• Volume 41, Issue 2

April 2018

• Metal–insulator transition in the high pressure cubic CaF$_2$-type structure of CrO$_2$

The total energy, magnetic moment, density of states and energy band structures of CrO$_2$ in the high pressure cubic CaF$_2$ (Fm-3m)-type structure are investigated for the first time by using first principles electronic structure calculations based on density functional theory in the local spin density approximation (LSDA) as well as using LSDA $+$ U method. It is revealed from the present study that CrO$_2$ is a ferromagnetic nearly half-metal in the LDA calculation due to almost occupied Cr-3de$_{\rm g}$ orbitals in the spin majority species and a tiny electron contribution at the Fermi level (E$_{\rm F}$) for spin minority species. This compound encounters metal–insulator transition (MIT) upon the application of Hubbard-type Coulomb repulsion $U = 1$ eV. Ferromagnetism is preserved in this transition. Application of U increases the electron correlation, which polarizes e$_{\rm g}$ orbitals far below E$_{\rm F}$ for spin majority channel while in the spin minority channel e$_{\rm g}$ orbitals are polarized well above E$_{\rm F}$, resulting in opening of a band gap ($E_{\rm g} \sim 1.05_{\rm eV}$) in the vicinity of E$_{\rm F}$. Coulomb repulsion increases hybridization between occupied Cr-3de$_{\rm g}$ and O-2p orbitals, which induces ferromagnetism both in half-metallic and insulating phases ofcubic CrO$_2$.

• New diphosphopentamolybdate (VI) (C$_6$H$_{14}$N)$_4$(NH$_4$)$_2$[P$_2$Mo$_5$O$_{23}$] · H$_2$O synthesis, crystal structure, experimental and theoretical studies

The title compound (C$_6$H$_{14}$N)$_4$(NH$_4$)$_2$[P$_2$Mo$_5$O$_{23}$]·H$_2$O (1) was obtained by solution method using ammonium molybdate tetrahydrate, phosphoric acid and cyclohexylamine reagents in aqueous solution.Asingle-crystalX-ray diffraction study shows that the compound crystallizes in triclinic crystal systemwith space group P-1 and cell constants $a = 10.7178(4)\,\AA$, $b = 15.0809(6) \AA$, $c = 15.7745(9) \AA$, $\alpha = 71.510(6)^{\circ}$, $\beta = 75.508(2)^{\circ}$ and \gamma = 88.493(8)^{\circ}$. Also, in this article,we report results of thermal, electrochemical and spectral studies. In addition, the majority of theoretical properties were carefully studied. • Fe$_2$O$_3$/MWCNTs nanocomposite decorated glassy carbon electrode for the determination of nitrite A novel ferric oxide/multi-walled carbon nanotubes (Fe$_2$O$_3$/MWCNTs)-modified glassy carbon electrode (GCE)was prepared by drop casting Fe$_2$O$_3$/MWCNTs onto the surface of GCE. Scanning electron microscopy (SEM) image shows that the Fe2O3/MWCNTs has a nanostructure. Cyclic voltammetry (CV) results show that the Fe$_2$O$_3$/MWCNTsmodifiedGCE presents excellent electrochemical activity in the presence of 1 mM nitrite in a 0.1 M phosphate-buffered saline (PBS) to compare the Fe$_2$O$_3$and MWCNTs-modified GCE. Differential pulse voltammetry (DPV) results also showthat the Fe$_2$O$_3$/MWCNTs has excellent electrocatalytic performance to nitrite in a pH 7.0 PBS. The amperometric response result shows that the Fe$_2$O$_3$/MWCNTs-modified GCE can be used to detect nitrite concentration in a wide linear range of 10–1000$\mu$M with a detection limit of 0.1$\mu$M. • Acid-activated bentonite (Maghnite-H$^+$) as a novel catalyst for the polymerization of decamethylcyclopentasiloxane In this study, we propose Maghnite-H$^+$, as an ecological, cost-effective and easily renewable catalyst, for the polymerization of decamethylcyclopentasiloxane (D5). The Maghnite is a clay consisting primarily of smectite minerals (montmorillonite group), which can be activated/reactivated through a simple process, by replacing interlayer cations by protons. Linear polymers with higher molecular mass and narrower molecular mass distribution (MMD) can be obtained with less cyclic by-products, using Maghnite-H$^+$. The reaction was investigated in bulk, taking into account the effect oftime, temperature and amount of catalyst on the monomer conversion and MMD.When the yield rises to 96%, the MMD is broadened, suggesting the formation of cyclic oligomers and/or crosslinking bonds, this was confirmed experimentally by infra-red spectroscopy, proton nuclear magnetic resonance (${}^1$H NMR) and${}^{13}$C NMR analyses. The kinetics have been also studied; the reaction is first order in the monomer. The proposed reaction