An ICT-based near-infrared fluorescent probe for smartphone-assisted visual detection of phosgene in solution, vapor...

As a highly toxic chemical warfare agent and hazardous industrial byproduct, phosgene poses severe threats to public health and ecological safety, necessitating rapid, sensitive and portable detection strategies. Herein, a novel quinoline-based fluorescent probe (NPK) via an intramolecular charge transfer (ICT) mechanism is rationally designed. Upon specific recognition of phosgene through an intramolecular cyclization reaction, the emission wavelength of probe NPK significantly shifts into the near-infrared I region within 20 s, and the fluorescence color of the solution changes from green to red. Integrated with smartphone-based RGB colorimetric analysis, the NPK probe enables real-time, quantitative monitoring of phosgene in both liquid and vapor phases, with high sensitivity and selectivity (3.27 nM-liquid/0.082 ppm-vapor for phosgene). The practical utility is further validated by tracking in-situ phosgene generation from chlorinated organic solvents under sunlight‑oxygen coupled conditions. Notably, leveraging its superior solid-state fluorescence, NPK serves as an efficient and non-destructive fluorescent developer for high-fidelity, high-contrast latent fingerprint visualization. This work presents a multifunctional ICT-type fluorescent probe that provides a reliable and versatile platform for hazardous gas trace detection and forensic fingerprint imaging, offering new guidance for the design of high-performance multifunctional sensing materials.