▎ 摘　　要

The article describes a fluorometric and sensitive assay for mercury(II) ions (Hg2+). It is based on the following scheme and experimental steps: (1) Hg2+ triggers the self-hybridization of thymine-rich ss-DNA labeled with a fluorescence tag to form a ds-DNA; (2) in the absence of Hg2+, labeled ss-DNA will be adsorbed on the surface of graphene oxide (GO) and its fluorescence is quenched; (3) the ds-DNA formed in the presence of Hg2+ is cleaved by the catalytic action of exonuclease III; (4) the cleaved labeled DNA fragments do not adsorb on the surface of GO, this resulting in an increase in fluorescence intensity. The induction of the process by Hg2+ leads to a strong amplification of fluorescence, while the fluorescence of uncleaved labeled ss-DNA is quenched because it is adsorbed on the surface of GO in the absence of Hg2+. This assay displays a detection limit of 0.1 nM (which is below the 10 nM upper limit in drinking water according to the US EPA and can be performed with 8 min.