• Volume 36, Issue 7

December 2013,   pages  1133-1382

• Preparation and characterization of DLC/SiO2/Al2O3 nanofiltration membrane

High quality ceramic thin films were fabricated by thin film deposition process in semiconductor field in order to fabricate high performance carbon/SiO2/Al2O3 membrane. 𝛼-Al2O3 substrate was used as a supporting material. A severe thermal stress and rough surface for active ceramic top layer such as zeolite were observed. To overcome thermal stress, intermediate layer of SiO2 and diamond-like carbon (DLC) thin films were used. SiO2 and DLC thin films on porous alumina support were deposited using plasma-enhanced chemical vapour deposition (PECVD). Homogeneous and smooth surfaces and interfaces of DLC/SiO2/Al2O3 membrane were observed by FESEM. The phases of DLC and SiO2 thin films were identified by X-ray diffraction pattern. Gas permeabilities of the nanofiltration membrane with DLC/SiO2/Al2O3 were observed at various annealing temperatures. Mixed gas permeability of the membrane with 1 𝜇m-thick SiO2 and 2 𝜇m-thick DLC thin filmannealed at 200 °C was ∼18 ccm at 1018 mb back pressure.

• Nanoindentation study on Gd-deposited YBaCuO superconductor

Nanoindentation technique was used to characterize the mechanical properties of Gd-deposited bulk YBaCuO superconductors fabricated by solid-state reaction method. In order to determine the hardness and reduced modulus of the samples, load-displacement data were analysed by using the Oliver–Pharr method. The hardness values exhibited significant peak load-dependence especially at lower peak loads, while the reduced modulus values were found to be nearly constant at studied loading range. In order to find true hardness of the samples, the peak load-dependency of hardness was analysed by using Meyer’s law,minimum resistance model, elastic/plastic deformation model, energy balance model, Nix–Gao model and Mukhopadhyay approach. Of the aforementioned models, energy balance model and Mukhopadhyay approach were found to be the most effective models to explain the load-dependency of hardness.

• Yb3+ and Er3+ co-doped Y2Ce2O7 nanoparticles: synthesis and spectroscopic properties

Yb3+ and Er3+ co-doped Y2Ce2O7 nanoparticles sintered at different temperatures were prepared by homogeneous co-precipitation method. The products were characterized by X-ray powder diffraction (XRD), energy-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The results indicated that the particle sizes and morphologies of the samples were heavily influenced by the sintering temperature. As temperature increased, the particle sizes became gradually larger and more agglomerate. The emissions including green and red upconversion emissions were investigated under 980 nm excitation. The emission intensities of the samples also depended on the sintering temperature. Two photon processes were mainly responsible for green and red upconversion emissions.

• Effect of variation of precursor concentration on structural, microstructural, optical and gas sensing properties of nanocrystalline TiO2 thin films prepared by spray pyrolysis techniques

The objective of the present paper is to investigate the effect of variation of precursor concentration (0.01, 0.02 and 0.03 M) on the structural, microstructural, optical and gas sensing properties of TiO2 thin films. Titanium dioxide (TiO2) films were prepared from aqueous solution of titanium chloride (TiCl3.6H2O, 99.9%pure, Merckmade, Germany) onto the glass substrates heated at a temperature of 350 °C by the spray pyrolysis technique. Bandgap energy of the films vary from 3.28 to 3.29 eV. X-ray diffraction shows that films to be nanocrystalline with anatase phase having tetragonal crystal structure. The 𝑑 values calculated from electron diffraction patterns (TEM) were observed to be matching with 𝑑 values calculated from XRD. Transmission electron microscopy (TEM) reveled that grain sizes were observed to increase (10–29 nm) with an increase in the concentration of precursor solution. The gas sensing performance of the films was tested.

