Photoluminescence of nanocrystalline ZnS thin film grown by sol-gel method.

Nano and polycrystalline ZnS thin films play a crucial role in photovoltaic technology and optoelectronic devices. In this work, we report the photoluminescence (PL) characterization of nanocrystalline ZnS thin films synthesized by dip coating method. The PL spectra exhibit broad nature with multiple emission peaks which are due to the different defect levels in the prepared film.

Impact of activator incorporation on red emitting rods of ZnGa2O4:Cr3+ phosphor.

Chromium doped zinc gallium oxide (ZnGa2O4:Cr3+) microrods were synthesized by simple solid state reaction method. The transformation on crystal structure and optical properties with molar concentration of Cr3+ were analyzed. The cubic spinel nature of ZnGa2O4:Cr3+phosphor and their crystalline nature were confirmed from x- ray diffractogram. The average grain size of the samples range between 24 and 29 nm, with lattice parameter values greater than that of bulk. Lattice strain produced in the lattice on doping was estimated from the Williamson-Hall plot. It increases on Cr3+ doping up to 3 mol% and then decreases. Rod like nature of zinc gallate was observed from the surface morphological analysis using SEM. X-ray photoelectron spectroscopy was used for the chemical state identification of the constituent elements in the compound. The photoluminescense spectra consists of various emission lines originated from the chromium ion in the spinel lattice. The purity of red emissions were observed from chromaticity diagram with a concentration quenching initiated from the dipole-dipole interaction, with increase in dopant concentration. Band gap of the samples were estimated using Kubelka-Munk equation which exhibited red shift compared to bulk due to band tailing effect.

Wet chemical synthesis of chitosan capped ZnO:Na nanoparticles for luminescence applications.

The structural and optical properties of nanomaterials exhibit severe changes when capped with organic polymers. In this work we focus on the effect of chitosan capping on ZnO:Na nanoparticles synthesized by wet chemical method. The main characteristics analyzed are x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and photoluminescence (PL). Hexagonal crystal formation of nanoparticles was confirmed from the XRD and the lattice strain was estimated from the Williamson Hall (WH) plot. Various bonds present in the synthesized sample were analyzed using FTIR. Capping results in the reduction in grain size thereby enhancement in the PL intensity. The yellow emission is in well agreement with the Commission International d'Eclairage (CIE) diagram.