Cyclodextrin-assisted L-cysteine–capped copper nanoclusters for dual detection of Hg2+ and Ag+

• We designed a single-fluorophore sensing platform for dual heavy metal detection. • γ-CD–Cys–Cu NCs can selectively detect both Ag + and Hg 2+ with high sensitivity. • Both static and dynamic pathways govern concentration-dependent sensing behaviour. • Practical applicability validated by accurate heavy-metal quantification in real samples. The sensitive and selective detection of toxic heavy metal ions in aqueous matrices remains an important analytical challenge. Here, a rapid and environmentally benign photoluminescence (PL) sensing platform was reported for the dual detection of Hg²⁺ and Ag⁺ ions using γ-cyclodextrin-assisted L-cysteine-capped copper nanoclusters (γ-CD–Cys–Cu NCs). Introduction of γ-cyclodextrin into pre-synthesized Cys-Cu NCs instantaneously induced controlled aggregation, resulting in pronounced emission enhancement with intense blue-green PL (λ em = 500 nm) upon excitation at 370 nm. Exploiting the strong coordination affinity of exposed thiol groups toward soft heavy metal ions, the aggregation-enhanced γ-CD–Cys–Cu NCs were employed as a single-fluorophore probe for the selective sensing of Hg 2+ and Ag + ions. Both analytes induced efficient PL quenching (∼90% at 250 μM), with limits of detection as low as 25 nM, well below the permissible limits for drinking water. Intensity-based and time-resolved PL studies revealed a combined static and dynamic quenching mechanism, consistent with metal–thiolate complex formation and concentration-dependent collisional processes. Dynamic light scattering (DLS) and high-resolution transmission electron microscopy (HRTEM) analyses further indicated that the metal-ion-triggered disassembly of the aggregated nanoclusters correlated with structural reorganization and PL quenching. Notably, Ag + additionally induced a distinct colorimetric response enabling complementary visual identification. The sensing platform enabled accurate quantification of Ag + and Hg 2+ in real water samples, demonstrating reliable analytical performance in real matrices. Overall, this work establishes γ-CD–Cys–Cu NCs as an efficient, selective, and practical single-fluorophore platform for dual heavy-metal detection in complex aqueous environments.