyethylene films: preparation, composition and their physical properties

To prepare high-density polyethylene (HDPE) films with excellent mechanical properties and lower haze, HDPE was modified by using linear low-density polyethylene (LLDPE) and polypropylene (PP), and their characterizationswere performed by melt index, light transmittance/haze, dart impact and elongation at break, infrared (IR) spectra, scanning electron microscopy image and IR image analyses. The results showed that the modifying effect of the 10% PP/30% LLDPE/60% HDPE composition was the best; the haze was reduced 6% and the translucency, dart impact strength, elongation at break and tensile strength were increased 1, 27.3, 29.4 and 1.0%, respectively. The blend of 10% PP/30% LLDPE/60% HDPE had good compatibility, and PP, LLDPE and HDPE were only the physical entanglement, and no chemical reaction, the modified HDPE films can partly replace polyvinyl chloride and LLDPE films.

• Carbon nanotube-incorporated cellulose nanocomposite sheet for flexible technology

A flexible, electrically conductive and low-cost composite sheet has been prepared combining multi-walled carbon nanotubes (MWCNTs) and cellulose pulp using simple solution mixing method. The uniform attachment of MWCNTs on to the cellulose fibres of the composites lead to a gradual decline of the sheet resistance with an enhanced electrical conductivity. The crystallinity of the composites is also found to be increased. The composites remain thermallystable up to 550 K as well as demonstrate improved flame retardancy. The conducting CNT networks of the composites are not disrupted even after 600 bending cycles, indicating almost no loss of conductivity. This conducting and flexible composite sheet can be used in different energy storage devices.

• Reversible hydration of the perchlorate-intercalated layered double hydroxides of Li and Al: structure models for the dehydrated phases

Imbibition of lithium sulphate into aluminium hydroxide is known to result in a sulphate-intercalated layered double hydroxide (LDH) of Li and Al. The perchlorate ion has the same size and molecular symmetry as the sulphate ion,but only half its charge. Consequently, twice the number of ClO$^−_4$ ions is needed to balance LDHs the charge on the metal hydroxide layer, compared to the SO$^{2−}_4$ ions. In this work, the ClO$^−_4$-intercalated LDHs were obtained from both the bayerite and gibbsite precursors. Inclusion of the hydration sphere along with the ClO$^−_4$ anion, induced turbostratic disorder in the stacking of the metal hydroxide layers. Temperature-induced dehydration ($T \sim 100$–140$^{\circ}$C) brought about a partial ordering in the interlayer region and the ClO$^−_4$ ion oriented itself with one of its $C_2$-axes parallel to the metal hydroxide layer. The close packing of ClO$^−_4$ ions could be realized by the complete dehydration of LDH and the distribution of the ClO$^−_4$ ions in all the available interlayer sites. In contrast, within the crystal of the sulphate analogue, the sulphate ions occupy only half the number of interlayer sites. The other half is occupied by the residual water molecules, as the sulphate analogue does not fully dehydrate even at elevated temperatures. This difference in the behaviour of the two LDHs has its origin in the largedifference in the hydration enthalpies of the two anions.

• Natural dyes in hybrid chalcogenide multi-layer thin films

New highly photoconductive hybrid multi-layer semiconductors have been developed, comprising cathodically electrodeposited CdSe or Zn$_x$Cd$_{1−x}$Se thin films and natural photosynthetic pigments, isolated from spinach. A layer of the organic dye, Chlorophyll α or Carotenes, is either deposited by spin coating technique over an inorganic thin film (two-layer structures) or ‘sandwiched’ between two inorganic semiconductive films (three-layer structures). X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, diffused reflectance spectroscopy and photoelectrochemical studies are employed, in order to fully characterize the received products. In the case of the three-layer hybrids, a significantly enhanced photo-response is observed, leading up to 300% improved photoelectrochemical efficiency values, compared to that of the pure inorganic films. This amelioration, stemming from the synergetic action of hybrids’ components, is more prominent in the case of Zn$_x$Cd$_{1−x}$Se systems, where a significant amount of Cd has been substituted by Zn: therefore, Znare considered environmentally friendlier alternatives to pure CdSe-based semiconductors.

• Metal–insulator transition and small-to-large polaron crossover in La$_2$NiO$_{4+\delta}$/BaTiO$_3$ composites

Structure and electrical resistivity of $(1 − x)$La$_2$NiO$_{4+\delta}$/$x$BaTiO$_3$ composites ($x = 0.05$, 0.1, 0.2, 0.3, 0.5) produced by combining the sol–gel and ceramic sintering methods have been investigated. Among the samples sintered at temperature 1300$^{\circ}$C for 16 h, the metal–insulator transition (MIT) temperature of $x = 0.1$ sample, which is $T_{\rm MI} = 700$ K, is lower than the MIT temperature (800 K) of the pristine La$_2$NiO$_{4+\delta}$ (LNO) perovskite. Reduction of resistivity of $x \leq 0.3$ composite is mainly due to decrease of the scattering of electrical carriers by composite large grain boundaries and the structural change of the LNO component. The temperature dependence of the resistivity of $(1 − x)$La$_2$NiO$_{4+\delta}$/$x$BaTiO$_3$ composites is well-explained by a two conducting component model consisting of small polarons (SP) and large polarons (LP). A crossover between SP and LP with increasing temperature is described by the probability volume fraction function $f$ for SP and $1 − f$ for LP, which are equal to $1/2$ at transition temperature $T_{\rm MI}$. The observed lowest resistivity $\rho =11$ m$\Omega$ cm for $x = 0.1$ sample corresponds to the lowest SP thermal activation energy $E_{\rm a}$, the contributions of residual and phonon resistivities at $T_{\rm MI}$. The MIT of these composites satisfies approximately the Mott criterion.

• A first-principles investigation on electronic, optical and thermoelectric properties of La$_2$Pd$_2$O$_5$ compound

A number of ternary-semiconductor oxides have shown promise for potential applications in catalysis, thermoelectricity, optoelectronics and electrochemistry. In this work, the thermoelectric and optoelectronic properties of La$_2$Pd$_2$O$_5$ compound are studied by the full-potential linearized augmented plane wave method based on density functional theory. The electronic band structure shows an indirect band gap of 1.342 eV for La$_2$Pd$_2$O$_5$. Partial and total density of states indicate strong hybridization among different electronic orbitals. The upper part of the valence band is dominated by the Pd-d and O-p states, while the lower conduction band originates mainly from the Pd-d state. Dielectric functions including the imaginary and real parts, along with other optical constants, such as absorption coefficient, energy loss function, reflectivity and refractive index, have been reported for the first time. Thermoelectric properties, including electrical and thermal conductivity, Seebeck coefficient and power factor with variation in temperature are also presented and discussed using semi-classical Boltzmann transport theory for the first time for La$_2$Pd$_2$O$_5$. It has been found that La$_2$Pd$_2$O$_5$ has attractive optoelectronic and thermal properties that can make it a suitable candidate for efficient thermoelectric and optoelectronic device applications.

• C$_3$N$_4$ supported on chitosan for simple and easy recovery of visible light active efficient photocatalysts

To investigate the photocatalytic activities of heterogeneous systems under visible light, graphitic carbon nitride (g-C$_3$N$_4$) and chitosan (CS) were chosen as a model system. By solution cast method, C$_3$N$_4$ were embedded into a CS biopolymer matrix in this study. The purpose is to degrade methyl orange (MO) using a novel C$_3$N$_4$/CS nanocomposite thin film. Using a visible light-equipped photoreactor with a tungsten incandescent lamp, photo-decolourization of dye was carried out. To catalyse the photodegradation of organic dye pollutant MO, a C$_3$N$_4$/CS nanocomposite film photocatalyst was found to be successful and a recovery of 100% of the photocatalyst is achieved by a simple new hand-picking technique.Usingscanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy and UV–visible diffuse reflectance spectroscopy, detailed characterization was carried out. C$_3$N$_4$/CS has high capacity and better photocatalytic activity compared to g-C$_3$N$_4$ and CS, because C$_3$N$_4$ possesses a larger surface area and CS has highabsorption efficiency which is indicated by the photocatalytic discolouration of MO under visible light irradiation. The C$_3$N$_4$/CS nanocomposite thin film photocatalyst is regarded as an excellent catalyst with 98% degradation efficiency and is prepared by the simple solution cast method. The total organic carbon value was measured to be 86%. These values evidencethat the mineralization of MO was carried out under these conditions.

• Fabrication of crystalline Sb$_2$S$_3$ sheaf structure composed of nanorods by a hot-injection method

Herein,we demonstrate a hot-injection method towards the fabrication of Sb$_2$S$_3$. The evolution from amorphous Sb$_2$S$_3$ nanoparticles to a sheaf of Sb$_2$S$_3$ nanorods cross-linked together occurring with the increase of reaction temperature and time is studied. The structural, compositional and morphological features of Sb$_2$S$_3$ products indicate the formation of crystalline Sb$_2$S$_3$ with orthorhombic phase and high purity. As the reaction proceeds, it can be observed that the individual nanorod grows along the elongated direction ($c$-axis), and it is noteworthy that its round cross-section could develop into the rectangular cross-section subsequently. In this study we also propose a possible formation mechanism for the growthprocess of Sb$_2$S$_3$, and it reveals that the present hot-injection could provide an ideal growth environment for synthesizing the nanostructured materials by optimizing the experimental parameters.

• Mechanical and biological properties of polycaprolactone/fibrin nanocomposite adhesive produced by electrospinning method

Biopolymer nanocomposites exhibit an important role in regulating cell function in tissue engineering applications. Rapid degradation and good biological activities of these nanocomposites make them suitable for use in orthopaedic and medical applications. In this study, a polycaprolactone (PCL) scaffold and fibrin gluewere used as a matrix and reinforcement,respectively. PCL/fibrin nanocomposites with different aspect ratios were synthesized and used as a bioactive adhesive. The tensile strength of PCL/fibrin was measured using a tensile machine-equipped polymer load cell. Microstructural analysis of PCL and PCL/fibrin nanocomposites was investigated by field emission scanning electron microscopy.Microstructure results showed suitable porosity with proper distribution and size in the PCL–fibrin nanocomposites with a 1/10 aspect ratio. The results of wettability showed that fibrin as reinforcement in PCL decreased the contact angle and improved hydrophilic properties. The adhesion properties of PCL and PCL/fibrin scaffolds were determined by the 4$^{\prime}$,6-diamidino-2-phenylindoletest. Mesenchymal stem cells were cultured on the PCL and PCL/fibrin scaffolds. The results showed more and better adhesion of cells on the PCL/fibrin adhesive. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test was performed on the scaffolds to determine cell viability and biocompatibility. The statistical results confirmed that the cell growth is higher on the PCL/fibrin after 4 days.

• Influence of incorporation of carbon on the transparent conducting properties of CdO thin films

Thin films of CdO incorporated with different amounts of carbon element have been deposited on glass substrates by using the vacuum thermal evaporation method aiming at improving their transparent conducting (TC) properties. Thestructural and opto-electrical properties of the host CdO films were systematically studied. X-ray diffraction and optical investigations confirmed the inclusion of C species in the CdO lattice. The obtained results were explained through theoccupation of interstitial positions and structural vacancies of the host CdO lattice by C species. It was observed that the inclusion of carbon into the CdO lattice blue-shifted the optical band gap by $\sim$5−7%, which was attributed to the Moss–Burstein (B–M) effect. The electrical studies showed that the carrier mobility increased steadily with the increase in the C% inclusion level, so that with 5 wt% it attained $\sim$7.5 times the carrier mobility in un-doped CdO. Therefore, the present study showed that the prepared host CdO–C films have controllable TC degenerate semiconducting properties, which could berequired in different optoelectronic applications.

• Chemical vapour deposited graphene: substrate pre-treatment, growth and demonstration as a simple graphene-based SERS substrate

In chemical vapour deposition (CVD) of graphene, surface roughness and purity of the copper substrate are very crucial for obtaining uniform films. Even though electrochemical polishing is an effective technique for obtaininghomogeneous graphene films, most of the experiments adopt complex experimental parameters like electrolyte heating, stirring and use of additives for better results. These are not applicable to thin copper foils used in CVD of graphene. In the present study, a simple electrochemical procedure is developed for deposition of high-quality graphene films with good coverage. The depositions of graphene films on bare and polished copper foils for the same growth conditions are analysed using various microscopic techniques. The uniformly grown graphene on copper is then directly employed as a surface-enhanced Raman scattering (SERS) substrate along with plasmonic silver nanoparticles. A simple SERS substrate having a reasonable detection limit of 10$^{−10}$ M for R6G is achieved with uniform SERS signals over a large area. Thehomogeneity of SERS substrate can be attributed to the uniformity of the deposited graphene film. A simple and efficient SERS substrate using conventional methods is achieved through the incorporation of chemical vapour deposited graphene. The study covers the growth of CVD graphene film starting from substrate pre-treatment, various analyses of the film andfinally the application in SERS.

• Shear thickening fluid based on silica with neodymium oxide nanoparticles

The rheological performance of shear thickening fluid (STF) based on silica with neodymium oxide nanoparticles (Nd$_2$O$_3$/SiO$_2$-STF) was investigated in this study. Nd$_2$O$_3$/SiO$_2$-STF suspensions of varied concentrations (9–15 wt%) were prepared using an ultrasonic oscillator. The presence of Nd$_2$O$_3$ particle and its interaction with silica nanoparticlesin the Nd$_2$O$_3$/SiO$_2$-STF were analysed using scanning electron microscopy, X-ray diffractometry and energy dispersive spectroscopy. Nd$_2$O$_3$/SiO$_2$ interaction demonstrated that silica nanoparticle could be completely attached on the needle branches of the Nd$_2$O$_3$ particles, and formed a considerable clustering effect. The steady rheological testing results indicated that an appropriate amount of Nd$_2$O$_3$ particle resulted in a marked increase in the peak viscosity from 51.95 (SiO$_2$-STF) to218.94 Pa.s (Nd$_2$O$_3$/SiO$_2$-STF), and a concomitant decrease in the critical shear rate from 199.65 (SiO$_2$-STF) to 50.18 s$^{−1}$ (Nd$_2$O$_3$/SiO$_2$-STF). Moreover, although the peak viscosity declined with the rise in temperature, shear thickening was remarkable compared to those of SiO$_2$-STF and became highly remarkable with Nd$_2$O$_3$ particle mass fraction increase.

• Development of nanocrystalline multilayer Ni–Fe alloy coatings: characterization and its corrosion behaviour at elevated temperature

The present work deals with the galvanostatic fabrication of Ni–Fe nanostructured composition-modulated multilayer alloy (CMMA) coatings on steel panel from the newly optimized acid-sulphate bath solution. The recurringcathode current density combination (RCCC) and the number of layers have been optimized for enhanced performance of the coatings against corrosion. Corrosion behaviour of the nanostructured multilayered coatings was evaluated by Tafel extrapolation and electrochemical impedance spectroscopy (EIS) methods in 3.5% NaCl solution. Under optimal conditions, the CMMA coatings developed were more corrosion-resistant than the monolithic alloy coatings obtained from the same bath. Least corrosion rate (CR) was witnessed at 300 layers, above which saturation of corrosion resistance at a high temperature was found, which is attributed to a shorter relaxation time for redistribution of metal ions during multilayer deposition. Hardness and roughness of the coatings were evaluated using Vickers hardness test and atomic force microscope,respectively. Phase structure of the coatings was discussed using X-ray diffraction technique. The cross-sectional view of the coatings was characterized by scanning electron microscope. CR analysis and the surface morphology of the optimized coatings exposed to high temperature revealed the better performance of CMMA coatings at the elevated temperatures compared to the monolithic coatings.

• Development of polymer-based superhydrophobic coating on cloth

Facile, one-step fabrication of durable, superhydrophobic (water contact angle $\sim$154$^{\circ}$) fluorine-free polymer coating on cotton cloth is presented. The microstructure of the coating is evaluated with electron microscopy and X-ray diffraction study. The detailed analysis reflects that the superhydrophobicity is rendered by intrinsic hydrophobic nature of thenon-polar polymer, isotactic polypropylene. The chemical and mechanical stability of the coating on cloth is evaluated and it shows that the coating is extremely resilient in nature without almost negligible sacrifice in water contact angle. Because of simplicity of fabrication technique and quality of coating, this study is expected to be worthy enough for commodity as well as high technology applications.

• Effect of processing route on the properties of LSCF-based composite cathode for IT-SOFC

A novel processing technique was developed to produce an in-situ nano-composite powder based on La$_{0.6}$Sr$_{0.4}$Co$_{0.2}$Fe$_{0.8}$O$_{3-\delta}$ (LSCF6428) and Gd$_{0.1}$Ce$_{0.9}$O$_{1.95}$ (GDC10) for application as cathode material in intermediate temperature solid oxide fuel cells (IT-SOFC). The nano-composite powder was produced using glycine-nitrate solution combustion technique starting from nitrates of six metal ions. The synthesized powder was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), particle size and BET surface area analyses. XRD analysis of as-produced nano-composite powder confirmed the formation of desired phases right after combustion synthesis. The structural parameters of different phases present in the powders were estimated through Rietveld refinement of XRD data. Tocompare the electrical properties of nano-composite cathode powder produced through the present method, nano-powders of GDC10 and LSCF6428 were individually produced through glycine nitrate process and subsequently mixed through solidstate technique and characterized for functional properties. Using this in-situ nano-composite material, lower polarization resistance was achieved as compared to the LSCF–GDC composite produced from mechanical mixtures of nano-powders of GDC10 and LSCF6428 when used as cathode in GDC10 electrolyte-based symmetrical cell. The effects of cathode layer thickness and electrode firing temperature on the cathodic polarization resistance were studied using in-situ nano-composite cathode powder.

• Insight view of mechanical, electronic and thermodynamic properties of the novel intermetallic REPt$_4$In$_4$ (RE $=$ Eu, Gd, Tb, Dy, Ho) compounds via ab initio calculations

In this study, the full potential linearized augmented plane wave method with the GGA approximation was employed to study the structural, elastic, electronic and thermal properties of the novel intermetallic REPt$_4$In$_4$ (RE$=$Eu,Gd, Tb, Dy, Ho) compounds. Our findings demonstrate that the equilibrium lattice parameters are in good agreement with the available experimental measurements. The elastic constants ($C_{\rm ij}$) were also calculated to understand the mechanical properties and structural stability of the compounds. Furthermore, the density of states and the charge density distributionsof the compounds were calculated to understand the nature of the bonding in the material. Our analysis of the calculated values of the Poisson’s ratio and the $B/G$ ratio shows their ductile structure. Additionally, the temperature-dependent thermodynamic parameters are computed by the quasi-harmonic Debye model in the range of 0–600 K, where the primitive cell volume and thermal expansion coefficients have been obtained successfully. Consequently, this study on the structural, elastic, bonding and thermal properties of REPt$_4$In$_4$ intermetallic compounds demonstrate that these compounds can be used as potential candidates in the domain of energy storage and electronic devices.

