DNA-templated silver nanocluster as a label-free fluorescent probe for the highly sensitive and selective detection of mercury ions

We have constructed a label-free fluorescent probe using ssDNA-templated silver nanoclusters (Ag NCs), and its quantum yield (QY) was significantly higher (∼29%) compared to traditional water-soluble fluorescent metal nanoclusters. The proposed approach is simple, non-toxic, sensitive, and selective for the detection of mercuric ion (Hg2+). The fluorescence intensity of ssDNA-Ag NCs was quenched significantly in the presence of Hg2+, which might be attributed to the strong interactions between them including the dynamic and static quenching mechanisms. Though Ag+ induced a moderate interference to Hg2+, there was a negligible quenching in the presence of other metal cations. In addition, Hg2+ could be detected as low as 4.5 nM, within a good linear range from 0 to 150 nM (R2 = 0.995). More importantly, this method has also been successfully applied to the detection of Hg2+ in the real water samples. Thus, the ssDNA-Ag NCs detection system is potentially suitable for Hg2+ sensing in environmental samples.