Fluorescence sensing system for detecting TNT explosives based on capillary microchannels

Detecting explosives is crucial for ensuring global public safety, enhancing counter-terrorism measures, and safeguarding the environment. Traditional detection methods struggle in high-traffic areas like airports and train stations, where portable systems must quickly and accurately detect targets amid dense crowds and strict security demands. Fluorescent film-based sensing technologies offer a promising solution in detecting trace explosive vapors. However, gas-phase detection with fluorescent films faces challenges in achieving stable and controllable detection due to the multi-step process involved, such as film preparation, gas transport, and optoelectronic conversion. In this study, we introduce an integrated film-based fluorescent sensor system that employs a microchannel structure to detect TNT vapor. Fluorescent microchannels are created by spin-coating a modified polystyrene polymer within a glass capillary tube. A sample collection module employing nylon test paper collects TNT samples, which are then heated within a compact gasification chamber before detection. The fluorescent microchannels are excited by ultraviolet light, and the emitted signals are detected perpendicularly to the excitation source. The optical and gas flow paths are arranged orthogonally, contributing to the system's portability and stability. The film-based sensor exhibits high sensitivity, with a detection limit of 0.01 ng/μL (liquid-phase), corresponding to a gas-phase concentration of approximately 1.2 ppb. The system achieves a rapid signal response time within 3 s and completes the detection process in under 60 s, while maintaining high selectivity and reusability.