A Coumarin-boronic Based Fluorescent ON-OFF Probe for Hg2+ in Aqueous Solution

In this work, we reported a simple coumarin-boronic acid ester fluorescent probe 1, which displayed very high ON-OFF fluorescence response for Hg2+ in an aqueous environment (H2O/CH3CN = 1:1, v/v) or in a PBS solution (pH = 7.4). With the addition of Hg2+ to the solution of probe, a color change from light yellow to orange could be observed by naked eye. The detection limits were lower than the permitted level of Hg2+ in drinking water defined by WHO. Infrared spectroscopy, mass spectroscopy and H-1 NMR titration studies showed that probe 1 formed a 1:1 complex with Hg2+. In addition, the probe was non-toxic to cells and could stain specifically the membrane region surrounding the HeLa cell.