Water-soluble near-infrared CuInS2/ZnS fluorescent quantum dots for Cu2+ detection and cellular imaging

•Water-soluble near-infrared QDs enable precise detection of intracellular copper ions with exceptional selectivity and sensitivity.•Low cytotoxicity and high biocompatibility of QDs ensure safe intracellular imaging applications.•Fluorescence bursts in response to changing copper ion content demonstrate QDs' excellent cellular imaging capabilities.•Synthesized QDs demonstrate stable and selective performance for precise quantification of copper content in biological systems.•This research contributes to understanding the physiological role of intracellular copper ions and advances biomedical imaging techniques.