Ultrasensitive Hg²⁺ Detection Using High Quantum Yield DNA-Templated Silver Nanoclusters for Environmental Monitoring

Mercury ions (Hg²⁺) pose severe environmental and health risks due to their persistence, bioaccumulation, and neurotoxicity. Here, we report a fluorescent probe for ultrasensitive Hg²⁺ detection, constructed from cytosine-rich hairpin DNA-templated silver nanoclusters (hpDNA/Ag NCs). Through multiparameter optimization (DNA/Ag⁺ stoichiometry, reduction kinetics, surface passivation, and the DNA template design), the hpDNA/Ag NCs achieve a high quantum yield of 72.55% and exceptional stability, retaining fluorescence even after 3 months. The probe exhibits a linear response to Hg²⁺ (0.1-50 nM) with a 0.03 nM detection limit, which is enabled by selective fluorescence quenching via thymine-Hg²⁺-thymine coordination and Ag/Hg amalgam formation. Rigorous interference tests confirm specificity against 15 competing ions, including Ag⁺ and Pb²⁺. Successful application in spiked environmental water samples demonstrates recovery rates of 96%-106%, validating its practicality for real-world monitoring. This work establishes a cost-effective, sensitive, and field-deployable platform for Hg²⁺ detection, addressing critical gaps in environmental pollution control.