Undoped and Copper (Cu) doped zinc oxide (ZnO) (Zn1-xCuxO, x = 0.01, 0.02, 0.03, 0.04 and 0.05) nanoparticles (NPs) capped with (1.0%) Thioglycerol (TG) have been successfully synthesized by co-precipitation method. The synthesized samples have been characterized by X-ray diffraction (XRD), Energy dispersive spectroscopy (EDS), Transmission electron microscopy (TEM), Photoluminescence (PL) and UV-Visible spectroscopy. Incorporation of impurity ions in pure ZnO NPs leads to a shift the spectra for both excitation and emission to visible region as compared to pure ZnO. The photocatalytic activity of undoped and Cu doped ZnO photocatalyst were investigated by the degradation of Crystal Violet (CV) dye in aqueous medium under exposure of UV Visible light irradiations. Firstly, degradation of CV dye has been studied with TG capped, undoped and Cu doped ZnO NPs synthesized at pH-8.0. From the results, it has been found that Cu doping concentration of 3.0% is optimal for higher photophysical and photocatalytic properties. When pH of optimum doped NPs was varied from 8.0 to 10.0, 78.7% to 96.5% of CV dye has been degraded after 3.5 h. Further increasing the pH to 12.0 for optimum doped NPs, 100% dye degrades in 2.5 h. This shows that the doping and pH has a pronounced effect on the photocatalytic activity of ZnO NPs. Loading of catalyst shows maximum photodegradation of CV dye at 3.0 g/L of Cu (3.0%) doped ZnO at pH-12.0 for 10 mg/L of CV dye. Kinetic studies shows that photo degradation of CV follow a pseudo first-order kinetic law. The reason for enhanced degradation with Cu doped NPs in comparison to undoped NPs has been described and discussed in this work. (C) 2014 Elsevier Ltd. All rights reserved.