Aqueous AgInS₂/ZnS Quantum Dot-Based Fluorescent Probes for Highly Selective Detection of Cu(II) Ions

There have been significant challenges in applying quantum dot (QD)-based fluorescent probes for the detection of heavy metals in food samples, primarily due to the aqueous stability of QDs, interference from complex sample matrices, and the need for high sensitivity and selectivity. Notably, I–III–VI semiconductors, such as CuInS 2 and AgInS 2, have emerged as promising alternatives to II–VI QDs because of their exceptional optoelectronic properties and the absence of toxic heavy metal ions. This study develops a fluorescence-based method for the detection of Cu 2+ ions using AgInS 2 /ZnS (AIS/ZnS) QDs. The AIS/ZnS QDs were synthesized through a straightforward, environmentally friendly, and cost-effective one-pot method in an aqueous solution. Under the optimized experimental parameters, the concentration of Cu 2+ exhibits a strong linear correlation with the relative fluorescence quenching of AIS/ZnS QDs within the range of 1.33–133 μM. The detection limit of AIS/ZnS QDs for Cu 2+ ions is 1.3 μM, indicating a high sensitivity for detecting trace amounts of Cu 2+ . This method is suitable for quantifying Cu 2+ ion concentrations in natural water and food samples, with results that correlate well with those from flame atomic absorption. These findings suggest that, as cadmium-free QDs, the AIS/ZnS QDs-based fluorescence sensor has considerable potential for determining Cu 2+ concentration in natural water, food, or biological imaging applications.