Ratiometric Fluorescent Detection of Phosgene in Liquid and Gas Phases Using a Tautomeric Dye: A Combined Experimental and Theoretical Study

Abstract

A new fluorescent probe, designated as ((E)-2-((2-hydroxy-3-methoxybenzylidene)amino)-2-(hydroxymethyl)propane-1,3-diol (HHP), was synthesized for selective detection of phosgene via a fluorescence-based cyclization mechanism. Initially HHP exhibits high fluorescence with a strong emission signal at 502 nm but the emission intensity was significantly reduced on gradual addition of phosgene with a ratiometric broad emission band at 450 nm, along with an isoemission point at 475 nm. Simultaneously, two strong absorption signals of HHP at 220 nm and 261 nm were diminished with an increase in a new red shifted absorption signal at 290 nm along with two isosbestic point observed at 272 nm and 312 nm. Within a very fast (30 sec) reaction time, the probe HHP detected phosgene with a limit of detection at 3.82 μM. The proton transfer pathway and the sensing mechanism of HHP with phosgene was demonstrated by theoretical study, which was also investigated using a variety of spectroscopic techniques, such as mass spectrometry, UV-vis and emission spectroscopy. In the practical applications, the sensor HHP can be used by the dipstick method for the detection of phosgene in the gaseous form by naked eye colorimetric analysis.