A Turn-On Fluorescence Probe Based on GSH-Protected Silver Nanoclusters for the Selective Detection of Pb²

Glutathione-protected silver nanoclusters (GSH-AgNCs) with good photostability were successfully synthesized through a one-pot heating process. The resultant GSH-AgNCs with an average diameter of ~1.6 nm exhibit red fluorescence (λ_em = 650 nm), and the fluorescence is excitation independent. Strong aggregation-induced emission (AIE) effect was observed in GSH-AgNCs, which can be induced by solvent and metal ions. In particular, a specific fluorescence enhancement was detected upon interaction with lead ions (Pb²⁺). A fluorescent probe was designed for off-on detection of Pb²⁺ based on as-synthesized GSH-AgNCs. Under the optimum parameters, two linear response intervals were found between the relative fluorescence intensity and the concentration of Pb²⁺ in the range of 10-250 μM (R² = 0.9900) and 400-1000 μM (R² = 0.9930). Significant fluorescence color evolutions observed under UV light, resulting in a semiquantitative visual detection of Pb²⁺. A possible detection mechanism based on the interaction between GSH-AgNCs and Pb²⁺ is discussed.