In this study, the photocatalytic degradation of Strychnine was investigated by ZnS quantum dots and doped with silver in UV systems. ZnS and Ag-ZnS quantum dots were synthesized by chemical method and characterized by powder X-ray diffraction, transmission electron microscopy, UV-vis spectra and photoluminescence. The charge transfer process on the semicon-ductor/electrolyte interface was investigated via electrochemical impedance spectroscopy (EIS) and time-resolved photoluminescence. The average diameters of ZnS and Ag doped ZnS QDs were 3.0-5.0 nm and 3.0-5.3 nm, respectively. The band gap of ZnS and Ag-ZnS QDs was computed as 3.47 and 3.1 eV, respectively. The surface area values of ZnS and Ag-ZnS QDs have been found as 78.25 and 89.54 m(2)/g, respectively. The influences of key operating parameters such as initial pH, catalyst dosage, UV radiation intensity, reaction time as well as the effect of initial Strychnine concentration on mineralization extents were studied. The results of the study showed that the maximum removal efficiency of Strychnine had been achieved by un-doped and Ag-doped ZnS QDs at radiation intensity of 100 W/m(2), at time of 60 min, pH of 3 and initial Strychnine concentration of 20 mg/ml. Also the observations clearly showed that the photocatalysis process with Ag doped ZnS QDs are more effective than un-doped ZnS QDs. (C) 2017 Elsevier Inc. All rights reserved.