mechanism shows clearly the role of Maghnite-H$^+$for D5 polymerization. • Controllable factors affecting the epitaxial quality of LaCoO$_3$films grown by polymer-assisted deposition LaCoO$_3$epitaxial films grown on (100) SrTiO$_3$substrates were prepared by the simple polymer-assisted deposition successfully. Based on the characteristics by X-ray diffractometer, infrared spectroscopy and thermal analyzer, the influence of molecular weight of polyethyleneimine, heat-treatment condition, spin-coating speed on the crystallinity and epitaxial quality of LaCoO$_3$films were discussed. It is found that the number of –NH groups plays a key role in the cationchelation of polyethyleneimine. Comparatively, more –NH groups existing in polyethyleneimine with larger molecular weight contribute to the improvement of epitaxial quality of LaCoO$_3$epitaxial film. When polyethyleneimine begins to release the bound metal ions, higher heat-treatment temperature and a relatively rapid rate of heating can effectively preventnucleus from growing in other orientations, thereby improving the epitaxial quality of film. Besides, the choice of spin speed will directly affect the thickness and surface roughness of the film, and may even affect the structure and performance of the film. The results will help to understand the cation-chelation mechanism of polyethyleneimine in the polymer-assisted deposition and extend this simple method for preparation of epitaxial films. • Facile synthesis and characterization of CsPbBr$_3$and CsPb$_2$Br$_5$powders All-inorganic caesium lead-halide perovskite CsPbBr$_3$and CsPb$_2$Br$_5$powders have emerged as attractive optoelectronic materials owing to their stabilities and highly efficient photoluminescence (PL). Herein we report a facile chemical route to prepare highly luminescent monoclinic CsPbBr$_3$and tetragonal CsPb$_2$Br$_5$powders at room temperature.The CsPbBr$_3$powders exhibit regular crystal shape and demonstrate polyhedral geometry with an average particle size of 10$\mu$m. The CsPb2Br$_5$powders show platelet morphologies and the lateral sizes of the particles are from 5 up to 200$\mu$m. Both CsPbBr$_3$and CsPb$_2$Br$_5$powders present a narrow emission line-width and PL emission of 528 and 527 nm, respectively. A direct band gap of 2.35 eV and an indirect band gap of 3.01 eV are calculated for CsPbBr$_3$and CsPb$_2$Br$_5$powders, respectively. In addition, the monoclinic CsPbBr$_3$can be transformed to tetragonal CsPb$_2$Br$_5$in the presence of water. The large-scale synthesis of CsPbBr$_3$and CsPb$_2$Br$_5$will be advantageous in future applications of optoelectronic devices. • On the preparation and characterization of superparamagnetic nanoparticles with Gelidium robustum agar coating for biomedical applications Superparamagnetic nanoparticles coated with natural polysaccharides are of great interest for biomedical applications due to their fast response to an external and high-frequency electromagnetic field and their biocompatibility. One of the greatest challenges in the development of these nanoparticles is related to the specific characteristics and properties of the polysaccharide used, which could guarantee the development of specific sizes, crystalline structure, magneticresponse and its reproducibility. In this study, we present the preparation of magnetite (Fe$_3$O$_4$) and cobalt ferrite (CoFe$_2$O$_4$) nanoparticles by the co-precipitation method in aqueous solutions at different concentrations (1, 2, 3, 4 and 5%) of a very well-characterized agar obtained from the red marine algae Gelidium robustum. It is shown that under the same experimental conditions and using the adequate precursors, coated high-crystallinity magnetite nanoparticles are obtained. In contrast, for cobalt ferrite, our results indicated the formation of coated low-crystallinity CoFe$_2$O$_4$particles. Superparamagnetic nanoparticles (with crystal grain size <8 nm) of Fe$_3$O$_4$agar coated at >3% agar showed high-saturation magnetization and high degree of biocompatibility and can be considered as promising candidates for biomedical applications. • Chemical synthesis of highly size-confined triethylamine-capped TiO$_2$nanoparticles and its dye-sensitized solar cell performance TiO$_2$nanoparticles were synthesized by a facile wet chemical synthesis using triethylamine (TEA) as a surface passivating agent. The role of TEA on the formation and functional