• Preparation and characteristics of nanotetrapods CdSe-polymer hybrid solar cells

Tetrapod-shaped CdSe nanocrystals were obtained using a simple method. HRTEM shows that the average size of the tetrapod core are about 4 nm, widths of the tetrapod arms are about 4 nm and lengths of the arms are about 20 nm. XRD patterns reveal that the OA-capped CdSe tetrapod nanocrystals have a hexagonal wurtzite structure. A hybrid solar cell fabricated based on an 8:1 (w/w) blend of CdSe tetrapod nanocrystals and MEH–PPV showed a maximum power conversion efficiency of 0.46% under an air mass 1.5 global condition. The effects of nanocrystal composition on the photovoltaic properties of hybrid solar cells based on nanotetrapods CdSe/MEH–PPV were investigated. The power conversion efficiency values initially increased and then decreased, but the 𝑉OC values linearly decreased from 1.1 to 0.25 V with increased CdSe nanotetrapod in the blend film. The significant quenching of PL with increased nanotetrapod concentration indicated photo-induced charge transfer between MEH–PPV and CdSe.

• Iron nanoparticles from blood coated with collagen as a matrix for synthesis of nanohydroxyapatite

A simple wet precipitation technique was used to prepare nanobiocomposite containing iron nanoparticles coated with collagen. This nanobiocomposite was used as matrix for the synthesis of nanohydroxyapatite. The physicochemical characteristic studies of the nanohydroxyapatite thus formed were carried out using fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, energydispersive X-ray spectroscopy and X-ray diffraction technique to confirm the formation of hydroxyapatite on iron nanoparticle–collagen complex. The results of the above studies supported the formation of iron nanoparticle–collagen–hydroxyapatite composite. The biological studies such as biocompatibility and hemocompatibility were carried out for nanohydroxyapatite using different cell lines and blood sample. The results of biocompatibility and hemolytic assay revealed that the prepared nanobiocomposite was 100 % biocompatible and hemocompatible. This nanobiocomposite may be used for biomedical application such as injectables for targeted delivery and as scaffold for tissue engineering.

• Supercapacitive performance of hydrous ruthenium oxide (RuO2.𝑛H2O) thin films synthesized by chemical route at low temperature

In the present investigation, we report the synthesis of ruthenium oxide (RuO2.𝑛H2O) thin films by simple chemical bath deposition (CBD) method at low temperature on the stainless steel substrate. The prepared thin films are characterized for their structural and morphological properties by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT–IR) and scanning electron microscopy (SEM). The structural study revealed that the ruthenium oxide thin films are amorphous. Scanning electron microscopy study shows compact morphology with small overgrown particles on the surface of the substrate. FT–IR study confirms the formation of RuO2.𝑛H2O material. The supercapacitor behaviour of RuO2.𝑛H2O thin film was studied using cyclic voltammetry (CV) technique in 0.5 M H2SO4 electrolyte. RuO2.𝑛H2O film showed maximum specific capacitance of 192 F.g-1 at a scan rate of 20 mV.s-1. The charge–discharge studies of RuO2.𝑛H2O carried out at 300 𝜇A.cm-2 current density revealed the specific power of 1.5 kW.kg-1 and specific energy of 41.6Wh.kg-1 with 95% coulombic efficiency.

• High growth rate of a-SiC:H films using ethane carbon source by HW-CVD method

Hydrogenated amorphous silicon carbide (a-SiC:H) thin films were prepared using pure silane (SiH4) and ethane (C2H6), a novel carbon source, without hydrogen dilution using hot wire chemical vapour deposition (HW-CVD) method at low substrate temperature (200 °C) and at reasonably higher deposition rate (19.5 Å/s &lt; 𝑟d &lt; 35.2 Å/s). Formation of a-SiC:H films has been confirmed from FTIR, Raman and XPS analysis. Influence of deposition pressure on compositional, structural, optical and electrical properties has been investigated. FTIR spectroscopy analysis revealed that there is decrease in C–H and Si–H bond densities while, Si–C bond density increases with increase in deposition pressure. Total hydrogen content drops from 22.6 to 14.4 at.% when deposition pressure is increased. Raman spectra show increase in structural disorder with increase in deposition pressure. It also confirms the formation of nearly stoichiometric a-SiC:H films. Bandgap calculated using both Tauc’s formulation and absorption at 104 cm-1 shows decreasing trend with increase in deposition pressure. Decrease in refractive index and increase in Urbach energy suggests increase in structural disorder and microvoid density in the films. Finally, it has been concluded that C2H6 can be used as an effective carbon source in HW-CVD method to prepare stoichiometric a-SiC:H films.

