Regulation of metal ion selectivity of fluorescent gold nanoclusters by metallophilic interactions

Although numerous sensors have been successfully fabricated for the detection of various heavy metal ions by employing fluorescent gold nanoclusters (AuNCs) as nanoprobes, serious cross-interference often occurs when these ions coexist in samples, which results in glaring errors in quantification. In this study, glutathione-protected AuNCs (GSH-AuNCs) were synthesized and found to respond to both Cu 2+ and Hg 2+ via fluorescence suppression. Intriguingly, addition of Ag + to GSH-AuNCs could completely inhibit the quenching effect of Hg 2+ while not affecting the Cu 2+ -mediated quenching process. Ag + can combine with Au + on the surface of AuNCs to form a strong Ag + -Au + metallic bond , which disrupts the interaction between Hg 2+ and Au + and thus eliminates the corresponding quenching effect. Based on this phenomenon, a simple sensing approach for highly selective and sensitive detection of Cu 2+ in aqueous solution was developed using the GSH-AuNC/Ag + complex as a fluorescent turn-off nanoprobe. The proposed method exhibited good linearity in the concentration range 0.02–10 μM with a limit of detection of 12 nM. This assay was demonstrated to be suitable for determination of Cu 2+ in real water samples even in the presence of Hg 2+ , showing great promise as a tool for assessment of environmental security and drinking water quality.