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Highly selective colorimetric and fluorometric probes for fluoride ions based on nitrobenzofurazan-containing polymers.

We report on a novel colorimetric and fluorometric chemosensor for fluoride ions based on 4-(2-acryloyloxyethylamino)-7-nitro-2,1,3-benzoxadiazole (NBDAE)-labeled polymers. Upon gradual addition of fluoride ions (F⁻), the green fluorescence emission of NBDAE moieties can be dramatically quenched, accompanied with the distinct colorimetric transition from green to yellow. NBDAE moieties are capable of selectively recognizing F⁻ ions via hydrogen-bonding (H-bonds) interactions at low F⁻ concentration and subjected to further deprotonation process at high F⁻ concentration. NBDAE-labeled polymers in organic solvents possess high selectivity and fluorescence "turn-off" characteristics toward the sensing of F⁻ ions with the detection limit down to ≈ 0.8 µM.