• Optimization of process parameters for synthesis of silica–Ni nanocomposite by design of experiment

The optimumcombination of experimental variable, temperature, time of heat treatment under nitrogen atmosphere and amount of Ni-salt was delineated to find out the maximum yield of nanophase Ni in the silica gel matrix. The size of Ni in the silica gel was found to be 34 and 45 nm for the two chosen compositions, respectively. A statistically adequate regression equation, within 95% confidence limit was developed by carrying out a set of active experiments within the framework of design of experiment. The regression equation is found to indicate the beneficial role of temperature and time of heat treatment.

• Luminescence properties of YAG:Nd3+ nano-sized ceramic powders via co-microemulsion and microwave heating

Nano-sized ceramic powders with weaker aggregation of Nd3+-doped yttrium aluminum garnet (YAG:Nd3+) were synthesized via co-microemulsion and microwave heating. This method provides a limited small space in a micelle for the formation of nano-sized precursors. It also requires a very short heating time, thus reducing energy consumption in comparison with conventional solid-state sintering processes. As a result, small-sized particles with narrow size distribution, weaker aggregation and high purity were obtained. Powder X-ray diffraction results revealed that the structure of pure YAG:Nd3+ nanoparticles was cubic garnet. Transmission electron microscopy results indicated that the synthesized particles were almost spherical with average diameters of 40 and 80 nm. The luminescent properties of YAG:Nd3+ were investigated through PL. Under excitation at 488 nm, YAG:Nd3+ nanosized ceramic powders showed main emission bands of 1045–1080 nm because of ${}^{4}F_{3/2} \rightarrow 4I_{11/2}$ transitions that are identical to those observed for a single YAG:Nd3+ crystal.

• Properties of porous FeAlO𝑦/FeAl𝑥 ceramic matrix composite influenced by mechanical activation of FeAl powder

Porous ceramic matrix composites FeAlO𝑦/FeAl𝑥 with incorporated metal inclusions (cermets) were synthesized by pressureless method, which includes hydrothermal treatment of mechanically alloyed FeAl powder followed by calcination. Their main structural, textural and mechanical features are described. Variation of FeAl powder alloying time results in non-monotonous changes of the porosity and mechanical strength. Details of the cermet microstructure and its relation to the mechanical properties are discussed.

• Biological synthesis and characterization of intracellular gold nanoparticles using biomass of Aspergillus fumigatus

Nanotechnology is emerging as one of the most important and revolutionizing area in research field. Nanoparticles are produced by various methods like physical, chemical, mechanical and biological. Biological methods of reduction of metal ions using plants or microorganisms are often preferred because they are clean, nontoxic, safe, biocompatible and environmentally acceptable. In the present study, Aspergillus fumigatus was used for the intracellular synthesis of gold nanoparticles. Stable nanoparticles were produced when an aqueous solution of chloroauric acid (HAuCl4) was reduced by A. fumigatus biomass as the reducing agent. Production of nanoparticles was confirmed by the colour change from yellow to pinkish violet after ∼72 h of reaction. The produced nanoparticles were then characterized by Fourier transform infrared spectroscopy (FT–IR), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction spectroscopy (XRD). SEM images of sample revealed that the nanoparticles were spherical, irregularly shaped with indefinite morphology. Biosynthesized gold nanoparticles were in the range of 85.1–210 nm in size. The presence of gold nanoparticle was confirmed by EDS analysis. Crystalline nature and face-centred cubic structure of synthesized gold nanoparticle was confirmed by XRD pattern.

• Fabrication of polystyrene/agave particle biocomposites using compression molding technique: evaluation of flammability, biodegradability, mechanical and thermal behaviour

Polystyrene (PS) composites reinforced with ungrafted and acrylonitrile (AN) grafted agave particles (AgP) have been prepared with 10–30% particle content by weight using compression molding technique. The composite specimens thus prepared were subjected to the evaluation of mechanical, chemical, flammability and biodegradability properties. PS composites with 20% particle loading exhibited optimum mechanical properties. AN grafted AgP/PS composites exhibited higher mechanical strength as compared to ungrafted AgP/PS composites. Further AN grafted AgP/PS composites exhibited better thermal properties and biodegradability as compared to PS matrix. Addition of fire retardant fillers such as magnesium hydroxide Mg(OH)2 and zinc borate lowered burning rate of PS composites considerably. Scanning electron microscopy (SEM) of tensile fracture surfaces of AN grafted AgP/PS composites showed better particle/matrix adhesion.