• A DFT investigation of performance of metal-doped nanotubes as acceptable catalysts to SiO oxidation

The Fe-doped nanotubes can be considered as novel catalysts to SiO oxidation. The information of SiO oxidation on nano-catalysts is not clear. In this study, the SiO oxidation on Fe-carbon nanotube (CNT) and Fe-boron nitride nanotube (BNNT) is examined through Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) paths. The SiO joins in the Fe atom of Fe-surface-O_2^* and Fe-surface-O^* to create important structures with minor barrier energy. Cis-Fe-surface-OSiOO^* in the ER is more stable than structures in LH pathway. In the LH and ER mechanisms the one and two SiO_2 are released at normal temperature, respectively. The abilities of Fe-CNT and Fe-BNNT to oxidation of SiO is investigated, and Fe-CNT and Fe-BNNT as novel metal-doped catalysts are proposed. • Characterization and application of cured epoxy resin reinforced with montmorillonite Epoxy/nanoclay composites based on diglycidyl ether of bisphenol-A was cured by isophoronediamine and different weight percents of organically modified montmorillonite (O-MMT) clay (3, 5 and 7 wt%). Epoxy/nanoclay compositeswere characterized by different techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. The compressive strength of the epoxy/nanoclay composite with a 3 wt% of O-MMT was higher than that of pure epoxy and other composites. Thermogravimetric analysis showed no change in the thermal behaviour of the cured epoxy after incorporation of O-MMT • Development of hydroxyl and carboxylic acid functionalized CNTs–polysulphone nanocomposite fouling-resistant ultrafiltration membranes for oil–water separation Fouling-resistant composite ultrafiltration (UF) membranes of hydroxyl functionalized multi-walled carbon nanotubes (MCNTs) ({}_{\rm OH}CNT)/polysulphone (PSF)/polyvinylpyrrolidone (PVP) and carboxylic acid functionalized MCNTs ({}_{\rm COOH}CNT)/PSF/PVP in weight ratios of 0.7/86.1/13.2 and 1.3/85.5/13.2 were prepared by phase inversion process from dimethylformamide solution. These membranes were characterized by infrared, scanning electron microscopy, atomic force microscopy, differential scanning calorimetry and water contact angle measurements. The molecular weight cut off values of these membranes were measured by permeating aqueous solutions of different molecular weight PEGs and dextrans. Among the fabricated UF membranes, {}_{\rm COOH}C_{1.3}PS_{85.5}PV_{13.2} composite membrane showed a lower average contact angle (62^{\circ}). The{}_{\rm COOH}C_{0.7}PS_{86.1}PV_{13.2} membrane exhibited higher flux (99 l m^{−2} h^{−1}) than all the fabricated membranes (62–78 l m^{−2} h^{−1}) at 2 bar pressure. The flux recovery ratio values for bovine serum albumin feed solution were in the range of 63–72% for{}_{\rm COOH}CNTs containing membranes and 53–64% for {}_{\rm OH}CNTs membranes, whereas PSF/PVP blend membrane exhibited45% at 2 bar applied pressure. The membranes containing 0.7 and 1.3 wt% carboxylic acid functionalized MCNTs showed 100% oil rejection when tested with an oil–water emulsion containing 1000 ppm lube oil. Conversely, membranes containing hydroxyl functionalized MCNTs showed relatively lower oil rejection (86–90%), whereas the PSF/PVP membrane showed 86% oil rejection. • Composite materials for printed electronics in Internet of Things applications Printed electronics belongs to one of the most prominent electronics technologies allowing us to manufacture electronic components and devices on different kinds of substrate materials. This manufacturing technology reveals to have significant potential to be used in Internet of Things (IoT) applications. In this paper, composite materials which are suitable for the production of a variety of IoT devices are discussed. Particular attention was focused on metal- and carbon-based composite materials allowing us to form conductive parts of the IoT devices produced. Further, sensor and encapsulation materials were reviewed as well. These conductive and sensor materials comprised of micro- and nano-particles, such as silver, copper, graphene oxide and its reduced forms, carbon nanotubes, carbon black or graphene nanoplatelets. Based on the conducted analysis, it was stated that further investigations of curing methods, fillers materials and composition of composites are recommended to be carried out in order to study mechanical, thermal and electrical properties of compositematerials required for IoT applications. • Resistive switching behaviour of amorphous silicon carbide thin films fabricated by a single composite magnetron sputter deposition method Amorphous silicon carbide (a-SiC) films of thickness 50–300 nm are deposited by a single composite target magnetron sputtering process. Metal–SiC–metal structures are fabricated to demonstrate resistive switching. The top metal electrode is Cu, Pt or Ag and the bottom electrode is fixed as Au. Reversible resistive switching from high to low resistance states is observed for SiC films at voltages between 1 and 5 V. The interface between metal electrode and a-SiC films plays a significant role in achieving optimal switching performance. Resistance OFF/ON ratios of 10^8, retention times >10^4 s and endurance of 50 cycles are achieved in the best devices. Cross-sectional scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy are employed to understand the mechanism of device operation. Raman spectroscopy indicates the formation of nanocrystalline graphite in these devices after a few cycles of operation. • Electronic, optical and magnetic properties of low concentration Ni-doped CdSe by first principle method The electronic, magnetic and optical properties of Ni-doped CdSe diluted magnetic semiconductors have been explored by density functional theory-based FPLAPW method as incorporated in the Wien2k code. The band structure anddensity of states analysis for up spin channel and down spin channel illustrate half-metallic ferromagnetic behaviour. The calculated values of the band gap in an insulating channel (down spin channel) increases from 0.4 to 0.8 eV with increasing the doping concentration of Ni from 6.25 to 25%. The magnetic moment of Ni decreases and magnetic moment on nonmagnetic side increases, which shows the strong pd-hybridization. Furthermore, the optical properties are characterized in terms of dielectric constants, refractive index, extinction coefficient, absorption coefficient and optical loss factor. The static valuesof the dielectric constant and refractive index are consistent with each other. • Electroanalytical characteristic of a novel biosensor designed with graphene–polymer-based quaternary and mesoporous nanomaterials Here, we propose the novel fabrication of graphene–polymer (GP)-based quaternary nanocomposite and mesoporous (MS) nanomaterials sensor [NaLa(MoO_4)_2-GO-PPy (NLMG-PPy), CuZnSnSe-GO-PPy (CZSG-PPy) and In_2O_3-G-SiO_2 20% (IGS20)] to address ignored challenges for Escherichia coli bacteria recognition in polluted samples.Synthesized samples were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), energydispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, nitrogen adsorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). The sensor could recognize an individual E. coli cell in 1\mul sample volume within 50 s. Through a low identification point of an individual cell, the MS and GP sensor had an absolute scope of 1–100 CFU per μl volume of sample (i.e. 103–105 CFU ml^{−1}). The high thickness of negative charge on the surface of E. coli cells actively regulates the concentration of dominant part charge carriers in the mesoporous and G-polymer monolayer, permitting an ongoing check of E. coli concentration in a known sample. Our biosensor is simple and low-cost with great selectivity and fast identification was effectively shown for E. coli detection. • Effect of transition metal doping on Cr–Ru alloys using first principles approach Ab-initio density functional theory calculations have been used to explore the effect of transition metal alloying on A15 Cr–Ru intermetallic alloys.We study the structural, electronic and mechanical properties of Ru3Cr and Cr_3Ru alloys doped with transition metals (M = Mn,Mo, Pt, Pd, Fe, Co, Re and Zr). Their thermodynamic and mechanical behaviours were deduced from the heat of formation, ratio of bulk to shear modulus, density of states (DOS) as well as elastic constants predictions.We find that Mn doping in these alloys leads to thermodynamic stability. These compounds also show a valence–conduction band overlap around the Fermi energy as depicted by the DOS. Furthermore, the Pugh ratio (the ratio of bulk to shear modulus) indicates the ductility character of these compounds. Their mechanical stability was illustrated by the Bohr mechanical stability criteria with all the elastic constants having a value >0. These results demonstrate that these systems can potentially be used as coating materials in high temperature structural applications. • DNA-assisted synthesis of nanoceria, its size dependent structural and optical properties for optoelectronic applications Cerium oxide (CeO_{2−x}) nanoparticles or nanoceria were synthesized by the chemical co-precipitation method using cerium nitrate hexahydrate and ammonium carbonate as starting materials and deoxyribonucleic acid (DNA) as acapping agent. The structural and optical characterization of the prepared nanoparticles was studied in depth by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy, Raman spectroscopy, UV–visible absorption and diffuse reflectance spectroscopy. The average crystallite size and latticeparameters of the cerium oxide nanoparticles at different calcination temperatures were studied using XRD analysis. The average crystallite size was found to be 6 nm and the size increases with calcination temperature. The polycrystalline nature and the size of the particles obtained are in close agreement with HRTEM and Raman analysis. The optical band gaps ofall samples were measured by Tauc plot which showed a blue shift with a decrease in size due to the quantum confinement effect. The optical absorption spectrum of the synthesized nanoparticles showed the absorption of UVA, UVB and UVC light, and the variation in structural and optical properties with size makes them suitable for the optoelectronic application. To the best of our knowledge, this is the first report on using DNA in the synthesis of nanostructured ceria. • Deposition and distribution of gold nanoparticles in a coffee-stain ring on the HOPG terraces Cetyltrimethylammonium bromide (CTAB)-stabilized low-aspect ratio gold nanorods have been synthesized using seed-mediated wet chemical approach. Freshly cleaved highly oriented pyrolytic graphite (HOPG) surface is used as asubstrate for the deposition of nanoparticles via the droplet drying technique. Owing to the presence of CTAB molecules in suspension, nanoparticles on the non-wetting HOPG surface get deposited in the form of a coffee-stain ring. Such deposits at various positions of the coffee-stain ring have been characterized by scanning helium ion microscopy (HIM) and atomic force microscopy (AFM). Besides the assembly of nanoparticles, AFM is specially employed to investigate the deposition of CTAB molecules. The deposition and distribution of nanoparticles are studied and quantified at various positions of thecoffee-stain ring. On flat HOPG terraces, HIM shows merely the deposits of the gold nanostructures whereas AFM reveals both nanoparticles and CTAB deposits over the surface. This research study primarily focused on the nanoparticle deposits within the coffee-stain ring formed over the non-wetting HOPG terraces. • Structural, optical, electrical and catalytic properties of precursor solution-aged spray deposited undoped, Zn-doped and Ag-doped CdO thin films Photocatalytic performance of precursor solution-aged undoped, Zn-doped CdO (CdO:Zn) and Ag-doped CdO (CdO:Ag) thin films has been reported in this paper. Perfume atomizer is adopted to deposit the films. CdO, CdO:Zn andCdO:Ag thin films exhibit cubic crystal structure. The crystallite size values were 34, 31 and 27 nm, respectively, for the CdO, CdO:Zn and CdO:Ag thin films. In the EDX spectra of the CdO:Zn and CdO:Ag thin films, Zn and Ag were observedalong with Cd and O. The CdO:Zn and CdO:Ag thin films exhibit increased transparency and widened band gap values. PL spectra showed peaks related to oxygen vacancies for all the films. Reduced resistivity was evinced for the CdO:Zn and CdO:Ag thin films. The degradation efficiencies of the CdO, CdO:Zn and CdO:Ag thin films against methyl orange after 75 min light exposure were 76.4, 84.3 and 90.4%, respectively. The CdO:Zn and CdO:Ag catalysts exhibit satisfactory stability with better reusable nature and are suitable for the effective treatment of organic toxic dyes. • Electromagnetic simulations of polarization-insensitive and wide-angle multiband metamaterial absorber by incorporating double asterisk resonator A novel multiband metamaterial absorber (MTMA) is proposed which is capable of well presenting a polarization-insensitive and wide incident angle stability in the microwave frequency range. The proposed MTMA comprisingtwo vertically stacked asterisk-based copper resonators separated by dielectric layer of flame retardant type four and backed with a thin copper film. High-frequency structure simulator was used to simulate the absorber and to depict surface current distribution. The results showed that the absorber is operated at three narrow bands with high absorptivity of about 92, 100 and 100% at frequencies of 2.75, 4.3 and 9.5 GHz, respectively. The position of the resonant peaks can be effectively tuned by adjusting the geometry parameters of the structure, thereby achieving a multiband, polarization-independent andwide-angle absorber. The designed structure is important for the application of sensors, thermal images and in constructing broad multiband signals for electromagnetic compatibility/interference. • Investigation of the effect of MAI and PbI_2 concentrations on the properties of perovskite solar cells Here, the effect of perovskites layer quality on the performance of compact-TiO_2/mesoporous-TiO_2/CH_3NH_3PbI_3/carbon solar cells was investigated. Different perovskite layers were prepared by varying concentrationsof PbI_2 and CH_3NH_3I, while reaction temperature and dipping time were fixed. The range of concentrations for PbI_2 and methylammonium iodide (MAI) were 1–1.4 M and 6–10 mg ml^{−1}, respectively. Fabricated perovskite layers were first coated by carbon electrodes (5-layer) and then, the champion one was coated by Spiro-OMeTAD (as a hole transport material) andAu-evaporated layer as a cathode (6-layer). Fabricated films were fully characterized by field emission scanning electron microscopy, X-ray diffraction analysis, UV–Vis spectroscopy and photoluminescence spectrum. Photovoltaic properties were measured under AM 1.5. Output currents of 5-layer cells were in the range of 228–476 \muA, of which the highest one was obtained by using 1.2M PbI_2 and 8 mg ml^{−1} MAI. Ultimately, the maximum power conversion efficiency of 9.1% was obtained with 6-layer cell. • Morphological features, dielectric and thermal properties of epoxy–copper cobaltite nanocomposites: preparation and characterization Epoxy (LY-556/HY-951) system was cured at ambient temperature and its copper cobaltite nanocomposites with different percentage loadings of nanoparticles were prepared via powered shear mixing with HY-951 (triethylene-tetraamine, TETA) hardener. Characterizations of the nanocomposites were done by various methods like XRD, TEM, FTIR, TGA, DSC, SEM, VNA, DETA and XPS. XRD, XPS and TEM showed the successful preparation of copper cobaltitenanoparticles. Further, FTIR studies confirmed accomplishment of curing and consequently the formation of cross-linked network in the nanocomposites. The morphological analysis revealed that the nanoparticles of the copper cobaltite were uniformly distributed inside the epoxy matrix to 5% loading. The enhancement in impact properties of nanocomposites with increase in filler content was supported by fractured surface studies for even distribution of copper cobaltite nanoparticles. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses showed enhancement in thermalstability as well as positive shift in the glass transition temperature for epoxy with copper cobaltite filler in comparison to neat epoxy resin. The positive shift in the glass transition temperature of the nanocomposites indicated improved interaction between copper cobaltite and epoxy matrix. These nanocomposites were also evaluated for their electromagnetic properties using dielectric thermal analyzer (DETA) and vector network analyzer (VNA) for determination of their permittivity and permeability, respectively. The improved thermal, mechanical and electromagnetic properties of epoxy–copper cobaltite nanocomposites make them potential candidates for microwave applications in a wide range of areas. • Novel 1:1 stoichiometric rare-earth HoX (X = Pd, Ag and Cd) intermetallic compounds: DFT-based study A systematic investigation on structural, electronic, elastic, mechanical and optical properties of novel 1:1 stoichiometric rare-earth HoX (X = Pd, Ag and Cd) intermetallic compounds has been made via ab-initio density functional theory-based linearized augmented plane wave method as coded in wien2k. An outline of local density approximation andgeneralized gradient approximation have been employed. Structural optimization established the stable CsCl-type cubic structure of HoX (X = Pd, Ag and Cd) compounds. The determined crystal structure stability, compressibility and fracture strength of compounds are enhanced with X in the order HoPd > HoAg > HoCd. The interlacing electron dispersion curves at Fermi-level in band structure and density of states substantiate the metallic nature of compounds. The splitting gap between the lower and upper valence bands monotonously becomes narrower with the substitution of heavier core-element(Pd \to Ag \to Cd). The mechanical constants i.e., bulk modulus (B), Young’s modulus (E), shear modulus (G_H), Pugh’s ratio (B/G_H), Poisson’s ratio (v) and anisotropic factor (A) have been calculated to corroborate the mechanical properties of compounds. The cationic nature of Ho-atoms and anionic nature of X-atoms has been evaluated through the effective charge (Q^∗) computations. The observed peaks in the low energy region of optical conductivity spectra attribute the intra-band, while the high energy structures are associated with inter-band transitions in HoX (X = Pd, Ag and Cd) compounds. The bond order calculations demonstrate the highest strength of HoCd compound among the herein studied compounds. • De-stabilization of charge-order state through in-homogeneity in random ionic distribution in the particles of polycrystalline Eu_{0.2}La_{0.3}Sr_{0.2}Ca_{0.3}MnO_3 sample In this study the perovskite manganite Eu_{0.2}La_{0.3}Sr_{0.2}Ca_{0.3}MnO_{3} batch integrated sample is studied, with special modification done to introduce localized structural strain without micro-level (grains) modification. This consequence successfully generates opposite nature of high orthorhombic strain along b-axis in these samples, although the general structure is same for both with Pnma space group. The sharp magnetic transitions (both Curie temperature and charge-ordertransition) are reported to be mixed in presence of random ionic distribution in its structure. The diffused insulator-metal behaviour, de-stabilization of magnetic state and phase transitions associated with inherent anisotropic strain is discussed and is explained based on chemical disorder-induced structural strain in the present system. • Magnetotactic curcumin iButtonbots as efficient bactericidal agents The microbial contamination of drinking water is one of the most major concerns of community health in the developing world. Numerous water-borne pathogens are rapidly evolving and becoming resistant to traditional antibiotics.To get an efficacious bactericidal response, an assembly of several antibiotics or increased dosage are being administered, which may produce adverse side effects after prolonged use. Here, we describe a proficient method for disinfecting waterborne coliform bacterial strains of Escherichia coli DH5\alpha from contaminated water samples using magnetic microbotsdecorated with curcumin (CU) conjugates. These magnetic microbots, namely, iButtonbots were composed of soft Agaricus bisporus (button mushroom) microcapsules with inherit antimicrobial properties. The locomotives were coated with magnetite nanoparticles for their remote guidance towards cells and collection along with CU for more enhanced bactericidal response. CU, a major active constituent of the Indian dietary spice turmeric and edible button mushrooms are known to exhibit antimicrobial activity against a wide range of bacterial species. The synergic antibacterial effect of CU and mushroomconstituents, imparts a profound bactericidal property to these magnetic microbots.We have demonstrated that microbots are capable of efficiently killing majority of bacterial cells in contaminated water samples. After extermination of bacteria, magnetic properties of embedded magnetite nanoparticles in porous mushroom matrix, allows collection of microbots from water samples. The presented biocompatible microbots offer an innovative method for rapid decontamination of bacteria-laden drinking water samples. • Electrochemical sensor based on Na^+-doped g-C_3N_4 for detection of phenol In this work, a novel and enhanced electrochemical sensor based on Na^+-doped g-C_3N_4 was constructed for the detection of phenol. First, the g-C_3N_4 was formed through polymerizing melamine under 520^{\circ}C. And then the Na^+-doped g-C_3N_4 was fabricated by a simple wet chemical method. The electrochemical sensor was constructed by modifying the carbon paper with the resulting Na^+-doped g-C_3N_4. The morphology, chemical compositions and structure of Na^+-dopedg-C_3N_4 were characterized by scanning electron microscopy, transmission electronic microscopy, energy-dispersive X-ray detector and X-ray diffraction. The Na^+-doped g-C_3N_4 electrode was used for the cyclic voltammetry and amperometric response detection of phenol in a 0.1 M phosphate buffer (pH 9.0). Under the optimal conditions, the prepared sensordisplayed good performance for the electrochemical detection of phenol with a wide linear range of 1–110 \muM, as well as low detection limit of 0.23 \muM. • Investigation of physicochemical and electrical properties of TiO_2 nanotubes/graphene oxide nanocomposite Graphene oxide (GO)-based nanocomposites have received a great attention due to their emerging applications. Here, we thoroughly examined the structural, electronic and surface properties of GO/TiO_2 nanotubes nanocomposite. The nanocomposite is prepared by simple impregnation of TiO_2 nanotubes (HNT400) with GO dispersion. GO is elaborated byan improved Hummer’s method, while HNT400 is obtained using alkaline hydrothermal treatment of TiO_2 P25, followed by calcination at 400^{\circ}C. XRD and Raman analyses show that GO nanosheets do not change the structural properties of TiO_2 nanotubes. TEM analysis confirms the formation of GO nanosheets assembled to TiO_2 nanotubes. XPS and EPR results confirm the electron transfer between GO and TiO_2 nanotubes. PL analysis reveals that GO inhibits the recombination of photogenerated electron–hole pairs in the nanocomposite. The ac conductivity measurements suggest the presence of grain and grain boundary effects in GO/HNT400. • Wear and corrosion resistance of titanium carbo-nitride coated Al-7075 produced through PVD Titanium carbo-nitride coatings were deposited using plasma-assisted physical vapour deposition technique on Al-7075 aluminium alloy plates. Studies were conducted to understand the bonding between the coating and substrate, and to examine the wear- and corrosion-resistant properties under heat treatments. The nature of bonding was characterized using scanning electron microscope. The pin-on-disc wear test, according to G99 ASTM standard, displayed the frictional force, coefficient of friction and wear for the samples. Simultaneously, the corrosion tests, according to G5-14 ASTM standard,performed for a period of 48 h, using electrochemical impedance and potentiodynamic polarization tests displayed the Nyquist and Tafel plots for analysis. The wear and corrosion rates of samples heat-treated at 500^{\circ}C for 1 h were found tobe 0.066e-6 g s^{−1} and 2.962e2 g mm^{−2} s^{−1}, respectively. While that of samples heat-treated at 500^{\circ}C for 12 h were found to be 0.366e-6 g s^{−1} and 4.177e2 g mm^{−2} s^{−1}. Both the wear and the corrosion performance investigations were in goodagreement with each other. Thus, the tribo-corrosive deterioration of titanium carbo-nitride coated Al-7075 had escalated with an increase in durations of the heat treatment. • Heavy metal removal by N-acetylcysteine-functionalized cryogels In the present work, N-acetylcysteine attached poly(acrylamide-co-methyl methacrylate) [poly(AAm-MMA)] cryogels were synthesized and used for removal of heavy metal ions (Zn(II), Cd(II) and Pb(II)). For this, poly(AAm-MMA)cryogels were synthesized by free radical cryopolymerization technique and then, modified by N-acetylcysteine. Synthesized cryogel was characterized by FTIR, SEM and EDX analyses. Removed amounts of heavy metal were demonstrated by stripping voltammetry and the heavy metal removal efficiency was found to be 98.33 for Zn(II), 90.74 for Cd(II) and 96.19% for Pb(II). Additionally, this newly synthesized cryogel was successfully used for removal of heavy metals fromenvironmental and biological media. • Influence of sodium pretreatments on the preparation of Ag-doped polycationic bentonite for antibacterial purposes Sodium bentonites have excellent cation exchange capacity (CEC) giving them great power of silver adsorption, which enables their use as precursors of antimicrobial materials. Countries like Brazil, however, do not have natural sources of sodium bentonite, only calcium or polycationic clays that do not show the same adsorption and ion exchange potential. In this study, the adsorption of silver in a polycationic bentonite from Quatro Barras, Brazil, previously subjected to a sodium treatment is evaluated. Samples were first modified with Na_2CO_3 or NaOH and then, subjected to silver impregnation in abatch system under