Effect of Cobalt doping on ZnS nanoparticles synthesized by microwave irradiation

Abstract

ZnS nanoparticles were prepared by microwave assisted chemical method using Polyvinylpyrrolidone (PVP) with different Cobalt (Co) concentration. We studied the compositional and structural properties of these samples by energy dispersive analysis of X-rays, X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. Size of the spherically shaped nanoparticles with aggregation is estimated to be in the range from 3 to 7 nm as seen from TEM images. Diffracted planes corresponding to cubic phase are observed in XRD pattern and average crystallite size is calculated through full width at half maximum from these diffracted planes. TO and LO phonon modes allowed in cubic phase for undoped and Co doped ZnS nanoparticles are studied by Raman spectroscopy whereas interaction between PVP with ZnS nanoparticles is studied using Fourier transform infrared spectroscopy (FTIR). Energy bandgap is calculated by UV–Vis absorption spectroscopy using Tauc plot and blue shift is observed with increased Co doping concentration into ZnS nanoparticles. Localized structure of the ZnS nanoparticles are strongly influenced by Co doping concentration as observed by photoluminescence (PL) spectroscopy which revealed the new emission peak at 519 nm. We could also observe quenching effect of PL intensity as a function of Co concentration in ZnS nanoparticles. Magnetic study on the 15% Co doped ZnS nanoparticles do not show ferromagnetic behavior. Antimicrobial effect is not observed against E. coli bacteria for Pure and 15% Co doped ZnS nanoparticles.