Pink fluorescence emitting fluoride ion sensor: investigation of the cascade sensing mechanism and bioimaging applications

Abstract

A resorufin based colorimetric and fluorescence off–on probe for selective fluoride ion detection is reported. ¹H-NMR and HPLC experiments confirm the formation of phthalide and resorufin in the deprotection–cyclization based sensing mechanism. The cascade reaction strategy ensures the rapid release (t_1/2 = 1.96 min) of pink fluorescent resorufin dye. Selective sensing of fluoride ions results in the 1820-fold fluorescence enhancement. The probe also displays a detection limit of 60 nM (i.e. 1.15 ppb) during the sensing of the ion in water. The permeability of the probe and sensing of intracellular fluoride ions is demonstrated by live cell imaging.