controlled ambient conditions. Antibacterial properties of silver-exchanged clays were evaluated by the disk susceptibility and the minimum inhibitory concentration tests on Escherichia coli and Staphylococcus aureus bacteria. Results show that the sodium treatment with Na_2CO_3 allowed higher concentrations within a shorter time, increasing the pH without compromising the montmorillonite structure, which resulted on greater CEC and swelling values. Such better performance of the samples previously treated with sodium carbonate also caused an enhanced silver adsorption, resultingon a material of greater antibacterial potential. Experimental adsorption data fitted well to Freundlich isotherm. • Growth of Ag_2O_2 micro-particles and Cu_2(OH)_3NO_3 nano-sheets by atmospheric pin-to-solution electrical discharge In this paper, interaction of the air plasma generated in an atmospheric pressure pin-to-solution electrical discharge with aqueous solutions of silver nitrate, copper nitrate and also their mixture is experimentally investigated inthe cathode-plasma electrolysis configuration. Experiments show that a black (green–blue) powder is obtained for pure solution of AgNO_3(Cu(NO_3)_2 ·3H_2O). Through X-ray diffraction (XRD) characterizations, the black (green–blue) powder is found to be Ag_2O_2(Cu_2(OH)_3NO_3). On the other hand, the electrolysis product for AgNO_3/Cu(NO_3)_2 · 3H_2O mixture solution is a black–brown powder. XRD and EDS analyses of the powder along with its FESEM images reveal that it is truly Cu_2(OH)_3NO_3 micro-plates covered sparsely with Ag_7NO_{11} nanoparticles of diameter \sim30 nm. • Study on the improvement of p-type multi-crystalline silicon material for solar cells by the hydrogenation with electron injection In this paper, we have found that the efficiency of p-type mono-crystalline silicon (mono-Si) passivated emitter and rear contact (PERC) solar cells can be increased by 0.12%abs. with the process of hydrogenation with electron injection(HEI). However, the same scheme was not suitable for p-type multi-crystalline silicon (mc-Si) solar cells. To promote power conversion efficiency (PCE) for the mc-Si solar cells, we have explored a developed HEI process for the mc-Si solar cells to improve the device performance. Meanwhile, we also analysed the mechanization inside the solar cells after applying the HEI process. Through the design of experiment (DOE), the correlation among injection current, temperature, injection time and efficiency improvement was analysed in detail. It was proved that mc-Si solar cells require higher current injection andtemperature to passivate the complex impurities in the bulk, when compared to mono-Si solar cells.With the optimal scheme explored by this paper, the open circuit voltage (Uoc), short circuit current density (Jsc) and fill factor (FF) of p-type mc-Si solar cells, respectively, increased by 1.2 mV, 0.11 mA cm^{−2} and 0.05% abs., respectively. The efficiency was improved about 0.11\pm 0.005% abs.. These results will provide a certain method and basis for further improving the efficiency of mc-Si PERC cells and overcoming the light-elevated temperature-induced degradation by HEI process. • Effect of carbon on structural and magnetic properties of Ge_{1−x}Mn_x nanocolumns We have investigated the structural and magnetic properties of Ge_{0.94}Mn_{0.06−\delta}C_{\delta} films (\delta = 0.005, 0.01 and0.02) using reflexion high-energy electron diffraction (RHEED) technique, transmission electron microscopy (TEM) and superconducting quantum interference device magnetometer. All films have been prepared by co-depositing Ge, Mn and C by molecular beam epitaxy. RHEED pattern shows the increase in sample surface roughness when doping carbon into the GeMn films. TEM analyses indicate that adding carbon greatly reduces the surface diffusion of both Ge and Mn elements. Ferromagnetic ordering in samples containing carbon contents of 0.01 and 0.02, persists at temperatures >400 K. An increasein net magnetization is found for carbon-doped samples with increasing carbon content from 0.01 to 0.02. However, we found a decrease in the net magnetization and the Curie temperature of the samples after annealing at 450 and 650^{\circ}C. The Curie temperature reduces down to about 300 K, which is comparable to the value of the free-carbon sample showing a harmful effect of the post-annealing on the magnetic properties of carbon-doped GeMn nanocolumns. • Optical properties and defects of ZnO nanorods that are modified by treatment with H_2O_2 and used as conductive filaments for poly(methyl methacrylate)-based resistive switching applications The optical and structural properties of ZnO nanorods that are modified using H_2O_2 and used as the conductive filament (CF) for poly(methyl methacrylate) (PMMA)-based resistive switching (Rs) applications are studied. ZnO nanorods are used as the CF for a PMMA-based Rs device, to determine their specific properties and to determine the effect of oxygen vacancies on the Rs performance in ZnO. The Rs performance for PMMA-based devices is affected by treatment with H_2O_2. An appropriate H_2O_2 treatment time produces a significant change in the Rs performance for a PMMA/ZnO nanorod array device, because there is a change in the number of oxygen vacancies in ZnO that is treated with H_2O_2 solution at 60^{\circ}C for60 s. This study demonstrates the operation of a PMMA-based Rs device that features a ZnO CF that undergoes treatment with H_2O_2. • Tensile strength and elongation of NBR/PVC/CuFe_2O_4 magnetic nanocomposites: a response surface methodology optimization This paper reports the development of nitrile butadiene rubber (NBR) nanocomposite toughened by the combination of polyvinyl chloride (PVC) and CuFe_2O_4 nanoparticles (NPs). CuFe_2O_4 NPs synthesized by sol–gel auto-combustion route. Response surface methodology was applied for optimization and modelling of the tensile strength and elongationof NBR/PVC/CuFe_2O_4 nanocomposite. By using XRD, SEM, EDX and VSM, we characterized CuFe_2O_4 NPs and the optimized NBR/PVC/CuFe_2O_4 nanocomposite, and investigated the mechanical properties of NBR/PVC/CuFe_2O_4 nanocomposite. Results showed that the surface cracking of NBR decreased as the PVC and CuFe_2O_4 content increased,which leads to better mechanical properties of NBR. • Electrochemical behaviour of bismuth in HCl solutions Measurements of open circuit potential and electrochemical impedance spectroscopy (EIS) at open circuit condition have been employed to characterize the behaviour of the mechanically polished bismuth surface in hydrochloricacid solution of various concentrations (0.01–1.0 M). The air-formed (pre-immersion) bismuth oxide grows on the surface in all the test solutions, but its thickness decreases as the HCl concentration increases. The impedance results showed that bismuth surface reactivity towards oxide thickening decreases as chloride ions concentration increases as a result of their aggressiveness nature. The equivalent circuit model for fitting the spectra of the EIS data of bismuth in HCl solution indicated that the mechanism of Bi corrosion is controlled by the charge-transfer and diffusion processes. The mechanically polished bismuth surface was examined by scanning electron microscopy before and after immersion in 0.023 M HCl solution. The scanning electron micrographs have shown that the flawed regions formed on the mechanically polished Bi surface were repaired after immersion in the acid solution due to thickening of the oxide film. • Effect of titanium oxide ceramic particles concentration on microstructure and corrosion behaviour of Ni–P–Al_2O_3–TiO_2 composite coating Composite coatings are coatings that have been considered in terms of properties, such as corrosion resistance, oxidation resistance and excellent hardness. In this study, Ni–P–Al_2O_3–TiO_2 composite coating was made on AISI 316 steel using direct current deposition technique. The microstructure of the coating and its corrosion resistance were studied bychanging the amount of titanium oxide (1, 2, 3 and 4 g l^{−1}) in the bath. To investigate the morphology of the coating and the analysis of the coated material, a scanning electron microscope (SEM) and EDS microscopy were conducted, respectively. The results showed that in the bath containing 4 g l^{−1} titanium oxide, the coating is perfectly uniform and continuous, while by reducing the amount of titanium oxide, it is not possible to form a suitable coating on the entire surface of the substrate. To investigate the corrosion resistance, the potentiodynamic polarization and electrochemical impedance spectroscopy testsin aqueous solution of 3.5% NaCl were carried out on coated and uncoated samples. The results of these tests were also correlated with microscopic images and showed that the coatings in a bath containing 4 g l^{−1} titanium oxide has the highest corrosion resistance. • Improved thermal stability and oxidation resistance of electrodeposited NiCrP amorphous alloy coatings Amorphous NiP and NiCrP alloy coatings were prepared on copper substrates by electrodeposition. The thermal stability of the obtained coatings were evaluated by the onset temperature of phase transformation identified with differential scanning calorimetry measurements, and their high temperature oxidation resistances were characterized by the oxidation kinetics curve and the oxidation activation energy. The mechanism of the doping effect of Cr element on crystallization temperature and oxidation resistance of the alloy coatings were discussed based on X-ray diffraction analysis. The results show that the crystallization temperature of NiP amorphous alloy was 344^{\circ}C, and the oxidation activation energy was calculated to be 1.54 \times 103 J mol^{−1}. As for NiCrP alloy coating with a Cr content of 1.8 wt%, the crystallization temperature increased to 403.8^{\circ}C and the calculated oxidation activation energy was 3.53 \times 104 J mol^{−1}, 2.29 times higher than theNiP coating. The remarkably enhanced high-temperature oxidation resistance of NiCrP alloy coating can be attributed to the compact metal oxide film formed on the surface. • Bi_2O_3-doped SnO_2 varistors with low breakdown electric fields This work presents Bi_2O_3-doped SnO_2 ceramic varistors prepared through conventional ceramic processing in the sintering temperature range of 1290–1320^{\circ}C. The sample sintered at 1300^{\circ}C exhibits a breakdown electric field as low as 11.6 V mm^{−1}. Scanning electron microscopy images reveal that all the samples have a compact structure, andenergy dispersive spectroscopy results for the sample sintered at 1300^{\circ}C indicate that Bi distributes homogeneously along the grain boundaries and aggregates inhomogeneously on the grain surfaces. With increasing sintering temperature, the grain boundary barrier height remains nearly constant at 0.80 eV. In both the dielectric loss and electric modulus spectra of the sample sintered at 1300^{\circ}C, obvious relaxations were observed and the activation energies obtained from the respectivespectra were 0.33 and 0.15 eV, which are expected to be related to oxygen vacancies and interstitial ions, respectively. Complex impedance spectra are employed to develop a non-typical equivalent circuit model for the Bi_2O_3-doped SnO_2 ceramic varistors at low voltage that yields an excellent fit to the data. • Electrochemical energy storage systems: India perspective Design and fabrication of energy storage systems (ESS) is of great importance to the sustainable development of human society. Great efforts have been made by India to build better energy storage systems. ESS, such as supercapacitors and batteries are the key elements for energy structure evolution. These devices have attracted enormous attention due to their potential applications in future electric vehicles, smart electric grids, etc. This paper first addresses the fundamental principles, structure and classification of supercapacitors and batteries, and then focus on the recent advances on thesedevices made by India especially from Centre for Materials for Electronics Technology (C-MET), a scientific society under the ministry of electronics and information technology, government of India. Also the current global market scenario and market in India are also discussed in detail to recognize the most appropriate energy systems for the emerging economy like India. • Impedance variation with different relative humidities of PAni/Mn nanofibres This paper presents the humidity sensing properties of surface-modified polyaniline (PAni). In this study, the impedance response and dielectric properties of pure- and doped-PAni have been investigated as a function of relativehumidity (RH%) and frequency. PAni and PAni/Mn composite samples are synthesized by one-step interfacial polymerization process. The structural properties and surface morphologies of the prepared materials have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. XRD confirms the formation of PAni and it shows semi-crystalline behaviour. FESEM shows granular, porous and well-distributed structure. It has been observed that the porosity and nanogranular structure increased with increasing doping percentage. Here, we observe thatporous and granular structure of Mn-doped PAni shows better response and recovery time (\sim28 s) and decreases in electrical impedance. Dielectric constants, dielectric loss and AC conductivity have also been discussed with variations in frequency and relative humidity. • Novel highly active Ni–Re super-alloy nanowire type catalysts for CO-free hydrogen generation from steam methane reforming Novel Ni–Re super-alloy nanowire type catalyst system is found for hydrogen generation from steam methane reforming. The novel nanowire type catalysts exhibit the super-high catalytic activity for hydrogen generation from steammethane reforming with CO-free in the product at lower reaction temperatures. The Ni–Re alloy nanowire type catalysts are active for converting methane and water to hydrogen and carbon dioxide at a low reaction temperature of about 623 K, which is about 200 K lower than that is needed for steam methane reforming on the conventional catalysts. The CO-free hydrogen is efficiently generated from steam methane reforming on the nanowire type catalysts at the lower reaction temperatures, in which water–gas shift reaction step is not needed for CO-free hydrogen production. • Silver nanoparticles biosynthesized by Anabaena flos-aquae enhance the apoptosis in breast cancer cell line Silver nanoparticles (AgNPs) are one of the new cancer treatment tools due to their unique properties that enhance potential therapeutic efficacy. In this study, we describe the extracellular biosynthesis and anticancer activity ofAgNPs using the Anabaena flos-aquae biomass extract as reducing agent. The formation of dark-brown AgNO_3/extract solution confirmed the reduction of silver ions into AgNPs. In addition, the ultraviolet–visible spectroscopy showed the surface plasmon peak at 425 nm as characteristic peak for AgNPs. Transmission electron microscopy and scanning electron microscopy showed highly stable and mostly spherical AgNPs with average size of 5–25 nm. Fourier transform infrared spectral analysis confirmed the presence of biomolecules in the extract involved in the reduction and stabilization of AgNPs. In vitro, study of anticancer and cytotoxic effect of AgNPs and extract against T47D cell lines by MTT assay and flowcytometry confirmed the anti-proliferation potential of AgNPs against breast cancer cells. In conclusion, our results revealed that Anabaena can be used as a good organism for biologically synthesis of AgNPs and confirmed the potent therapeutic value of these nanoparticles as anticancer drugs. • Study of physicochemical properties of nanohydroxyapatite–chitosan composites Hydroxyapatite nanoparticles were synthesized using modified sol–gel approach. Its biocompatibility was proved by in vitro experiments with diploid fibroblasts. The experiment showed that the presence of hydroxyapatite in the environment of cells does not reduce their viability. The observed phase transition of hydroxyapatite was explained as order/disorder transition, saving the crystal structure symmetry. Organo–inorganic composites of chitosan and hydroxyapatite were obtained by preparing a joint solution and pouring onto a glass substrate. According to XRD and DTA data, addition ofhydroxyapatite reduces the softening and decomposition temperature of chitosan. This information is necessary to optimize the manufacturing processes of organo–inorganic scaffolds. • Effect of intercalated anions on the electrical and dielectric properties of NiAl-X layered double hydroxide ({\rm X} = {\rm CO}^{2−}_3, NO^−_3 and H_2PO^−_4): investigation by impedance spectroscopy This paper reports the effect of interlayer species on the electrical and dielectric behaviours of a lamellar structure. The successful intercalation of three oxyanions (CO^{2−}_3, NO^−_3 and H_2PO^−_4) in the interlayer space of NiAl-layered double hydroxide (LDH) was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysisand inductively coupled plasma. Using complex impedance spectroscopy measurements, equivalent circuit consisting of three serially connected R-CPE units was established for each sample. Each unit contains a resistance and a constant phase element representing contributions of grain, grain boundary and electrode interface, which allowed the determination of their electrical parameters. The adjustment of experimental data of conductivity by the double power law allowed the determination of \sigma_{\rm dc} and other conductivity parameters, and therefore, the investigation of the effect of intercalated anions on NiAl LDH electrical behaviour. Indeed, dihydrogenophosphates intercalated sample was found to decrease \sigma_{\rm ac} over the frequency range of measure, comparing to the other anions. The intercalation of this anion has also an effect on dielectric properties, it reduces the value of dielectric constant of NiAl LDH, and shifts the maximum of \tan \delta towards medium frequencies with a decrease in the value of loss tangent above 10^5 Hz. Carbonate and nitrate intercalated LDH showed a similarity in their effect on electrical and dielectric properties of NiAl LDH. • Tribological properties of compatabilizer and graphene oxide-filled polypropylene nanocomposites Effect of maleic-anhydride-grafted-polypropylene (PP-g-MA) and graphene oxide (GO) addition on the tribological properties of polypropylene (PP) nanocomposites were investigated in this study. Graphene oxides with differentlevels (0.05 and 0.15 wt%) were used as reinforcing filler for PP nanocomposites. Maleic-anhydride-grafted-polypropylene (3 wt%) was added as a compatibilizer agent to increase the interaction between the GO and PP matrix. GO-filled PPnanocomposites with and without PP-g-MA were produced by a twin-screw extruder followed by injection moulding.Wear tests were carried out under dry sliding conditions against AISI 1040 steel disc using a pin-on-disc device at 0.4–1.6 m s^{−1} sliding speed and 10–40 N loads. The tribological test results showed that the coefficient of friction and wear rate of PP nanocomposites increased with applied loads and sliding speeds. The coefficient of friction decreased by 8.2, 14.2, 37.3 and 74.7% under 1.2 m s^{−1} sliding speed and 40 N load with the addition of PP-g-MA and GO to the PP nanocomposites. Thewear rate of PP and its nanocomposites was 10^{−13} m^2 N^{−1}. The minimum wear rate was obtained for 0.15 wt% GO and 3 wt% PP-g-MA-filled PP nanocomposites with a value of 5.7537E^{−14} m^2 N^{−1} at 0.4 m s^{−1} sliding speed and 10 N load in this study. • Effect of thermal cycling on mechanical and thermal properties of basalt fibre-reinforced epoxy composites Current study investigated the effect of thermal fatigue on mechanical and thermal properties of basalt fibrereinforced polymer (BFRP) composites. To this, basalt fibre textiles in 2/2 twill pattern was used to fabricate BFRPcomposites. Thermal cycling experiment was carried out between −40 and +120^{\circ}C for 20, 40, 60, 80 and 120 cycles. Moreover, dynamic mechanical analyzer (DMA) was used to evaluate the effect of thermal cycling on thermal properties of BFRPs. Moreover, we compared the extracted viscoelastic characteristics, such as storage modulus, loss modulus and loss factor curves with original thermal-treated BFRP specimens. Based on the results, thermal cycling affected the characteristics of composites in the post-curing stage due to an increase in temperature. Finally, the effect of thermal cycling on waterabsorption properties of BFRP composites was examined by hydrophobicity test. The results showed that tensile strength, flexural modulus and ILSS values increased with the increase in the number of cycles up to 80 cycles. In other words, an increase in the number of cycles increased the hydrophobicity of BFRP composites by decreasing the contact angles. Finally, the mechanical properties of tested composites were significantly decreased when the number of cycles reached 120. This was due to the mismatch of thermal expansion coefficient and long crack formation in the structure of composite. • Effect of heat treatment on the optical properties of layered muscovite single crystal sheets Naturally, thin sheets of layered, dioctahedral muscovite single crystals are transparent to visible light. Upon heat treatments performed up to 900^{\circ}C, the single crystal sheets of thickness \sim200 \mum exhibited changes in its optical transparent character. The muscovite sheets exhibited either translucent or nontransparent, dark-brown, gold or copper like luster, varying optical band gap (from \sim3.7 to 2.7 eV) and photoluminescence (PL) properties, which depend on the temperature of the heat treatment. A comprehensive investigation has been made using X-ray diffraction, thermal analyses, energy dispersive X-ray and Raman spectroscopies to understand how/why the optical properties of the muscovite sheets changed up on heat treatments. Besides, no phase changes were found in the layered, lamellar crystal structure, evidences for the known dehydroxylation of muscovite were clearly seen from the thermal analyses data. Further, the Raman spectrum of the muscovite sheet heat treated at 900^{\circ}C showed no evidence for the presence of hydroxyl group (OH^−), which confirmed the completion of the dehydroxylation. The dihydroxylation-induced changes in the structural-elements (for example, Al-(O,OH)_6 partly or fully changing to Al-O_5/O_6 and its effects on the lattice constants, and also the defect levels introduced by the heat treatments are responsible for the changes in the optical transparency, colour of appearance, band gap and PL of the muscovite natural single crystal sheets. • Step-edge guided growth of nanowires on three-fold symmetric vicinal Si(111) surfaces Clean vicinal surfaces exhibit a stepped pattern due to the presence of narrow terraces formed on a clean surface. Therefore, this provides a platform for the aligned growth of nanowires. Using this type of surface as a template, we have grown nanowires of iron di-silicide, which are preferentially directed along the length of the terraces and are following the step-edges. These nanowires do not follow underlying three-fold symmetry of the substrate. We have thus shown two-fold symmetric growth on a three-fold symmetric surface, where diffusion barrier energy plays an important role in determining the shape of the islands. The orientations of nanowires are governed primarily by the presence of step-edges. However, the crystallographic symmetry properties of the underlying substrate have also played its role in controlling the nanowire orientation. The system was grown by molecular beam epitaxy and analysed by scanning tunneling microscopy. • Synergistic effect of manganese and nitrogen codoping on photocatalytic properties of titania nanoparticles Titanium dioxide is an n-type semiconductor widely used in applications like catalysts, optoelectonic materials, ceramics, H_2 generation, self-cleaning, water purification and solar cells. Sol–gel method has been chosen for nanoparticle synthesis because of its easy stoichiometry control, cost effectiveness and low temperature synthesis. In this study, titanium dioxide nanoparticles doped with different amounts of manganese (Mn) and nitrogen (N) were synthesized with sol–gel method. Crystal structure of undoped, Mn-doped, and Mn–N-codoped nanoparticles were determined with X-ray diffraction (XRD) analysis. Fourier transform infrared spectroscopy (FTIR) analysis was performed to identify the functional groups of nanoparticles. Photocatalytic analysis was carried out by methylene blue degredation under UV light for 1 h. X-rayphotoelectron spectroscopy (XPS) analysis was conducted to identify the chemical state and composition of the nanoparticles. Compared to the undoped TiO_2, which had 79.37% efficiency, Mn-doped and Mn–N-codoped TiO_2 nanoparticles have shown greater photocatalytic efficiency with 86.25 and 99.11% efficiencies, respectively. The results confirm that doping ofmanganese and nitrogen has affirmative effect on photocatalytic properties of synthesized nanoparticles. • New age monolithic design-based visible light responsive and reusable photocatalyst material using iron oxide-modified mesoporous titania framework In this work, we report a facile route for the synthesis of worm-like mesoporous Fe_2O_3-doped TiO_2 monolithic composites through a direct template sol–gel method, for the photocatalytic degradation of textile dye (acid blue 113) pollutants. The monolith surface morphology and structural properties have been characterized using p-XRD, HR-SEM–EDAX, HR-TEM–SAED, TGA, UV–Vis–DRS, PLS, FTIR, XPS and BET analyses. The stoichiometric doping of Fe_2O_3 unleashes visible light photocatalytic activity through a red shift in the light absorption character of TiO_2, thereby narrowing the energy band gap, and an eventual increase in e^−/h$^+$ separation centres. The monolithic photocatalyst exhibits better properties in terms of surface area, pore volume and diameter. The physico-chemical parameters, such as solution pH, dopant stoichiometry, catalyst quantity, dye concentration, photo-sensitizers and light intensity have been optimized to enhance the photocatalysis efficiency. The photocatalyst exhibits complete dye mineralization within 0.5 h, and also reusable for five continuous cycles.

