A naphthalene benzimidazole-based chemosensor for the colorimetric and on-off fluorescent detection of fluoride ion.

A novel naphthalene benzimidazole (NBI)-based chemosensor (D2) was developed for fluoride ion (F−) detection. The absorption spectrum of D2 changed dramatically from yellow to blue in the visible region accompanied with a 225nm red shift of its absorption maximum upon the addition of F− in DMSO. D2 also exhibited a fluorescence turn-off response towards the fluoride ion. The emission intensity of D2 decreased drastically along the increasing F− concentration and the detection limit for F− was as low as 3.2×10−9mol/L. 1H NMR and HRMS-ESI results indicated that the formation of NBI-O− through the desilylation reaction of F− with NBI-OSi was responsible for the spectral changes. Overall, this kind of NBI-type molecules represent a new type chemosensor for the spectral detection of fluoride ion in solution.