Nanoclusters prepared from a silver/gold alloy as a fluorescent probe for selective and sensitive determination of lead(II)

We report on the preparation of water-soluble and fluorescent silver/gold alloy nanoclusters (Ag/Au NCs) by a galvanic replacement reaction. The alloy NCs have an average diameter of 1.5 nm and are shown to be viable fluorescent probes for the determination of lead(II) due to aggregation-induced quenching of fluorescence. The alloy NCs are characterized in terms of photoluminescence spectrum, photoluminescence excitation spectrum, transmission electron microscopy and X-ray photoelectron spectroscopy which confirm the presence of alloy NCs. Bovine serum albumin, a well known stabilizing agent, has a high-affinity site for Pb2+ ion, and the resulting complex acts as a quencher of fluorescence. This finding has led to a method for selective determination of Pb2+ with a limit of detection of about 2 nM.