• Synthesis and surface characterization of electrodeposited quaternary chalcogenide Cu$_2$Zn$_x$Sn$_y$S$_{1+x+2y}$ thin film as transparent contact electrode

A low-cost technique, electrochemical deposition has been used to grow nanocrystalline quaternary Cu–Zn–Sn–S (CZTS) on indium tin oxide (ITO)-coated glass substrate. Effects of variations in deposition potentials and sulphurcontent on the chemical composition, optical, morphological, structural and electrical properties of the deposited films have been investigated. The morphologies showed and confirmed the results from XRD analysis that the films are of polycrystalline grains. Average interplanar spacing of the films is 3.376 $\AA$. The average film’s thickness as estimated from Rutherford back-scattered spectroscopy studies was 34 nm. The estimated stoichiometry was found to be that of Cu$_2$ZnSnS$_4$ tetragonal kesterite structure. Optical studies showed that the absorption characteristic of the deposited CZTS film across thewavelength region is significantly dependent on growth deposition potentials and electrolyte concentration. Estimated band gap is between 1.75 and 1.81 eV. The electrical studies showed that the deposited films exhibit ohmic characteristics. This study demonstrated successful deposition of tetragonal kesterite structures of CZTS using a two-electrode cell approach. It also revealed the novel route of growing CZTS thin film over the conventional three electrode cells.

• BaZrO$_3$ doping in (Na, K)(Nb, Ta)O$_3$: investigating the phase transformation behaviour, piezoelectric, dielectric, ferroelectric properties and their stability

This study highlights the effect of BaZrO$_3$ doping on (Na$_{0.52}$K$_{0.48}$)(Nb$_{0.95}$Ta$_{0.05}$)O$_3$ lead-free composition. The doping, interestingly, reveals the formation of a new polymorphic phase boundary between rhombohedral and tetragonalphases, while eliminating the orthorhombic phase. Rietveld refinement of temperature dependent X-ray diffraction data, in conjunction with dielectric studies, was utilized to corroborate the findings. The study also addresses in detail the process optimization methodology, involving calcination, sintering and poling process, which is highly relevant to the research community. Two mol% BaZrO$_3$-doped samples exhibited better piezoelectric, ferroelectric and dielectric properties. The doping also substantially improved the stability of properties during ageing, under thermal and cyclic electrical loadings.

• Study on thermodynamic, electronic and magnetic properties of RE$_2$Cu$_2$Cd (RE $=$ Dy $−$Tm) intermetallics: first-principle calculation

RE$_2$Cu$_2$Cd (RE $=$ heavy rare earth elements: Dy, Ho, Er, Tm) intermetallics show the interesting physical, magnetic and chemical properties with reference to magnetocaloric effect. To explore the relevant complex performance of RE$_2$Cu$_2$Cd materials, which crystallizes in Mo$_2$B$_2$Fe-type structure with space group P4/$mbm$; electronic, magnetic and thermodynamic properties have been studied using first principle theory. Electronic properties, i.e. spin-polarized electron dispersion curves (band structure) and density of state calculations showthat (Dy/Ho/Er/Tm)$_2$Cu$_2$Cd compounds aremetallic with dominant character of Dy-f spin down channels. Whereas magnetic and electron spin-polarization calculations show that studied materials behave like metallic ferromagnet having nearly fully spin-polarized characteristics. The effect of temperature on bulk modulus, $B$, volume of unit cell, $V$, entropy, $S$ and specific heat, $C_{\rm v}$ has also been studied using quasi-harmonic Debye model.

• Substitution tuned electronic absorption, charge transfer and non-linear optical properties of some D–A type 2,4,6-trisubstituted-1,3,5-triazines: a DFT study

We have investigated theoretically a series of donor–acceptor (D–A) type star-shaped triazine derivatives by employing density functional theory using 6-311G(d,p) basis set to understand the effect of variable substitution (on triazinecore with substituents having diverse electron releasing or withdrawing capabilities) on their linear and non-linear optical properties (first hyperpolarizabilities). The investigation of influence of various electron donors/acceptors on the charge transfer characteristics of triazine molecules under study was also conducted. Present computational study reveals that thesubstitution of strong electron donors and greater charge delocalization enhance the first hyperpolarizability of the molecules.

• Fabrication of two-dimensional chemically reduced graphene oxide nanosheets for the electrochemical determination of epinephrine

A simple and selective electrochemical sensor for the determination of epinephrine (EP) was developed using chemically reduced graphene oxide nanosheets (CRGO). The CRGO nanosheets were prepared using modified Hummer’s method and the material was characterized using transmission electronmicroscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and UV–visible spectroscopy, respectively. The CRGO modified glassy carbon electrode (GCE) was employed for the electrochemical studies on EP using cyclic voltammetry (CV). The modified electrode showed significant catalytic activity compared to GO/GCE and bare GCE. The electron transfer kinetics revealed a two electron transfer for all the electrodes with CRGO/GCE exhibiting a high heterogeneous rate constant (0.127 s$^{−1}$). The detectionwas carried out using differential pulse voltammetry (DPV) through reduction of epinephrine chrome to leucoepinephrine chrome. The detection through the electrochemical reduction avoids the interference of similar analytes and improves the selectivity of the sensor. The detection limit was found to be 1.6 $\mu$M with two different linear ranges viz. 10–300 and400–1300 $\mu$M. Further, the electrode was subjected to stability, reproducibility and interference studies. The reliability of the proposed sensor was tested in the presence of biological serum samples.

• A study on defect annealing in GaAs nanostructures by ion beam irradiation

In this study, annealing of deep level (EL2) defect in gallium arsenide (GaAs) nanostructures by argon ion beam irradiation has been reported. GaAs nanodots of diameter ranging from 15 to 22 nm were deposited on silicon substratesusing the ions of GaAs generated by hot, dense and extremely non-equilibrium argon plasma in a modified dense plasma focus device. GaAs nanodots thus obtained were irradiated by Ar$^{2+}$ ion beam of energy 200 keV with varying ion fluences from $1 \times 10^{13}$ to $5 \times 10^{15}$ ions cm$^{−2}$ in the low energy ion-beam facility. The ion-beam irradiation transformed the as deposited GaAs nanodots into uniform GaAs nanostructured films of thickness $\sim$30 nm. The obtained nanostructured films are polycrystalline with paucity of arsenic antisite (EL2) deep level defect. The excess arsenic present in the as-deposited GaAs nanodots is the main cause of EL2 defect. Raman and photoluminescence measurements of GaAs nanostructured films indicates removal of excess arsenic, which was present in as-deposited GaAs nanodots, thereby suggesting annealing of EL2 defect from the ion-irradiated GaAs nanostructured films. The change in conductivity type from n- to p-type obtainedfrom Hall measurement further confirms annealing of EL2 defects. The ion-irradiated GaAs nanostructured films have low leakage current due to removal of defects as obtained in current–voltage study, which corroborate the annealing of EL2 defect. The defect-free GaAs nanostructured films thus obtained have potential applications in fabrication of highly efficient optoelectronic and electronic devices.

• AC impedance measurement for the enzyme kinetics of urea–urease system: a model for impedimetric biosensor

The measurement of time evolution of electrochemical impedance enables enzymatic kinetic studies in realtime, and obviates the need of using additional reagents as in many popular spectroscopic methods. This can eventually leadto the development of enzyme biosensors.We have used the urea–urease system as a model for this study. The usage of a free enzyme (without any immobilization steps) in this work makes the technique very simple and unique for electrochemical measurement on urease. The impedance vs. time measurement of urease exhibits Michaelis–Menten (MM) behaviour with the MM constant ($K_{\rm m}$) of 0.8 mM and maximum velocity ($V_{\rm max}$) of 5000 ohms min$^{−1}$. This $K_{\rm m}$ value closely matched the one, which is obtained from the conventional colorimetric method (values). The enzyme kinetics was performed in a standard three-electrode system and reproduced in a fabricated mini electrochemical cell in an Eppendorf tube, which couldpave the way for the development of impedimetric biosensors for a variety of enzyme systems, especially the ones for which spectrometric techniques cannot be readily applied.

• Investigation of potentials of C$_{30}$ and Ge$_{30}$ as anode in metal-ion batteries

Performances of C$_{30}$ and Ge$_{30}$ nanocages for anode electrodes in metal-ion battery (MI-B) are studied. Abilities of halogens (F, Br and Cl) adsorption on C$_{30}$ and Ge$_{30}$ potential for anode electrodes of MI-Bs were investigated. Gibbs free energy, voltage of cell, adsorption energy and orbital energy values of studied complexes were calculated and werecompared. Results displayed the $V_{\rm cell}$ of K-Ge$_{30}$ was higher than Na- and Li-Ge$_{30}$ 0.15 and 0.29 V. $V_{\rm cell}$ of K, Na and Li onGe$_{30}$ were higher than C$_{30}$ 0.18, 0.17 and 0.15 V. The G$_{\rm ad}$ of halogens (F, Br and Cl) on Ge$_{30}$ were higher than C$_{30}$ 5.19,4.63 and 4.91 eV. $V_{\rm cell}$ of K-halogen-, Na-halogen- and Li-halogen-Ge$_{30}$ are higher than C$_{30}$ 0.39, 0.36 and 0.32 V. G$_{\rm ad}$ of2, 3 and 4 halogens (F, Br and Cl) on Ge$_{30}$ are higher than C$_{30}$ ca 5.12, 3.29 and 4.64 eV, respectively. Finally, the F-Ge$_{29}$ with high performance and $V_{\rm cell}$ was proposed as anode electrode of potassium ion battery.

• Quasi-solid sodium ions electrolyte of Na$_2$O−B$_2$O$_3$−SiO$_2$−H$_2$O system hydrated glass

Na$_2$O−B$_2$O$_3$−SiO$_2$−H$_2$O system hydrated glass with $T_{\rm g}$ ranges from $−$10 to 150$^{\circ}$C is synthesized by aqueouschemical methods and is applied to symmetrical cells as quasi-solid electrolyte. At the temperature around $T_{\rm g}$, the solid state transforms to quasi-solid state, whose mechanical property keeps like gel electrolyte, but the conductivity leaps from $5.31 \times 10^{−6}$ S cm$^{−1}$ to $5.43 \times 10^{−3}$ S cm$^{−1}$, much higher than most of the glass–ceramic electrolytes. As most of the solvated water is evaporated, H$_2$O left in the system distributes in the intervals as hydroxyl, which is much benefit to the ions transportation, and more important is to increase the voltage window to 2.24 V and even higher. The cycle performance is also researched. After 1000 circulations, there is still 65% capacity retention and no obvious damage is discovered in the electrolyte, which means much better cycle property of the electrolyte than gel electrolyte. Other compositions in the quasi-solid system including different contents of B$_2$O$_3$, Na$_2$SO$_4$ and m in sodium silicate NaO$_2$·mSiO$_2$ are also studied. In general, quasi-solid Na$_2$O−B$_2$O$_3$−SiO$_2$−H$_2$O system owns better conductivity and cycle performance than mostglass–ceramic solid electrolyte, and it is environment-friendly, inexpensive and practical to be used as sodium ions quasi-solid electrolyte.

• Quality evaluation of solvent-cast 3D printing of poly(lactic acid) films

This study aims to analyse the process conditions in the production of poly(lactic acid) (PLA) films by solventcast 3D printing. The films were evaluated according to thickness, roughness and visual aspect. An experimental design22 was performed with centre point in triplicate to study solvent/PLA ratio and printing speed. The solvent/PLA ratio and printing speed had a significant negative effect on film thickness and positive effect on film roughness. The film that presented the best classification in the visual aspect was the one moulded with the highest printing speed and solvent/PLA ratio.

• Synthesis of mesoporous manganese dioxide/expanded graphite composite and its lithium-storage performance

A mesoporous manganese dioxide (MnO$_2$)/expanded graphite (EG) composite was successfully fabricated using mesoporous silica decorated EG (KIT-6/EG) as a hard template. Different amounts of EG were introduced to thesynthetic system to adjust the MnO$_2$:EG mass ratio of the composite. X-ray diffraction, transmission electron microscopy, scanning electron microscopy and nitrogen adsorption–desorption analyses were employed to characterize the structure and morphology of the composite. Results show that the distribution of MnO$_2$ nanoparticles grown on the EG layers decreases gradually with increasing EG content. Moreover, in the presence of excess EG, the specific surface area of the samples dramatically decreases. As the anode electrode of a Li-ion battery (LIB), the composite (MnO$_2$:EG $=$ 34% w/w) exhibitsa specific capacity of $\sim$250 mAh g$^{−1}$ at a current density of 200 mA g$^{−1}$ for up to 100 cycles, this capacity is much higher than that of pure MnO$_2$ ($\sim$10 mAh g$^{−1}$) due to its improved electrical conductivity. The composite also shows good rating performance when the current density is tuned. These results indicate that the composite has potential application as ananode material for next-generation LIBs.

• Tuning the electronic and optical properties of [26] annulene by electron donor and acceptor groups (push–pull system)

This study was aimed at investigating the effect of electron donor and acceptor groups on electrical and optical properties of pi-conjugated [26] annulene. The results of the study showed that almost all selected substitutions reduced the value of $E_{\rm g}$ compared with pristine annulene. Calculated dipole moments for the sandwiched forms of annulene are noticeably greater than those of its pristine form, of which the ED2–ANN–QB2 had the maximum value for dipole moment. It was found that the influence of electron donor and acceptor groups on annulene optical properties is very significant. Moreoptical activity improvement was seen in the case of using QB2 and QB3 in one side and other electron donor groups in opposite side of [26] annulene molecule. The higher optical activity of these sandwiched molecules corresponds to higherelectron transfer in them. The results of this research may be useful in designing new photosensitizers.