properties of TiO$_2$nanoparticles were investigated.Particle agglomeration was restricted and nanoparticle size was limited to 5 nm by passivating the amine molecule. Photoanodes were fabricated by spray deposition method using synthesized TiO$_2$nanoparticles. The efficiency of 5.91%was obtained by the dye-sensitized solar cells. • Properties of ternary NiFeW alloy coating by jet electrodeposition In this paper, ternary NiFeW alloy coatings were prepared by jet electrodeposition, and the effects of lord salt concentration, jet speed, current density and temperature on the properties of the coatings, including the composition, microhardness, surface morphology, structure and corrosion resistance, were investigated. Results reveal that the depositionrate reaches a maximum value of 27.30$\mu$m h$^{−1}$, and the total current efficiency is above 85%. The maximum microhardness is 605 HV, and the wear and corrosion resistance values of the alloy coating are good. Moreover, the ternary NiFeW alloy coating is smooth and bright, and it presents a dense cellular growth. The alloy plating is nanocrystalline and has face-centered cubic structure. • Synthesis and characterization of SPIO-loaded PEG-b-PS micelles as contrast agent for long-term nanoparticle-based MRI phantom Nanoparticle-based magnetic resonance imaging (MRI) phantom was developed from the suspension of magnetic nanoparticles composing methoxy poly(ethylene glycol)-block-poly(styrene) (PEG-b-PS) micelles and superparamagnetic iron oxide (SPIO) nanoparticles in the core of micelles. The size of SPIO-loaded micelles was determined by dynamic light scattering (DLS) and transmission electron microscopy. Larger-size micelles were found when SPIO loading was increased. The effect of the hydrophobic section of block copolymer on the size of micelles was studied by DLS. Transverserelaxivity was evaluated on both 1.5 and 3 T clinical MRI scanner. Higher SPIO-loading provided higher relaxivity, where the relaxivity of 10% SPIO-loaded PEG(5 kDa)-b-PS(5 kDa) were 144.0 and 174.0 mM$^{−1}$s$^{−1}$for 1.5 and 3 TMRI, respectively. This formulation showed stability over a 10-week period, and the standard deviations of the relaxivities were 3.0 and 8.0% for 1.5 and 3 T MRI, respectively. Thus, SPIO-loaded PEG-b-PS micelles have a potential to be applied as a contrast agent for nanoparticle-based MRI phantom. • Effects of static electricity and fabrication parameters on PVDF film properties Degree of crystallinity and$\beta$-phase fraction are important factors in determining electroactive polymers performance. In the present work, effects of intrinsic static electricity, substrate type, PVDF solution concentration anddrying temperature on$\beta$-phase fraction and degree of crystallinity in fabricated PVDF films were studied using XRD, Raman spectroscopy and FTIR techniques. In particular, this paper investigates the influence of static electricity on PVDF film properties for the first time. The results show that discharging static electricity from the PVDF solution is highly effective in reducing the amount of residual solvent. It was found that a lower amount of residual solvent and higher drying temperature resulted in a higher degree of crystallinity. Further, a high fraction of β phase was observed in all PVDF films due to more polar solvent effect that it was hardly affected by other parameters such as static electricity. • 3D Architectured polyazomethine gel synthesis: its self-assembled intercalating complexation with nitro aromatic acceptor Azomethine is the key linkage in all Schiff base reactions. The present context has efficiently emphasized on the utilization of Schiff base strategy effectively in the synthesis of polyazomethine polymer gel materials. The synthesized polymer gel is characterized by different physical techniques for testing its proper existence such as FESEM analysis, thermal gravimetric analysis, differential scanning calorimeter analysis, FTIR analysis and electron dispersive X-ray scattering analysis. The morphological study has revealed that the material is having 3D lamellar-layered architecture, i.e., layerby-layer array of polymer chains. The synthesis governs several advantages, such as executing without using any catalyst and water as a green solvent. The present study also checked its complexion ability with nitro aromatic acceptors. The intercalation of nitro aromatic molecule