Recognition of Cu2+ and Hg2+ in physiological conditions by a new rhodamine based dual channel fluorescent probe

A new rhodamine-based fluorescent probe RFP3 was synthesized for selective recognition Hg2+ and Cu2+ in EtOH–HEPES buffer solution (20.0 mM HEPES, 30:70, v/v, pH 7.0). This reagent could be used as a dual probe and allowed detection of Cu2+ and Hg2+ by monitoring changes in absorption and the fluorescence spectral pattern. UV–vis spectroscopy indicates that RFP3 is a good chromogenic chemosensor for Cu2+. Whereas the other ions, such as Na+, K+, Mg2+, Fe3+, Ca2+, Zn2+, Pb2+, Hg2+, Cd2+, Ba2+, Ni2+, Mn2+ and Ag+ failed to generate a palpable response. However, the color solution of RFP3 caused by the binding of Cu2+ has no fluorescence, which may be ascribed to the quenching of the fluorescence by Cu2+. Fluorescence spectral data reveals that RFP3 is an excellent fluorescent chemosensor for Hg2+ and other metal ions show no obvious interference for Hg2+ detection. Finally, RFP3 was successfully applied to the imaging of Hg2+ in living HL-7702 cells.