Thiophene and diethylaminophenol-based “turn-on” fluorescence chemosensor for detection of Al³⁺ and F⁻ in a near-perfect aqueous solution

A new fluorescent sensor 1, based on thiophene and diethylaminophenol moieties, has been synthesized and its binding capabilities for metal-ion and anion recognition were investigated. The sensor 1 showed ‘turn-on’ fluorescence in the presence of Al³⁺ and F⁻. The sensing behaviors of 1 with Al³⁺ and F⁻ were studied by using photophysical experiments, ¹H NMR titration, and ESI-mass spectrometry analysis. The detection limits for the analysis of Al³⁺ and F⁻ were found to be 0.41 μM and 14.36 μM, respectively, which are below the WHO guidelines for drinking water (7.41 μM for Al³⁺ and 79 μM for F⁻). Moreover, turn-on fluorescence of 1 toward Al³⁺ and F⁻ caused by intramolecular charge transfer (ICT) was well explained by density functional theory (DFT) calculations. Importantly, 1 could be used to detect Al³⁺ in the living cells.