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The graphene oxide and metal oxide–grafted graphene composites are studied on their promising electrochemical properties for high-performance supercapacitor applications. The identical decoration of metal oxide nanomaterials over the graphene structure reveals enhanced structural, thermal, and electrochemical stability to fabricate stable electrode materials. In the study, we review our recent studies on the utilization of graphene oxide and metal oxide–graphene grafted nanocomposites for energy storing applications.

This study demonstrates the successful synthesis of SrZr(PO4)2:Dy2O3solid solutions via solution combustion method, employing glycine as fuel. Powder X-ray diffraction (XRD) confirmed the crystal structure, while scanning electron microscopy (SEM) provided detailed insights into the surface morphology. Fourier transform infrared (FT-IR) spectroscopy identified the functional groups present, further revealing the material's composition. Photoluminescence (PL) measurements reveal excitation bands at 350, 365, 390, 425, and 450 nm; emission bands at 480, 580, and 665 nm. Emission color of the sample plot in the CIE x,y co-ordinates reveal white emission close to the standard white (0.33,0.33) demanded by the international television committee. Finally, dielectric studies revealed promising potential for long-term energy storage applications, particularly in super-capacitors.

Ozone-sensing characteristics of pure WO3and hybrid rGO/WO3nanocomposite materials synthesised by hydrothermal method were investigated. The physicochemical properties of prepared samples were studied by XRD, FTIR, Raman, HR-SEM, HR-TEM, and XPS analysis. The XRD analysis confirmed the monoclinic structure of WO3with an average crystallite size of 22 nm and the WO3nanoparticles were finely embedded on the surface and between the nanosheets of rGO as confirmed by SEM and TEM analysis. The XPS analysis confirms the presence of C, W, and O elements and their valence states with respect to binding energies in the rGO/WO3nanocomposite. The prepared rGO/WO3nanocomposites were developed as thin film with different thickness of conductive polymer matrix layer of 2, 4, and 6 μm to study the effect of thickness on the ozone-sensing characteristics of the sample. An increase of conductive layer thickness could enhance the sensing response of the hybrid rGO/WO3nanocomposite films and exhibited better sensing performance than pure WO3film. Moreover, the AFM studies show the formation of cavities and surface uniformity after the exposure of ozone gas. In addition, the calculated ID/IGratio (~ 1.84) of an optimised rGO/WO3sensing film was increased dramatically after the ozone exposure, owed to the reduction of rGO through an interaction between ozone molecules and sensing film. The experimental results suggest that the hybrid rGO/WO3nanocomposite sensing film could be a potential candidate for sensing of ozone molecule at even low ppm level in ambient temperature.

This investigation emphasizes on the facile, one spot in-situ microwave irradiation method used to synthesize cuprous oxide/graphene (Cu2O/G) nanocomposite without any templates. Microwave irradiation method assisted the conversion of graphene oxide to graphene in presence of Cu2+ions in the water medium, and self-assembled Cu2O on graphene layers reveal the resultant Cu2O/G nanocomposite. X-ray diffraction pattern reflects the structure of Cu2O nanoparticles and graphene sheet. The morphology of electrode materials was studied with SEM and TEM to confirm the intercalation of Cu2O on graphene sheets. FTIR analysis confirmed the reduction of oxygen functional groups. The cyclic voltammetry and charge/discharge analysis in 1 M H2SO4electrolyte reveals the electrochemical properties. The specific capacitance of Cu2O/G nanocomposite is 611 Fg−1compared to the graphene (290 Fg−1) and Cu2O (160 Fg−1) at a current density of 1 Ag−1.The experiment under similar conditions revealed 100% retention in capacitance after 5000 charge-discharge cycles. The electrochemical impedance spectroscopy of Cu2O/G nanocomposite suggests the excellent supercapacitor performance with higher ion transport ensuring enhanced electrochemical performance.

