Optical and Dielectric Properties of Poly(Vinyl Pyrrolidone-co-Vinyl Acetate)-Capped ZnS Nanoparticles

ZnS nanoparticles were synthesized by a wet chemical method using copolymer poly(vinyl pyrrolidone-co-vinyl acetate) as capping agent in the presence of microwave irradiation. Zinc acetate was used as the Zn precursor and thioacetamide as the sulfur precursor. X-ray diffraction measurements indicated the structure of nanoparticles to be the cubic form of ZnS. Both uncapped and capped ZnS samples were found to exhibit quantum size effects. Also, band gap energies were estimated, and the capped ZnS showed a decrease in band gap value compared to uncapped ZnS. Photoluminescence measurements of the capped sample indicated the elimination of surface defect-related emissions around 440 nm, observed in the uncapped sample. Further, the frequency response of the dielectric constant was studied in the range 100 Hz–5 MHz at different temperatures. At low frequencies and lower-temperature conditions, dielectric constant values were higher for both samples, and decreased at higher temperatures for the copolymer-capped ZnS.