between the two straight chains of the polymer gel is the beautiful peculiarity of these red-coloured complexes. • Effect of annealing treatment on optical properties and microstructural variation of WO$_3$/Ag/WO$_3$multilayer nano-films Structural and optical properties of WO$_3$/Ag/WO$_3$nano-multilayer compositeswere investigated for heat mirror applications. WO$_3$/Ag/WO$_3$thin films were fabricated through a physical vapour deposition method by using electronbeam evaporation at the vacuum chamber at 10$^{−5}$Torr. WO$_3$nano-layer was fabricated at 40 nm. Annealing treatment was carried out at 100, 200, 300 and 400$^{\circ}$C for 1 h after the deposition of first layer of WO$_3$on the glass. On WO$_3$film, Ag nano-layers with 10, 12 or 14 nm thickness were deposited. Individual layers morphology was investigated using atomicforce microscopy (AFM) and deduced that a smoother layer can be achieved after the annealing at 300◦C. Ellipsometry analysis was executed to determine both layers, Ag film thickness and inter-diffusion between the WO$_3$–Ag–WO$_3$layers. It was inferred that there was almost no interfering among the WO$_3$–WO$_3$layers in the samples with 12 and 14 nm Ag thickness; while silver was deposited on the annealed WO$_3$layer at 300$^{\circ}$C. UV–visible spectrophotometer showed that the annealing treatment of the first WO$_3$layer enhanced the transparency of films in the visible region. The innovations of the present study have been based on the annealing of the films and finding an optimum thickness for the Ag film at 12–14 nm. Heat mirrors efficiency was assessed according to the principle of their optical behaviour and optimum performance obtained for 14 nm of Ag film, deposited on annealed tungsten oxide at 300$^{\circ}$C. • Physical properties of lauric acid crystals grown with KBr in aqueous solution Lauric acid crystals were grown with potassium bromide (LAPB) in aqueous solution at room temperatureby slow solvent evaporation technique. The monoclinic structure of grown single crystal wa s studied by single-crystalX-ray diffraction and powder X-ray diffraction analyses. The Fourier transform infrared spectrum incorporates signatures of functional groups. The optical absorbance study reveals the UV cut-off wavelength as 230 nm. The Kurtz powder technique ensures that LAPB crystal has 1.1 times greater second harmonic generation efficiency than that of KDP crystals. The thermogravimetricand differential thermal analyses ensure that the material has good thermal stability. A dielectric behaviour of the sample material is studied in the frequency range 10$^1$–10$^6$Hz. • Assessment of cellulose acetate/manganese oxide thin film as adsorbent for selective extraction of flavone The present study depicts the efficiency of cellulose acetate/manganese oxide thin films as adsorbents for selective extraction and detection of flavone in environmental waters. The selectivity of thin films (CA/Mn-1 and CA/Mn-2)was evaluated towards several organic compounds. Based on selectivity study results, CA/Mn-2 thin film was the most selective towards flavone among other compounds. In addition, the effect of other parameters such as contact time andinitial concentration of flavone was investigated to optimize adsorption conditions. The adsorption capacity of flavone was experimentally obtained as 57.96 mg g$^{−1}$and theoretically calculated from Langmuir equation as 58.48 mg g$^{−1}$, which indicates the high agreement of the results. Moreover, data obtained from kinetic study suggested that the adsorption of flavone onto CA/Mn-1 phase followed a pseudo-second-order kinetic model. Finally, validation of this method has attained reasonable results for determination of flavone in real water samples. • Structures and electronic properties of W$_m$Cu$_n$($n + m \leq 7$) clusters Geometric and electronic structures of W$_m$Cu$_n$($m + n \leq 7$) cluster have been systematically calculated by density functional theory at the generalized gradient approximation level for ground-state structures. W$_m$Cu$_n$clusters with$n = 1, 3, 5$tend to form bipyramid structures, whereas WCu$_n$favour planar shapes except for WCu$_5$. The configurations of W$_m$Cu$_n$clusters are more sensitive to the Cu atoms than the W atoms, while the average atomic binding energies and the totalmagnetic moments are determined by W atoms. The calculated second-order differences in energies