Sensitive and selective detection of Hg2+ and Cu2+ ions by fluorescent Ag nanoclusters synthesized via a hydrothermal method.

An easily prepared fluorescent Ag nanoclusters (Ag NCs) probe for the sensitive and selective detection of Hg(2+) and Cu(2+) ions was developed here. The Ag NCs were synthesized by using polymethacrylic acid sodium salt as a template via a convenient hydrothermal process. The as-prepared fluorescent Ag NCs were monodispersed, uniform and less than 2 nm in diameter, and can be quenched in the presence of mercury (Hg(2+)) or copper (Cu(2+)) ions. Excellent linear relationships existed between the quenching degree of the Ag NCs and the concentrations of Hg(2+) or Cu(2+) ions in the range of 10 nM to 20 μM or 10 nM to 30 μM, respectively. By using ethylenediaminetetraacetate (EDTA) as the masking agent of Cu(2+), Hg(2+) was exclusively detected in coexistence with Cu(2+) with high sensitivity (LOD = 10 nM), which also provided a reusable detection method for Cu(2+). Furthermore, the different quenching phenomena caused by the two metals ions such as changes in visible colour, shifts of UV absorbance peaks and changes in size of Ag NCs make it easy to distinguish between them. Therefore the easily synthesized fluorescent Ag NCs may have great potential as Hg(2+) and Cu(2+) ions sensors.