A new coumarin–rhodamine FRET system as an efficient ratiometric fluorescent probe for Hg2+ in aqueous solution and in living cells

•A new Coumarin–Rhodamine FRET system was produced.•This FRET system can detect Hg2+ with high selectivity and sensitivity in a wide pH range.•This FRET system can detect Hg2+ in aqueous solution and in living cells.

A coumarin–rhodamine based ratiometric fluorescent probe was designed and successfully synthesized. The probe can detect Hg2+ with high selectivity over other metal ions and high sensitivity with the most sensitive readout signal in aqueous solution. There is a good linear relationship between the fluorescence ratio I587/I478 and the concentration of Hg2+ ranging from 0.5 uM to 1.5 uM and the detection limit was calculated to be as low as 3.2 nM. In addition, the probe can quickly detect Hg2+ over a wide pH range from 4 to 11. Furthermore, the probe is cell membrane permeable and can detect Hg2+ in living cells.

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