Gd2O3:RE³âº and GdAlO3:RE³âº (RE = Eu, Dy) Phosphor: Synthesis, Characterization and Bioimaging Application.

Citrate based sol­gel method is used to synthesize Gd2O3:RE³âº and GdAlO3:RE³âº (RE = Eu, Dy) phosphors. In the present work, the phosphors are characterized using the techniques like X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). Fluorescence confocal microscopy reveals the potential usage of phosphors in biological medium for biolabeling application. XRD patterns confirm the phase purity of Gd2O3 and GdAlO3. The crystallite size and lattice parameters are estimated from XRD result. FTIR spectra are used to investigate the functional group present in the phosphor. The optical emission properties imply that the emission peak positions on Eu³âº or Dy³âº ion are size and host independent. Finally, RAW 264.7 macrophages cell line is used to test the bioimaging performance of the phosphors.

Preparation of h-MoO3 and α-MoO3 nanocrystals: comparative study on photocatalytic degradation of methylene blue under visible light irradiation.

A detailed study on visible light photocatalytic degradation of methylene blue (MB) has been investigated in aqueous heterogeneous media containing hexagonal phase molybdenum oxide (h-MoO3) nanocrystals (NCs) which was identified as a new material for visible light driven photocatalysis. A simple and template-free solution based chemical precipitation method was employed to synthesize h-MoO3 NCs by reacting ammonium heptamolybdate tetrahydrate (AHM) with nitric acid. The formation and growth mechanism of h-MoO3 microstructures was explained. In addition, by annealing the h-MoO3 sample, the phase stability of hexagonal was retained up to 410 °C and showed an irreversible phase transition from hexagonal (h-MoO3) to highly stable orthorhombic phase (α-MoO3). Finally, the photocatalytic activities of h-MoO3 and α-MoO3 samples were evaluated using the degradation of MB, representing an organic pollutant of dye wastewater. The effects of various experimental parameters such as catalyst loading, initial dye concentration, light intensity, and operating temperature were analyzed for the degradation of MB. The results demonstrated that the efficiency of visible light assisted MB degradation using h-MoO3 NCs can be effectively enhanced by catalyst loading, light intensity, and operating temperature. However, the efficiency declined with the increase in initial dye concentration. Optimum conditions for higher photocatalytic performance were recognized as a catalyst loading of 100 mg L(-1), a dye concentration of 12 mg L(-1), a light intensity of 350 mW cm(-2), and an operating temperature of 45 °C.

Dopant induced bandgap narrowing in Y-doped zinc oxide nanostructures.

In this report, hydrothermal synthesis and the absorption properties of the cubic shaped zinc oxide nanostructures doped with different amount of yttrium (Y) metal cation (0 to 15 at.%) are demonstrated. The structural and optical properties of chemically synthesized pure and Y doped ZnO powders are investigated by using powder X-ray diffraction (XRD), field emission scanning electron spectroscopy (FESEM) and transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorbance, photoluminescence (PL), and Fourier transform infra-red spectroscopy (FT-IR). It is found that the dopant ions stabilize in wurtzite hexagonal phase of ZnO upto the concentration of less than 6 at.%, which is mainly due to the fact that the ZnO lattice expands and the optical bandgap energy decreases at this level. Increasing the dopant concentration to greater than 6 at.% leads to a contraction of the lattice, which in turn produces a significant structural disorder evidenced by shift in the XRD peaks due to additional interstitial incorporation of Y. The vibrational modes of the metal oxide groups have been identified from the IR transmission spectra. The optical absorption results show that the optical bandgap energy of Y:ZnO nanocrystals is much less as compared to that of the pure bulk ZnO particles. Doping ZnO with trivalent Y produces excess number of electrons in the conduction band and thus, shifts the absorption edge and narrows down to 80 meV approximately. PL spectra are used to study the dependence of doping on the deep-level emission, which show an enhanced blue emission after Y doping. The existence of near band edge (NBE) emission and blue emission, related to zinc interstitials are observed in the luminescence spectra of Zn(1-x)Y(x)O nanostructures.

Band Gap Tuning of h-MoO3 Nanocrystals for Efficient Visible Light Photocatalytic Activity Against Methylene Blue Dye.

The photocatalytic degradation of methylene blue (MB) dye in aqueous solution was investigated using hexagonal molybdenum oxide (h-MoO3) nanocrystals under visible light irradiation. Chemical precipitation method was utilized to synthesize h-MoO3 and control over the crystal size, shape and distribution were characterized by using HNO3 and HCl as precipitating reagents. The photocatalysts were examined through X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDX) for structural, functional, surface morphology and elemental analysis, respectively. The XRD results revealed that the samples were in single phase hexagonal crystal structure. XRD peak broadening analysis was used for crystallite size and strain estimation. The particles were anisotropic in nature and showed one dimensional (1-D) rod structure with hexagonal cross section. Further, the crystal phase stability, optical absorption and emission properties were studied by thermo gravimetric analysis (TGA), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) measurements, respectively. The photocatalytic results demonstrated that the photocatalytic activity of h-MoO3 synthesized using HCl was improved, in comparison to that of HNO3 utilized h-MoO3 sample.

Nonlinear I-V characteristics of nanocrystalline SnO2.

Current versus voltage characteristics (I-V) of nanocrystalline SnO2 materials have been investigated in air at room temperature. The samples were prepared by the inert gas condensation technique (IGCT) as well as by chemical methods. X-ray diffraction studies showed a tetragonal rutile structure for all the samples. Microstructural studies were performed with transmission electron microscopy. All the samples exhibited nonlinear I-V characteristics of the current-controlled negative resistance (CCNR) type. The results show that the threshold field (break down) voltage is higher for the samples prepared by the IGCT method than for those prepared by the chemical method due to the formation of a tin oxide layer over the crystalline tin. It is also found that the threshold field increases with the decrease in grain size.