Advanced Materials Research Vol. 678

Abstract: Fe and Fe2 O3 nanoparticle have been synthesized by chemical precipitation method. The x-ray diffraction studies indicate the formation of Fe and Fe2 O3 nanoparticles with cubic phase and no secondary phase was observed. Surface morphology of Fe and Fe2 O3 has been studied using scanning electron microscopy (SEM). Transmission electron microscopy (TEM) images reveal that Fe and Fe2 O3 nanoparticle have size ranging from 25-41 nm.

Abstract: Nano CuO-ZrO2 mixed oxides were prepared by wet chemical method by mixing equimolar solutions (0.45M) of cupric chloride (1.92g) and Zirconium oxychloride (3.63g) in aqueous Sodium hydroxide and refluxed at elevated temperature. The prepared nano CuOZrO2 mixed oxides were characterized by FT-IR, SEM, EDAX, XRD, DSC and CV studies. From XRD studies the size of the nano CuO and ZrO2 are found to be 25 and 9.5nm respectively through Debye-Scherrer's formula. The sizes of the CuO-ZrO2 mixed oxide particles have also been characterized and the average grain size of the particles is found to be 24nm in diameter. The nano particle composition and morphology of CuO, ZrO2 and mixed oxide have been analysed by EDAX set up attached with scanning electron microscope (SEM). EDAX analysis indicates the presence of Cu, Zr and O. SEM morphological studies of CuO, ZrO2 and mixed CuO-ZrO2 revealed the particle distribution with uniform granular structure. Cyclic Voltammetric studies exhibit good adherent behaviour on electrode surface and good electroactivity at pH 1.0. Nano CuO, ZrO2 and mixed CuO-ZrO2 under goes oxidation at 0.224V, 0.092V -0.072V and0.198V respectively. DSC thermogram of CuO, ZrO2 and mixed CuO-ZrO2 are recorded at the heating rate of 10o/ min. The glass transition temperature (Tg), the crystallization temperature (Tc) and melting point (TM) of the mixed oxide are determined from the DSC curve. The Tg value of CuOZrO2 mixed oxide is -50o C the Tc value is 20o C and melts at a temperature of 116o C.

Abstract: Reduced graphene oxide is an excellent candidate for various electronic devices such as high performance gas sensors. In this work Graphene oxide was prepared by oxidizing graphite to form graphite oxide. From XRD analysis the peak around 11.5o confirmed that the oxygen was intercalated into graphite. By using hydrazine hydrate, the epoxy group in graphite oxide was reduced then the solution of reduced graphite oxide (rGO) is exfoliated. Raman spectrum of rGO contains both G band (1580 cm-1), D band (1350 cm-1). The remarkable structural changes reveals that reduction of graphene oxide from the values of ID/IG ratio that increase from 0.727 (GO) to 1.414 (rGO). The exfoliated reduced graphite oxide solution is spin coated on to the SiO2/Si substrates.

Abstract: ZnS and Mn²⁺ doped ZnS nanoparticles are synthesized through a simple solvothermal method. The structural and optical properties of pure and doped ZnS nanoparticles were studied using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), UV-vis absorption and photoluminescence spectroscopy (PL). X-ray diffraction analysis reveals that undoped and Mn²⁺ doped ZnS crystallizes in cubic structures. The average grain size of the nanoparticles lies in the range of 2.2 to 4.8 nm. The SEM image shows that pure and doped nanoparticles are in spherical shape. The optical absorption spectrum exhibits a clear blue shift for ZnS and Mn²⁺ doped ZnS nanoparticles when compared with bulk ZnS. Photoluminescence spectra recorded for ZnS nanoparticles exhibits an emission peak centered around 428 nm for an excitation wavelength of 330 nm. However, for Mn²⁺ doped samples, an yellow–orange emission is observed along with the blue emission.

Abstract: Theoretical and experimental investigations are made here on the mean square displacement (MSD) and Debye Waller Factor (DWF) of rutile structure of tin dioxide nanoparticles. SnO₂ nanoparticles are synthesized by simple co-precipitation method and structurally characterized by X-Ray diffraction which revealed tetragonal rutile structure. Rietveld analysis of XRD measurements and phonon moments are used to deduce the MSD and DWF of nano SnO₂. DWF of nano SnO₂ obtained from Rietveld analysis (0.21 Ų) is large when compared to the value reported for bulk (0.0035 Ų) which is due to the high surface to volume ratio of the nanoparticles.