Novel Ag2S/ZnS and ZnS/Ag2S nanocomposites were synthesized by a simple chemical method in air. Different morphologies were obtained for Ag2S/ZnS nanocomposites annealed at different temperatures. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible absorption, and photoluminescence (PL) spectroscopy. Thermal stability and phase transition of the sample were studied by TG–DTA. Compared the PL spectra of Ag2S/ZnS at 640 nm, it was significantly red shifted from 640 to 670 nm for reversed ZnS/Ag2S nanocomposites. The band gaps of nanocomposites were lying between 2.25 and 2.55 eV range. It has been found that as-synthesized powder has excellent photocatalytic activity toward degradation of methylene blue (MB) under visible light and electrochemical activity, indicating that Ag2S/ZnS and ZnS/Ag2S nanocomposites can play an important role as semiconductor photocatalyst and energy storage applications.

Development of simple UV detection system using CdTe quantum dots (QDs) as primary detector with scintillating property on exposure to UV rays is reported. CdTe, CdTe/ZnS and CdTe/CdS QDs were synthesized in aqueous phase using mercaptosuccinic acid (MSA) as a capping agent and studied for its properties like crystallite size, band gap energy, fluorescence emission intensity and uniformity in size distribution. The prepared QDs were exposed to different radiations such as infrared (IR), ultraviolet (UV) and X-rays. The fluorescent emission was recorded by an optoelectronic circuit in terms of electrical signal. The result of this study shows that CdTe/ZnS QDs is better suited for the detection and measurement of UV rays. Hence these QDs could be used as a sensing element while fabricating nanosensor for UV detection.

C14TAB-assisted cerium oxide (CeO2) mesocrystals have been synthesized via wet chemical route. XRD, SEM, AFM, EDS, FTIR, Raman, UV–vis and PL spectroscopy were employed to characterize the crystal phase, morphology, chemical composition and optical properties of the CeO2mesocrystals. The experimental results showed that the product owned mesocrystal structure with self-assembly cubic architecture in the presence of C14TAB as a template. The growth mechanism of CeO2mesocrystals has been predicted to explain the formation of CeO2mesocrystals. CeO2mesocrystals exhibit a very strong violet/blue emission centered at 421 nm and a weak green luminescence emission at around 524 nm.

Single crystals of K0.5Na0.5NbO3 (KNN) and 5wt%, 10wt%, 15wt% of Sb doped KNN crystals were grown by flux method. The formation of crystalline structure, microstructure, domain structure and the dielectric properties were investigated for both pure and Sb doped KNN single crystals. X-ray diffraction (XRD) pattern shows that pure and doped KNN single crystals have orthorhombic perovskite structure. The doped crystals have slight shrinkage in the unit cell volume. The partial substitution of the B-site ion Nb5+ by the Sb5+ ion in the KNN single crystal results in decreasing phase transition temperatures TO-T and Curie temperatures TC of the doped crystals with increasing amount of Sb. The dielectric properties of the doped crystals show significant improvement with doping concentration. The peaks slightly shift towards lower frequencies with increasing dopant concentration.

Multiferroic YMnO3 nanorods were synthesized by hydrothermal process at 200ºC. Hexagonal structure of the synthesized sample was confirmed by powder X-ray diffraction analysis. High resolution scanning electron microscope analysis shows uniform nanorods with average diameter of about 350nm and length of 10µm. Transmission electron microscope and selected area electron diffraction studies reveal the single crystalline nature of nanorods and the lattice fringe width of nanorod is about 0.296nm for the (111) plane with the growth direction along (001) plane (c-axis). The zero-field-cooled and field-cooled magnetization studies show a complicated magnetic transition occurred in the temperature range from 20 to 300K as confirmed by magnetic hysteresis loops.

Picolinium maleate (PM), a novel organic compound has been synthesised and bulk crystal has been grown from the aqueous solution by slow evaporation technique. The structure of the grown crystal was elucidated by using single crystal XRD analysis and powder XRD pattern further confirmed the crystallinity of the grown PM crystal. The presence of functional groups in PM were identified by FTIR spectral analysis. UV-Vis spectral studies revealed that PM crystals are transparent in the wavelength region 327–1100 nm. The laser damage threshold value of PM crystal was measured using Nd:YAG laser. The second harmonic conversion property was studied by Kurtz and Perry powder technique.

