A highly selective chromo-fluorogenic probe for specific detection of sarin gas simulant diethylchlorophosphate in liquid and vapor phases†

Among the various organophosphorus-based chemical warfare agents, nerve agents pose severe threats to national defense and public safety. Among them, sarin gas is a severe one that has been employed in various terrorist activities recently. The development of chromo-fluorogenic probes for their detection is still in its infancy. Aiming in this direction, the present article introduces a highly selective and specific chromo-fluorogenic probe, (E)-3-(((4-(benzo[d]oxazol-2-yl)phenyl)imino)methyl)-2-methoxy-2H-chromen-4-ol (TSB) embracing chromone and benzoxazole moieties, for the recognition of diethyl chlorophosphate (DCP), a sarin gas surrogate, in both gaseous and solution phases, respectively. Upon adding DCP to the TSB solution in pure DMSO and 50% v/v water–DMSO mixture, there is an observable change from very pale yellow to colorless. Additionally, there is a transition from no fluorescence to intense blue-violet photoluminescence enhancement under exposure to a 365 nm UV lamp. These optical signals are found to be due to the development of phosphorylated TSB–DCP products, inhibiting intramolecular charge transfer (ICT) and the excited state intramolecular proton transfer (ESIPT) mechanism involved in TSB. The developed sensor demonstrated the ability to detect DCP even in the presence of various other challenging guest analytes, achieving a recognition and quantification limit in the μM range. Furthermore, to achieve on-site detection of DCP and investigate the practical utility of the developed probe, we have demonstrated the use of a paper strip-based test kit, the “dip-stick” method, and, notably, conducted real sample analysis on spiked soil samples.