Highly selective and sensitive nanoprobes for Hg(II) ions based on photoluminescent gold nanoclusters

We report a facile strategy to synthesize a novel fluorescent gold nanoclusters (NAC-AuNCs) in one step by using only the reactants of HAuCl4 and N-acetyl-l-cysteine. The as-prepared AuNCs exhibited a fluorescence emission at 590 nm and a quantum yield of 13.6%. On the basis of metallophilic Hg2+-Au+ interaction-induced fluorescence quenching mechanism, the fluorescent NAC-AuNCs offer highly sensitivity with a limit of detection of 0.2 nM for determination of Hg2+ ions, which is 50 times lower than the limit value (10 nM) defined by the U.S. Environmental Protection Agency in drinkable water. The proposed fluorescent probe has a linear response range of 2.0-3200 nM Hg2+ ions and good repeatable response to 20 nM Hg2+ with a relative standard deviation of 3.2% (n = 6). Also, the luminescence response of the NAC-AuNCs probe in the presence of EDTA is especially selective to Hg2+. The proposed method has been successfully applied for determination of Hg2+ in various water samples, and the results agreed well with those obtained by the ICP-AES method.