• Influence of Bi$_2$O$_3$, Sb$_2$O$_3$ and Y$_2$O$_3$ on optical properties of Er$_2$O$_3$-doped CaO–P$_2$O$_5$–B$_2$O$_3$ glasses

The glasses of the composition 25CaO–10(M$_2$O$_3$)–14P$_2$O$_5$–50B$_2$O$_3$:1Er$_2$O$_3$ (where M$=$Bi/Sb/Y) are prepared. The prepared samples are characterized by XRD, thermoluminescence (TL),UVand photoluminescence (PL) techniques. TL reports suggest that the sample of 10 mol%Y2O3 concentration (EY) exhibiting good shape symmetry factor ($u = 0.484$) and low AEs ($E_{\tau} = 1.189$, $E_{\delta} = 1.218$ and $E_{\omega} = 1.210$) under $\gamma$-irradiation might be a good TL asset. The optical absorptions of present glasses are studied well through the Judd–Ofelt theory.The evaluations such as Judd–Ofelt parameters are additionallyprojected. They are found to be the best ($\Omega_2 = 1.62 \times 10^{−21}$ cm$^2$, $\Omega_4 = 1.56 \times 10^{−21}$ cm$^2$ and $\Omega_6 = 0.59 \times 10^{−21}$ cm$^2$) for the sample of 10 mol% Y$_2$O$_3$ concentration (E$_{\rm Y}$), which may be a good optical asset to develop a novel class of laser resources. The radiative evolutions corresponding to the emissive transition ${}^4$S$_{3/2}$ $\to$ ${}^4$I$_{15/2}$ are assessed by PL technique. The evaluations are found to be the best ($A_t = 7089$ s$^{−1}$, $\tau_{\rm rad} = 140$ $\mu$s and $\beta = 96.1$%) for the sample of 10 mol% Y$_2$O$_3$concentration (E$_{\rm Y}$), which may be a useful luminescent resource.

• pH and secondary structure instructed aggregation to a thixotropic hydrogel by a peptide amphiphile

Peptide-amphiphile (PA)-based supramolecular thixotropic hydrogels are useful in medical sciences due to multiple advantageous features along with its biocompatibility and biodegradability. In this work, we have developed aself-assembled peptide-based hydrogel from a $\beta$-sheet forming short PA. Hydrogelation of the PA is controlled by pH and consequent changes in secondary structures attained by the PA. Under acidic conditions, the PA remains in random coil conformation. While increasing the pH to 9, a rapid transformation to anti-parallel β-sheet leads to a strong hydrogel. Interestingly, the disulphide-linked dimer of the PA failed to attain such aggregation pattern. The pH-induced sol–gel–sol transition can be achieved for several cycles without any change in aggregation pattern. The hydrogel was also found to show thixotropic rheological behaviour and thus, it can be utilized as an injectable hydrogel for biomedical applications.

• Ion recognition and fluorescent imaging of conjugated polymer fluorescent probes for Fe(III)

Novel polymer fluorescent probes for Fe(III) were synthesized to achieve a steady combination of ferric ions. In the Schiff base reaction of probes’ synthetic process, $o$-, $m$- and $p$-phenylenediamine were respectively introduced toresult in a series of new conjugated polymer fluorescent probes. Analyses on optical properties of the probes and probe-Fe(III) characteristic recognition through FS showed an application of the conjugated probes in quantitative identification and detection of Fe(III) with quick responses. Fluorescent imaging of the probes and probe-Fe(III) in living cells in vitro revealedlow toxicity of the probes and predicted the probes’ further application for instant Fe$^{3+}$ detection in clinical diagnosis and dynamic tracing of Fe$^{3+}$ in biological systems.

• Effect of thermal spray process on chemical composition, magnetic behaviour, structure and mechanical properties of coatings based on milled Fe, Co and Al$_2$O$_3$ powder

Coated steel substrate by FeCo/Al$_2$O$_3$ nanoparticle with various Co concentrations realized by a thermal spraying process, preliminary powder alloy was elaborated by mechanical alloying technique for 20 h of milling time. The aims of this work are to study the effect of thermal spraying process and mechanical alloying on chemical composition, magnetic behaviour, structure and mechanical properties of coating. After mechanical alloying, the crystallite sizes of the powder were decreased from 18 to 7 nm and the lattice strains increased from 0.36 to 0.56%. This is due to the phenomenon of diffusion of cobalt in the iron lattice and the milling effect. After thermal spraying, many different phases appeared in the coating, such as Al$_2$FeO$_4$, CoAl$_2$O$_4$, CoFe and CoFe$_2$O$_4$. Magnetic behaviour was influenced by this change in the chemical composition of coating. The maximum saturation magnetization was found in Fe$_{40}$Co$_{20}$(Al$_2$O$_3$)$_{40}$ sprayed powder, however, the minimum coercivity was found in Fe$_{50}$Co$_{10}$(Al$_2$O$_3$)$_{40}$ sprayed powder. Mechanical properties’ parameters such as microhardeness andYoung’s modulus were enhanced by the change in chemical composition during mechanical alloying and thermal spraying process.

• Preparation and characterization of porous (Si$_{1−x}$Ti$_x$)O$_2$ ($x \leq 0.25$) prepared by sol–gel hydrothermal process

An experimental strategy was developed to obtain (Si$_{1−x}$Ti$_x$ )O$_2$ ($x \leq 0.25$) porous materials via the sol–gel hydrothermal process. The sol was prepared from Si(OEt)$_4$ (TEOS), Ti(OBu)$_4$ (OBu: OCH$_2$CH$_2$CH$_2$CH$_3$), anhydrous ethanol, deionized water and nitric acid. The reagents were mixed at room temperature (293 K) to obtain a homogeneous colourless liquid which was subjected to a hydrothermal process at 473 K using a stainless steel container. Finally, the material obtained was treated at 873 K in air. The surface area of the treated solids was determined by N$_2$ adsorption/desorption isotherms. The corresponding average pore diameter was evaluated using the Barret, Joiner and Halenda and Horváth-Kawazoe methods. Porous structures were obtained, in which the average pore diameter of the microporous ones was 1.4 nm. The characterization techniques employed were Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, Raman spectroscopy, scanning electron microscopy, thermal gravimetric analysis, differential scanning calorimetry and UV–Vis diffuse reflectance spectroscopy. The Si–O–Ti bonds were detected by FTIR.

• Synthesis and characterization of Cu–Ni/Gr nanocomposite coatings by electro-co-deposition method: effect of current density

Cu–Ni alloys are widely used and implemented due to their remarkable mechanical and electrochemical properties in most of the engineering applications. The reinforcement of graphene nanoplatelets (Gr) in Cu–Ni alloy can be utilized to enhance the properties of Cu–Ni alloy. In the present work, Ni as an alloying element and graphene nanoplatelets as reinforcing element were co-deposited with Cu to prepare Cu–Ni/Gr composite coatings by electro-co-deposition method. The influence of various current densities on surface morphology, composition, microstructure, crystallite size, lattice strain,microhardness, coefficient of friction and corrosion resistance of the resulting composite coatings were investigated and were presented in detail. Based on the experimental results, the coatings prepared at 6 A dm$^{−2}$, exhibit a reduced grain size with enhanced mechanical properties and corrosion resistance.

• Few-layer-graphene as intercalating agent for spray-pyrolysed fluorine-doped tin oxide transparent conducting electrode

In this work, the development of a robust method for the fabrication of a low-cost transparent conducting electrode (TCE) via the addition of graphene in the spray-pyrolysis of fluorine-doped tin oxide (FTO) is explained. Alcoholic suspensions of few-layer-graphene were produced via the liquid exfoliation of graphite in different alcoholic solutions as sonicating solvent. These mixtures were then mixed with ammonium fluoride and tin (II) chloride dihydrate precursors to fabricate graphene/FTO composite through spray pyrolysis. Graphene exfoliated with 50% aqueous ethanol proved to yield improved TCE properties with nearly two-fold enhancement in figure of merit (FOM) measured in terms of the ratio of optical transmittance and sheet resistance. Using optimized spraying conditions, graphene/FTO coatings still yielded slightly higher FOM compared to plain FTO. The increase in FOM is largely attributed to the decrease in sheet resistance with the incorporation of graphene flakes.

• Monovalent (Li$^{+1}$) doping effect in multiferroic GdMnO$_3$

This paper reports the temperature- and field-dependent magnetic properties of monovalent-doped polycrystalline sample Gd$_{0.85}$Li$_{0.15}$MnO$_3$ (GLMO) prepared by conventional solid-state reaction route. Final sintering at 1673 K for 18 h yields in the formation of well-grown, impurity phase free, single-phased, orthorhombic structured (with Pbnm space group) crystal. The optical properties have been investigated by UV-absorption spectra. The room temperature UV-absorption spectrum using Tauc’s formula gives an optical band gap of $\sim$3.12 eV. The paramagnetic (PM) state to incommensurateantiferromagnetic (ICAFM) state transition temperature increases due to Li doping. Magnetic hysteresis curve at 5 K signifies the Gd spin ordering.

• Effect of sintering pressure on electrical transport and thermoelectric properties of polycrystalline SnSe

Tin selenide (SnSe), which has high thermoelectric (TE) performance due to its low thermal conductivity, is considered as a promising TE material. It is good that TE properties were reported in single crystal form because polycrystalline SnSe exhibits low electrical conductivity compared to that of single crystal SnSe. To improve the electrical conductivity of polycrystalline SnSe, the effects of the pressure applied during spark plasma sintering (SPS) on the electrical charge transport and the TE properties of the polycrystalline SnSe were investigated. Degree of texture was enhanced with increasing sintering pressure from 30 to 120 MPa during SPS, which lead to the increase in carrier mobility, which resultedin the increase in electrical conductivity. Increase in pressure led to a significant increase in thermal conductivity due to an increase in the lattice thermal conductivity, which can be attributed to the decrease in phonon scattering at the grain boundary. A ZT of $\sim$0.7 was obtained at 823 K from the polycrystalline SnSe sintered with a pressure of 60 MPa, which can result from large increase in electrical conductivity with very small increase in the thermal conductivity. This study shows that the TE properties of the polycrystalline SnSe can be enhanced by controlling the degree of texture which can be accomplished by changing the pressure applied during SPS.

• Tailoring LaB$_6$ nanoparticle-based self-healing film for heat-shielding window

Effective insulation of near-infrared (NIR) from solar energy via the use of transparent coating on the windows is one of the most essential issues in energy savings. In this work, a novel lanthanum hexaboride (LaB$_6$)/poly(methacrylate-2-ureido-4[1H]-pyrimidinone) functionalized poly($n$-butyl acrylate) (PnBA-$r$-PMAUPy) film was prepared via an in-situ radical polymerization method to achieve heat insulation and self-healing performance. LaB$_6$ nanoparticles synthesized bya low-temperature method were employed as a NIR shielding material, while PnBA-$r$-PMAUPy was utilized as a material to enhance the reliability of long-term service. Benefitting from hydrogen bonding interaction, the film showed a marked progress in self-healing property at ambient temperature. As displayed by optical absorption results, the increase of LaB$_6$ content can effectively enhance the NIR shielding ability. The NIR blocking ratio of the thermal barrier film with a thickness of 0.64 mm can reach 97.5%, and the self-healing rate is about 84% for 20 mg LaB$_6$, respectively. The self-healing film forheat-shielding window can be a promising candidate with long-term service.

• Thin film chemiresistive gas sensor on single-walled carbon nanotubes-functionalized with polyethylenimine (PEI) for NO$_2$ gas sensing

Chemical detection of toxic gases, such as greenhouse gases is still very important as a research topic. To design gas sensor detectors based on single-walled carbon nanotubes (SWCNTs) with high sensitivity and selectivity for the toxic environment is a continuous process. The aim is to detect NO$_2$ gas with better sensitivity. In the present work, the thin-film sensor is fabricated on SiO$_2$ substrate and it is functionalized with polyethylenimine (PEI). It has been established that PEI functionalized SWCNTs (F-SWCNTs) show high sensitivity towards strong electron-withdrawing particles. It was found that at room temperature, SWCNTs-PEI functionalized gas sensor exhibited a higher sensitivity of 37.00% as compared with bare SWCNTs gas sensor. The gas sensor has shown the repeatable response for the entire concentration range studied.The sensing properties and the PEI functionalization duration effects on the behaviour of SWCNTs-based gas sensors were demonstrated.

• Effect of back electrode on trap energy and interfacial barrier height of crystal violet dye-based organic device

In this work, we have studied the effect of aluminium-coated mylar (Al–M) sheet-based back electrode and aluminium (Al)-coated back electrode on trap energy ($E_{\rm t}$) and barrier height ($\phi_{\rm b}$) of crystal violet (CV) dye-based organic device. Two devices have been prepared using two different back electrodes. In both the devices, ITO-coated glass is used as front electrode. Both the organic devices have been prepared by using spin-coating techniques. We have measured the steady state current–voltage ($I –V$) characteristics of these devices to estimate the trap energy ($E_{\rm t}$) and barrier height ($\phi_{\rm b}$) of the devices. Because of the insertion of a reflecting back electrode, the charge carriers are confined in the active layer, which reduces the $E_{\rm t}$ from 0.044 to 0.034 eV and $\phi_{\rm b}$ is reduced from 0.80 to 0.77 eV. The barrier height is also estimated by using another alternative method, which is known as Norde method. By using Norde method, $\phi_{\rm b}$ is estimated, which reduces from 0.83 to 0.79 eV in the presence of reflecting back electrode. Both the methods show good consistency with each other. The reductions of these parameters indicate the enhancement of charge injection through the metal-organic dye interface. With the use of polished back electrode in the CV dye-based organic device, it is possible to modify the barrier height and trap energy and thereby modifies the conductivity.

• Structural, mechanical and optoelectronic properties of cubic Be$_x$Mg$_{1−x}$S, Be$_x$Mg$_{1−x}$Se and Be$_x$Mg$_{1−x}$Te semiconductor ternary alloys: a density functional study

Structural,mechanical and optoelectronic features of cubic Be$_x$Mg$_{1−x}$S, Be$_x$Mg$_{1−x}$Se and Be$_x$Mg$_{1−x}$Te alloyshave been explored by DFT-based FP-LAPW approach. Nonlinear reduction in lattice constant, but increment in bulk modulus and each of the elastic constants $C_{11}$, $C_{12}$ and $C_{44}$, occurs with increasing Be-concentration $x$ in each system. All the specimens exhibit elastic anisotropy. Specimens at $x = 0.0$, 0.25 and 0.50 show ductility, but remaining specimens at $x = 0.75$ and 1.0 show brittleness. Each ternary alloy is a direct ($\Gamma$−$\Gamma$) band gap ($E_{\rm g}$) semiconductor. Almost linear decrease in $E_{\rm g}$ with increase in $x$ is observed in each alloy system. Ionic bonding exists among the constituents of all specimens. The occupied valence chalcogen-p as initial and unoccupied conduction Be-3s, 2p and Mg-4s, 3p as final states play a keyrole in optical transitions. Nature of variation of zero-frequency limit in each of the $\epsilon_1(\omega)$, $n(\omega)$ and $R(\omega)$ spectra with $x$ isopposite to, while critical point in each of the $\epsilon_2(\omega)$, $k(\omega)$, $\sigma(\omega)$ and $\alpha(\omega)$ spectra with $x$ is similar to, the nature of variation of $E_{\rm g}$ with $x$.

• Effect of barium sulphate on mechanical, DMA and thermal behaviour of woven aloevera/flax hybrid composites

The natural fibre-reinforced polymeric composites attract themanufacturing industries due to their recyclability, cost-effectiveness and eco-friendly nature. The natural hybrid reinforced polymeric (HNRP) composite overcomes thelimitations in mechanical properties of the mono-natural fibre-reinforced composites. In this research work, the effect of barium sulphate (BaSO$_4$) on the mechanical characterization of HNRP (aloevera/flax/barium sulphate) composites was examined as per ASTM standard. BaSO$_4$ is preferred as a filler based on the absence of self-motion, high density and high melting point (1580◦C). The thermal stability of the HNRP composite was determined by thermogravimetric analysis (Model: TG/DTA 6200). The water absorption and dynamic mechanical properties of the HNRP composites were estimated.The fractography images were analysed to recognize the fractured surface morphology using a scanning electron microscope. The HNRP5 composite has the maximum tensile strength of 34.72 MPa, predominantly based on the interlocking of the flax fibre and plasticity of the composite improved by the influence of BaSO$_4$. The impact strength decreased noticeably with theaddition of barium sulphate in the composite. The weight reduction of around 7–9% was observed in the temperature range of 100–200$^{\circ}$C. The mono-composites (HNRP1&2) absorbed, respectively, 4.8 and 3.5% of moisture; with the addition of BaSO$_4$, the same combination absorbed 4.2 and 3.2% of water content, which was due to the low water absorption capability of BaSO$_4$. The storage modulus of the HNRP5 composite has maximum magnitude in the glassy region and minimum in the rubber region.

• Green synthesis and structural characterization of gold nanoparticles from Achillea wilhelmsii leaf infusion and in vitro evaluation

The aim of this study is to green-synthesize gold nanoparticles (GNPs) by leaf infusion of Achillea wilhelmsii (AW) and to evaluate their biological effects. The synthesized AW-GNPs were characterized by UV–Vis spectroscopy, Fourier transform infrared, X-ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic light scattering analyses. The antibacterial and cytotoxicity activities of AW infusion and AW-GNPs were evaluated. Antioxidant activity was evaluated by 1, 1-diphenyl-2-picrylhydrazyl test. Moreover, the electrochemical activity of AW-GNPs as a modifier ata glassy carbon electrode (GCE) was studied. The surface plasmon resonance absorption band at 540nm in the UV–Vis spectrum discloses the reduction of gold cations into GNPs. The XRD pattern of GNPs shows the crystal structure of AW-GNPs, and TEM image displays the spherical shape of GNPs with small size (2.7–38.7 nm). The AWinfusion and AW-GNPs demonstrated a maximum antioxidant activity of 68 and 58%, respectively. AW-GNPs showed antibacterial activity against gram-positive bacteria, without affecting gram-negative bacteria. Also, AW-GNPs exhibited the cytotoxicity effects against MDA-MB-468 cancer cell line, and the electrochemical study indicated a significant electrocatalytic activity of AW-GNPs. The results indicate the advantages of using AW leaf infusion for the production of GNPs with antibacterial, antioxidant, cytotoxic and electrocatalytic activities.

• Pristine and modified-mesoporous alumina: molecular assistance-based drug loading and sustained release activity

The present article reports on the synthesis of mesoporous alumina and its modification through $\beta$-cyclodextrin (BCD) incorporation for loading and release studies of amoxicillin. The drug loading in the mesoporous matrices was found to be activated upon providing molecular assistance by amino acids, L-methionine, L-proline and L-phenylalanine. The effect of molecular assistance has been attributed to intermolecular interactions between the drug and the individual amino acids which have been further confirmed by different spectroscopic studies. The drug-loaded material with BCD modification wasfound to exhibit a sustained release mechanism in physiological pH and is suggested as a proposed material for hip joint prosthesis.

• Synthesis and characterization of Dy-doped Lu$_1$Gd$_2$Ga$_2$Al$_3$O$_{12}$ phosphor for LEDs

The synthesis and characterization of Dy-doped Lu$_1$Gd$_2$Ga$_2$Al$_3$O$_{12}$ are reported in this article. Solid-statereaction method is used to synthesize the material. X-ray diffraction and scanning electron microscopy characterization techniques are used to study the phase and structure of the synthesized material. Luminescence, which is the main propertyof the phosphor material, is characterized by UV- and X-ray-induced luminescence spectroscopy. Lu$_1$Gd$_2$Ga$_2$Al$_3$O$_{12}$:Dy$^{3+}$phosphor shows its highest emission spectra in blue and yellow regions. A combination of yellow and blue gives us white light, displayed by chromaticity diagram for this phosphor. Hence, this phosphor may be used in white-light-emitting diodes. The absorption spectra of our material match well with spectral curve of LEDs. Therefore, it may be used in LEDs applications.

