A label-free and signal-on supersandwich fluorescent platform for Hg2+ sensing

•A supersandwich fluorescent platform has been reported for the first time.•The supersandwich structure is formed through T-Hg2+-T coordination.•The label-free platform can detect Hg2+ with a detection limit of 2.5 nM.•It is a signal-on sensing platform with fast response and good selectivity.•It is based on fluorescence enhancement of Genefinder by intercalation with dsDNA.

A label-free supersandwich fluorescent assay was demonstrated for the first time by taking Hg2+ as a detection candidate. The principle of the proposed supersandwich fluorescent platform is based on the formation of supersandwich structure by T-Hg2+-T coordination and the fluorescence enhancement of the intercalated Genefinder (GF) in double strand DNA (dsDNA). Such supersandwich fluorescent DNA sensor exhibits a linear range of 10–300 nM for the detection of Hg2+, with a detection limit of 2.5 nM on the basis of the 3σ/slope (σ represents the standard deviation of the blank samples), which is well below the permit of the U.S. Environmental Protection Agency (<10 nM). The detection can be fulfilled in less than 10 min. The proposed mix-and-detect fluorescent platform exhibits excellent sensitivity, selectivity, and convenient manipulation. The assay was successfully used to detect Hg2+ in the lake water samples, which suggested its potential in practical samples.

Graphical abstractA novel label-free supersandwich fluorescent detection platform has been demonstrated for the first time. The platform allows sensitive, selective and rapid detection of Hg2+.Figure optionsDownload full-size imageDownload as PowerPoint slide