Improved Luminescence Properties and Thermal Stability of ZnSQuantum Dots by Organic and Inorganic Passivation

ZnS quantum dots (QDs) synthesized in water and ethanol solutions were coated with polystyrene (PS) and SiO₂ shells, respectively. The band edge emission was enhanced by nearly five times after PS coating and about 13 times after SiO₂ coating, because the surface trap states were removed. From the photoluminescence properties of ZnS QDs coated with PS and SiO₂ shells we have detected the improvement of thermal stability. This is due to the fact that the surface passivation can prevent the further growth of the ZnS QDs and the diffusion of oxygen on the surface of ZnS QDs during thermal oxidation.