Arumugam Chandra Bose

Investigation of defect related photoluminescence property of multicolour emitting Gd2O3:Dy3+ phosphor

Multicolour emitting Gd2O3:Dy3+ phosphor is prepared by citrate based sol–gel method as a function of annealing temperature of the sample and its emission property dependence with lattice defects is elaborated. The annealed phosphors are characterized by X-ray powder diffraction (XRD), Raman spectroscopy, diffuse reflectance spectroscopy (DRS), photoluminescence (PL), fluorescence lifetime and positron annihilation lifetime spectroscopy (PALS). The phosphors annealed at different temperatures greatly influence the defect and emission intensities, as revealed from PL and PALS measurements, respectively. The efficient energy transfer (ET) from the Gd3+ ion to Dy3+ ion is schematically illustrated with the aid of an energy level diagram. The PL spectra clearly conclude that Dy3+ with an ionic radius close to the Gd3+ ion prefers to occupy the C2 site in the Gd2O3 matrix. The positron lifetime spectroscopy qualitatively explains the concentration of defects (vacancy and voids) which are minimized with the increase in the annealing temperature. The correlation between PL emission and lattice defects is also reported in detail.

Gas‐Sensing Properties of Needle‐Shaped Ni‐Doped SnO2 Nanocrystals Prepared by a Simple Sol–Gel Chemical Precipitation Method

The preparation of needle-shaped SnO(2) nanocrystals doped with different concentration of nickel by a simple sol-gel chemical precipitation method is demonstrated. By varying the Ni-dopant concentration from 0 to 5 wt%, the phase purity and morphology of the SnO(2) nanocrystals are significantly changed. Powder XRD results reveal that the SnO(2) doped with a nickel concentration of up to 1 wt% shows a single crystalline tetragonal rutile phase, whereas a slight change in the crystallite structure is observed for samples with nickel above 1wt%. High resolution scanning electron microscopy (HRSEM) results reveal the change in morphology of the materials from spherical, for SnO(2), to very fine needle-like nanocrystals, for Ni-doped SnO(2), annealed at different temperatures. The gas sensing properties of the SnO(2) nanocrystals are significantly enhanced after the nickel doping.

High-efficiency new visible light-driven Ag2MoO4–Ag3PO4 composite photocatalyst towards degradation of industrial dyes

High-efficiency new visible light-driven Ag2MoO4–Ag3PO4 composite photocatalysts with different weight ratios were successfully synthesized by a facile solution-based in situ preparation method and characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence spectroscopy (PL), and zeta potential measurement. Under visible light irradiation, the 10 wt% Ag2MoO4–Ag3PO4 composite photocatalyst exhibits enhanced photocatalytic degradation efficiency compared to other composites of Ag2MoO4–Ag3PO4, pure Ag3PO4 and pure Ag2MoO4 for the degradation of methylene blue (cationic dye). 10 wt% Ag2MoO4–Ag3PO4 composite photocatalyst is further used to investigate the photocatalytic degradation of rhodamine B (cationic dye) and methyl orange (anionic dye). The higher photocatalytic degradation efficiency of 10 wt% Ag2MoO4–Ag3PO4 towards cationic dye is closely related to its surface potential, and the observed degradation efficiency of MB is 2.7 and 16.87 times higher than that of RhB and MO, respectively. Based on the bandgap alignment, the photocatalytic degradation mechanism of Ag2MoO4–Ag3PO4 composite photocatalysts was examined. In addition, the quenching effect of different scavenger tests shows that holes and O2−˙ are the most reactive species which play a major role in photocatalytic degradation of MB. The UV-vis DRS and photoluminescence study also support the higher photocatalytic degradation. TOC analysis was done to confirm the mineralization of dyes. The Ag2MoO4–Ag3PO4 composite photocatalyst is highly stable and 89% MB photocatalytic degradation was achieved after 4 recycle measurements under visible light irradiation. In addition, no phase changes of Ag2MoO4–Ag3PO4 composite photocatalyst and degraded product were confirmed.