• Temperature-dependence calculation of lattice thermal conductivity and related parameters for the zinc blende and wurtzite structures of InAs nanowires

Theoretical calculations are performed on lattice thermal conductivity (LTC) and related parameters for the zinc blende and wurtzite structure of InAs nanowires (NWs) with diameters of 50, 63, 66, 100 and 148 nm through the Morelli–Callaway model. For the model to be efficiently applicable, the longitudinal and transverse modes are considered. The melting point of the various-sized NWs is considered to estimate the Debye and phonon group velocities. The impacts of Grüneisen parameter, dislocations and surface roughness are also successfully utilized to address the calculated and measured LTC of the semiconductor under investigation. Results show that the Grüneisen parameter increases with decreasing NW diameter and that phonon confinement leads to an observable deviation of the calculated LTC curve from that of the experimental one in the case of bulk InAs. We assume that NW boundaries, dislocations and imperfections are responsible for the scattering of phonons along with electrons and other phonons because of normal and Umklapp processes. Therefore, at a specified temperature, LTC depends on the size and crystal structure of the semiconductor. As such, the thermal and mechanicalparameters of InAs can be greatly modified by decreasing the size and dimension of the semiconductor as a result of the quantum-confinement effect.

• Gold-nanoparticle- and nanostar-loaded paper-based SERS substrates for sensing nanogram-level Picric acid with a portable Raman spectrometer

Nanoparticle (NP)-loaded filter paper (FP)-based surface-enhanced Raman scattering (SERS) substrates have been prepared using differently shaped gold (Au) NPs. The shape of Au NPs plays a significant role in the amplification ofSERS signal. Here, two differently shaped Au NPs were synthesized using two different techniques: (a) femtosecond (fs) laser ablation in liquid and (b) chemical method. Spherical shaped Au NPs were obtained using fs ablation of a bulk Autarget in distilled water and Au nanostars (NSs) were achieved through chemical process utilizing N-vinyl-2-pyrrolidone as a reducing/capping agent. The size and shapes of these synthesized NPs and NSs were investigated meticulously usingdifferent characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy and X-ray diffraction. Both the NPs and NSs were subsequently loaded onto commercially available FP by simple drop casting method. To achieve higher number of hot spots, the aggregated spherical NPs were obtained by addition of NaCl. The non-aggregated spherical, aggregated spherical, and star Au NPs loaded on FP were used for the detection of a dye (Nile blue) and an explosive molecule (Picric acid).

• Comparative analysis on optical and photocatalytic properties of chlorophyll/curumin-sensitized TiO$_2$ nanoparticles for phenol degradation

In this work, natural-dye-sensitized photocatalysts (NDSPs) of TiO$_2$ were prepared by a simple wetness impregnation method, in which natural pigments of chlorophyll and curcumin were initially extracted from fresh parsley leaves andlong roots of dried turmeric, respectively. The as-prepared NDSPs were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and UV–vis diffuse reflectance (DRS) spectroscopy. XRD and SEM studies verified intact structural and morphological properties for NDSPs of TiO$_2$ compared to non-sensitized nanostructures, while FT-IR and DRS analyses confirmed the presence of dye pigments on the surface of TiO$_2$ photocatalysts after the photosensitization process. A red-shift towards longer wavelengths was observed in band-gap energies ofdye-sensitized samples. These NDSPs indicated efficient photocatalytic performances towards decomposing phenol in visible light irradiation. Phenol degradation experiments are systematically conducted to optimize four key operating parameters, including irradiation time, initial pH of the reaction mixture, dye-sensitized TiO$_2$ dosage and initial phenol concentration. Dye-sensitization using chlorophyll pigments results in the highest phenol degradation rate (85%) compared with that of samples sensitized with curcumin pigments (75%), which is perfectly in agreement with the corresponding band-gap energies. Photodegradation processes were modelled by the Langmuir–Hinshelwood kinetics, while the adsorption equilibrium was investigated based on Langmuir and Freundlich isotherms. Lastly, possible mechanisms involved in the process of phenol photodecomposition were proposed.

• Eu(III)-doped barium tellurooxyphosphate phosphor with orange-red emission

Eu$^{3+}$ photoluminescence (PL) is studied in the tellurooxyphosphate, Ba$_2$TeO(PO$_4$)$_2$, host. A series of phosphor compositions with varying concentrations of Eu$^{3+}$ dopant in Ba$_2$TeO(PO$_4$)$_2$ are synthesized by high temperature solid-state reaction and the PL spectra are recorded. Under 395 nm wavelength excitation, the emission spectrum shows a single peak corresponding to the non-degenerate transition, ${}^5$D$_0$ $\to$ ${}^7$F$_0$ indicating that Eu$^{3+}$ preferentially occupies a singlecrystallographic site. The peak due to the degenerate hypersensitive ${}^5$D$_0$ $\to$ ${}^7$F$_2$ electric dipole transition of Eu$^{3+}$ in theemission spectrum indicates that the site occupied by Eu$^{3+}$ in the tellurooxyphosphate host lattice is non-centrosymmetric. The CIE coordinate values are $x = 0.61$ and $y = 0.34$ and are found to be close to the values of the reference phosphor Y$_2$O$_3$:Eu$^{3+}$.

• An improved synthesis of iron phosphate as a precursor to synthesize lithium iron phosphate

Two different kinds of FePO$_4$: amorphous FePO$_4$ and crystalline FePO$_4$, were synthesized as a precursor to synthesize LiFePO$_4$/C. The crystalline FePO$_4$ was obtained by treating amorphous FePO$_4$ with phosphoric acid refluxing. Inductively coupled plasma-atomic emission spectrometry was used to evaluate the impurity content. The obtained materialswere characterized by chemical analysis, scanning electron microscopy and X-ray diffraction. The results showed that the performance of LiFePO$_4$/C synthesized by crystalline FePO$_4$ is significantly better than when LiFePO$_4$/C is synthesized from amorphous FePO$_4$. The capacity retention and capacity fade of LiFePO4/C synthesized from crystalline FePO$_4$ was 70.9% at $−$20$^{\circ}$C and 0.012% per cycle after 150 cycles at 1$C$, respectively. The better performance from using crystalline precursor resulted from a more uniform powder with fewer crystalline defects and impurities.

• Theoretical examination of oxygen reduction reaction (ORR) on carbon nanocone (CNC) for fuel cells

Recently, various studies were performed to propose and discover acceptable catalysts for oxygen reduction reaction (ORR) in various fuel cells. Here, performance of boron-doped carbon nanocone (CNC) as catalyst to ORR via theoretical methods is examined. The ORR paths through ER and LH mechanisms were studied. Results showed that onsetpotentialand over-potential on ORR of boron–CNC were 0.73 and 0.50 V, respectively. The calculated exchange current density and transfer coefficient of B–CNC were $ca.$ $6.5 \times 10^{−6}$ A cm$^{−2}$ and 0.52, respectively. Results demonstrate that boron-doped CNC is a high-potential catalyst to ORR.

• Time-resolved fluorescence decay and Gaussian analysis of P3HT-derived Ho$^{3+}$- and Tm$^{3+}$-doped ZnO nanostructures

The fluorescence vibrational features of as-synthesized P3HT–ZnO:Ho${}^{3+}$ and P3HT–ZnO:Tm${}^{3+} thin films were investigated using Gaussian analysis. Relative to P3HT–ZnO:Tm$^{3+}$film, detailed Gaussian analysis of the fluorescence spectra revealed weaker intensity exhibited in P3HT–ZnO:Ho$^{3+}$film due to better charge transfer. Moreover, we comparatively present the Huang–Rhys factor and relaxation energy of the samples, which are calculated using relations derived from the Franck–Condon theory. Furthermore, P3HT–ZnO:Ho$^{3+}$film exhibits lower relaxation energy as compared with P3HT–ZnO:Tm$^{3+}$film, which implies better conjugation length. Finally, the singlet exciton lifetime of P3HT–ZnO:Ho$^{3+}$samplewas found to be shorter as compared with P3HT–ZnO:Tm$^{3+}$, while the calculated exciton diffusion length was 6.4 and 10.3 nm, respectively. • Titania-based porous nanocomposites for potential environmental applications Titania–zeolite Y composites were synthesized by a facile solid-state dispersion method. The synergistic effects of porous zeolite structure and novel photocatalysis properties of titania nanoparticles were exploited. The physical properties of the composites were characterized by scanning electron microscopy, energy-dispersive X-ray, X-ray diffraction, diffuse reflectance spectroscopy, fourier transform infra-red spectroscopy and photoluminescence spectroscopy. Porosity and surface area of the composites were determined from Brunauer–Emmett–Teller studies. The antibacterial effect and the photocatalysis properties of these composites were studied. Composites exhibited higher growth reduction of Escherichia coli and Staphylococcus aureus as compared with the pure forms ($P$25 titania and zeolite Y). Maximum growth reduction of both types of bacterial cells (gram-positive as well as gram-negative) was observed with 20% titania–zeolite composite. The composite demonstrated 40 and 30% enhancement in the growth reduction of E. coli and S. aureus, respectively, as compared with the pure forms; 10% composite exhibited 50% enhancement in the photocatalysis efficiency of methylene blue dye degradation as compared with$P$25 titania nanoparticles and led to a complete removal of the dye in the first 60 min of photocatalysis process. Mechanisms for both applications have been proposed in light of the observed results. • Synthesis, characterization and anticorrosion behaviour of a novel hydrazide derivative on mild steel in hydrochloric acid medium A novel corrosion inhibitor, namely$N'$-[(4-methyl-1$H$-imidazole-5-yl)methylidene]-2-(naphthalen-2-yloxy) acetohydrazide (IMNH), has been synthesized and characterized by${}^1$H NMR and FTIR spectroscopic techniques. The anticorrosion behaviour of IMNH on mild steel in 1M hydrochloric acid (HCl) medium was studied by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. The percentage inhibition efficiency of IMNH increased with increase in its concentration and temperature. The adsorption of IMNH followed chemisorption andobeyed Langmuir’s adsorption isotherm. PDP study revealed that IMNH functioned as a mixed type inhibitor. Theoretical study of the adsorption behaviour of this inhibitor was carried out by quantum chemical calculations using density functional theory (DFT). Scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy-dispersive X-ray spectroscopy (EDX) studies confirmed the formation of a protective film of IMNH on the mild steel surface. • Synthesis, characterization and quantum chemical study of optoelectronic nature of ferrocene derivatives Two new ferrocene derivatives N-(2-hydroxy-5-methylphenyl) ferrocylideneamine (Fe1) and N-(2-hydroxy-5-chlorophenyl) ferrocylideneamine (Fe2) have been synthesized to study the effect on electronic, optical and charge transfer properties while changing the electron donating group with electron withdrawing group. The synthesized compounds were characterized by different spectroscopic (FTIR, UV–Vis,${}^1$H NMR,${}^{13}$C NMR) and spectrometric (EI) techniques. Thegeometries for ground and excited states were optimized by density functional theory (DFT/B3lyp/6-31G$^{**}$, LANL2DZ) and time-dependent DFT (TD-B3lyp/6-31G$^{**}$, LANL2DZ) levels, respectively. The absorption, fluorescence and phosphorescence spectra were estimated using TD-B3LYP and TD-wB97XD functionals and 6-31G$^{**}$basis set for C, H, N, O and LANL2DZ for Fe atoms in dichloromethane. • Atom probe analysis of Ni–Nb–Zr metallic glasses Atomic short arrangements of two Ni–Nb–Zr glassy alloys (doped and undoped) were examined through the 3D atomic reconstruction technique, atom probe tomography (APT). The chemical short configurations predicted accordingto two distinct theoretical models were compared with APT reconstructions, and inconsistencies were found. Additionally, diffraction experiments confirmed that the alloys under investigation were amorphous in nature. • Effect of amino-functionalization of MWCNTs on the mechanical and thermal properties of MWCNTs/epoxy composites The study investigates the tensile, flexural and thermal properties of epoxy resin matrix reinforced with pristine as well as amino-functionalized multi-walled carbon nanotubes (MWCNTs, 0, 0.25 and 0.50 wt%). The combination ofultrasonication and magnetic stirring has been used for the fabrication of MWCNTs/epoxy composite samples. The epoxy composite reinforced with 0.50 wt% amino-functionalized MWCNTs exhibits superior mechanical and thermal properties. The tensile and flexural strengths of this composite are noticed to be higher by about 13.5 and 17%, respectively, as compared with the neat epoxy specimen. The improvement in properties offered by amino-functionalized MWCNTs/epoxy composites is attributed to uniform distribution of MWCNTs in epoxy matrix as well as better interfacial adhesion between MWCNTsreinforcement and epoxy matrix,when compared with those noticed for epoxy composite reinforced with pristine MWCNTs. • Synthesis and characterization of inherently radiopaque nanocomposites using biocompatible iodinated poly(methyl methacrylate-$co$-acrylamide) and graphene oxide New inherently radiopaque nanocomposites were prepared using iodine-containing poly(methyl methacrylateco-acrylamide) and graphene oxide. For this purpose, P(MMA-$co$-AA) was synthesized via copolymerization of methylmethacrylate and acrylic acid, and modified with 4-iodophenyl isocyanate and 3,4,5-triiodophenyl isocyanate to form poly[(methyl methacrylate-$co$-(N-4-iodophenyl)acrylamide)] (1I-P(MMA-$co$-AA)) and poly[(methyl methacrylate-$co$-(N-3,4,5-triiodophenyl)acrylamide)] (3I-P(MMA-$co$-AA)), respectively. For comparative evaluation, the non-iodinatedcopolymer (PIC-P(MMA-$co$-AA)) was prepared via reaction of the P(MMA-$co$-AA) with phenyl isocyanate to investigate the effect of iodinated substituents on the morphology and thermal characteristics of the nanocomposites. All the nanocomposites were characterized by X-ray diffraction analysis, scanning electron microscopy, X-radiography and thermogravimetricanalysis. The results proved that thermal properties of the nanocomposites improved by the introduction of different amounts of graphene oxide into the copolymers’matrix. Radiopacity measurements showed the excellent radiopacityof iodinated nanocomposites and proved that 3I-GO-5 had radiopacity equivalent to that of an aluminium wedge with 2-mm thickness. • Growth, spectral, mechanical, electrical and optical characterization of guanidinium hydrogen succinate single crystal Slow evaporation method was employed to grow an organic crystal: guanidinium hydrogen succinate (GHS). Monoclinic structure of GHS was confirmed by single-crystal X-ray diffraction study and its space group was determined to be$P2_1/c$. Different functional groups present in GHS were estimated qualitatively by Fourier transform infrared analysis. The crystalline quality of the grown GHS was ascertained by high-resolution X-ray diffraction study. The UV–Vis absorption spectrum reveals a lower cut-off wavelength of 235 nm. The minimum absorption shows the wide optical transparency in the entire visible region.Work hardening co-efficient value ($n = 1.7$) shows that the GHS crystal belongs to soft material category. Behaviour of dipoles in the crystal was examined through dielectric study. The third-order nonlinear optical analysis wascarried out on GHS crystal through Z-scan technique. The nonlinear refractive index ($n_2$), nonlinear absorption coefficient ($\beta$) and third-order nonlinear optical susceptibility ($\chi^{(3)}$) were estimated to be$−5.78\times 10^{−8}$cm$^2$W$^{−1}$,$0.72\times 10^{−4}$cm W$^{−1}$and$8.09 \times 10^{−6}$esu, respectively. • Effect of tertiary butylpyridine in stability of methylammonium lead iodide perovskite thin films Perovskite material is a great visible light absorber in perovskite solar cells (PSCs). PSC has reported power conversion efficiency (PCE) of 22.1%. However, performance instability of the solar device base on this material hampersits commercialization. One of the factors responsible for performance instability in the cell is temperature. In this work, we carried out stability study of perovskite film treated with tertiary butylpyridine (tBP) as a surface modifier. Concentrationsof tBP added in perovskite material film were varied and the samples were subjected to temperature degradation test in a temperature-controlled chamber for 120 h. Ultraviolet–visible (UV–Vis) spectrophotometers, Fourier-transform infrared (FT-IR) spectrometers andX-ray diffractometers (XRD) were used to characterize the properties of the temperature-stabilitytested samples. The results show that the sample treated with 100$\mu$l of tBP has the best resistance to temperature degradation after the duration of the test. The surface-modified perovskite films, with 100$\mu$l of tBP, may reduce the degradation of PSCs. • Mesoporous$x$[Cu(II)O] nanoclusters dispersed and immobilized on$y$[SiO$_2$] matrix: structure and effective controlled biocidal activity against Pseudomonas aeruginosa and Bacillus subtilis Herein we report the synthesis of mesoporous nanostructures comprising copper (II) oxide {$x$[Cu(II)O]} immobilized on silica$y$[SiO$_2$] template for release of copper ions by precipitation via sol–gel technique. Three different specimens with increasing amount of Cu in the matrix with amount of Si being the same in all the samples, viz. ‘6Cu:5Si’, ‘4.5Cu:5Si’ and ‘3Cu:5Si’ where the numbers refer to the respective molar ratios of their respective domains, were prepared. Increase of crystallinity in the mesoporous material with increase in incorporation of copper domains consisting of CuO in SiO$_2$matrix has been established. The average size of the CuO nanoparticle (NP) (domain) is 20–30 nm. The BET surface area has been found to be 276–390 m$^2$g$^{−1}$and Langmuir surface area has been found to be 422–605.9 m2 g−1 for the samples5Si:3Cu–5Si:6Cu, respectively, having pore size of 4–6.5 nm. The cytotoxicity data show that the NPs are less toxic below concentration of 125$\mu$g ml$^{−1}$. A steady increase in percentage of bacterial-‘Escherichia coli’, ‘Pseudomonas aeruginosa’ and ‘Bacillus subtilis’ cell death (indicated by decrease in optical density) due to increase in concentrations of NPs after incubation for 14 h, showing sensitivity even at very low concentrations (5–20$\mu$g), has been observed. A comparative antibacterial activity test among the three prepared specimens has been reported, which shows better antibacterial activity with the lowest copper concentration. Better antibacterial sensitivity when compared with equivalent amount of commercial CuO is established. • Thermal stability and flame-retardant characteristic of irradiated LDPE and composites Magnesium hydroxide (MH) and alumina trihydrate (ATH) are extensively consumed as fillers in polyolefins to fabricate naturally responsive cables. Halogen-free wires, and especially cross-linked or thermoplastic elastomers, arefurther prevalent in worldwide use. The limited oxygen index (LOI), cone calorimeter, smoke density and thermogravimetry (TGA) experiments explain the thermal decomposition, flame-retardant and physical characteristics of samples. Results from studies of TGA, smoke emission and LOI testers showed that the thermal strength and flame-retardant characteristics of the samples containing MH compared with corresponding specimens containing ATH have superior thermal stability. The flame-retardant and heat resistance characteristics of samples were improved due to irradiation and the development of cross-linking bonds in the polymer framework. The results of the smoke density experiment show that adding MH to low-density polyethylene (LDPE) results in the lowest smoke density associated with LDPE and LDPE/ATH compounds. This study proved that the inclusion of MH and irradiation of specimens caused a greater thermal strength and also a superior flame-retardant polymeric product compared with the inclusion of ATH to similar irradiated specimens. These successes are useful and appropriate specifically for cable companies to deliver halogen-free flame-retardant cable materials. • Design of Permalloy–ferrite–polymer soft magnetic composites doped by ferrite nanoparticles and visualization of magnetic domains Soft magnetic composite materials were prepared by powder metallurgy technology. The composition of the new family of the materials was based on Permalloy type of ferromagnetic particles covered by Ni$_{0.2}$Zn$_{0.8}$Fe$_2$O$_4$nanoparticles. The spinel ferrite was prepared by electrospinning technology for achieving high-quality nanoparticles. A small amount of organic additives was included in final samples. The influence of magnetic ferrite dielectric coating on the magnetic properties of prepared composites was studied. The relatively high electrical resistivity leads to the real part of complex permeability up to 52 with stability up to high frequencies of about 1 MHz. SEM and TEM analyses were employed for composite characterization. The preparation of samples for magnetic force microscopic analysis is outlined in detail. The visualization of magnetic domain structure was done in order to understand the material behaviour of magnetic materials. • Crystallization and kinetics studies of Ti$_{20}$Zr$_{20}$Cu$_{60−x}$Ni$_x$($x = 10$, 20, 30 and 40) metallic glasses Synthesis and characterization of Ti$_{20}$Zr$_{20}Cu$_{60−x}$ Ni$_x$ ($x = 10$, 20, 30 and 40) metallic glasses are reported in this paper. Glassy ribbons are produced by rapid quenching using the standard copper wheel roller technique in argon atmosphere. Their structural characterization is carried out by X-ray diffraction (XRD) and thermal behaviour (crystallization) study by differential scanning calorimetry (DSC). Results of XRD on both sides of each ribbon sample confirmed that each sample was indeed amorphous/glassy as only a very broad peak in XRD pattern was observed. Metallic glass Ti$_{20}$Zr$_{20}$Cu$_{50}$Ni$_{10}$ shows three crystallization peaks in non-isothermal DSC scans while other three samples show only a single crystallization peak. The activation energy of crystallization for each sample has been calculated using three available models, namely, those of Kissinger, Augis–Bennett and Ozawa. All the three models gave nearly similar activation energies for a given sample within 10%.

