Confined Growth of Quantum Dots in Silica Spheres by Ion Exchange of Trapped NH4+ for White-Light Emission

Great interest has recently emerged in the development of quantum dots (QDs) that are capable of direct white-light emission for solid-state lighting. The conventional synthesis routes often involve surface modification and ligand displacement, which usually lead to undesired QD aggregation and fluorescence quenching. Here, we report a new strategy to synthesize QDs (ZnS, CdS, CdTe, and CsPbBrxI3-x) directly in colloidal SiO2 to produce QD@SiO2 composites, displaying direct white-light emissions. By taking advantage of the NH4+ trapped inside the silica colloids, we introduce metal cations through ion-exchange reactions into the microporous network of silica and then produce QDs directly within the silica colloids. This trapped-NH4+ strategy represents a new platform for the synthesis of novel functional nanocomposites by allowing convenient incorporation of various nanoparticles into sol-gel-derived colloidal matrices.