Fluoride detection with a colorimetric and fluorescent dual‐mode chemosensor

We designed a colorimetric and fluorescent dual‐mode chemosensor ADM ((E)‐2‐(((2‐amino‐4,5‐dichlorophenyl)imino)methyl)‐6‐methoxyphenol) for detecting fluoride (F−). The sensor ADM can detect F− by colour and fluorescence changes. The colour change is from colourless to yellow, and the fluorescence change is a yellow turn‐on. With the results of Job plot and electrospray ionisation mass spectrometry, the reaction of F− and ADM turned out to be a 1:1 binding. The detection limits for F− of ADM were 5.00 μM in ultraviolet–visible and 4.16 μM in fluorescence. The detecting process of F− by ADM was demonstrated by ultraviolet–visible and fluorescent titrations, electrospray ionisation mass spectrometry, proton nuclear magnetic resonance titration and theoretical calculations.