A novel NBD-based fluorescent turn-on probe for detection of phosgene in solution and the gas phase

Abstract

As a highly toxic gas, phosgene (COCl₂) is widely used in chemical industry processes. Because of its colorlessness and acute effects, the detection of phosgene is important for public health safety. In this work, we report a novel 7-nitro-2,1,3-benzoxadiazole (NBD)-based fluorescent probe. It is constructed with the 1,4,7-triazacyclononane moiety as the active site, which includes two aliphatic secondary amines and one aromatic tertiary amine. The 1-nitrogen atom connected to the aromatic ring facilitates the intramolecular charge transfer (ICT) process, providing high quality of fluorescence potential. The 4- and 7-nitrogen atoms are used as double-site recognition groups and also as effective photoinduced electron transfer (PET) donors. The NBD-1,4,7-triazacyclononane probe can be bis-carbamylated with phosgene to block the PET effect, which gives a turn-on fluorescence response at 525 nm. The sensing reaction can be achieved within 20 s in solution. The probe's response to triphosgene is highly sensitive and selective, and the detection limit is as low as 1.2 nM to triphosgene in solution. Furthermore, a portable filter paper has been produced for real-time detection of phosgene in the gas phase.