Interfacial Fluorescent Nanofilms for Rapid and Discriminative Detection of Diethyl Chlorophosphate and Thionyl Chloride

Diethyl chlorophosphate (DCP) and thionyl chloride (SOCl 2 ) are highly toxic volatile chemicals that pose severe threats to environmental safety and public health, creating an urgent demand for sensing platforms capable of rapid, intuitive, and selective detection. Herein, we report a free-standing fluorescent nanofilm fabricated via an air/DMSO interfacial self-assembly strategy using an azetidinone hydrazide derivative (DATH) and a tetraphenylethylene-based aldehyde (TFPE) as building blocks. The as-obtained nanofilm features a smooth and homogeneous morphology, tunable thickness and size, excellent substrate adaptability, and facile integration into functional sensing devices. Notably, the prepared nanofilm is initially nonfluorescent but displays pronounced fluorescence enhancement accompanied by distinct emission color changes upon exposure to DCP and SOCl 2 vapors, enabling intuitive visual identification under 365 nm UV light. More importantly, the nanofilm exhibits different optical responses toward the two analytes, allowing effective discrimination according to their different emission wavelengths and response kinetics. By integration of the nanofilm into a lab-built sensing platform, real-time and online monitoring of DCP and SOCl 2 was successfully realized, with a response time within 3.0 s and detection limits of 0.52 ppm for DCP and 1.31 ppt for SOCl 2, respectively. The sensor also displays excellent repeatability over 40 cycles and reliable anti-interference performance against common volatile organic compounds. These results underscore the great potential of interfacial-assembled fluorescent nanofilms as a versatile material platform for rapid and discriminative detection of highly hazardous vapors, offering promising applications for environmental safety monitoring and early warning applications.