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 ¹H 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.