Polyvinylpyrrolidone-Capped CuInS2 Colloidal Quantum Dots: Synthesis, Optical and Structural Assessment

Ternary metal chalcogenide quantum dots (QDs), such as CuInS2, have attracted significant attention due to their lower toxicity compared to binary counterparts containing cadmium or lead, making them promising candidates for biomedical imaging and solar energy applications. The surfactant choice is critical for controlling nanocrystal nucleation, growth kinetics, and functionalization. This directly affects the toxicity and applications of QDs. In this work, we report a synthesis protocol for PVP-capped CuInS2 QDs in an aqueous solution. Using density functional theory (DFT) calculations, we predicted the coordination patterns of PVP on the CuInS2 QDs surface, providing insights into the stabilization mechanism. The synthesized QDs were characterized using TEM, XRD, XPS, and FTIR to assess their morphology, chemical composition, and surface chemistry. The QDs exhibited dual photoluminescence (PL) maxima at 550 nm and 680 nm, attributed to defect-related emissions, making them suitable for cell imaging applications. Cytotoxicity studies and cell imaging experiments demonstrate the excellent biocompatibility and effective staining capabilities of the PVP-capped CuInS2 QDs, highlighting their potential as fluorescent probes for long-term, multicolor cell imaging including two-photon microscopy.