Rapid colorimetric and ratiometric fluorescence method for on-site detection and visualization of phosgene by amino-functionalized carbon dot-based portable droplet system

Phosgene is a very dangerous but important industrial intermediate and is a significant threat to public health. There is, therefore, an urgent need to develop a rapid, visual, and on-site detection method for phosgene. Sensitive and selective phosgene responsive carbon dots (CDs) were synthesized by employing 2-nitro-4-aminodiphenylamine as precursors. The amine group of the CDs can interact selectively with phosgene to effect acylation reactions, which cause color changes from yellow to amaranth and remarkable changes in fluorescence from bright yellow to orange-red due to modification of the CDs’ intramolecular charge transfer (ICT) process. The CDs exhibited fast response (<2 s) for detection of phosgene with an ultralow detection limit (0.63 nM). Furthermore, a portable CD/polystyrene droplet system was developed for rapid and on-site visualization of phosgene. Specifically, the droplet system not only can realize rapid on-spot visual inspection of gaseous phosgene in the liquid phase with the naked eye, but also could make long-term visualization in the solid phase via a polystyrene membrane after solvent volatilization. This study has expanded the scope for application of CDs in sensing field, and provides a new and effective strategy for fabrication excellent platform for real-time detection of phosgene leakage in industrial and public safety applications.