A novel xanthene-based fluorescence turn-on probe for highly selective detection of Hg2+ in water samples and living cells

•The probe exhibited excellently selective and sensitive detection for Hg2+ over other relevant analytes.•The fluorescent response was fast within 120 s and a dramatic color changes (from colorless to light green) could be observed by naked eyes.•The detection limit of the probe was 0.019 μM.•The probe was successfully applied to detecting Hg2+ in real water samples and HeLa cells. Mercury ions are highly toxic to living organisms and environment, hence Monitoring and quantification of mercury ions remain great significance. Herein, we have designed and synthesized a novel reaction-based fluorescence probe RANS for detection of Hg2+ by using a xanthene derivate as fluorophore and a thiosemicarbazide moiety as the recognition site. By applying mercury-promoted desulfurization reactions, probe RANS exhibited excellent capability of detecting Hg2+, such as rapid response (120 s), high sensitivity (0.019 μM) and good selectivity. Upon reaction with Hg2+, the thiosemicarbazide group of probe RANS formed 1,3,4-oxadiazole along with a significant color change from colorless to light green. Importantly, RANS has been successfully applied to selectively imaging Hg2+ in living cells with low cytotoxicity and quantitative detection of Hg2+ in real water samples. [Display omitted]