Abstract: SILAR method is adopted for the deposition of titanium dioxide (TiO₂) thin films. Titanium trichloride and ammonium hydroxide are used as the cationic and anionic precursors respectively. Deposition parameters such as growth rate, individual dipping and rinsing times and precursor concentration are optimized to obtain uniform, adherent films. As-deposited TiO₂ films are annealed at 300°C and 400° C. The crystallization behaviour of TiO₂ thin films is analysed by X-ray diffraction. Optical constants of the films are evaluated using UV-Vis spectrophotometry. Effect of deposition parameters on the optical properties of the films is analysed.The direct and indirect band gap values of the TiO₂ thin films is in the range of 3.4-3.8 eV and 2.1-3.8 eV respectively.

Abstract: Thin films of TiO2 have been deposited on well cleaned glass substrates by Sol-Gel dip-drive coating technique. The films have been prepared at three different pH values (1, 3.5 & 9) of Sol and annealed in muffle furnace at 550°C for one hour and are allowed to cool to room temperature. The films were characterized by XRD, EDAX, SEM and UV-Vis Spectrophotometer. The as deposited films were found to be amorphous in nature. The annealed films exhibit anatase in crystalline structure. The EDAX results have shown that all the films are maintained with TiO2 in composition. The XRD results reveal that they are nano-crystalline in nature and the crystalline nature increases with pH of the Sol. The transmittance and absorbance spectra have shown that the films are transparent and band gap of the films are of the order of 3.2eV. The ab initio studies of TiO2 (using GGA) was performed with Vienna ab initio Simulation package and the band structure and effective masses of the electrons and holes were determined.

Abstract: Intensive and innovative research is focused on the preparation of various nanostructured materials especially nanostructured metal oxides as applicable to number of applications.The present work mainly emphasis a single step synthesis of ZnO nanoparticles by employing surfactant free forced condensation method. Surface morphology of the sample was precisely controlled by varying the calcination conditions. Investigation on the structure, surface and composition of ZnO nanoparticles is of both fundamental interest and technological importance. X-ray diffraction (XRD) analysis reviled that the ZnO nanoparticles exhibits crystalline with the preferential orientation along (1 0 0) plane. SEM image shows the nanoparticles are in the range of 75 to 150 nm with spherical shape. The room temperature PL spectra of ZnO particles exhibited strong ultraviolet photoluminescence around 380 nm at room temperature.

Abstract: Flower-like ZnO nanostructures have been synthesized using zinc nitrate hexahydrate and hexamethylenetetramine (HMT) by a low-temperature hydrothermal technique. The prepared ZnO nanostructures exhibit hexagonal wurtzite structure, well-defined flower-like morphology, and a strong blue emission photoluminescence. Flower-like ZnO nanostructures consisting of multilayered petals are formed with the length of about 1 μm. All the flower petals exhibit the tapering feature with the root size of 300-500 nm and tip size of 50-100 nm. The prepared ZnO sample has been studied using x-ray diffraction technique, energy dispersive x-ray analysis, scanning electron microscope and FTIR spectroscopy. The photoluminescence spectrum demonstrated two emission bands, a near band edge (NBE) emission in the UV region centering at 386 nm and a high intensity deep band emission (DBE) in the visible region centering at 483 nm.

Abstract: ZnO nanocrystalline thin films have been prepared on glass substrates by sol-gel dip coating method. The ZnO thin films have been coated at room temperature for the pH value of 10 and annealed at 300°, 400° and 500°C respectively. The X- ray diffraction pattern shows that ZnO nanocrystalline thin films are of hexagonal structure and the grain size is found to be in the range of 25-45 nm. Scanning electron microscope images show that the surface morphology improves with increase of annealing temperature. The TEM analysis reveals the formation of ZnO nanocrystalline with an average grain size of 44 nm. The compositional analysis results show that Zn and O are present in the sample. The optical studies shows that the films are highly transparent and exhibit a direct band gap. The band gap has been found to lie in the range of 3.07 to 3.32 nm depending on the annealed temperature suggesting the formation of ZnO nanocrystalline thin films.