Ni doped ZnS nanoparticles as photocatalyst: Can mixed phase be optimized for better performance?

Abstract ZnS nanoparticles with Ni 2+ as dopant ions, have been synthesized and characterized by X-ray Diffraction, Inductive Coupled Plasma-Atomic Emission spectroscopy and Transmission Electron Microscopy. UV–vis absorption and photoluminescence spectroscopies were employed to investigate different photo-processes occurring on exposure to UV–vis light. The synthesized NPs were evaluated as photocatalyst for the removal of the color of aqueous solution of rhodamine B (RhB) dye as test solution under 250 W High Pressure Mercury Vapor lamp. Mott-Schottky, Cyclic Voltammetery, and hot-probe measurements suggest the change in the ‘type’ of semiconductor from n to p as well as phase change (cubic to wurtzite) take place on increasing the amount of dopant to 10%. The newly appeared phase forms ‘local pockets’ in an overall cubic matrix of ZnS NPs, this way created defects at the local grain boundaries of dissimilar phases. These provide active sites for the adsorption of dye molecules, in turn, improve the efficiency of the material as photocatalyst.