• Volume 43, All articles

      Continuous Article Publishing mode

    • Novel highly active Ni–Re super-alloy nanowire type catalysts for CO-free hydrogen generation from steam methane reforming

      LINSHENG WANG

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      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

      Z EBRAHIMZADEH A SALEHZADEH A S NAEEMI A JALALI

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      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

      EVGENY BULANOV NADEZHDA SILINA MAXIM LELET ALEXANDER KNYAZEV LARISA SMIRNOVA DIANA ALEYNIK IRINA CHARYKOVA

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      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$_2$PO$^−_4$): investigation by impedance spectroscopy

      F Z BOURAGBA W ELHATIMI R LAHKALE E M MOUJAHID E SABBAR

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      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$_2$PO$^−_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

      S H YETGIN

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      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

      FARZIN AZIMPOUR-SHISHEVAN HAMIT AKBULUT M A MOHTADI-BONAB

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      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

      M KIRUBANITHY N SIVANANTHAM N GOPALAKRISHNAN K BALAMURUGAN

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      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 $\sim$200 $\mu$m 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 $\sim$3.7 to 2.7 eV) and photoluminescence (PL) properties, which depend on the temperature of the heat treatment. A comprehensive investigation has been made using X-ray diffraction, thermal analyses, energy dispersive X-ray and Raman spectroscopies to understand how/why the optical properties of the muscovite sheets changed up on heat treatments. Besides, no phase changes were found in the layered, lamellar crystal structure, evidences for the known dehydroxylation of muscovite were clearly seen from the thermal analyses data. Further, the Raman spectrum of the muscovite sheet heat treated at 900$^{\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

      DEBOLINA DAS TIRTHANKAR CHOUDHURY

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      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

      I BIRLIK D DAGDELEN

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      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

      S NAVEEN KUMAR VIVEK JAMES VINEETH JAMES M AKHILA MAHESWARI N SIVARAMAN C V S BRAHMANANDA RAO D PRABHAKARAN

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      In this work, we report a facile route for the synthesis of worm-like mesoporous Fe$_2$O$_3$-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$_2$O$_3$ 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

      R A BUSARI B A TALEATU S A ADEWINBI O E ADEWUMI E OMOTOSO K O OYEDOTUN A Y FASASI

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      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

      BHUPENDER RAWAL PRASHANT DIXIT N N WATHORE B PRAVEENKUMAR H S PANDA

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      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

      NAVEEN KUMAR SACHIN KUMAR KAMNA YADAV ARVIND KUMAR PAWAN K SINGH NEELABH SRIVASTAVA RISHI P SINGH

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      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

      V M VIDYA CHETTI PRABHAKAR

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      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

      SUSAN IMMANUEL R SIVASUBRAMANIAN

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      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

      ONKAR MANGLA SAVITA ROY S ANNAPOORNI K ASOKAN

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      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

      MOHANARANGAN SUNDARARAM KUMAR JANAKIRAMAN ANNAMALAI SENTHIL KUMAR V LAKSHMINARAYANAN KRISHNAN SANKARAN

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      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

      ZENGCAI MI KAIJIN ZHU LIFENG DING MEYSAM NAJAFI

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      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

      YINGMING ZHAO FAN TONG CHENYAO FAN SIQI YU BING HAN JIAYANG GAO YUNCHAO LOU PENGLIN JIANG ZHIYU WANG

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      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

      MARINA FERNANDES COSATE DE ANDRADE RENATO CARAJELESCOV NONATO RENATO BOTTINI ANA RITA MORALES

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      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

      YAN LIN XIE LIU XIAO-QIN LIU LIN-BING SUN FENG CHEN CHENGBAO LIU ZHENGYING WU ZHIGANG CHEN

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      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)

      SEYYEDE MEHRANGIZ ATYABI HAMID REZA SHAMLOUEI GODARZ MOHSENI ROOZBAHANI ELHAM ASGARI

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      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

      G RAVI KUMAR CH SRINIVASA RAO

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      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

      PAYEL DOWARI BAPAN PRAMANIK DEBAPRATIM DAS

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      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)

      LEI ZHENG ZHAO CHENG HAO HE HAO XU FEI LIANG LONG PANG

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      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

      A YOUNES N DILMI A BOUAMER

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      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

