Karthikeyan Balasubramanian

Optical, phonon and efficient visible and infrared photocatalytic activity of Cu doped ZnS micro crystals.

We report, the enhanced photocatalytic behaviour of Cu doped ZnS micro crystals. ZnS and different concentrations of Cu doped ZnS microcrystals were prepared. X-ray diffraction confirms the crystalline and phase of the particles. Morphology and sizes were studied using Scanning Electron Microscopy (SEM). Recorded optical absorption spectra show a band for around 365nm for pure ZnS, but there is a broad band in the near infrared regime for the Cu-doped ZnS microcrystals which are attributed to the d-d transitions of Cu2+ ions. Phonon properties of as-prepared samples were investigated using Raman spectroscopy. Present work we investigate the potential of ZnS and Cu doped ZnS as a photocatalyst. For this from the degradation of methylene blue dye in aqueous media the photocatalytic activity of pure and highest doped ZnS samples with the irradiation of white light and infrared, enhanced photocatalytic activity were observed. Mechanism of white light an IR light based photocatalytic activity is explained based on the electron-hole pair production.

Dopant induced local vibrational modes and Fano scattering in Ag doped ZnO microrods

We discussed the influence of Ag doping on the crystallite size of ZnO and enhanced Raman spectroscopy properties. We reported optical and vibrational properties of Ag-doped ZnO microrods which have been prepared through reflux method. Dopant induced shift and asymmetric broadening of Raman modes have been discussed. In Raman spectra, silver doping induces a lower wavenumber shift in E2H mode. Moreover, the appearance of some additional peaks after Ag-doping were successfully studied and the doping is confirmed by the local vibration modes obtained at 230 and 390cm-1. Effect of doping is studied by calculating the crystallite size and we discussed the variations in full width half maximum (FWHM), phonon lifetime with respect to varying crystallite size. Phonon lifetime decreases with increasing Ag concentration. The asymmetric broadening in Raman modes E2H and E2L with the addition of Ag are analysed with Fano fitting.

Effect of morphology on optical and efficiently enhanced electrical properties of W-ZnS for UV sensor applications

The influence of the morphology on the electron transport properties of ZnS nanostructures has been assessed by the electrical measurements on different ZnS nanostructures. High-quality poly(vinylpyrrolidone) capped wurtzite-ZnS micro- and nanostructures have been prepared by one step hydrothermal methods at low temperatures. Detailed structural investigation based on X-ray diffraction results and morphological analyses have been carried out using field emission scanning electron microscopy, transmission electron microscopy, selected area diffraction pattern, and high-resolution transmission electron microscopy techniques. In order to examine the formation of compound ZnS, the atomic ratio of Zn to S has been found from Energy Dispersion Spectroscopy. The bandgap of the samples has been calculated from the UV-visible absorption spectra in the reflectance mode at room temperature. The dependence of size and shape on excitonic and trap-state emission features of the nanostructures has been studied from the photoluminescence (PL) studies, and the enhancement of PL intensity in 1D nanostructures has also been discussed. High yield and highly crystalline long nanorods and nanowires have been found to be best suited for advanced optoelectronic systems because they have better photoconductivity than microparticles and nanoparticles.The influence of the morphology on the electron transport properties of ZnS nanostructures has been assessed by the electrical measurements on different ZnS nanostructures. High-quality poly(vinylpyrrolidone) capped wurtzite-ZnS micro- and nanostructures have been prepared by one step hydrothermal methods at low temperatures. Detailed structural investigation based on X-ray diffraction results and morphological analyses have been carried out using field emission scanning electron microscopy, transmission electron microscopy, selected area diffraction pattern, and high-resolution transmission electron microscopy techniques. In order to examine the formation of compound ZnS, the atomic ratio of Zn to S has been found from Energy Dispersion Spectroscopy. The bandgap of the samples has been calculated from the UV-visible absorption spectra in the reflectance mode at room temperature. The dependence of size and shape on excitonic and trap-state emission features of the nanostructures has been studied from the ...