Abstract: Cubic phase gadolinium oxide nanoparticles were prepared by hydrothermal method at various reaction temperatures like 60 °C, 120 °C, 180 °C and 240 °C. X-ray Diffraction (XRD) studies confirmed the formation of cubic phase Gd2O3. The broadening of XRD peak, due to crystallite size was investigated with the aid of gaussian and voigt peak fitting function and its comparisons were also performed. Crystallite size calculated from Scherrer formula for Gd2O3 nanoparticles for various reactions temperatures varies between 21 nm and 39 nm. Thermal analysis of as-prepared sample was done and the decomposition temperature was found to be 433 °C for the formation of Gd2O3. The metal-oxygen band in Fourier Transform Infrared Spectroscopy (FTIR) spectra confirmed the presence of Gd2O3. Band gap studies from Diffuse Reflectance Spectroscopy (DRS) revealed the decrease in band gap with respect to the increase in crystallite size. In Photoluminescence (PL) spectra, a broad ultra violet emission is observed between 320 nm and 400 nm. Irrespective of reaction temperature, Scanning Electron Microscopy (SEM) images reported the formation of nanorods.
Abstract: Single phase hexagonal molybdenum oxide (h-MoO3) nanocrystals were successfully synthesized by solution based chemical precipitation method. The effect of mineralizer (KNO3 salt) on hexagonal phase, crystallite size, and surface morphologies of MoO3 was investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) analysis. The XRD result indicates that the diffractograms exhibit characteristic hexagonal phase of MoO3. From the line broadening analysis, the average crystallite size was calculated and estimated. A less crystallite size of 34 nm was obtained in the presence of mineralizing agent KNO3 in comparison to without mineralizer (46 nm). The particle exhibits rod like morphology with perfect hexagonal cross-section and well faceted top and side surfaces. Further, the thermal and optical properties were studied by thermo gravimetric analysis (TGA) and diffuse reflectance spectroscopy (DRS) measurements. The weight loss due to decomposition of intercalated water and ammonia were observed. By TGA analysis, the mineralizer assisted sample shows higher phase stability with the phase transition temperature of 520 °C due to the incorporation of K+ in MoO3 structure. The optical band gap energy was calculated using Kubelka-Muck function and the values were found to be 3.11 eV and 2.97 eV for KNO3 assisted and non-assisted MoO3 samples respectively. The observed increase in optical band gap (Eg) for h-MoO3 synthesized in the presence of KNO3 was attributed to the size dependent optical properties.
Abstract: Since the discovery, gold nanoparticles (GNPs) have been attracting scientific and research communities owing to their biocompatibility, excellent thermal conductivity, low cytotoxicity, ease of processability, and highly functionalization capability. In this report, we discuss synthesis of gold nanoparticles with poly(vinyl pyrrolidone) (PVP) in 1–butanol from gold hydroxide, a new precursor salt. An emergence of a strong surface plasmon absorption band at 535 nm confirms formation of GNPs in the colloidal solution. The stability of Au colloid was studied by using UV–Visible and zeta potential measurements. The interfacial interaction between GNP and PVP molecules was studied in terms of Fourier transform infrared and X–ray photoemission spectrum (XPS). Marked enhancement in some of the vibrational bands (e.g., C=O, C–H, and C–N stretching) of PVP molecules in presence of GNPs reveals existence of an interaction between this two major constituents. However a small red-shift in the C=O stretching frequency of pyrrolidone group of PVP molecule implies that a weak interaction occurs via O–atom of carbonyl group. Appearance of Au4f doublet band at 82.7 and 86.4 eV in XPS spectrum with a chemical shift of 3.7 eV further confirms formation of GNPs by reduction of Au3+ to Au0 chemical state in presence of PVP. A noticeable negative shift in the binding energies of Au4f doublet band as compared to bulk Au atom suggests an interfacial interaction between GNP and PVP molecules. Transmission electron microscopic images propose that Au crystalline core is covered by an amorphous layer of PVP molecules.
Abstract: In the present work we have used Physical vapour deposition (PVD) technique followed by thermal annealing to synthesize Ag-soda glass nanocomposite samples. This technique offers a great deal of promise in terms of general simplicity of operation, minimal requirements for sample preparation, ease of adaptation to automated operation, and potential for scale up to production levels of material throughput. Ag-glass nanocomposites were synthesized by deposited Ag on glass slides and the resulting samples were annealed in air at various temperatures from 400 °C to 550 °C for 1 hour. Optical absorption spectrum of the resulting nanocomposites was measured in the range from 190 nm to 900 nm using UV-Visible absorption spectroscopy. The appearance of SPR peak characteristic of Ag nanoparticle formation around 420 nm in optical spectra of annealed samples indicates towards the formation of silver nanoparticles in soda glass. The size of silver nanoparticles has been found to increase with increase in annealing temperatures. Structural properties of resulting nanocomposites were also studied using TEM and FE-SEM alongwith EDAX spectra. Synthesized composites are more conducting than pristine glass and conductivity increases with increase in size of Ag nanoparticles embedded in glass. Possible mechanism for increase in conductivity has been discussed.
