Bromine atom introduction improves the F− sensing ability of an indolo[3,2-b]carbazole-salicylaldehyde-based fluorescence turn-on sensor

Abstract

The heavy-atom effect usually quenches fluorescence, but scarcely enhances it. Herein, fluorescence turn-on sensors without or with a bromine atom for F⁻ detection are presented, achieving fast response time within 1 min, and the LODs of 1.9 × 10⁻⁷ and 8.5 × 10⁻⁸ M, reflecting that halogen atom introduction is beneficial for F⁻ detection ability improvement. The sensing mechanism of –OH unit deprotonation is confirmed based on the results of a 1 : 2 stoichiometric ratio, ¹H NMR titration and TD-DFT calculation. The water environment F⁻ detection and spiked recovery experiments demonstrate their potential for real sample detection.