R. Viswanath

Synthesis, enhanced optical and photocatalytic study of Cd–Zn ferrites under sunlight

Nanocrystalline CdxZn1−xFe2O4 (where x = 0.0, 0.3, 0.7, 1.0) were prepared successfully by a soft chemical synthesis method and were characterized by XRD, SEM, XEDS, FTIR and UV–vis techniques. X-Ray diffraction studies revealed the formation of single phase spinel structure of the samples. Light absorption properties of the Cd–Zn ferrite nanocrystals were studied by a UV–Vis spectrophotometer. It was found that the energy band gap of cadmium ferrite is 1.46 eV, which is smaller than that of prepared zinc ferrite (1.95 eV). Thus cadmium substitution into zinc ferrite results in substantial shifting of the absorption edge of zinc ferrite to red and enhancement of visible light absorption. The photocatalytic results for degradation of methyl orange (MO) indicated that the cadmium substitution dramatically enhances the catalytic activity of zinc ferrite. This means that cadmium substituted zinc ferrite shows the highest photocatalytic activity under solar light irradiation. Thus cadmium substituted zinc ferrite utilizes the possibility of solar energy in the solar spectrum.

Synthesis, Optical and Electrical Properties of ZnFe2O4 Nanocomposites

ZnFe2O4 nanocomposites have been prepared by a simple co-precipitation method. The prepared samples were characterized by Scanning Electron Microscopy (SEM), Powder X-ray Diffraction (XRD), Energy ...

Luminescence properties of blue–red emitting multilayer coated single structure ZnS/MnS/ZnS nanocomposites

Uncoated ZnS, MnS and ZnS/MnS/ZnS nanocomposites were successfully synthesized by chemical co-precipitation method in air atmosphere by varying the thicknesses of MnS layer. Characterization techniques such as X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), UV-visible absorption and photoluminescence (PL) spectroscopy were used to characterize the novel ZnS/MnS/ZnS nanocomposites. The obtained particles were highly crystalline and monodispersed with an average particles size of 4.5-6.5 nm. The room temperature photoluminescence (PL) study of ZnS/MnS/ZnS nanocomposites showed an enhanced intensity with different concentration of manganese acetate. The presences of MnS layer in the nanocomposite have tuned the PL emission in the IR region. Addition of manganese acetate (0.1-0.4 M) in the nanocomposite showed a distinct PL emission peak centered at 740 nm i.e. in the red region with significant red shift. The PL emission of ZnS and MnS were tuned in the nonvisible IR region. It is shown that the variation in thickness of MnS layer leads to an enhanced photoluminescence intensity/efficiency of ZnS/MnS/ZnS nanocomposites.

Tuneable luminescence properties of EDTA‐assisted ZnS:Mn nanocrystals from a yellow‐orange to a red emission band

Luminescence technology has been improved with the help of semiconductor nanoparticles that possess novel optical and electrical properties compared with their bulk counterpart. The aim of this study was to design semiconductor nanocrystals in their pure (ZnS) or doped form (ZnS:Mn) with different concentrations of Mn2+ ions by a wet chemical route stabilized by ethylenediamine tetra-acetic acid (EDTA) and to evaluate their luminescence properties. The nanocrystals were characterized by physicochemical techniques such as X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SEAD), EDS, and ultraviolet (UV)-visible light and photoluminescence (PL) studies. These results showed the presence of cubic phase and spherically shaped nanocrystals. A blue shift with respect to their bulk counterpart was observed. PL emission spectra were observed with a fixed blue peak and the yellow-orange bands were red shifted towards the red region under the same excitation wavelength. The orange-red bands were attributed to the radiation transition of electrons in 3d5 unfilled shells of Mn2+ ions [4 T1 (4 G)-6 A1 (6 S)]; the ZnS matrix varied with Mn2+ concentration. Shift and increase in the intensity of the PL and absorption bands were observed with increase in Mn content. The study showed that Mn2+ -doped ZnS nanocrystal emission bands can be tuned from the yellow-orange to the red regions under a controlled synthesis process and could be used as promising luminescent emitters in the biology field upon functionalization with suitable materials. Further studies on construction with various other materials will be useful for practical applications.