A colorimetric and ratiometric fluorescent probe for recognizing fluoride ion based on new chromophore reaction

Fluoride ion plays crucial roles in many biological, chemical, medical and environmental processes. Constructing a highly sensitive florescent probe for naked-eye detection F⁻ is of particular importance but remains challenging. In this work, we developed a colorimetric and ratiometric fluorescent probe of pyrrolopyrrole aza-BODIPY (PPAB)-based polymer (P1) for recognizing F⁻. In presence of F⁻, P1 showed obvious color change from green to yellow with absorption maximum blueshift from 670 nm to 340 nm. The weak emission of 697 nm changed to strong orange fluorescence with appearance of new broad emission with maximum bands at 520 and 642 nm. P1 was capable of sensitively and selectively detecting F⁻ with a low detection limit of 0.07 μM. The sensing mechanism revealed that B–N bond cleavage and following hydrolysis of P1 induced by F⁻ was responsible for the distinct colorimetric and ratiometric fluorescent signals. The results indicated that PPAB core was an efficient recognition unit for F⁻ detection for the first time. Finally, P1-loaded silicone or test paper could detect F⁻ by naked-eye signals. The probe can be successfully applied in real water samples to detect F⁻ concentration.