and HOMO–LOMO energy gaps show pronounced odd–even oscillating behaviours. From the Mulliken electron population analysis, we found that Cu 4p and W 6p orbitals exhibit electronic charges and both Cu 4s and W 6s orbitals transfer electronic charges to the W 5d orbital, which lead to the extension of W–Cu bond lengths. • Synthesis and characterization of metal ion-imprinted polymers In this study, ion-imprinted polymeric materials from an aqueous solution were prepared to remove metal ions (M$^{2+}$) like Ni$^{2+}$, Co$^{2+}$, etc. To prepare ion-imprinted polymers (IIPs), acrylic acid derivatives (XA) like acrylamide (AAm), methacrylic acid and itaconic acid were chosen as monomers. Metal ions formed binary chelate complexes with the help of 8-hydroxyquinoline (8-HQ).The solution containing functional monomers and the binary complex were polymerizedwith the help of various cross-linkers [ethylene glycol dimethylacrylate (EGDMA) or trimethylpropane trimethacrylate (TMPTMA)] and the target ion was removed from this polymer through an applicable method to produce IIPs. Furthermore, the control polymers (CPs) were synthesized through the same method without using metal ion. Characterization of the polymericmaterials was investigated through spectroscopic (FTIR/ATR), thermal (TGA, DSC) and surface (SEM and XRD) analyses. Functional monomers, cross-linkers and the target ion’s species were changed during preparation of IIPs to observe their effect on imprinting of the target ion. Adsorption of the target ion to the prepared IIPs and the factors affecting the adsorption like concentration, pH, temperature, mass, etc. were studied. • Green synthesis of zinc oxide nanoparticles using aqueous extract of Garcinia mangostana fruit pericarp and their photocatalytic activity We reported a facile, green and eco-friendly approach for the synthesis of zinc oxide nanoparticles (ZnO NPs) using aqueous extract of Garcinia mangostana (G. mangostana) fruit pericarp as reducing agent as well as capping agent. Biosynthesized ZnO NPs were characterized by various analytical tools using X-ray diffraction, Fourier transform infraredspectroscopy, field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and UV–Vis spectroscopy. The results showed that ZnO NPs synthesized by aqueous extract of G. mangostana fruit pericarp with high purity, mostly spherical in shape with an average size of 21 nm. The photocatalytic activity of biosynthesized ZnO NPs was evaluated by carrying out the degradation of malachite green dye under solar irradiation. The extent of MG dye degradation was monitored spectrophotometrically by measuring absorbance at its characteristics$\lambda_{\max}$value of 615 nm. Degradation products were detected using liquid chromatography–mass spectrophotometry technique. Thebiosynthesized ZnO NPs showed an excellent photocatalyst performance due to the small size and high purity. • Effect of oxygen vacancies on Li-storage of anatase TiO$_2$(001) facets: a first principles study Effect of oxygen vacancies on Li-storage of anatase TiO$_2$(001) facets was stimulated by density functional theory (DFT). The lattice parameters, adsorbed energy and energy barriers of TiO$_2$with oxygen vacancies were calculated. High adsorption energy of 5.91 eV for Li atoms indicates that oxygen vacancies have a positive effect on the Li storage of nanostructured anatase TiO$_2$. The theoretical capacity was enhanced by an extra Li atom storaged at the oxygen vacancies. • Effect of borax additive on the dielectric response of polypyrrole The main aim of this study is to produce added polypyrrole (PPy) borax compositeswith high dielectric properties for technological applications. For this purpose, PPy–borax compositeswith different borax concentrations varying from 10 to 50 wt% have been prepared. To reveal their structural and morphological attributes, the composites have been characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. The real and imaginary parts of complex dielectric function, the imaginary component of complex electrical modulus and ac conductivity have been investigated at room temperature as a function of frequency in the range 100 Hz–15 MHz. It has been found that addition of borax increases the dielectric constant of pure PPy. In this respect, PPy–borax composites with the highest dielectric constant at low frequency may be utilized in charge storing devices. On the other