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

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 x 10(-7) and 8.5 x 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, H-1 NMR titration and TD-DFT calculation. The water environment F- detection and spiked recovery experiments demonstrate their potential for real sample detection.