A highly selective and ratiometric fluorescence probe for the detection of Hg2+ and pH change based on coumarin in aqueous solution

A simple but highly selective coumarin-based fluorescence probe 1 , 8-(1,3-dithiane)-7-hydroxycoumarin was designed and synthesized for both the ratiometric detection of Hg 2+ and the on–off response to pH change in aqueous solution. The sensor detected Hg 2+ selectively via Hg 2+ -promoted thioacetal deprotection reaction within five minutes and reflected pH in the range from 7.8 to 11.9 as a result of the equilibrium between weak-fluorescent acid form and strong-fluorescent base form. In addition, the probe has an excellent selectivity towards Hg 2+ over other competitive metal ions for biomedical and environmental applications. The sensing behavior of our probe was studied by UV–visible absorption spectra and fluorescence spectra .