Hydrothermal Synthesis and Fluorescence Properties of AgInS2/ZnS Core/Shell Quantum Dots

Water-soluble AgInS2/ZnS (AIS/ZnS) core/shell quantum dots (QDs) were synthesized by hydrothermal method using thiourea (TU) as sulfur source, glutathione (GSH) and sodium citrate (SC) as ligands. The effects of reaction temperature and addition amount of ligands on the synthesis and fluorescence properties of AIS/ZnS QDs were systematically studied by XRD, TEM, UV-Vis absorption spectra and PL spectra, respectively, and their stability was also investigated. The results show that the emissive intensity of AIS/ZnS core/shell QDs is significantly improved by increasing the reaction temperature from 70 to 90 degrees C. The increase of temperature promotes the growth of ZnS shell, on which the surface defects is effectively passivated. Meanwhile, the emissive peak showed a blue-shift from 600 nm to 580 nm. Furthermore, the ligands could balance the chemical reactivity of Zn2+, slow the growth rate of ZnS shell, inhibit the interface defects formation and eliminate the surface states. The AIS/ZnS core/shell QDs showed the strongest emission with n(GSH)/n(Zn2+) of 2.0 and n(SC)/n(Zn2+) of 2.5. Importantly, the obtained AIS/ZnS core/shell QDs exhibited excellent optical stability.