Facile and rapid synthesis of water-soluble fluorescent gold nanoclusters for sensitive and selective detection of Ag+

We report a direct one-pot approach, employing tetrakis(hydroxymethyl)phosphonium chloride (THPC) and 11-mercaptoundecanoic acid (11-MUA) as combined reducing/capping agents, for the rapid preparation of fluorescent gold nanoclusters (AuNCs) from HAuCl4 in aqueous solution at room temperature. The as-prepared AuNCs exhibit a fluorescence emission at 535 nm, a quantum yield of 1.8% and average diameters of 2.0 ± 0.5 nm. The resultant MUA/THPC–AuNCs have been exploited, for the first time, for the highly sensitive and selective detection of silver ions (Ag+) in aqueous solution when using EDTA as a masking agent for Hg2+. The fluorescence intensity quenches linearly within the range of 25 nM to 3 μM with high sensitivity (LOD = 9 nM, S/N = 3) and this sensing system has been applied for environmental water sample analysis.