Encapsulation of AgInS2/GaSx core/shell quantum dots in In-fumarate metal–organic frameworks for stability enhancement

Abstract

Silver indium sulfide/gallium sulfide (AgInS₂/GaS_x) core/shell quantum dots (QDs), among the cadmium-free alternatives that possess a narrow band-edge emission, have attracted immense attention in recent years. However, the insufficient stability of photoluminescence (PL) due to chemically sensitive GaS_x shells, which is partly caused by easy desorption of passivated ligands, remained a problem for their practical application. In this study, a simple and efficient method to protect these QDs is presented. The AgInS₂/GaS_x core/shell QDs are encapsulated into metal–organic frameworks (MOFs) consisting of an indium-fumarate ordered structure (InMOFs). Whereas damage to the shell during the encapsulation reaction can potentially occur, the obtained composite (AgInS₂/GaS_x@InMOFs) maintains a narrow band-edge emission that is mostly identical to the pristine AgInS₂/GaS_x core/shell QDs with a PL quantum yield (PL QY) of 12.6% after optimization of the synthesis-solution pH. The encapsulation result enables the spectral shape and PL QY of the composite to be maintained after 7 days, which demonstrates the high stability of the QDs encapsulated in InMOFs.