Xanthene-based fluorescence turn-on detection of phosgene via analyte-triggered isocyanate formation

The degree of ease of use and the readily observable signals associated with the detection process are critical factors in determining the success of a detection strategy. Considering this perspective, we report the detection of phosgene by modulating the photophysical characteristics of a molecular probe, Xanth-NH 2 . The probe is non-emissive in nature, but the presence of phosgene facilitates the probe's radiative decay, which enables phosgene detection via fluorescence turn-on change. The fluorescence changes vary linearly with phosgene concentration, contributing to a nanomolar level detection limit for phosgene. Additionally, under a controlled set of conditions, the half-time for the reaction of Xanth-NH 2 with phosgene is 68 s. To demonstrate the potential application of Xanth-NH 2 , probe-loaded paper strips or silica gel were developed as an economic tool for the detection of phosgene in vapor or solution phase. Phosgene detection has been accomplished with a portable UV light source and a smartphone to track minute changes during the detection event.