      ROBERTO MENDOZA-SERNA JOSÉ OCOTLÁN FLORES-FLORES MARINA CABALLERO-DÍAZ ATENEA JOSEFINA CHONG-SANTIAGO LUCILA VALDEZ-CASTRO ROBERTO YSACC SATO-BERRÚ

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      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

      AJAY D PINGALE SACHIN U BELGAMWAR JITENDRA S RATHORE

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      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

      L GO L MACARAIG E ENRIQUEZ

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      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$_3$

      RINKU SARKAR BIDYUT SARKAR SUDIPTA PAL

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      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

      J Y CHO M SIYAR S H BAE J S MUN M Y KIM S H HONG C PARK

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      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

      QIAN LIU CHAOFAN ZHANG LIXIA YANG LIANGJIU BAI YING LIANG WENXIANG WANG HUAWEI YANG DONGLEI WEI HOU CHEN

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      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

      SUNIL KUMAR VLADIMIR PAVELYEV PRABHASH MISHRA NISHANT TRIPATHI

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      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

      SUDIPTA SEN N B MANIK

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      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

      BIMAL DEBNATH MANISH DEBBARMA DEBANKITA GHOSH SAYANTIKA CHANDA RAHUL BHATTACHARJEE SURYA CHATTOPADHYAYA

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      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

      M ARULMURUGAN A S SELVAKUMAR KRISHNASAMY PRABU G RAJAMURUGAN

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      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

      MARYAM ASARIHA AZAM CHAHARDOLI NADIA KARIMI MARYAM GHOLAMHOSSEINPOUR ALIREZA KHOSHROO HOUSHANG NEMATI YALDA SHOKOOHINIA ALI FATTAHI

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      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

      PRITAM SINGH P K MAITI KAMALIKA SEN

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      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

      U FAWAD IBRAHIM GUL H J KIM WAZIR MUHAMMAD MATIULLAH KHAN

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      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

      HAWBASH H KARIM M S OMAR

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      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

      SREE SATYA BHARATI MORAM CHANDU BYRAM VENUGOPAL RAO SOMA

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      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

      AZADEH HAGHIGHATZADEH

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      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

      K MOHANRAO HANSNATH TIWARI S ASIRI NAIDU U V VARADARAJU

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      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

      DANPING JIANG XIANGJUN ZHANG TING ZHAO BINGXUE LIU RONG YANG HONGKUN ZHANG TENGFEI FAN FAN WANG

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      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

      XIAOMIN SHANG MENG SUN MINGXIAO JIN XIAOQIU LIU MEYSAM NAJAFI

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      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

      G L KABONGO P SMBULE G H MHLONGO B M MOTHUDI M S DHLAMINI

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      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

      S WADHWA A MATHUR R PENDURTHI U SINGHAL M KHANUJA S S ROY

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      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

      P PREETHI KUMARI PRAKASH SHETTY SUMA A RAO DHANYA SUNIL T VISHWANATH

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      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

      AHMAD IRFAN FIRAS KHALIL AL-ZEIDANEEN ISHTIAQ AHMED ABDULLAH G AL-SEHEMI MOHAMMED A ASSIRI SAMI ULLAH GHULAM ABBAS

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      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

      LEONARDO PRATAVIEIRA DEO STEFAN NIKODEMSKI

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      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

      ARISHA KASHYAP NAVJOT PAL SINGH SHALINI ARORA VASUNDHARA SINGH V K GUPTA

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      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

      SAEED SHIRALIZADEH HOSSEIN NASR-ISFAHANI AMIR HOSSEIN AMIN MOSTAFA AZIMZADEH RAMEZAN ALI TAHERI

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      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

      K KRISHNARAJ N SIVAKUMAR P PRAVEEN KUMAR

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      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

      S C EZIKE A B ALABI A N OSSAI A O AINA

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      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

      DHIMAN BANIK S CHENNAKESAVULU MONIKA SINGH NIDHI PANDEY RAGINI TILAK ARAMATI BINDU MADHAVA REDDY PRADIP PAIK

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      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

      MAZIYAR SABET HASSAN SOLEIMANI SEYEDNOOROLDIN HOSSEINI

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      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

      M STRECKOVA J SZABO I BATKO M BATKOVA Z BIRCAKOVA J FUZER P KOLLAR A KOVALCIKOVA R BURES L MEDVECKY

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      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