• Influence of curing agents on gelation and exotherm behaviour of an unsaturated polyester resin

A judicious choice of curing agents such as initiator and promoter and their ratio to the resin can avoid reduced gel-time and shortened exothermic reactions in applications such as liquid compositemoulding processes. In this study, effects of different ratio of initiator and promoter to the unsaturated polyester resin on curing of the resin were investigated by measuring gel-time and peak exotherm using ASTM D2471 standards. Methyl ethyl ketone peroxide (MEKP) was used as an initiator and a cobalt salt was employed as an accelerator for the free radical polymerization of curing resin at ambient temperatures. It was observed that the resin gelation starts closely with the initial rise in exotherm temperature and time of gelation decreases with the increase in initiator or accelerator volume proportions. It was also found that the exotherm-peak and rate of temperature rise indicating that the curing rate increases with the initiator or accelerator proportions also increased. A nonlinear regression analysis of all geltime and cure data were performed to quantify the dependence of curing parameters on the volume proportions of accelerator and initiator. Thus, for this polymerization initiation system, the gel-time and cure parameters can be predicted for any initiator and cobalt levels within the ranges studied.

• Electrical and dielectric properties of TiO2 and Fe2O3 doped fly ash

Electrical properties of ceramic materials has become an area of increasing interest in research because these materials possess a great potential for solid-state devices. Conducting polymer composites have attracted considerable interest in recent years because of their numerous applications in a variety of electric and electronic devices. It has been observed that these materials possess a very high relative dielectric constant and high electrical properties at room temperature. Such a high dielectric constant is one of the important parameters in capacitor fabrication and a high electrical conductivity can be used for ionic batteries and electrochemical sensors.

• Study of optical characteristics of tin oxide thin film prepared by sol–gel method

In this paper, we present details of preparation of tin oxide (SnO2) thin film by sol–gel process. The film was synthesized on a glass (Corning 7059) plate by dip coating method. Here, we used tin (II) chloride as precursor and methanol as solvent. Optical characteristics and physical properties like refractive index, absorption coefficient and thickness of thin film were calculated from the study of transmission spectrum (wavelength vs transmission curve) data given by UV/VIS Spectrophotometer. Effect of number of coatings on transmittance and refractive index was also examined. It was observed that refractive index decreases with the number of coating and transmission value was more than 80% at wavelength greater than 450 nm in all cases. Structural analysis was studied by XRD measurement by using diffractometer which confirms tetragonal rutile structure of SnO2. Surface morphology was analysed from SEM micrograph and change in morphology on number of coat was discussed.

• Investigation of optical, structural and morphological properties of nanostructured boron doped TiO2 thin films

Pure and different ratios (1, 3, 5, 7 and 10%) of boron doped TiO2 thin films were grown on the glass substrate by using sol–gel dip coating method having some benefits such as basic and easy applicability compared to other thin film production methods. To investigate the effect of boron doped on the physical properties of TiO2, structural, morphological and optical properties of growth thin films were examined. 1% boron-doping has no effect on optical properties of TiO2 thin film; however, optical properties vary with &gt; 1%. From X-ray diffraction spectra, it is seen that TiO2 thin films together with doping of boron were formed along with TiB2 hexagonal structure having (111) orientation, B2O3 cubic structure having (310) orientation, TiB0.024O2 tetragonal structure having rutile phase (110) orientation and polycrystalline structures. From SEM images, it is seen that particles together with doping of boron have homogeneously distributed and held onto surface.

• Structural, magnetic and electronic transport studies of RAgSn2 compounds (R = Y, Tb, Dy, Ho and Er) with Cu3Au-type

RAgSn2 compounds, where R = Y, Tb, Dy, Ho and Er, were synthesized by arc-melting and subsequent annealing at 870 K. The formation of cubic phases with Cu3Au-type structure (space group 𝑃𝑚$\bar{3}$𝑚) was studied. Magnetic property measurements showed that in paramagnetic state, the compounds with magnetic rareearth atoms are Curie–Weiss paramagnets and order antiferromagnetically at low temperatures. YAgSn2 is a Pauli paramagnet in 100–300 K temperature range. The electrical properties of RAgSn2 compounds were investigated by means of electrical resistivity and Seebeck coefficient measurements in 4.2–300 K temperature range. All investigated compounds exhibit metallic type of conductivity. Electronic structure calculations based on full potential linearized augmented plane wave (FLAPW)method is also carried out to probe themagnetic and electronic structures of RAgSn2 compounds. Comparisons between experimental data and calculations are discussed.

