Single fluorescent chemosensor for multiple targets: Sequential detection of Al³⁺ and pyrophosphate and selective detection of F^- in near-perfect aqueous solution

A simple and easily fabricated chemosensor (1), based on 2-furoic hydrazide and diethylaminosalicylaldehyde moieties, was devised and synthesized. Sensor 1 showed selective changes in fluorescence behavior toward three analytes in near-perfect aqueous solution. Al³⁺ and F^- recognized by fluorescence enhancement of 1 and their limits of detection (0.19 μM for Al³⁺ and 1.9 μM for F^-) were markedly low compared to World Health Organization guidelines (7.4 μM for Al³⁺ and 79 μM for F^-) for drinking water. Furthermore, sensor 1 was used to quantify Al³⁺ and F^- in real water samples and image Al³⁺ in living cells. Interestingly, the resulting 1-Al³⁺ complex could be used to discriminate pyrophosphate (PPi) over competing anions, including phosphate-based anions, by decreased fluorescence. Sensing mechanisms of 1 toward Al³⁺, PPi, and F^- were proposed based on photophysical studies and theoretical calculations.