• Characterization of organic light-emitting diode using a rubrene interlayer between electrode and hole transport layer

In this paper, we report the characteristic properties of an organic light-emitting diode (OLED) using a rubrene buffer layer over the fluorine-doped tin oxide (FTO) surface. Our study includes both electrical and optical properties of the device. Here, we study the OLED devices at different thicknesses of the buffer layer, which varies from 3 to 11 nm. For device fabrication, we use a thermal evaporation unit. Finally, we report that device performance in a bilayer anode form is always higher than that of a single-FTO-based device. Maximum device efficiency is found to be 6.31 cd A$^{−1}$ around 8-nm thickness of rubrene layer over the FTO surface.We also study the stability of both the single-layer and double-layer anode OLED devices. Through this study, we found that both device efficiency and luminance intensity of the bilayer anode OLED remain more stable for more number of days compared with the single-FTO OLED device.

• Microstructure and optical characterization of mechanosynthesized nanostructured TiSi$_x$N$_{(1−x)}$ cermets

Nanocrystalline cubic titanium silicon nitrides (TiSi$_x$N$_{(1−x)}$) with different Si concentrations have been synthesized at room temperature by mechanical alloying the stoichiometric compositions of ingredient powders in a nitrogenatmosphere. Structure and microstructure characterizations of unmilled and all ball-milled powders are carried out byanalysing respective X-ray diffraction patterns employing the Rietveld structure and microstructure refinement method.The presence of titanium, silicon and nitrogen in TiSi$_x$N$_{(1−x)}$ has been confirmed by energy-dispersive X-ray transmission electron microscopy analysis. Transmission electron microscopy image reveals that the average size of the spherical particles of 9-h-milled powder is $\sim$5 nm and size distribution is almost monodispersed, which corroborates well with the result of the Rietveld analysis. Bandgap energies of these solid solutions are determined by analysing respective UV–Vis absorption spectrum and it is found that the addition of silicon to insulating nanocrystalline TiN results in a reduction of bandgap energy and all solid solutions become wide-bandgap semiconductors with the addition of Si in different proportions.

• Effect of bismuth oxide nanoparticles on the physicochemical properties of porous silicon thin films

In this work, bismuth oxide nanoparticles were successfully deposited on porous silicon (PSi) in order to enhancethe light absorption and reduce the optical losses. The obtained bismuth oxide (Bi$_2$O$_3$)/PSi samples were characterizedby means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electronmicroscopy (SEM) combined with energy-dispersive spectroscopy (EDS), atomic force microscopy (AFM), photoluminescence(PL), UV–visible absorption and reflection spectroscopy techniques. The XRD studies revealed the formation of themonoclinic $\alpha$-Bi$_2$O$_3$ phase. The XPS analysis demonstrates the formation of highly pure Bi$_2$O$_3$ nanoparticles in accordance with XRD results. The SEM and AFM analyses confirmed that the bismuth oxide nanoparticles are well incorporated and uniformly distributed over the surface of PSi without changes in the arrangement and shape of the pores, resulting in an optimized microstructure. The Bi$_2$O$_3$/PSi films showed better absorption than PSi layers as indicated by UV–Vis absorption technique. The reflection measurements confirmed a further reduction in reflectivity of PSi from 6.4 to 3.5% after the inclusion of Bi$_2$O$_3$ nanoparticles, which is of significant importance for solar cells application since it can enhance its conversion efficiency. The Bi$_2$O$_3$/PSi films have a great promise to be used as efficient antireflection coatings in innovative concepts of higher efficiency and cost-effective solar cells.

• Investigation of optical properties and glass transition temperature of nano-epoxy matrix

In this research work, nanocomposites were synthesized by addition of fractions (0.0, 0.02, 0.04 and 0.06) of multi-wall carbon nanotubes (MWCNTs) to epoxy resin to investigate the optical properties and glass transition temperature. Optical measurement shows that epoxy matrix films have high absorption at the different MWCNTs fractions (0.0, 0.02, 0.04 and 0.06). The optical energy gaps for allowed direct transition were evaluated and found to decrease with increasing film fractions, precisely, from 2.85 to 1.32 eV when fractions increased from 0.0 to 0.06 of the matrix weights that indicated strong shifts at 435–935 nm with increasing fraction. The values of the absorption coefficient and extinction coefficientincreased with fractions of MWCNTs while the refractive index and the real part of dielectric constant decreased with the fractions of MWCNTs. Also, the glass transition temperature was investigated and was found to increase with increasing fraction of carbon nanotube in the matrix.

• Fabrication of micro–nano-roughened surface with superhydrophobic character on an aluminium alloy surface by a facile chemical etching process

In the present work, we have fabricated a superhydrophobic surface on aluminium alloy 2024 through a simpleimmersion chemical etching method in hydrochloric acid followed by a functionalization step in stearic acid solution. Theimpact of etching time on water contact angle was investigated and a contact angle of $\sim$167$^{\circ}$ was reached on the superhydrophobic surface, which was etched for 4 min. Morphology of the surface was evaluated by scanning electron microscopy and the surface chemical analysis was performed by energy-dispersive X-ray spectroscopy and Raman spectroscopy. We show that the fabricated superhydrophobic samples can besides water, also repel other liquids.We also demonstrate the selfcleaning properties of the fabricated samples using graphite particles as contaminants. Ultimately, we assessed the corrosionresistance properties of the fabricated surfaces by the potentiodynamic polarization method. The superhydrophobic surface exhibited increased corrosion potential and polarization resistance along with reduced corrosion current density, all of which are indicative of a significant improvement in corrosion performance of the superhydrophobic surface in comparison withtypical aluminium 2024. The cheap and facile superhydrophobic surface fabrication method presented in this study can beapplied to large scale samples with no need for electricity or expensive raw materials.

• Influence of NH$_4$Br as an ionic source on the structural/electrical properties of dextran-based biopolymer electrolytes and EDLC application

Biopolymer electrolytes (BPEs), consisting of ammonium bromide (NH$_4$Br) as the ionic provider and dextran(Leuconostoc mesenteroides) as the polymer host, are prepared by the solution cast technique. Interactions of cations from the salt have been confirmed with hydroxyl (OH) and glycosidic linkage (C–O–C) groups of dextran via Fourier transforminfrared analysis. Electrolyte with 20 wt% NH4Br maximized the ionic conductivity up to $(1.67 \pm 0.36) \times 10^{−6}$ S cm$^{−1}$. The trend of conductivity has been verified by field emission scanning electron microscopy, where the electrolyte surface became rough as the concentration of NH4Br exceeded 20 wt%. The contribution of ions as the main charge carrier in theBPE is confirmed by transference number analysis as $t_{\rm ion} = 0.92$ and $t_e = 0.08$. From linear sweep voltammetry, it is found that the highest conducting BPE in this work is electrochemically stable from 0 to 1.62 V. The fabricated electrochemical double-layer capacitor (EDLC) has been tested for 100 charge–discharge cycles and verified by cyclic voltammetry.

