using the sonochemical method. X-ray diffraction patterns proved the formation of the ZnS cubic phase without
any phase separation with the doping process. The dependence of the crystallite size and the internal micro-strain on the dopant type was demonstrated. Optical absorption spectra of doped ZnS NPs revealed a decrease in the optical band gap due to the formation of extended defect states below the conduction band. Photoluminescence spectra of the doped samples revealed the enhancement of visible light emission intensity compared with the as-prepared ZnS NPs. The AC electrical properties of the trivalent elements doped ZnS NPs were studied at room temperature in the frequency range from 2 kHz to 1 MHz, where In-doped ZnS NPs had the lowest dielectric constant and largest conductivity compared with the other samples.