In a typical experiment, 0.2 g of ZnO QDs was added in aqueous solution of MO (10 ppm) under constant stirring. Prior to irradiation, the mixture was stirred in the dark for 1 h, to ensure the development of adsorption– desorption equilibrium between MO and ZnO QDs photocatalyst.The aqueous dye solution was then exposed under UV light with constant stirring.