A novel dye based on phenolphthalein-fluorescein as a fluorescent probe for the dual-channel detection of Hg2+ and Zn2+

A novel phenolphthalein-fluorescein dye derivative (PF) was designed, synthesized and characterized. PF showed an effectively selective and sensitive recognition toward Zn2+ and Hg2+ ions as a dual channel probe in EtOH-H2O (v/v = 8/2, 5 mM, HEPES, pH 7.0) over other cations and the remarkable enhancement in fluorescence emission centered at 500 and 520 nm was observed in the presence of Zn2+ and Hg2+, respectively. The probe PF binds to Zn2+ and Hg2+ in 1:2 stoichiometry as determined by a Job's plot, and the binding constants were calculated as 6.45 × 1010 M−2 and 2.11 × 1010 M−2 with detection limits of 0.54 μM for Zn2+ and 1.16 μM for Hg2+. Moreover, the results demonstrated that the binding between probe PF and Zn2+/Hg2+ is chemically reversible. To test the practical use of the probe, the determination of Zn2+ and Hg2+ in water samples was also evaluated.