Nucleation parameters such as metastable zone width, induction period and interfacial energy have been determined for the aqueous solution growth of bis thiourea cadmium acetate (BTCA) single crystals. Solubility of BTCA has been determined for various temperatures. Metastable zone width and induction period values have been estimated in order to optimize the growth parameters. The interfacial tension values derived from experimentally determined induction period are found to be comparable with theoretical values. Bulk crystals of BTCA have been grown using the optimized growth parameters. The grown crystals have been subjected to structural, optical and mechanical property studies. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Single crystals of potassium ferrocyanide trihydrate, K4[Fe(CN)6·3H2O (KFCT), a ferroelectric material with Curie temperature 251K were grown in silica gel at room temperature for the first time by the solubility reduction method. Resorcinol and ethyl alcohol were used for the purpose of gel setting and supernatant liquid respectively. Optical and mechanical properties were studied for the grown crystal. The structure of the grown crystal was confirmed by X-ray diffraction analysis. Fourier Transform Infrared (FTIR) and FT Raman spectral analysis of the crystalline samples reveal that the crystalline sample consist consists of all functional groups. Thermal analysis of the crystalline sample was performed by TGA and DTA methods. The Vicker's micro hardness value was measured for KFCT crystals. The square etch pits with a hopper-like structure is an indicative of 2D nucleation mechanism. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Single crystals of tris allylthiourea mercury chloride (ATMC), a semi-organic nonlinear optical material, have been grown from a low-temperature solution growth technique by slow cooling method. In the present work, we have grown ATMC crystal which is a new nonlinear optical material (NLO) having high optical quality and its second harmonic generation (SHG) efficiency is thrice that of Urea. The grown crystals have also been subjected to various characterization studies like X-ray diffraction, UV-VIS, FT-IR and TGA-DTA. X-ray powder diffraction study confirmed the crystal structure of ATMC, UV-VIS /FT-IR spectral analysis showed the crystal has good optical transmission in the entire visible region and TGA-DTA studies showed the thermal properties and complex degradation of ATMC crystal. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Tri Glycinsulphate with partial substitution of phosphoric acid, namely Tri Glycine Sulpho Phosphate (TGSP) has been grown by slow cooling method. Habit modifications have been observed with change in the concentration of ortho phosphoric acid (H3PO4). Monoclinic structure of the grown crystals has been confirmed using X-ray diffraction analysis. TGSP crystals doped with L – Asparagine were also grown. The doping effect is qualitatively estimated using FTIR analysis. TGA, DTA studies and dielectric measurements were carried out for pure and L-Asparagine doped TGSP crystals to investigate the thermal and electrical properties of the crystals. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Electrospun ZnO nanofibers were obtained by calcinating PVA/Zinc Acetate composite fibers at various temperatures. Atomic Force Microscopy (AFM) revealed that the ZnO fibers have diameters in the range of 100-200 nm. The fibers were characterized by FT- IR, TGA-DTA, and XRD studies. The XRD results showed that the crystal structure and the morphology of the fibers were largely dependent on the calcination temperature (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The thermal stability of different lead oxide films prepared by reactive dc magnetron sputtering from a Pb target has been investigated. The temperature dependence of composition as well as structural and optical properties have been studied by Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD) and variable-angle spectroscopic ellipsometry (VASE). Both XRD and RBS experiments confirm that different kinds of lead oxides are formed upon increasing the oxygen flow. Upon annealing at 500 °C, all samples form orthorhombic PbO. VASE studies show that the refractive index n and the band gap energy Eg increase with increasing annealing temperature. For films annealed at 500 °C, n is approximately 2.7 at 650 nm and a band gap energy of 2.8 eV is obtained, which corresponds to the value for bulk PbO. The stoichiometric changes observed by XRD on increasing the annealing temperature are discussed and supported by thermodynamics arguments.

l -arginine fluoride (LAF) is one of the potential semi-organic materials for nonlinear optical applications. In the present study, synthesis, material purification and crystal growth of LAF have been carried out. Since the material has high solubility in water, the growth parameters have been optimized for the growth of good-quality crystals. X-ray powder diffraction studies have been carried out in order to calculate the lattice parameter values using its monoclinic crystallographic equation. From Fourier transform infrared spectroscopic analysis, different modes of vibration due to various functional groups present in LAF have been observed. In order to find the range and percentage of optical transmission, the UV-VIS spectrum was recorded for the crystal. The thermal behaviour of the LAF sample has been investigated from differential thermal and thermogravimetric analyses.

