A new near-infrared fluorescent chemodosimeter for discrimination of sulfide from disulfide

A new near-infrared fluorescent "turn-on" chemodosimeter (probe 1) based on dicyanomethylene-4H-chromene fluorophore for sulfide was developed. Probe 1 showed good fluorescence selectivity to sulfide over other anions and thiol-containing compounds. The discrimination of sulfide from disulfide could be achieved by comparison of the spectral difference of probe 1 after interaction with them. The absorption of probe 1 at 437 nm decreased, accompanied by red-shifting to 470 nm as a shoulder, and a strong peak at 610 nm appeared in the presence of sulfide. The absorption of 1 was slightly red-shifted to 452 nm with increased absorbance in the presence of disulfide. Probe 1 showed more than 1000-fold fluorescence enhancement at 712 nm with a Stokes shift of 102 nm in the presence of sulfide. The probe exhibited a good sensitivity in detection of sulfide with a wide pH span (4.0-11.0). The absorption change and fluorescence enhancement could be attributed to thiolysis of the dinitrophenyl ether group in probe 1 by the sulfide. The proposed mechanism was proved by H-1 NMR spectra and EI-MS explorations. The probe was successfully applied for the detection of sulfide anions in real water samples.