Abstract: Fabrication of ZnO nanowires (NWs) by thermal oxidation method has been studied in this work. The ZnO NWs have been grown by oxidation of Zn metal foil under oxygen environment for two typical oxidation durations. We have investigated the behavior of the as-grown ZnO NWs with the change in oxidation duration at particular temperature. The changes in surface morphology and chemical composition with the variation of oxidation duration have been analyzed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) respectively. From EDS spectra, it is confirmed that Zn metal has completely oxidized into ZnO for higher oxidation duration. In this work, the optimized duration of oxidation for growth of ZnO NWs is found to be ~60 minutes at particular temperature of 600oC. The present method provides a possible mechanism for the growth of ZnO NWs on the p-Si substrates.
Abstract: Undoped and Eu3+doped ZnO nanostructure were successfully grown under hydrothermal method and europium doping concentration were varied as 1, 3 and 5 (at %). All the peaks in the XRD diffraction pattern are assigned to the typical hexagonal wurtzite structure of ZnO. Average crystallite size was calculated from scherrer formula and it indicated an increase in crystallite size with doping concentration. Scanning electron microscopy (SEM) for undoped and 1% doped samples shows spherical shape particles whereas for higher doping concentrations (3 and 5 at %), rod shaped particle are observed. The presence of Eu was confirmed by Energy dispersive X-ray analysis (EDX). Fourier transforms infrared spectroscopy (FT-IR) spectra are used to identify the strong metal oxide (Zn-O) interaction. Ultra violet visible (UV-vis) spectroscopy indicted an absorption peak at 375 nm. Red emission peak in photoluminescence (PL) spectra at 642 nm arises due to intra 4f-5d transition in Eu3+.
Abstract: Nanocomposite films of Poly (methylmethacrylate) with different concentration of silver nanoparticles were prepared by ex-situ method. Firstly, silver nanoparticles were obtained by reducing the aqueous solution of silver nitrate with sodium borohydride then Ag-PMMA films were prepared by mixing colloidal solution of silver nanoparticles with solution of polymer. Thin solid films were structurally characterized using UV-VIS spectroscopy and TEM. The appearance of surface plasmon resonance peak, characteristic of silver nanoparticles at 420 nm in UV-VIS absorption spectra of Ag-PMMA films confirms the formation of Ag-PMMA nanocomposite. TEM showed Ag nanoparticles of average size 8 nm embedded in PMMA matrix. Analysis of absorption and reflection data indicates towards the reduction in optical band gap and increase in refractive index of the resulting nanocomposite. The synthesized Ag-PMMA nanocomposite has been found to be more conducting than PMMA as ascertained using I-V studies. The decrease in band gap and increase in conductivity can be correlated due to the formation of localized electronic states in PMMA matrix due to insertion of Ag nanoparticles. The PMMA thin films with dispersed silver nanoparticles may be useful for nanophotonic devices.
Abstract: Swift heavy ion induced modification in the optical properties of TiO2/Poly (Methyl methacrylate) nanocomposites is reported in this paper. The as prepared anatase TiO2 nanoparticles were uniformly dispersed in PMMA matrix using solution casting method. These nanocomposites were then irradiated with Ag+12 (120 MeV) ion beam and characterized by X-ray diffraction, scanning electron microscopy, UV-Vis spectroscopy, PL and Raman spectroscopy. The PL spectra exhibited an enhanced broad emission peak in visible region (400 nm - 750 nm) while UV-Vis spectroscopy revealed an increased absorption in visible region in irradiated specimen in comparison to unirradiated sample.
Abstract: In this nanoregime attempts to bring forth nanoparticles and nanomaterials are myriads, with there interesting and demanding applications in almost every field. Today the field of nanoscience has bloomed with the confluence of nanotechnology with material science, biology, biotechnology and medicine and the need for nanotechnology will only increase as miniaturization becomes extremely important in various arrays of life. Since time immemorial silver nanoparticles have been extensively used for hygienic and healing purposes, and even until most recently, it has indispensible vital role especially in the biomedical arena. Thus in an attempt to generate silver nanoparticles employing green, environmentally benign route, we have designed to converge mythology with technology, with the mystical production of silver nanoparticles, enabled by the blueberry beads of the plant Elaeocarpus granitrus Roxb., the Rudraksha. This non-degradable bead does not disintegrate, but retains the potentiality, even after unlimited production of silver nanoparticles, assisting infinite times. The extremely cost-efficient nanoparticles thus developed in a superiorly efficient manner were characterized through different techniques; like UV/visible spectroscopy, PL spectroscopy, transmission electron microscopy, energy dispersive X-ray analysis and nanoparticle size analysis.
Abstract: The work is primarily concerned with the development of nanocrystalline Nd-Fe-B, based permanent magnet with high Curie temperature. An alloy of composition Fe81Nd7Al2B10 has been prepared using vacuum arc furnace and subjected to using Melt-Spinning process for preparation of amorphous flakes. Differential scanning calorimetry (DSC) has been performed to determine the crystallization temperature and activation energy of the melt spun amorphous ribbons. Subsequently the melt spun ribbon was subjected to annealing at below and above the crystallization temperatures to identify effect of Al on the Curie temperature. It was noteworthy for the effect of alloying Al above crystallization temperature. The Curie temperature increases to by almost 1.3 times with increase in annealing temperature.