Nerve agents gained infamy as chemical-warfare agents (CWA) used in wars in undeveloped countries with hundreds of thousands of victims. Their high toxicity is due to their strong capability of nucleophilic attack of the hydroxyl group of a serine residue at the active site of the enzyme on the electrophilic phosphorous, rendering the enzyme inoperative, and then effectively paralyzes the central nervous system.
Among them, phosgene is so toxic that has become a serious potential threating to health safety. Exposure to phosgene has sever acute respiratory effects, including noncardiogenic pulmonary edema, pulmonary emphysema, and even death. Notably, unlike other CWAs, phosgene has a unique toxicological concern owing to the existence of an unpredictable asymptomatic latent phase that takes place prior to the onset of life-threatening pulmonary edema.
Since 2(2-aminophenyl)benzothiazole (ABT) generates dual sites for the reaction with phosgene by undergoing an ESIPT process, we have developed the new fluorescence probe which can detect phosgene colorimetrically and ratiometrically. The probe can represent this toxic agent sensed by both methods in solutions and the gas phase. The visible color change from colorless to yellow, as well as the fluorescence color change from blue to green can be easily observed by the naked eyes. Furthermore, the probe shows high sensitivity, low detection limit as low as 0.14 ppm and also selectivity compared to other analytes including triphosgene. These results suggest that this probe is a promising addition to the highly limited family of ratiometric fluorescence probes for phosgene. Investigations of differently substituted ABT derivatives for detecting phosgene are ongoing in our laboratory.