Colorimetric, turn-on fluorescence detection of fluoride ions using simple indole-based receptors in living cells

Abstract

Herein, an indole-attached fluorescein dye (FI-1) was designed and synthesized as an excellent sensor for fluoride ions. The probe FI-1 strikingly changed from colorless to yellow and exhibited a turn-on fluorescence response towards fluoride with superior sensitivity and selectivity in an aqueous medium; the fluoride ions facilitated the ring opening of the fluorescein spiro ring; this caused changes in the absorbance and fluorescence, supported by the results of ¹H-NMR titrations. The observed UV-vis and fluorescence changes are supported by the density functional theory calculations. Thus, the proposed probe can be applied to detect fluoride ions with the lowest range of 31.8 nM; moreover, the probe can be applied for the imaging of fluoride ions in living cells using fluorescence microscopy.