A Handy Chemical Sensor Based on Benzaldehyde and Imidazo[1,2-a]pyridine Mixture for Naked-eye Colorimetric and Fluorescent Detection of F.

Upon the Schiff base condensation reaction of imidazo[1,2-a]pyridine-2-carbohydrazide and 2,5-dihydroxybenzaldehyde, a bimodal colorimetric and fluorescent chemosensor 1o for assaying fluoride (F) in DMSO was synthesized. The characterization of 1o structure was obtained by H NMR, C NMR and MS.The structure of 1o was characterized by H NMR, C NMR and MS. Under the presence of various anions, 1o could be applied for naked-eye and fluorescent detection of F (naked eye: colorless to yellow; fluorescence: dark to green) and displayed promising performance, such as high selectivity and sensitivity, as well as a low detection limit. Upon calculation, the detection limit of chemosensor 1o for F was 193.5 nM, which is well below the allowed maximum value of F (1.5 mg/L) by WHO. As the intermolecular proton transfer mechanism induced "turn-on" fluorescent signal and naked-eye color change of F to 1o through deprotonation effect, which was confirmed by Job's plot curve, mass spectrometry and H NMR titration. Alternatively, the chemosensor 1o can be effectively manufactured into test strips to detect fluoride in solid state, which is user-friendly with no additional equipment required.