‘Off‐the‐Shelf’ Material for Ratiometric Sensing of Phosgene at Nanomolar Level Both in Solution and Gaseous Phase

Abstract

AbstractCommercially available fluorogenic probe, 2‐ (2‐hydroxyphenyl) benzimidazole has been involved in detecting phosgene via ratiometric color changing response (cyan to blue). Mechanistic studies indicate formation of oxazolidone ring via double carbamylation reaction with phosgene, which significantly curb the extent of excited‐state proton transfer. On the other hand, involvement of weakly alkaline phenolic group as nucleophilic site ensures high specificity over structurally similar competitive analyte, such as triphosgene. Moreover, the present system can detect as low as 14.5 nM phosgene, which is ∼140 fold lower than the threshold value (2 ppm), known to cause immediate danger to health and life (IDLH). Also, detection of phosgene in gaseous state was achieved using dye‐coated paper strips (LOD: ∼0.16 ppm). A quenching in blue fluorescence was noticed when the strips were exposed to phosgene gas phase. Since no sophisticated analytical instrument, trained personnel or constant power supply is required, these paper‐based sensory devices are inexpensive and highly user‐friendly.