• Phonon, magnon and electron contributions to low temperature specific heat in metallic state of La0.85Sr0.15MnO3 and Er0.8Y0.2MnO3 manganites

The reported specific heat 𝐶\ (𝑇) data of the perovskite manganites, La0.85Sr0.15MnO3 and Er0.8Y0.2MnO3, is theoretically investigated in the temperature domain 3 ≤ 𝑇 ≤ 50 K. Calculations of 𝐶\ (𝑇) have been made within the three-component scheme: one is the fermion and the others are boson (phonon and magnon) contributions.Lattice specific heat is well estimated fromthe Debye temperature for La0.85Sr0.15MnO3 and Er0.8Y0.2MnO3 manganites. Fermion component as the electronic specific heat coefficient is deduced using the band structure calculations. Later on, following double-exchange mechanism the role of magnon is assessed towards specific heat and found that at much low temperature, specific heat shows almost T3/2 dependence on the temperature. The present investigation allows us to believe that electron correlations are essential to enhance the density of states over simple Fermi-liquid approximation in the metallic phase of both the manganite systems. The present numerical analysis of specific heat shows similar results as those revealed from experiments.

• Mn valence state and electrode performance of perovskite-type cathode La0.8Sr0.2Mn1−𝑥Cu𝑥O3−𝛿 (𝑥 = 0, 0.2) for intermediate-temperature solid oxide fuel cells

Cu-free and Cu-doped LSM system, La0.8Sr0.2Mn1−𝑥Cu𝑥O3−𝛿 (𝑥 = 0, 0.2), with perovskite structure were prepared using an EDTA combined citrate process and the effects of Cu ion at B-site were investigated. Electrical conductivity and polarization resistance of the Cu-doped LSM were 210 S.cm-1 at 750 °C, and 2.54 𝛺. cm2 at 800 °C, respectively which were better than those of the Cu-free LSM. This indicated that the electrode performance of LSM was improved by the addition of Cu. The oxidation state of Mn ions increased with addition of Cu. The increase in the oxidation state of Mn ions was due to the formation of Mn4+ ions and oxygen vacancies. The addition of Cu ions to LSM systems could lead to enhanced electrode performance for oxygen reduction reactions originating from the change in valence of Mn ions.

• Iron-substituted AB5-type MH electrode

The present investigation is aimed to study MmNi5-type (Mm = Mischmetal) hydrogen storage alloys with composition, Mm0.8La0.2Ni3.7Al0.38Co0.3Mn0.6−𝑥Mo0.02Fe𝑥 (𝑥 = 0, 0.1, 0.2 and 0.3). The alloys are synthesized by radio-frequency inductionmelting. To study their electrochemical properties viameasurements of discharge capacity, activation process, rate capability and cyclic stability, electrodes are fabricated using as-synthesized and annealed version of the alloys. The maximum discharge capacity is recorded as 288 mAhg-1 for the iron concentration, 𝑥 = 0.1, as compared to 270 mAhg-1 for the alloy electrode without iron. Similarly, 99% cyclic stability is observed in annealed alloy electrode (𝑥 = 0.1) as compared to 78% in the alloy electrode without iron. Hence, small amount of iron-substitution (𝑥 = 0.1) in the alloy is found to improve the electrochemical properties. This improvement is thought to be due to less pulverization of the alloy in electrochemically-cycled alloy, as confirmed through structural and microstructural characterizations carried out by X-ray diffraction phase analysis and scanning electron microscopy of as-fabricated and electrochemically-cycled electrodes.

• Preparation of Zr50Al15−𝑥Ni10Cu25Y𝑥 amorphous powders by mechanical alloying and thermodynamic calculation

Amorphous Zr50Al15−𝑥Ni10Cu25Y𝑥 powders were fabricated by mechanical alloying at a low rotation speed from commercial pure element powders. The beneficial effect of Al partially substituted by Y in Zr50Al15Ni10Cu25 on glass-forming ability was investigated. The as-milled powders were characterized by X-ray diffraction and transmission electron microscopy. The results show that partial substitution of Al by Y can improve the glass-forming ability of Zr50Al15Ni10Cu25 alloy. Thermodynamic calculation of equivalent free energy shows that Zr50Al13.8Ni10Cu25Y1.2 alloy has the highest glass-forming ability, which is in good agreement with the report of orthogonal experiments.

