Enhanced sensing selectivity through steric and electronic synergistic effects in a BODIPY-triphenylamine-7-nitro-2,1,3-benzoxadiazole system for optical detection of sulfide: Synthesis, structure, and performance.

The detection of hydrogen sulfide (H2S) becomes an important research topic due to its new role as an endogenous signaling molecule in various biological processes. To improve sensing selectivity and decrease reaction time, in this work, two BODIPY-cored probes, B-T-NBD and B-T-(NBD)2, were designed (BODIPY = boron dipyrromethene difluoride). An electron-donating triphenylamine unit was introduced into the BODIPY core to reduce the reaction time. Then, to improve sensing selectivity, the NBD (7-nitro-2,1,3-benzoxadiazole) group was introduced via an esterification reaction to form sterically hindered sensing sites. The emission quantum yields of B-T-NBD and B-T-(NBD)2 decreased to 3% and 2% due to the PET (photoinduced energy transfer) process. After reacting with S2-, the emission-quenching NBD group cleaved, and the emission quantum yields recovered to 35% and 22%. The absorption-based linear calibrations of B-T-NBD:S2- and B-T-(NBD)2:S2- showed LOD values of 0.45 μM and 0.20 μM, respectively, and the emission-based linear calibrations showed LOD values of 0.20 μM and 0.75 μM, respectively. Improved sensing selectivity, especially against competing thiol-containing amino acids, and a short reaction time of ∼2000 s was observed.