X-Ray Peak Profile Analysis of Nanostructured Hydroxyapatite and Fluorapatite

389  Abstract—In present study, X-ray peak profile analysis (XPPA) by modified Williamson-Hall (W-H) models, namely W-H-isotropic strain model (W-H-ISM), W-H-anisotropic strain model (W-H-ASM) and W-H-energy density model (W-H-EDM), was employed to estimate the microstructural parameters such as, crystallite size, lattice strain, lattice deformation stress and deformation energy density from the powder diffraction data obtained for the microwave synthesized hydroxyapatite (HA) and fluorapatite (FA) nanoparticles prepared under identical processing conditions of mixing and aging. The as-prepared powder particles were also characterized by transmission electron microscopy (TEM) method. The average crystallite size values estimated for HA and FA by XPPA were correlated to their respective transmission electron microscopy (TEM) analysis results. In addition, the estimated values of HA and FA were correlated to their in-vitro dissolution characteristics studied by ethylenediamine tetra-acetic acid (EDTA) titrimetric method. It is found that the average crystallite size estimated by W-H models is in good agreement with TEM results. The controlled in-vitro dissolution behavior of FA was found to be resulted out of its higher crystallite size, lower lattice strain and lower dislocation density compared to that of HA.

Fabrication of RuO 2 -Ag 3 PO 4 heterostructure nanocomposites: Investigations of band alignment on the enhanced visible light photocatalytic activity

The RuO2-Ag3PO4 heterostructured nanocomposite was successfully synthesized by facile in situ deposition of porous ruthenium oxide (RuO2) nanoparticles on the surface of the silver phosphate (Ag3PO4). Under visible light irradiation, the 0.5wt.% RuO2-Ag3PO4 heterostructure photocatalyst exhibits enhanced photocatalytic efficiency compared to other composites of RuO2-Ag3PO4 and Ag3PO4. The optimized 0.5wt.% RuO2-Ag3PO4 nanocomposites exhibited 1.5 times enhanced photocatalytic activity towards the degradation of methylene blue (MB) than Ag3PO4. Moreover, the degradation rate of 0.5wt.% RuO2-Ag3PO4 nanocomposite towards the cationic dyes MB and rhodamine B (RhB) was nearly 6.6 times and 4.7 times higher than that towards the anionic dye methyl orange (MO). The formed heterojunction electric field of 310mV at the interface between RuO2 and Ag3PO4 heterostructure induces downward band bending of Ag3PO4. Also, this electric field increases the separation efficiency of electrons-holes resulting higher degradation efficiency. The quenching effect of scavengers test confirms that holes are reactive species and the RuO2-Ag3PO4 nanocomposite is highly stable, exhibited 88% of MB degradation after 4 recycles. The RuO2-Ag3PO4 nanocomposites inhibit self oxidation of Ag3PO4 resulting improved efficiency and stability.

Effect of Electrolyte Chemistry on the Structural, Morphological and Corrosion Characteristics of Titania Films Developed on Ti-6Al-4V Implant Material by Plasma Electrolytic Oxidation

The present work is aimed at the optimisation of an electrolyte system for the development of an oxide layer on Ti-6Al-4V implant material by plasma electrolytic oxidation (PEO) process, to improve its corrosion resistance under 4.5 pH osteoclast bioresorption and 7.4 pH simulated body fluid physiological conditions. All the PEO experiments were conducted for 12 min in constant current mode by a DC power supply unit with 7 different electrolyte systems consisting of methodically varied concentrations of tri-sodium ortho phosphate (Na3PO4.12H2O), sodium meta silicate (Na2SiO3.9H2O) and potassium hydroxide (KOH). The phase composition of the fabricated oxide coatings was analyzed by X-ray diffraction (XRD) technique. The morphology and thickness of the coatings were determined by scanning electron microscopy (SEM) and the corrosion characteristics were assessed by potentiodynamic polarization and electrochemical impedance spectroscopic techniques. The XRD results demonstrated that the oxide coatings mainly consisted of anatase and rutile phases with different proportions. While the average surface pore size was in the range of 3 to 6 µm, the thickness of the coating varied from 5 to 20 µm. A significant improvement in the corrosion resistance and an added capacitive nature was observed for the PEO treated Ti-6Al-4V implant material compared to that of the untreated. The variation in the proportions of anatase and rutile phases, the surface pore size distribution, the thickness of the coating and the corrosion characteristics of the developed coatings were correlated with the composition and concentration of the electrolyte system. Of the seven different electrolyte systems employed in the present study, the one consisting of 10 g Na3PO4.12H2O, 2 g Na2SiO3.9H2O and 2 g of KOH was established to be an optimized electrolyte system for developing oxide coatings on Ti-6Al-4V to minimise corrosion and thereby reduce the metal ion release under physiological conditions.

