Preparation of water-soluble ZnS quantum dots by hydrodynamic cavitation technology and related stability exploration

In this study, ZnS quantum dots (QDs) were prepared on a large-scale by hydrodynamic cavitation (HC) technology using the method of "top to bottom". These ZnS QDs have the advantages of small particle size (1.75 nm), narrow size distribution range (1.0–3.0 nm) and high fluorescence quantum yield (37.45 %), which show wide application potential. However, the stability of QDs solution is crucial in their practical application, so the surface modification is systematically studied for enhancing the ZnS QDs solution stability. The effects of temperature, time, pH value and different surface modifiers (L-cys, TGA, PEG and TPT) on the optical properties of ZnS QDs were investigated. The experimental results show that ZnS QDs are not easy to agglomerate in solution under the conditions of low temperature, weak alkali and dark conditions, and the fluorescence intensity of ZnS QDs solution remains high after six weeks of storage. In addition, the surface modification of ZnS QDs can significantly improve their stability and solubility in aqueous solution. Under 365 nm ultraviolet lamp irradiation for 2.0 h, the fluorescence intensity of ZnS QDs solution still maintained about 80 % of its original value. These experimental results provide an important theoretical basis and practical guidance for the optimization of synthesis conditions and practical application of ZnS QDs.