hand, the dielectric loss is also very high in low-frequency region for the composites with high borax content. Exploiting this property, the material may also be used in decoupling capacitor applications. The relaxation mechanisms of the samples have also been determined as non-Debye type. The Nyquist curves of the samples have been analysed for calculating the grain and grain boundary resistance andcapacitance values. In conclusion, borax has a promising potential to be used as a cheap and effective filler for improving the dielectric properties of PPy polymer.Keywords. Polypyrrole; borax; dielectric properties; Nyquist plot; non-Debye-type relaxation; Cole–Cole equation. • Unique reduced graphene oxide as efficient anode material in Li ion battery Unique reduced graphene oxide named solar reduced graphene oxide (SRGO) was found to be anexce llent anode material in Li ion battery. SRGO exhibited first cycle discharge- and charge-capacities as high as 1480 and 880 mAh g$^{−1}$, respectively. Moreover, the columbic efficiency was found to be >95% and the specific capacity retention even after 60 cycles was >500 mAh g$^{−1}$. • One-step hydrothermal synthesis of flower-like CoS hierarchitectures for application in supercapacitors Flower-like CoS hierarchitectures were successfully synthesized through a hydrothermal route in the presence of ethylenediamine as ligand and structure-directing agent. The structure and morphology of the products were characterized by X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy and N$_2$adsorption–desorption isotherm. Flower-like CoS hierarchitectures are constructed by two-dimensional CoS nanopedals interlaced and stacked with each other. When tested as electrode material for supercapacitors, the as-fabricated CoS delivers a specific capacitance of 357 F g$^{−1}$at 0.5 A g$^{−1}$. After 2000 repetitive charge–discharge cycles, there is only 12.7% loss of the original specific capacitance. The results signify that the CoS supercapacitor possesses good electrochemical performances, suggesting its potential application in supercapacitor. • Green synthesis of silver nanoparticles and biopolymer nanocomposites: a comparative study on physico-chemical, antimicrobial and anticancer activity The current report was intended towards comparative study of green-synthesized biogenic Rhubarb silver nanoparticles (RS-AgNPs) and chitosan crosslinked silver nanocomposites (CSHD-AgNCs). The physico-chemical characterization was done by UV–visible, FTIR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), EDX, TGA, XRD and zeta potential ($\zeta$). The analysis and spectroscopic characterization was done by SEM and TEM and their results reveal that the nanoparticles are spherical in shape, with average size ranges from 5 to 50 nm, and was gatheredby face centered cubic (FCC) structure throughout the polymer matrix and stable without any protecting or capping reagents over 450 days. The antimicrobial property of RS-AgNPs and CSHD-AgNCs ($\zeta = +29.6$and$+$32.8 mV) was evaluated against E. coli and S. aureus and showed an effective inhibitory property. The RS-AgNPs and CSHD-AgNCs were assessedfor their anticancer activity against HeLa cell line by MTT method, and it reveals a dose–response activity, time and cell line-dependent cytotoxicity. Based on the results obtained, the RS-AgNPs exhibited higher toxicity over CSHD-AgNCsafter 24 h incubation of HeLa cells with different concentrations and is negligible for the aqueous Rhubarb extract. It was concluded that the changes in anticancer activity towards HeLa cells due to biological activity of silver nanoparticles depend on their method of biosynthesis and their physico-chemical nature. • Tuning the BODIPY core for its potential use in DSSC: a quantum chemical approach Boron dipyrromethene (BODIPY) is a highly promising candidate for use in dye-sensitized solar cell (DSSC), because of its attractive absorption characteristics such as strong extinction coefficients in the visible and near-IR ranges (70000–80000 M$^{−1}$cm$^{−1}$), large quantum yields, longer excited-state lifetime and also high solubility in many organic solvents.Moreover, the absorption peaks can be shifted towards longer wavelengths when functionalized at suitable positions of the BODIPY core. Herein, on the basis of density functional theory (DFT) and time-dependent DFT, we provide theopto-electronic properties of BODIPY