Microwave-assisted hydrothermal synthesis of water-soluble AgInS2 quantum dots with enhanced photoluminescence

Abstract We systematically investigated the hydrothermal synthesis of water-soluble AgInS2 (AIS) quantum dots (QDs) using N-acetyl-L-cysteine ligands, focusing on the effects of precursor composition, pH, ligand concentration, and reaction temperature on photoluminescence (PL) properties. Optimization of the precursor solution enabled the synthesis of AIS QDs with a PL quantum yield (QY) of 32% in aqueous solution. Furthermore, ZnS treatment significantly enhanced the PLQY to 68%. Structural analyses using X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy confirmed the formation of chalcopyrite-type AIS QDs and suggested the presence of Zn-containing surface species consistent with ZnS shell formation. PL decay measurements suggested that the broad PL of AIS QDs is consistent with donor–acceptor-pair-related emission, and optimization of precursor composition was suggested to suppress nonradiative recombination. These results provide important insights for the direct synthesis and PL enhancement of water-soluble cadmium-free QDs.