Niobium oxide films have been prepared on glass and Si(100) substrates by reactive dc magnetron sputtering of a metallic Nb target in an argon-oxygen atmosphere. The properties of the films as a function of oxygen partial pressure have been studied systematically by Rutherford backscattering spectroscopy, X-ray diffraction, X-ray reflectometry and optical spectroscopy. Rutherford backscattering studies show that the films are substoichiometric at lower oxygen flow while stoichiometric films can be formed above 7.5 sccm O2 flow. Grazing incidence X-ray diffraction studies show that the films are amorphous. X-ray reflectometry was used to determine the sputter rate, density and surface roughness of the films. The films prepared at lower oxygen flow rates had a higher density than those prepared at higher oxygen flow rates. For appropriate oxygen flow rates fully transparent niobium oxide films can be grown with rates up to 0.5 nm/s for a constant cathode current of 900 mA. From optical spectroscopy measurements of reflectance and transmittance we have determined the optical constants such as the refractive index (n), extinction coefficient (k) and band gap (Eg) as well as the film thickness. For the fully transparent films prepared above 7.5 sccm O2 flow rate a band gap of 3.5 to 3.6 eV is obtained. Optical spectroscopy measurements show that the refractive index of the films decreases upon increasing oxygen flow rate and this finding is related to a decrease of density upon increasing oxygen flow.

Nb substituted barium strontium titanate single crystals were grown by the high-temperature solution growth technique with different Nb concentrations. The growth conditions were optimized to grow good quality large sized single crystals. Nb doping reduced the twin formation considerably and yielded bulk single crystals. A surface morphology observation indicates layer and hopper growth mechanisms. Powder X-ray diffraction studies show an increase in c/aratio with Nb content, and ferroelectric studies revealed a decrease in curie temperature and a sharp increase in dielectric constant and spontaneous polarization.

The crystal structure, surface morphology, compositional homogeneity and electrical properties of barium strontium titanate (BST) thin films are investigated. The films were deposited on bare silicon and platinum coated silicon substrates by spin coating process. The precursor solution with Ba/Sr ratio 70/30 was prepared by sol‐gel synthesis using metal alkoxides. The crystalline nature and morphology of the films are found to be strongly influenced by the heating cycle adopted to form the Ba0.7Sr0.3TiO3layer. The elemental composition analysis on the surface and in‐depth confirms the stoichiometry of the films. The dielectric constant at 100 kHz and dissipation factor at room temperature is found to be 120 and 0.0236 for the films with 400nm thickness annealed at 700°C for 2 hrs. The leakage current density of the film is found to be 4x10‐8A/cm2from I‐V measurements.

Abstract: Investigations on nucleation thermodynamical parameters are very essential for the successful growth of good quality single crystals from high temperature solution. A theoretical estimation of the nucleation thermodynamical parameters like interfacial energy between the solid Nd123 and its flux BaO-CuO, metastable zone-width, Gibbs free energy, critical energy barrier for nucleation and critical nucleation radius have been calculated from the knowledge of solubility data and by applying the classical nucleation theory. Results are discussed to understand the growth kinetics of Nd123 crystals.

The nucleation parameters, such as radius of the critical nucleus and critical free energy change have been evaluated for LAP single crystals. The interfacial tension determined by conducting the induction period measurements has been used for the evaluation of nucleation parameters. The determined interfacial tension is found to be comparable with theoretical literature values.

Pure and doped (Benzophenone and Urea) triglycine sulphate (TGS) crystals have been grown from aqueous solution by slow cooling method. The influence of doping of benzophenone and urea on the growth and electrical properties have been investigated. The pyroelectric coefficient increases with the addition of benzophenone and urea. It has been observed that the pyroelectric figure of merit of benzophenone doped TGS crystals is less than urea doped crystals. This is attributed to the higher permittivity of benzophenone doped TGS crystals. The Vicker's hardness number was found to be increased for doped crystals.