A novel “turn-on” thiooxofluorescein-based colorimetric and fluorescent sensor for Hg2+ and its application in living cells

A novel water-soluble fluorescent probe FLS2 based on the thiooxofluorescein derivative has been firstly designed and synthesized. UV–vis absorption and fluorescence spectra studies showed that the FLS2 as a colorimetric and ratiometric fluorescent probe exhibited high selectivity and sensitivity towards Hg 2+ , which was mainly attributed to the special binding with the receptor unit accompanied with the spirolactam ring-opening progress. In addition, the probe FLS2 could be used as a naked-eye indicator for Hg 2+ with reversible response. It displayed approximate 37-fold fluorescent enhancement at 529   nm in the presence of only 2.0 equiv. Hg 2+ and the detection limit was calculated at about 39   nM. What's more, cellular imaging experiment revealed that the sensor had excellent biocompatibility and low cytotoxicity that could be utilized for monitoring Hg 2+ in living cells.