Detection of landmines by amplified fluorescence quenching of polymer films: A man-portable chemical sniffer for detection of ultra-trace concentrations of explosives emanating from landmines

The explosive charge within a landmine is the source for a mixture of chemical vapors that form a distinctive 'chemical signature' indicative of a landmine. The concentration of these compounds in the air over landmines is extremely low (parts-per-trillion or lower), well below the minimum detection limits of most field-portable chemical sensors. Described in this paper is a man-portable landmine detection system that has for the first time demonstrated the ability to detect landmines by direct sensing of the vapors of signature compounds in the air over landmines. The system utilizes fluorescent polymers developed by collaborators at the Massachusetts Institute of Technology. The sensor can detect ultra-trace concentrations of trinitrotoluene (TNT) vapor and other nitroaromatic compounds found in many landmine explosives. Thin films of the polymers exhibit intense fluorescence, but when exposed to vapors of nitroaromatic explosives the intensity of the light emitted from the films decreases. A single molecule of TNT binding to a receptor site quenches the fluorescence from many polymer repeat units, increasing the sensitivity by orders of magnitude. A sensor prototype has been developed that responds in near real-time to low femtogram quantities of nitroaromatic explosives. The prototype is portable, lightweight, has low power consumption, is simple to operate, and is relatively inexpensive. Simultaneous field testing of the sensor and experienced canine landmine detection teams was recently completed. Although the testing was limited in scope, the performance of the sensor met or exceeded that of the canines against buried landmines.