Rapid phosgene detection with red emissive probe in solution and Vapor Phase: Emergence of delayed fluorescence

Phosgene is a highly toxic, volatile, and notorious gas that needs quick attention due to its significant threats to public safety and humanity that could arise from unexpected terrorist attacks and industrial disasters. Although multiple approaches based on diverse concepts have been published for phosgene detection, they are still hampered by low mobility, high cost, and complex processes. Hence, quick, convenient, and accurate detection of phosgene is a current need of the time. Therefore, user-friendly alternatives that are easy to manage, have quick response times, and bear the potential for real-time monitoring were required.

This study aims to present the development of a highly selective and sensitive colorimetric and fluorometric probe that can detect phosgene in a turn-on fluorescence mode, having a 15-fold increase in intensity, with a visible colour change from yellow to blue, allowing for visual identification without the requirement of specialized bulky equipment. Additionally, the probe itself had a distinct response to pH and viscosity. The probe exhibits a high level of selectivity for phosgene in the presence of other interfering substances. The final formed compound with phosgene shows a new property of thermally activated delayed fluorescence, having a lifetime of 7.78 μs. This response was due to an acylation process that led to the formation of a new product, investigated through various analytical tools such as HPLC, IR, Mass, and other analytical tools.

The probe reacts in less than 5 s and has a detection limit of 17.7 ppb. It is able to detect the presence of phosgene in various soil samples. An easy and handy smartphone-based paper test kit was fabricated, which gave a distinct colour in different channels, showing superior capability of sensing phosgene in any possible channel available.