ESIPT-PET based triphenylamine-anthraquinone probe for the detection of phosgene: DFT studies, real-time application in soil samples and test strips

Public health and safety are gravely jeopardised by phosgene, a highly toxic gas. In this study, phosgene was detected by the excited-state intramolecular proton transfer (ESIPT) and photoelectron transfer (PET) mechanisms utilising a fluorescent probe built from a triphenylamine-anthraquinone core structure (TPAAQ) with carbonyl and imidazole moieties as recognition sites. TPAAQ undergoes nucleophilic substitution and cyclization reactions with phosgene to form a six-membered ring. This results in a quick reaction with good selectivity, high sensitivity, and a detection limit of 22.83 nM. With the aid of high-resolution mass spectrometry and 1H NMR spectroscopy, the mechanism for sensing was verified. The ESIPT and PET mechanism of the probe was confirmed through DFT and TDDFT studies. In addition, we could detect phosgene in soil samples with detection limits of 0.1583 ppm, 0.233 ppm and 1.047 ppm for field soil, clay soil and sandy soil, respectively, and created a fluorescent test strip to identify phosgene. The fluorescent test strip's colour change from light reddish to yellow is visible to the unaided eye under 365 nm UV light.