• Electrochemical copolymerization of 𝑁-methylpyrrole and 2,2'-bithitiophene; characterization, micro-capacitor study, and equivalent circuit model evaluation

𝑁-methylpyrrole (𝑁-MPy) and 2,2'-bithiophene (BTh) were electrocopolymerized in 0.2 Macetonitrile–sodium perchlorate solvent–electrolyte couple on a glassy carbon electrode (GCE) by cyclic voltammetry (CV). The resulting homopolymers and copolymers in different initial feed ratios of [𝑁-MPy]0/[BTh]0 = 1/1, 1/2, 1/5 and 1/10 were characterized by CV, Fourier-transform infrared reflectance attenuated transmittance (FTIR–ATR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and electrochemical impedance spectroscopy (EIS). The capacitive behaviours of the modified electrodes were defined via Nyquist, Bode-magnitude, Bode-phase and admittance plots. The equivalent circuitmodel of R(C(R)(QR)(CR)) was performed to fit theoretical and experimental data. The highest low-frequency capacitance (𝐶LF) were obtained as 𝐶LF = ∼ 1.23 × 10-4 mF cm-2 for P(N-MPy), 𝐶LF = ∼ 2.09 × 10-4 mF cm-2 for P(BTh) and 𝐶LF = ∼ 5.54 × 10-4 mF cm-2 for copolymer in the inital feed ratio of [𝑁-MPy]0/[BTh]0 = 1/2.

• Influence of Al content on textural properties and catalytic activity of hierarchical porous aluminosilicate materials

A series of hierarchical porous aluminosilicate materials were prepared using hydrothermal treatment of the composite formed by polystyrene colloidal spheres and aluminosilicate gel. Influence of Al content on the textural properties, acidic properties and catalytic activity of the hierarchical porous aluminosilicate materials was studied. The results showed that textural and acidic properties of the hierarchical porous aluminosilicate materials were strongly related to Al content. As Al content is increased (𝑛Si/𝑛Al = 25), the hierarchical porous catalysts exhibited higher catalytic activity and major product selectivity for alkylation of phenol with tert-butanol than the catalysts with a lower Al content (𝑛Si/𝑛Al = 50).

• Structural characterization and complex impedance studies on fast ion conducting mixed system (SbI3)𝑥–(Ag2CrO4)1−𝑥

This paper deals with preparation and physico-chemical characterization of a new mixed system, (SbI3)𝑥–(Ag2CrO4)1−𝑥 (0.1 ≤ 𝑥 ≤ 0.9), undertaken with a view to evaluate silver ion transport properties and identify those fast ion conducting compositions. Polycrystalline samples of various compositions were synthesized by rapid melt-quenching method. Powder X-ray diffraction (XRD) analysis in conjunction with differential scanning calorimetry (DSC) and electrical transport evaluation involving silver ionic transport number and temperaturedependent electrical complex impedance measurements were carried out in order to identify the different phases responsible for the conduction mechanism. Realization of a fast ionic conductivity value of 3.2 × 10-2 S cm-1 in the case of the composition, (SbI3)0.3–(Ag2CrO4)0.7, at room temperature due to silver ion transport has been discussed in terms of observed structural and thermal characteristics. A detailed analysis of conductivity spectra pertaining to the best conducting system, (SbI3)0.3–(Ag2CrO4)0.7, has also been presented.

• Quantitative structure-property relationships of electroluminescent materials: Artificial neural networks and support vector machines to predict electroluminescence of organic molecules

Electroluminescent compounds are extensively used as materials for application in OLED. In order to understand the chemical features related to electroluminescence of such compounds, QSPR study based on neural network model and support vector machine was developed on a series of organic compounds commonly used in OLED development. Radial-basis function-SVM model was able to predict the electroluminescence with good accuracy (𝑅 = 0.90). Moreover, RMSE of support vector machine model is approximately half of RMSE observed for artificial neural networks model, which is significant from the point of view of model precision, as the dataset is very small. Thus, support vector machine is a good method to build QSPR models to predict the electroluminescence of materials when applied to small datasets. It was observed that descriptors related to chemical bonding and electronic structure are highly correlated with electroluminescence properties. The obtained results can help in understating the structural features related to the electroluminescence, and supporting the development of new electroluminescent materials.

