Effect of Capping Agent Concentration on Photophysical Properties of Zinc Sulfide Nanocrystals

Abstract

Zinc Sulfide (ZnS) nanoparticles with varying concentration of capping agent were prepared using chemical technique. These particles were characterized using scanning electron microscope (SEM), atomic force microscope (AFM) and x-ray diffraction (XRD). It is observed that particle size decreases with increasing capping agent concentra-tion. Optical absorption studies show that the absorption edge shifts towards blue region as the capping agent concentra-tion is increased indicating that effective band gap energy increases with decreasing the particle size. Using the effective mass approximation model the particle size of nanoparticles has been estimated from the increased band gap, which is practically the same as obtained by XRD. Photoluminescence (PL) investigations show that ZnS samples give single peak with stoke shift. PL emission peak is obtained at 460 nm for uncapped nanoparticles. The PL spectra of ZnS nanoparticles with different capping agent concentration reveals that the emission becomes more intensive and shifts towards blue as the size of the particles is reduced.