Se4+ doped ZnS nanoparticles is synthesized by electrochemical method which is capable of producing flower-like nanoparticles in a size range about 10-30 nm, under ambient conditions. UV-VIS spectra discusses the band gap of Se4+ doped ZnS to be 2.1 eV which is much lower than that of commercial ZnS (3.68 eV). The photocatalytic activity was evaluated on the degradation of indigo carmine dye both under ultraviolet (UV) and sunlight illumination which follows first-order kinetics. It was found that Se doped ZnS photocatalyst showed much higher photodegradation efficiency (6-8 times) than commercial ZnS. A linear correlation is achieved for photo-degradation and inactivation of bacteria as both are ROS dependent phenomena. Hydroxyl radical scavenging ability of these particles was evaluated. The impact of enhanced ROS generation was consistent with higher photocatalytic dye degradation and antibacterial activity of Se4+ doped ZnS nanoparticles. (C) 2014 Elsevier B.V. All rights reserved.