• Synthesis and characterization of electrochemically-reduced graphene

Graphene has superior electrical conductivity than graphite and other allotropes of carbon because of its high surface area and chemical tolerance. Electrochemically processed graphene sheets were obtained through the reduction of graphene oxide from hydrazine hydrate. The prepared samples were heated to different temperatures such as 673 and 873 K. X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), transmission electron microscopy (TEM), Raman spectra and conductivity measurements were made for as-prepared and heat-treated graphene samples. XRD pattern of graphene shows a sharp and intensive peak centred at a diffraction angle (2𝜃) of 26.350. FTIR spectra of as-prepared and heated graphene were used to confirm the oxidation of graphite. TEM results indicated that the defect density and number of layers of graphene sheets were varied with heating temperature. The hexagonal sheet morphology and purity of as-prepared and heat treated samples were confirmed by SEM–EDX and Raman spectroscopy. The conductivity measurements revealed that the conductivity of graphene was decreased with an increase in heating temperature. The present study explains that graphene with enhanced functional properties can be achieved from the as-prepared sample.

• Structural characterization of electrodeposited boron

Structural characterization of electrodeposited boron was carried out by using transmission electron microscopy and Raman spectroscopy. Electron diffraction and phase contrast imaging were carried out by using transmission electron microscopy. Phase identification was done based on the analysis of electron diffraction patterns and the power spectrum calculated from the lattice images from thin regions of the sample. Raman spectroscopic examination was carried out to study the nature of bonding and the allotropic form of boron obtained after electrodeposition. The results obtained from transmission electron microscopy showed the presence of nanocrystallites embedded in an amorphous mass of boron. Raman microscopic studies showed that amorphous boron could be converted to its crystalline form at high temperatures.

• Electrochemical potentials of layered oxide and olivine phosphate with aluminum substitution: A first principles study

First-principles prediction of enhancement in the electrochemical potential of LiCoO2 with aluminum substitution has been realized through earlier experiments. For safer and less expensive Li-ion batteries, it is desirable to have a similar enhancement for alternative cathode materials, LiFePO4 and LiCoPO4. Here, we present first-principles density functional theory based analysis of the effects of aluminum substitution on electrochemical potential of LiCoO2, LiFePO4 and LiCoPO4. While Al substitution for transition metal results in increase in electrochemical potential of LiCoO2, it leads to reduction in LiFePO4 and LiCoPO4. Through comparative topological analysis of charge density of these materials, we identify a ratio of Bader charges that correlates with electrochemical potential and determine the chemical origin of these contrasting effects: while electronic charge from lithium is transferred largely to oxygen in LiCoO2, it gets shared by the oxygen and Co/Fe in olivine phosphates due to strong covalency between O and Co/Fe. Our work shows that covalency of transition metal–oxygen bond plays a key role in determining battery potential.

• Synthesis, characterization and evaluation of bioactivity and antibacterial activity of quinary glass system (SiO2–CaO–P2O5–MgO–ZnO): In vitro study

Bioactive glasses in the systems SiO2–CaO–P2O5–MgO (BGZn0) and SiO2–CaO–P2O5–MgO–ZnO (BGZn5), were prepared by sol–gel method and then characterized. Surface reactivity was studied in simulated body fluid (SBF) to determine the effect of zinc (Zn) addition as a trace element. The effect of Zn addition to the glass matrix on the formation of apatite layer on the glass surface was investigated through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT–IR) and scanning electron microscopy (SEM). Also, inductively coupled plasma–optical emission spectroscopy (ICP–OES) was used to determine the concentrations of released ions in SBF solution after different time intervals in SBF solution. The antibacterial activity of Zn containing glass against Pseudomonas aeruginosa was measured by the halo zone test. The presence of Zn in glass composition improved chemical durability, slowed down the formation rate of Ca–P layer and decreased the size of crystalline apatite particles. Zn containing glass exhibited an excellent antibacterial activity against P. aeruginosa which could demonstrate its ability to treat bone infection.

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