A Dibenzo-18-crown-6-based Symmetric Dual-coumarin Lead Ion Fluorescent Probe and Its Imaging in Living Cells

Herein, a turn-on fluorescent probe for the detection of lead ions was developed using 7-diethylaminocoumarin as the fluorophore and dibenzo-18-crown-6 as the recognition unit. The response performance to lead ions was systematically studied. The probe showed specific selectivity and high sensitivity to lead ions, with fluorescence intensity at 496 nm increasing linearly with lead ion concentration (R²=0.995) over the range of 1.0×10⁻⁷–1.0×10⁻⁶ mol/L, and an LOD of 11.4 nmol/L. Job’s plot revealed that the probe forms a 1:1 stoichiometry complex with lead ions during the recognition process. Furthermore, the sensing mechanism of the probe was confirmed by density functional theory calculations, indicating that the recognition mechanism is based on photoinduced electron transfer (PET). The introduction of lead ions blocks PET, resulting in fluorescence enhancement. Finally, it was applied in the detection of practical water samples and bioimaging, demonstrating high application value in the field of chemosensors.