• Fabrication of MOF-177 for electrochemical detection of toxic Pb$^{2+}$ and Cd$^{2+} ions We have studied the electrochemical behaviour of room-temperature synthesized MOF-177. The MOF-177sample was characterized by various techniques like Fourier transform infrared spectroscopy, scanning electron microscopy,energy dispersive X-ray, powder X-ray diffraction, nuclear magnetic resonance and CHNS elemental analysis. The MOF-177 electrode was prepared and electrochemical performance was carried out to explore the electrical activity of MOF-177.Cyclic voltammetry studies were performed in 0.05 M K$_4$Fe(CN)$_6$solution and electrochemical sensing experiments were performed in 0.05MH$_2$SO$_4$and pH 7 buffer solution. A significantly increased electron transfer property has been observed and it has been explored for the electrochemical detection of heavy metal ions. The MOF-177/cp electrode has shown excellent sensitivity towards toxic heavy metal ions such as Pb$^{2+}$and Cd$^{2+}$at the limit of detection of 0.004 and 0.03$\mu$M, respectively. • Titanium-doped carbon and boron nitride nanocages (Ti–C$_{48}$and Ti–B$_{24}$N$_{24}$) as catalysts for ClO$+$1/2O$_2\to$ClO$_2$reaction: theoretical study The performances of Ti-doped carbon and boron nitride nanocages towards chloride monoxide (ClO) oxidation were examined. Details of mechanisms of oxidation of ClO on Ti-doped carbon and boron nitride nanocages were examined. Ti atoms of Ti–C$_{48}$and Ti–B$_{24}$N$_{24}$show catalytic activity towards ClO adsorption with low-barrier energies. Resultsdisplayed that the Ti-doped carbon and boron nitride nanocages oxidized ClO by the mechanisms of Eley–Rideal (ER) and Langmuir–Hinshelwood (LH). Catalytic activities in the LH path were limited by irremediable adsorption of chloridedioxide (ClO$_2$) on Ti–C$_{48}$and Ti–B$_{24}$N$_{24}$.While, in the ER path, the first and second ClO$_2$were separated, directly. Finally,the results proved that the Ti–C$_{48}$and Ti–B$_{24}$N$_{24}$show suitable catalytic abilities towards ClO oxidation via the ER path. • A kaolinite/TiO$_2$/ZnO-based novel ternary composite for photocatalytic degradation of anionic azo dyes Solar-assisted photocatalytic degradation of organic pollutants has emerged as efficient technology for the effective treatment of industrial wastewater. Here, we report a simple technique for the fabrication of a novel ternary photocatalystfrom kaolinite (K), TiO$_2$(T) and ZnO (Z). The most efficient catalyst was prepared at a calcination temperature of 60$^{\circ}$C. The fabricated ternary composite was characterized using different analytical techniques including Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, field emission-scanning electronmicroscopy and energy dispersive X-ray spectroscopy. The photocatalytic degradation was performed at room temperature (25$^{\circ}$C) using Remazol Red (RR), an anionic azo dye, as the model compound. A maximum of 98% degradation of RR was found with the ternary catalyst K$_{0.50}$T$_{0.45}$Z$_{0.05}$, which was prepared from 50% kaolinite (w/w), 45% TiO$_2$(w/w) and 5% ZnO (w/w). The catalyst was found to be suitable for long-term repeated applications. Mechanistic investigation through radical trapping experiments confirmed hydroxyl radicals as the potential contributor to the photocatalytic degradation of RR. It is highly expected that a novel photocatalyst design such as this will pave way towards further development ofmaterials capable of hazardous dye removal from industrial effluents. • A proof of concept for low-cost rechargeable aqueous aluminium-ion batteries In an effort to develop Al$^{3+}$ion-based rechargeable electrochemical cells, there is massive exploration of appropriate electrode materials in contemporary times. Aluminium is a natural choice due to its high abundance, low cost and easy processing. Herein, the working of rechargeable aqueous aluminium-ion batteries which comprise graphite from pencil sketch as the cathode, TiO$_2$as the anode and an Al$^{3+}$ion conducting aqueous electrolyte is demonstrated for the first time. The aluminium-ion cell delivers a discharge voltage of 1.5 V and stable specific capacities of 25 mAh g$^1{−1}$over 1000 cycles. This proof of concept emphasizes on the possibility of achieving sustainable, easy to assemble and low-cost rechargeable batteries. • Synthesis and evaluation of antibacterial properties of magnesium oxide nanoparticles In this paper we studied the efficiency of magnesium oxide (MgO) nanoparticles with an average size of 27 nm synthesized by a simple soft chemical method, in killing both Gram negative and Gram positive pathogenic bacteria. The antibacterial activity was determined by a minimum inhibitory concentration technique, agar cup method and live count technique. These nanoparticles show the maximum antibacterial activity towards Bacillus sp. in comparison with Escherichia coli. Transmission electron microscopy analyses of the treated-bacterial strains showed a morphological deformation with increased cell wall disruption. From the analysis of the antibacterial activity of MgO nanoparticles it is revealed that6$\mu$g ml$^{−1}$of dose is sufficient for killing Bacillus sp. whereas it is 7.5$\mu$g ml$^{−1}$for E. coli. These doses may be used in medical application. MgO nanoparticles could be used as antibacterial agents after completion of successful in vivo trials. • Synthesis of cerium-oxide NPs and their surface morphology effect on biological activities Herein, reliable work has been carried out on the synthesis of cerium-oxide (CeO$_2$) nanoparticles (NPs) viahydrothermal and co-precipitation methods. We emphasize the highly adequate hydrothermal method for synthesizingCeO$_2$NPs for biomedical applications. Absorption spectra showed peaks at 283 and 274 nm, which confirm the formationof CeO$_2$NPs for hydrothermal (HYNPs) and co-precipitation (CONPs) methods, respectively. Functional group analysisfirmly showed the presence of organic and inorganic species, which revealed similar characteristics of both HYNPs andCONPs. The cubic structure and the average crystallite size of the synthesized NPs are determined using Scherrer’s andWilliamson–Hall methods. The obtained average particle size is compared by using high-resolution transmission electronmicroscopy, which is around 10 and 5 nm for HYNPs and CONPs, respectively. Further, we studied their antimicrobial activities and consequently, the synthesized CeO$_2$NPs showed excellent antimicrobial activities. Moreover, HYNPs yieldedpromising antioxidant activity with the lowest IC$_{50}$as compared with CONPs. Owing to the biological activity of CeO$_2$NPs, HYNPs act as best therapeutic agents in biomedical applications as well as its vital role in antibiotics. • Constitutive modelling of Al7075 using the Johnson–Cook model In this paper, hot compression behaviour of Al7075 in the temperature range of 573–723 K and the strain rate range of 0.001–0.1 s$^{−1}$, based on standard requirements, was studied. The prediction of flow stress was performed using constitutive equations based on the basic and modified-Johnson–Cook model and the accuracy of the proposed models was estimated by comparing with the experimental results by the statistical error analysis method. Based on the experimental results, flow stress is changed significantly with changes in the strain rate and temperature. However, the basic model cannot predict the correlated effects of these parameters which decrease its accuracy of model, the flow stress of the materials especially at high temperatures. During the calculation of the constants based on the modified model, the effects of hardening and softening behaviour were included in addition to considering the correlated effects of the parameters. The accuracy of the modified model increased significantly when compared with experimental results. • First-principles computations of Y$_x$Ga$_{1−x}$As-ternary alloys: a study on structural, electronic, optical and elastic properties In this work, the first-principles computational study on the structural, elastic, electronic and optical propertiesof Y$_x$Ga$_{1−x}$As as a function of yttrium concentration ($x$) is presented. The computations are performed using the fullpotential linearized augmented plane wave plus local orbital method designed within density functional theory. Firstly,we performed our calculations on the most stable phases, NaCl and zinc blende, then their transition pressure for eachconcentration is determined and analysed. Our computed results for the zero yttrium concentration are found consistentwith the available experimental measurements as well as with theoretical predictions. Moreover, the dependencies of theseparameters upon yttrium concentration ($x$) were found to be non-linear.We also report computed results on electronic-bandstructure, electronic energy band gap results and density of states. A systematic study on optical properties to analyse itsoptoelectronic character and elastic properties is presented. • Cyclic oxidation of Ni–Fe$_2$O$_3$composite coating electrodeposited on AISI 304 stainless steel Protective coatings can be applied to enhance the performance of interconnects in solid oxide fuel cells. In this study, AISI 304 steel was coated with a Ni–Fe$_2$O$_3$composite to form a modified-Watt’s type electrolyte by the conventional electro co-deposition method. The characterization of the coatings before and after cyclic oxidation was performed by scanning electron microscopy and X-ray diffraction. In order to evaluate the oxidation behaviour, thermal cycling was carried out in a furnace at 850$^{\circ}$C. The results indicated that the coated steel had better oxidation resistance in comparison with the uncoated steel. After 60 cycles of oxidation, the Ni–Fe$_2$O$_3$composite coating was converted to FeNi$_2$O$_4$, NiCrO$_4$, MnFe$_2$O$_4$and Fe$_2$NiO$_4$. The Fe$_2$O$_3$/NiFe$_2$O$_4$composite coating reduced the outward migration of chromium and the growth rate ofthe Cr$_2$O$_3$layer. • The effect of shape and size of ZnO nanoparticles on their antimicrobial and photocatalytic activities: a green approach In this paper, ZnO nanoparticles (NPs) having potent photocatalytic and antimicrobial activities have been synthesized by using the aloe vera plant extract. The ZnO NPs have been synthesized using (Zn(CH$_3$COO)$_2$·2H$_2$O) (5, 10 and 50 mmol kg$^{−1}$), at temperature 70$^{\circ}$C and pH 11.5. The synthesized NPs were examined using UV–Visible, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy(TEM) characterization techniques. TEM analysis confirms the synthesis of ZnO NPs with hexagonal, spherical, cylindrical and cuboidal shapes decorated under different concentrations of precursor metal salt. UV–Visible studies revealed thatZnO NPs have a wide energy band gap varying from 3.36 to 3.43 eV. The synthesized ZnO NPs were examined for the photocatalytic degradation of methyl orange dye which resulted in up to 95% degradation. ZnO NPs are also inspected for the antibacterial activity against Bacillus subtilis (MTCC 441), Staphylococcus aureus (MTCC 737) and Escherichia coli (MTCC 739) pathogenic bacteria. • Investigation of flow behaviour and lubrication capabilities of MoS$_2$Flow behaviour of lubricants largely depends on their rheological properties which in turn strongly influence their lubrication capabilities and ultimately the machine life. Modern chemistry plays a great role in the synthesis of nano-additives that help in enhancing the rheological and tribological properties of the lubricants. In the present study, the rheological and tribological studies of MoS$_2$nanofluids are presented in order to determine their flow behaviour and lubrication capabilities. For studying the effect of MoS$_2$nanoparticles on the flow behaviour and lubrication capabilities of lubricants, two commercially available blended synthetic engine oils of SAE grades 5W-40 were selected. MoS$_2$nanoparticles were synthesized by hydrothermal methods. Surface modification of the synthesized MoS$_2$nanoparticles was performedbefore blending them with the base lubricants in 0.1, 0.15 and 0.2% concentrations. Standard ASTM and IS procedures were used to determine physicochemical properties and tribo-performance behaviour of oils, respectively. The rheological parameters of MoS$_2$nanofluids were determined using a rheometer. The study reveals that tested MoS$_2$nanofluids behavedas non-Newtonian lubricants with shear thinning behaviour at all tested temperatures and exhibited viscoelastic behaviour at small-shear rates. As a result of this anti-wear property showed a significant enhancement up to 20% for 0.2% MoS$_2$indicating better anti-wear properties of MoS$_2$nanofluids. However, a marginal reduction in friction for the tuning of 4% observed for 0.2 wt% of MoS$_2$nanoparticles in the tested lubricants indicates that finished products have little scope to improve anti-friction properties under the influence of the already present additives. • Antibacterial activity of ZnO nanoflowers deposited on biodegradable acrylic acid hydrogel by chemical bath deposition In the first part of this study, acrylic acid (AA) hydrogels were produced by a free radical reaction. Chemical and morphological structures of AA-hydrogels were specified by using Fourier transform infrared (FT-IR) spectroscopy andscanning electron microscopy (SEM) techniques. In the second part of the study, ZnO nanoflowers were synthesized on the AA-hydrogel by using a chemical bath deposition (CBD) technique for the first time in the literature. The AA-hydrogel acted as the substrate in the CBD process. The deposition time effect on the morphological properties of ZnO nanoflowers was determined by applying SEM. According to the SEM results, the deposition time in the production of ZnO nanoflowers has played a vital role in the surface morphology. Chemical, morphological and thermal properties of the ZnO nanoflowers were determined by applying FT-IR, scanning electron microscopy-energy dispersive X-ray spectroscopy and thermogravimetric analysis techniques. Elemental mapping of ZnO nanostructures was carried out using SEM. The antibacterial activity of theZnO nanoflower-deposited AA-hydrogel was determined against Gram-negative and Gram-positive bacteria. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used as test microorganisms. Gram-negative bacteria were moreresistant to hydrogels and ZnO nanoflowers compared to Gram-positive bacteria. • A remarkable enhancement between optical transparency and SHG efficiency on doped-KHP single crystals Potassium hydrogen phthalate (KHP) single crystals are non-linear optical materials and their transmittance window are remarkably enhanced by an organic dopant such as resorcinol. The present study was mainly focused on the growth and characterization of the single-crystal KHP doped with resorcinol which was synthesized by a slow evaporation solution technique and its dimension was found to be$8 \times 7 \times 2.75$mm$^3at ambient temperature. Vibrationalassignments of the functional groups confirmed the presence of dopants. The optical behaviour of the grown crystal was explored by ultraviolet–visible–near-infrared studies which result in 99% of the transmittance with the cut-off wavelength of 250 nm. The mechanical property was analysed by the Vickers microhardness test. The apparent microhardness increases with increasing applied indentation load revealing the reverse indentation size effect behaviour. Organic impurity increases the second harmonic generation efficiency of KHP, suggesting that the molecular alignment in the presence of resorcinolresults in enhanced non-linearity. • Silicone rubber composites fabricated using KH550-modified poplar leaves graphene Silicone rubber (SR) composites were fabricated using poplar leaves graphene (PG). PG was synthesized from poplar leaves and modified-poplar leaves graphene (MPG) was obtained by treating graphene with a silane coupling agent\gamma$-aminopropyltriethoxysilane (KH550). The biosynthesized PG and MPG were characterized by using organic elemental analysis, X-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy (SEM). The PGmodified SR composites were studied by using their mechanical properties, Fourier transform infrared spectroscopy, SEM and thermogravimetric analysis. The results showed that the PG synthesized by poplar leaves had high-carbon content and purity. The MPG was more evenly dispersed into SR than the PG, the mechanical properties of the MPG/SR composites were better than those of the PG/SR when the MPG content was 0.1 phr (parts per hundred rubber), the tensile strength and elongation at break were increased by 36.2 and 19.4% respectively and the wear resistance was increased by 57.1%. The thermal stability of the MPG/SR was higher than that of the PG/SR and SR. This important discovery could not only solve the problem of the origin of graphene, but also broaden the application of SR composites. • Investigating the role of amides on the textural and optical properties of mesoporous-nanostructured$\theta$-Al$_2$O3 Mesoporous-nanostructured$\theta$-Al$_2$O$_3$was synthesized by an autoclaving technique using different amidesi.e., formamide (F), dimethyl formamide (DMF) and diethyl formamide (DEF) at 150$^{\circ}$C/24 h followed by calcinationat 1000$^{\circ}$C. Crystallization and structural behaviour of the as-synthesized materials were characterized by X-raydiffraction and Fourier transform infrared spectroscopy. The porosity study was carried out by N2 adsorption–desorption(BET) technique. Microstructural features were measured by transmission electron microscopy (TEM). The amidebasedsolvents played a deliberate role in microstructural and textural features of$\theta$-Al$_2$O$_3$. The DMF-based solventshowed an enhanced surface area of 158 m$2^$g$^{−1}$. The as-prepared$\theta$-Al$_2$O$_3$rendered a nano-sheet, nano-rod and nano-flake like morphology for F, DMF and DEF derived products, respectively. From the UV–Vis spectroscopic measurement, the estimated band-gap of$\theta$-Al$_2$O$_3$was found to be 5.16–5.40 eV. Photoluminescence investigation further revealed blue emission particularly for excitation at a wavelength of 252 nm. A DMF-derived sample rendered thelowest band gap due to its smaller crystallite size and higher surface area compared to that of F- and DEF-derivedsamples. • Comparative machinability characterization of wire electrical discharge machining on different specialized AISI steels In this work, we have attempted to prepare a comparative machinability study of wire electrical discharge machining of different difficult-to-machine materials, viz., stainless steel (SS) 316, H21 hot work tool steel and M42 highspeedsteel (HSS). The key features, which are compared during the analysis, are mainly material removal rate, average surface roughness, kerf width, wire consumption rate (WCR), recast layer (RL), elemental diffusion, surface morphology and micro-hardness of the machined surface. They are found to be greatly influenced by pulse energy. The pulse energy is calculated in terms of ‘specific discharge energy’. Apart from the discharge energy, the thermal conductivity of the material also plays an important role in the formation of RL and inclusion of foreign elements such as carbon, oxygen, copper andzinc in RL. H21 steel has been found to be more prone to thermal defects due to its high-thermal conductivity and high tensile residual stresses, whereas more re-solidification of foreign materials is observed in SS316 and M42 HSS due to theirhigh adhesive properties and low-thermal conductivity. But, in low-energy cutting, more uniform surfaces are observed in H21 steel in comparison with other two types of steel. • Enhanced topical econazole antifungal efficacy by amine-functionalized silica nanoparticles The present study aims at developing efficient econazole (ECO) platforms as topical creams for the treatment offungal skin infections. The hexagonalmesoporous silica nanoparticle, known as MCM41,was synthesized and functionalized by aminopropyl groups (MCM41-NH$_2$). Various ECO concentrations were loaded into MCM41 and MCM41-NH$_2$(MSNs); the optimized complexes with the highest entrapment efficiencies were characterized by X-ray powder diffraction, scanning electron microscopy (SEM) and gas-volumetric analysis (BET). SEM images showed a spherical shape of the parent nanoparticles—higher drug loading and incorporation into the nanoparticles were obtained by amino-functionalized MCM41. Cytotoxicity assays of MCM41 and MCM41-NH$_2$and the ECO inclusion complexes elucidated no toxicity to human dermal fibroblast cell lines. Enhanced antifungal activity against Candida albicans was observed for ECO/MCM41-NH$_2$compared with ECO/MCM41 and simple cream. No irritation was observed by the cream containing ECO/MSN application on white male rabbit skin after 72 h. MSNs were stable within 1 year storage. ECO-loaded silica nanoparticles can be considered for the development of reliable alternatives to ECO cream for the treatment of skin fungal infections. • Synthesis of ZrO$_2$nanostructure for gas sensing application ZrO$_2$nanopowder has been synthesized by the conventional precipitation method for gas-sensing application. The synthesized powder was dropcast and subsequently annealed at 100$^{\circ}$C. The drop-casted film has been subjected to X-ray diffraction analysis, scanning electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence study and$I –V$measurement in order to observe its structural, morphological, optical and electrical properties. The gas sensing measurement has been performed for the thus prepared ZrO$_2$film by an exposure to different reducing gases(ammonia, ethanol, formaldehyde, acetone and xylene) at different temperatures for various gas concentrations. It has been observed that the film shows a better response towards ammonia (about 18%) compared to all other gases due to faster diffusion. Also, a quick response and recovery time have been found as 70 and 70 s, respectively, for ammonia. • High-temperature corrosion of aluminized-AISI 1020 steel with NaCl and Na$_2$SO$_4$deposits High-temperature corrosion of aluminized-American Iron and Steel Institute (AISI) 1020 steel with sodium chloride (NaCl) and sodium sulphate (Na$_2$SO$_4$) deposits was studied using isothermal oxidization in a dry air environment at 700$^{\circ}$C for 49 h. NaCl and Na$_2$SO$_4$deposits on the aluminide layer interfered with protective alumina/aluminium oxide(Al$_2$O$_3$) scale formation on the steel substrate. Chlorine and sulphur gases (Cl$_{2g}$and S$_g$, respectively) released into the atmosphere corroded the protective Al$_2$O$_3$layer. Corrosion of the Al$_2$O$_3$layer was also due to local formation of iron oxide (Fe$_2$O$_3$). Fe$_2$O$_3$growth is attributed to ferric chloride (FeCl$_3$) vaporization. S$_g$diffusion into the Al$_2$O$_3$scale via Al$^{3+}$vacancy defects led to the formation of aluminium sulphide on the aluminide layer surface. Cl and S consequently induced hot corrosion of the aluminized steel, thereby increasing cyclic oxychloridation and sulphidation rates at high temperatures. • An in vitro comparative study of layered-double hydroxide nanoconjugate in the delivery of small interference and short-hairpin ribonucleic acid Alzheimer’s disease is a disease which cannot be cured completely. In this aspect ribonucleic acid interference(RNAi) therapy is a prospective therapeutic mechanism which can be used for identifying a future curative procedure. RNAitherapy comprises small interfering RNA (siRNA), short hairpin (shRNA) and micro-RNA therapeutics. Within these threemechanisms we have identified two of them as an effective method of combating this genetic incurable disease. siRNAs andshRNAs are very much effective in vitro that is already proved in many research work. In our study we have used a very potent, biocompatible nanoparticle-layered double hydroxide for delivering these macromolecules. However, the intercalation and cellular internalization of these macromolecules demonstrated significant differences. As siRNAs have low-molecular weight than shRNAs they demonstrated different characteristics in the case of internalization within layered-double hydroxide and while cellular internalization. At the end of this study it has been found that both of these macromolecules may be used as a therapeutic approach of Alzheimer’s disease after studying it in future in animal and human subjects. • Adsorption of benzene, aniline and benzoic acid in water by fullerene (C$_{60}$) and fullerene nanowhiskers Most aromatic hydrocarbons and their derivatives are harmful organic molecules. Despite their low solubility, trace amounts of aromatic hydrocarbons can be present in water. If water is contaminated by aromatic hydrocarbons, it isvery difficult to remove these from water. Through contaminated water, these compounds can exert deleterious effects in plants and animals, as well as on human health. Fullerenes and their derivatives typically exhibit hydrophobic characteristics, and are therefore considered as good adsorbents for the removal of aromatic hydrocarbons. Herein, the removal of benzene,aniline and benzoic acid by fullerene and fullerene nanowhiskers was evaluated. While benzene was removed satisfactorily from water, aniline and benzoic acid were not, owing to the presence of ionized functional groups. However, adjustment of the solution pH to values where the functional groups of aniline or benzoic acid do not have any charge, resulted in an increase in their adsorption. High pH values were found to have a positive effect on the removal of aniline, while low pH values were beneficial for the adsorption of benzoic acid. Fullerenes and fullerene nanowhiskers were thus found to be promising adsorbents for the removal of aromatic hydrocarbons. • Study on the corrosion and wear characteristics of magnesium alloy AZ91D in simulated body fluids Bioimplants made of metallic materials induce a stress-shielding effect and delayed osteoblast activity during in-vivo experiments. Bioimplants also suffer corrosion, wear and combined effect of corrosion–wear during their service time. Bioimplants made of magnesium alloys result in a negligible stress shielding effect, owing to their similarity with bone’s elastic modulus. However, the soft matrix of the magnesium alloy is susceptible to high-wear rates. In this study, magnesiumalloy AZ91D is subjected to the corrosion test (immersion and electrochemical), adhesive wear and simultaneous corrosion–wear test to test the significance of the body fluid in the corrosion–wear rate of the bioimplants. The surface morphology,elemental composition and phase composition of the specimens are characterized using field emission scanning electronmicroscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analytic techniques. The results indicate that thesimulated-body fluid has a significant effect on the corrosion rate and corrosion–wear rate of the specimens. • Candle soot-coated egg carton material for oil water separation and detergent adsorption A hydrophobic and superoleophilic adsorbent was prepared by coating candle soot (CS) on the surface of a recycled egg carton material (ECM). This waste material has been explored as a cost-effective adsorbent to remove oiland detergent from water. The surface of the material was coated with CS solution prepared by mixing soot with acetone and characterized by scanning electron microscopy and contact angle measurements. The rate of fall of contact angle for water and oil was evident of water rejection and oil absorption capability of the coated-waste material. Further, the effect of temperature on the contact angle between water and surface was observed. The carbon-coated ECM demonstrates good absorption capacity with oils of different densities, without pre-treatments and surface modifications. It also shows its capability to absorb detergent from water with a pH value declining towards 7. Thus, a waste material can act as an effective alternative for filtering of oil and detergent water for households and industries. • Enhancement of impact strength of poly(lactic acid)/silicon carbide nanocomposites through surface modification with titanate-coupling agents In this study, poly(lactic acid) (PLA)-based nanocomposites were fabricated from PLA and silicon carbide (SiC) using solution blending. The surfaces of SiC nanoparticles were treated with a titanate-coupling agent. The influence of the SiC content on thermal stability, flexural properties, impact strength and fracture morphology of the nanocomposites was investigated. The impact strength of the nanocomposites was increased by the introduction of SiC nanoparticles. The nanocomposites containing SiC nanoparticles treated with a titanate-coupling agent (termed T-SiC) exhibited higher impact strengths than the nanocomposites containing neat SiC nanoparticles under the same conditions. Scanning electron microscopy results showed good compatibility between the T-SiC nanoparticles and the PLA matrix. • Self-support wood-derived carbon/polyaniline composite for high-performance supercapacitor electrodes Wood-derived carbon is a neoteric self-supporter electrode material for supercapacitors or batteries. To improve the electrochemical characteristics, polyaniline (PANI) was deposited on wood carbon (WC) by an in-situ polymerization method. The sandwich-like symmetrical solid-state supercapacitor was developed by preparing WC/PANI composites andtheir electrochemical properties were examined. The device showed an excellent capacity retention and displayed the maximum specific capacitance of 22.5 mF cm$^{−2}$at a scan rate of 10 mV s$^^{−1}$. It was also demonstrated an excellent electrical conductivity and an outstanding retention of$\sim$82%. It was suggested that the PANI accommodated into WC without any significant morphological change during the charge–discharge cycling of the hybrid WC-based composites. The microstructure and chemical structure of WC/PANI composites were also characterized by the Fourier-transform infrared, Ramanspectroscopy and X-ray diffraction techniques. • Synthesis and electrochemical properties of Co-doped ZnMn$_2$O$_4$hollow nanospheres Spinel structure Co-doped ZnMn$_2$O$_4$nanocrystals were successfully synthesized by a hydrothermal method. The effects of Co-doping concentration on the structure and electrochemical properties of the samples were investigated.The experimental results manifest that all samples exhibit a single-phase with a tetragonal structure, and morphologies are regular hollow microspheres. Cyclic voltammetry curves for all samples are similar to a rectangular shape with symmetric nature and no obvious redox peak.Galvanostatic charge–discharge curves were triangular and symmetric. Impedance spectra revealed that Zn$_{1−x}$Co$_x$Mn$_2$O$_4$possess low resistance. Better electrochemical properties of the ZnMn$_2$O$_4$electrode could be obtained when the Co-doping ratio is 0.3. Zn$_{0.7}$Co$_{0.3}$Mn$_{2}$O$_4$exhibits much higher specific capacitance (306 F g$^{−1}$) at a scan rate of 5 mV s$^{−1}$, and shows excellent cycling stability and retains 98.2% of its initial capacitance after 1000 cycles. The enhanced capacitive performance in this work can be attributed to the incorporation of Co ions doped into the ZnMn$_2$O$_4$host lattice. • Removal of Cu(II), Co(II) and Cd(II) from water solutions by layered-double hydroxides with different [Mg(II)]/[Fe(III)] molar ratios This work presents a study of sorption of heavy metals (HMs)—Cu(II), Co(II) and Cd(II)—from water media by carbonated and calcined forms of layered-double hydroxides (LDH) with various Mg(II)/Fe(III) molar ratios, whichare obtained by precipitation. It is ascertained that the maximum sorption (99.9%) of the HM ions stated is observed with the use of calcined forms of LDH at pH > 2.8 (pH after sorption$\geq$8.3). Such an increase in the pH of the aqueous suspension causes sorption of the HM ions by the mechanism of their precipitation in the form of hydroxides or hydroxocarbonates (for Cu(II)). Sufficiently high degrees of sorption of HMs, even at low pH of the aqueous medium, are apparently caused not only by the precipitation of their hydroxide forms, but also due to the complex formation with ferrinol groups of brucite sorbent layers. An increase in the Mg/Fe ratio from 2 to 4 and a corresponding decrease in the positive charge of the layers, which determines the size of the interlayer space in the LDH, have virtually no effect on the degree of extraction of HMs. The presented results suggest that the use of the studied-LDH in practice might be promising. • Effects of different polymers and solvents on crystallization of the NaYF$_4$:Yb/Er phase Up-converting NaYF$_4$:Yb,Er nanoparticles were obtained by polymer-assisted solvothermal synthesis using a common solution of hydrated RE nitrates in ethanol or ethylene glycol. It was shown that polymer choice (polyacrylic acid—PAA, polyvinylpyrrolidone—PVP and chitosan—CS) controls the size and shape of NaYF$_4$:Yb,Er nanoparticles, while the solvent type and pH value affect their crystallinity. Consequently, the spherical nanoparticles of a cubic ($\alpha$) phase, the average size of which ranged from 60 to 140 nm, were obtained either when PVP/ethanol or PVP/ethylene glycol were used solely during synthesis, whereas NaOH addition induced hexagonal ($\beta$) phase nucleation. The formation of the hierarchically organized spherical aggregates and nanofoils was observed when CS and PAA were used during synthesis, respectively. The average crystallite size, microstrain, doping level, lattice parameters, as well as, the presence of the certain ligands on the particle surface were determined and correlated with the intensity of visible-light emission observed under 980 nm laser-diode excitation. • Some aspects of new Cu(NbC) films In this study, new barrier-free Cu(NbC) alloy films with two different thicknesses, i.e., 8 and 300 nm, containing 0.3 at% C and 0.5 at% Nb, which are deposited via co-sputtering on three types of substrates, viz., Si, stainless steel and polyimide (PI), have been developed, annealed, measured and analysed. The resistivity value of the new 300-nm-thick films atop Si substrates is 3.07$\mu\Omega$cm after annealing at 450$^{\circ}$C for 200 h. The low resistivity and diffusion depth of the new films exhibit their good quality in anti-oxidation stability in a high-temperature environment. The films also display high-adhesive strength atop either stainless-steel or PI substrates,$\sim$7–8 times greater than that of their pure-Cu counterparts. In sharp contrast, the antibacterial ratio of the new films is$\sim\$96% while that of their pure-Cu counterparts is 0%. In addition, the contact angles of Cu(NbC) films are greater than those of their pure-Cu counterparts, resulting in a far superior antibacterialefficacy for the new films to pure-Cu films against, for example, Staphylococcus aureus BCRC 10451.With these desirable merits, the new films seem to be a good candidate material for bacteria killing and prevention, reduction of legionella spread inside hospitals and/or large buildings, biological medical care systems and advanced surgical tools. The new films deposited on PI substrates also seem to be suitable for making supple electrically conductive parts or devices, such as flexible panels, keyboards, screens, smartphones embedded in smart textiles and so forth.

• Bulletin of Materials Science

Volume 43, 2020
All articles
Continuous Article Publishing mode

• Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020