core-functionalized dyes to see their applicability in organic DSSC. Our systematic analyses reveal that the 2,6 substituted dyes show better photovoltaic properties compared to the 3,5 substituted ones. On the basis of empirical relationship, we have also calculated the photo-induced electron injection times of some dye-TiO$_2$composites, which seem to be in the ultrafast time scale, thus rendering them a promising candidate for DSSC applications. Our theoretical studies provide that judiciously designed BODIPY core-derived dyes show certain unique spectroscopic andelectronic features that make them highly advantageous in DSSC applications as compared to other organic dyes. • Milling effect on the photo-activated properties of TiO$_2$nanoparticles: electronic and structural investigations Commercial PC105 titanium dioxide nanoparticles were studied under mechanical milling process. The effect of milling time and speed on the structural and electronic properties of TiO$_2$powder was then investigated using X-raypowder diffraction (XRD), dynamic light scattering (DLS), transmission electronic microscopy (TEM), electron paramagnetic resonance (EPR) and UV–visible spectroscopy. The related photo-catalytic properties of the milled nanoparticleswere probed following the degradation rate of methylene orange (MO) under UV-light irradiation and through EPR spinscavenging approach. Comparison with pristine powder shows that milled nanoparticles are significantly less reactive upon illumination, despite decreased radius and hence, higher specific area. Such low yield of reactive species is attributed to the apparition of the amorphous TiO$_2$and brookite phase upon milling, as well as increased charge carrier recombination as pointed out by the presence of sacrificial electron donor. • Sunlight-enhanced catalytic degradation over Ag–CuO nanoparticles thin films prepared by DC/RF sputtering technique Herein, we report sunlight-activated photo-catalysis response of direct current radio frequency (DC/RF)-sputtered Ag–CuO nanoparticles thin films.We have adopted this approach for facile removal and easy recovery of thin filmsafter use. Ag was incorporated at 2.5 and 5.4 wt% with reference to pure CuO. Structural analysis through X-ray diffraction showed successful incorporation of Ag into the CuO lattice. Surface morphological observation was carried out using a field emission scanning electron microscope, which showed a uniform deposition of the subjected thin films. The surface composition and change in the chemical state of pure and incorporated thin films were studied by X-ray photoelectron spectroscopy. In addition to structural and surface analysis, optical band gap evolution was also studied through UV–visible spectroscopy. The obtained results reflected that optical band gap decreased from 1.84 to 1.77 and 1.61eV for 0, 2.5 and 5.4wt% Ag, respectively. Methylene blue dye was used to investigate the photo-catalytic degradation response of deposited thin films in sunlight. Furthermore, the effect of pH and dye concentration was also taken into account. The degradation results indicate the acceleration of degradation process with the Ag incorporation into CuO lattice. Moreover, the pH alsocontributes positively to the degradation progression. This research study could provide a platform to understand and develop metal oxide thin films with an efficient photo-catalytic response in sunlight. • In vitro bioactivity evaluation of$\alpha$-calcium sulphate hemihydrate and bioactive glass composites for their potential use in bone regeneration To combine the self-setting property of$\alpha$-calcium sulphate hemihydrate ($\alpha$-CSH) with the bioactive property of bioactive glass (BG), BG was added into$\alpha$-CSH to prepare$\alpha$-CSH/BG composites. The in vitro bioactivity and cytocompatibility of the$\alpha$-CSH/BG composites were assessed by soaking the composites in simulated body fluid (SBF) andco-culturing with the osteoblasts, respectively. Formation of a bone-like apatite layer on the composite surface was studied by X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM) andenergy-dispersive spectroscopy (EDS). Variations in ionic concentration and pH of the SBF solution were detected. The incorporation of BG into$\alpha$-CSH, effectively compensated for the pH decrease caused by the dissolution of$\alpha$-CSH and the ion exchange.Osteoblast-like cells (MG63) were