Red-Emitting Glutathione-Templated Copper Nanoclusters for Fluorescence Enhancement–Based Detection of Arsenic(III) Contamination in Water

Arsenic contamination in drinking water continues to pose serious risks to public health, particularly because detection of its most toxic trivalent form remains a challenge. In this work, glutathione-templated copper nanoclusters (Cu NCs) were prepared via a chemical reduction approach, yielding red-emissive, water-dispersible, and stable nanoprobes. These Cu NCs show weak photoluminescence at 644 nm when excited at 370 nm, and their fluorescence is notably enhanced in the presence of As3+ due to aggregation-induced emission. The sensing approach allows reliable quantification of As3+ down to 1.27 μM with excellent linearity (R2 = 0.9995), high reproducibility across multiple measurements, and high selectivity against common metal ions, nonmetallic interferents, and complex biological matrices. The method was successfully validated using MCF-7 cell lysates and Drosophila melanogaster gut tissues, where significant fluorescence enhancement (p < 0.01) confirmed As3+ detection. The Cu NCs also enable clear fluorescence imaging of intracellular As3+ in Drosophila melanogaster tissues and MCF-7 human cell lines, demonstrating increased fluorescence both within the tissue and at the cellular level, which confirms their biocompatibility and suitability for biological studies. Structural and surface analyses (TEM, AFM, FTIR, XPS) show that the nanoclusters are consistently templated and well-formed. Overall, this study demonstrates that GSH-templated Cu NCs are scalable and cost-effective as practical probes for both As3+ detection and bioimaging, making routine monitoring of environmental and biological arsenic exposure possible.