Facile fabrication of polycaprolactone/h-MoO3 nanocomposites and their structural, optical and electrical properties

Hexagonal molybdenum oxide (h-MoO3) nanocrystals with a flower-like hierarchical structure were successfully incorporated into polycaprolactone (PCL) matrix by a simple solution casting technique. Initially, the PCL was prepared by a catalytic ring-opening polymerization (ROP) of e-caprolactone (e-CL) under solvent free condition. Thiosemicarbazide and 4-phenylthiosemicarbazide based metal (Zn2+ and Cu2+) complexes were prepared and employed as catalysts for the ROP of e-CL. The catalytic reaction conditions were optimized in detail. The resultant PCL was used to fabricate the PCL/h-MoO3 nanocomposites. The h-MoO3 with three different weight percentages (1, 3 and 5 wt%) was chosen. The structural, functional and morphological properties of nanocomposites were investigated by various spectroscopic and microscopic techniques. The merit of the PCL/h-MoO3 nanocomposites was realized from the improved AC conductivity, dielectric and optical properties compared to the pure PCL.

Optical Study on Gadolinium Oxide Nanoparticles Synthesized by Hydrothermal Method

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.

Influence of Iron Dopant on Structure, Surface Morphology and Optical Properties of ZnO Nanoparticles

Pure and two different concentration of Iron (Fe) doped Zinc Oxide (ZnO) nanoparticles (Zn(1-x)FexO) with x = 0.03 and 0.05 were synthesized by chemical co-precipitation method. The structural characterizations of the samples were done by X-ray powder Diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD data indicate that the replacement of Zn2+ ion by Fe3+ ion does not influence the wurtzite structure of ZnO samples. With increase in annealing temperature the intensity of the Zn(1-x)FexO (0 0 2) diffraction peak increases, indicating that the crystallinity quality of the particle improves. Using Scherrer equation the average particle sizes of Zn(1-x)FexO are calculated. The strain-induced broadening at Full Width Half Maximum (FWHM) of the XRD profile of Zn(1-x)FexO were estimated from Williamson Hall (W-H) plot. The results of SEM apparently show that the sample comprises of highly agglomerated particles with no definite shape. Optical absorption Ultraviolet-visible (UV-vis) and Photo Luminescence (PL) properties have been characterized and the effect of Fe addition on optical properties of ZnO has been discussed.

Effect of Micro Arc Oxidation Treatment Time on In-Vitro Corrosion Characteristics of Titania Films on Cp Ti.

 Abstract—The present work is aimed at the optimisation of treatment time for the development of an oxide film on commercially pure titanium (Cp Ti) implant material by micro arc oxidation (MAO) process, to improve its corrosion resistance under 7.4 pH simulated body fluid physiological conditions. The MAO treatments were conducted for 4, 8 and 12 min in constant current mode by a DC power supply unit with an aqueous electrolyte solution comprising 15 g/l of tri-sodium ortho phosphate (Na3PO4.12H2O). The phase composition of the fabricated films was analyzed by X-ray diffraction (XRD) technique. The morphology and thickness of the films were determined by scanning electron microscopy (SEM) and the corrosion characteristics were assessed by potentiodynamic polarization technique. The XRD results demonstrated that the oxide films mainly consisted of anatase phase. While the average size of isolated surface pores was in the range of 0.5 to 5 µm, the thickness of the film varied from 24 to 55 µm. A significant improvement in the corrosion resistance was observed for the MAO treated Cp Ti implant material compared to that of the untreated. The surface pore features, the thickness of the film and the corrosion characteristics of the developed films were correlated with the MAO treatment time. Of the three different MAO treatment times employed in the present study, 8 min treatment time was established to be an optimized one for developing oxide films on Cp Ti to provide an optimal surface porosity and to minimise corrosion rate under physiological conditions.