cultured on the samples, and theMTTresults confirmed that the compositescontaining BG were more favourable for the proliferation of these cells. Hence,$\alpha$-CSH/BG composites might have great potential for the use as a bone regeneration material. • Magnetic measurements, Raman and infrared spectra of metal–ligand complex derived from CoCl$_2$· 6H$_2$O and 2-benzoyl pyridine Nanocrystalline complex of CoCl$_2$·6H$_2$O−2-benzoyl pyridine is prepared by chemical route. Each component of the desired complex is identified by analysing the X-ray diffractograms. Energy-dispersive X-ray analysis (EDX) data confirmed the presence of the desired elements of the sample. Theoretical optimized structure of the complex was derived using ab initio density functional level of theory (DFT) method of calculation. The average nanocrystallite size estimated from the XRD data is$\sim$43 nm. Static magnetic property of the complex is studied in the temperature range from 300 K down to 14 K. The estimated magnetic moment of the complex is high when compared to that of the free ion magnetic moment of Co$^{2+}$and this is attributed to the less effect of the crystal field acting on the ion in the organic complex due to whichorbital moments are not fully quenched. The magnetic property of the complex is also remarkably enhanced compared to that of the diamagnetic 2-benzoyl pyridine which may be suitable for applications in devices. FTIR and Raman spectra of the ligand, 2-benzoyl pyridine and the synthesized complex are recorded at room temperature, which not only confirm the presence of each phase in the complex, but some interesting results are also extracted from the analyses of different Raman active modes of the complex. • A facile approach for the synthesis of porous KTiNbO$_5$catalyst with good activity for hydrogenation of p-nitrophenol Through simple ions exchange and hydrothermal reaction, the porous structure of MnO$_2$-pillared KTiNbO$_5$composites were synthesized. The fabricated porous structure makes KTiNbO$_5$as good absorbance property for methylthionine chloride (MB). Furthermore, the as-synthesized porous KTiNbO$_5$can perform photocatalytic degradation of MB with good effectivity. What’s more, after loading Au nanoparticles into it, a novel catalyst for catalytic hydrogenation of p-nitrophenolwas obtained. The possible ‘layer-by-layer quilt expose’ mode of Au-MnO$_2$-KTiNbO$_5$composites for catalytichydrogenation of p-nitrophenol was proposed. • Materials in harnessing solar power Harnessing renewable solar energy through different technologies is greatly dependent on the advancement of solar grade materials’ science and engineering. In this article, the prominent solar energy technologies, namely solarphotovoltaic and concentrated solar power and other relevant technologies, and aspects related to various solar grade materials, influence of nanomaterials on enhancement of solar energy harvest, technology–market relations, development of hybrid systems etc., are discussed. The inspiration to write this article is not only to review the existing technologies to harvest solar energy but also to highlight the pertinent and possible solutions thereof, especially from materials perspective. • Studies of thermally assisted interactions of polysulphide polymer with ionic liquids The present paper, for the first time, reports analysis regarding the structural interactions of polysulphide polymer with ionic liquids (ILs), which have been studied by thermo-gravimetry analysis (TGA). A systematic thermal analysis of polysulphide polymer has been carried out, based on polymerization and series of ILs like tetrabutyl ammonium hexa-fluorophosphate [TBA][PF$_6$], N-butylpyridinium bromide [Bpy][Br] and 1-butyl-3-methyl imidazolium bromide [Bmim][Br] using a thermal gravimetry analyser. The plausible mechanism of the interactions and thermally induced reactions of polysulphide polymer with ILs has been advanced and discussed. The probable interactions of polysulphide polymer with [Bmim][Br] and [TBA][PF$_6\$] are also discussed. The interactions between polysulphide polymer and ILs were confirmed by Fourier transform-infrared spectroscopy, TGA–differential thermo-gravimetry analysis and field emission scanning electron microscopy analysis.

• # Bulletin of Materials Science

Current Issue
Volume 42 | Issue 5
October 2019

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019