Pure and Cu doped ZnS (ZnS:Cu) nanoparticle thin films were synthesized by Successive Ion Layer Absorption and Reaction (SILAR) method. The obtained thin films were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), FESEM and absorption spectra. Photo-catalytic degradation of dye molecules (methylene blue) was investigated by monitoring of the residual concentration of methylene blue (MB) solution using UV–vis absorption spectrometry. Studying of the variation of Cu concentration in ZnS nanoparticle thin films showed that the sample containing of 2 wt% Cu is very efficient for degradation of dye molecules. Hereon, the degradation efficiency of the photo-catalyst thin films after 30 min irradiation time was about 36%. Higher degradation efficiency (56%) was achieved by increasing the exposure time to 360 min.