      P RAMA RAO ANIL K BHATNAGAR BHASKAR MAJUMDAR

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      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

      DHRUBAJYOTI SAIKIA RANJIT SARMA

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      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

      UJJWAL KUMAR BHASKAR S K PRADHAN

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      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

      S OUSSIDHOUM D HOCINE M O BENSIDHOUM D CHAUMONT E BOURENNANE S BOUDINAR A MOUSSI E LESNIEWSKA N GEOFFROY M S BELAKID

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      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

      TAGREED M AL-SAADI BUSHRA H HUSSEIN SUAD H ALEABI

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      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

      MOHAMMAD REZA ATTAR EHSAN KHAJAVIAN SAMAN HOSSEINPOUR ALI DAVOODI

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      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

      M H HAMSAN M F SHUKUR SHUJAHADEEN B AZIZ Y M YUSOF M F Z KADIR

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      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

      S SANGEETHA G KRISHNAMURTHY

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      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

      CHAO SUI ZHIPING ZHANG XUE CAI QI ZHOU MEYSAM NAJAFI

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      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

      A K M MAKSUDUL HASAN SHAIKAT CHANDRA DEY MUHAMMAD MOMINUR RAHMAN ABDULLAH MUHAMMAD ZAKARIA MITHUN SARKER MD ASHADUZZAMAN SAYED MD SHAMSUDDIN

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      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

      SUNNY NANDI HOMEN LAHAN SHYAMAL K DAS

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      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

      JOYSHREE MAJI SANJEEV PANDEY SOUMEN BASU

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      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

      MALATESH S PUJAR SHIRAJAHAMMAD M HUNAGUND DELICIA A BARRETTO VANI R DESAI SHIVAPRASADAGOUDA PATIL SHYAM KUMAR VOOTLA ASHOK H SIDARAI

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      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

      SAJAD RASAEE A H MIRZAEI D ALMASI

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      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

      S TOUAM R BELGHIT R MAHDJOUBI Y MEGDOUD H MERADJI MUHAMMAD SHEHRYAR KHAN R AHMED R KHENATA S GHEMID D P RAI Y AL-DOURI

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      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

      MOHSEN ABAEI MORTEZA ZANDRAHIMI HADI EBRAHIMIFAR

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      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

      SAURABH SHARMA KULDEEP KUMAR NAVEEN THAKUR S CHAUHAN M S CHAUHAN

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      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$_2$

      P THAPLIYAL G D THAKRE

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      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

      SINAN TEMEL FATMA OZGE GOKMEN ELIF YAMAN

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      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

      J AARTHI S GOWRI C S KAVIYA S A BHEETER

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      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$^3$ at 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

      WEILI WU HE HUANG

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      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

      SOURAV GHOSH SUKANYA KUNDU RITUPARNA DAS MILAN KANTI NASKAR

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      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

      B CHOUDHURI R SEN S K GHOSH S C SAHA

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      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

      M MONTAZERI M RAZZAGHI-ABYANEH S A NASROLLAHI H MAIBACH S NAFISI

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      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

      E HEMALATHA N GOPALAKRISHNAN

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      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

      M BADARUDDIN SUGIYANTO D ASMI

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      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

      RITUPARNA ACHARYA MONISHA CHAKRABORTY JUI CHAKRABORTY

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      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

      HIDEO HASHIZUME CHIKA HIRATA KUN’ICHI MIYAZAWA

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      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

      R VAIRA VIGNESH R PADMANABAN M GOVINDARAJU

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      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

      PUNEET AZAD SAMRIDDHI RAUT RAHUL VAISH

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      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

      JI-BO ZHANG HENG ZHANG FAN-LONG JIN SOO-JIN PARK

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      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

      JIANGTAO SHI MUMUKSHU D PATEL LIPING CAI WONBONG CHOI SHELDON Q SHI

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      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

      XUELIANG ZHU ZHIQIANG WEI LONG MA JIAHAO LIANG XUDONG ZHANG

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      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

      L N PUZYRNAYA G N PSHINKO V YA ZUB O V ZUY

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      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

      M VUKOVIC I DINIC M G NIKOLIC B A MARINKOVIC A M L M COSTA K RADULOVIC O MILOSEVIC L MANCIC

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      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

      CHON-HSIN LIN

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      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.

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