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.