Direct synthesis of eco-friendly carboxymethyl chitosan functionalized AgInS2/ZnS quantum dots: Utilization in ink and flexible film, warm-white LED, NIR-LED and counterfeit prevention

In this study, we present a novel synthesis system for AgInS 2 /ZnS (AIS/ZnS) core/shell quantum dots (QDs) terminated with carboxymethyl chitosan (CMC) as a ligand, which has not been previously documented. By varying the Ag/In ratio, we achieved emission wavelengths ranging from 590 to 697 nm, with the maximum photoluminescence quantum yield (PLQY) of 33.1 %. The synthesized AIS/ZnS QDs powder was mixed with YAG phosphor and combined with a blue gallium nitride (GaN) chip to produce a warm white light-emitting diode (WLED), resulting in the color rendering index (CRI) increase from 74 to 82 and the correlated color temperature (CCT) decrease from 6486 K to 3873 K. Additionally, the AIS/ZnS QDs powder can be directly utilized with a blue GaN chip to create a near-infrared light-emitting diode (NIR-LED) capable of night vision. By adjusting the concentration of CMC in the AIS/ZnS QDs solution, the material can be directly used for writing and screen printing, or dried to obtain a highly transparent and luminescent flexible composite film. This research demonstrates the significant potential of CMC-ligated AIS/ZnS core/shell QDs in display technologies and flexible device applications.