Detection of explosives using orthogonal gas sensors

An orthogonal detection system comprised of two independent sensing platforms integrated into a single sensor was recently developed to detect trace levels of explosives including TATP, 2,6-DNT and ammonium nitrate in the vapor phase. The orthogonal sensor consists of a thermodynamic based sensing platform, which measures the heat effect associated with the interaction of specific target molecules with various metal oxide catalysts (ZnO and SnO₂), and a conductometric sensing platform, which monitors the electrical conductivity changes of the same catalyst when exposed to the explosive molecules. The experimental results to date indicated that the orthogonal sensor platform was very effective in identifying explosives at the ppb level. At the same time, the additional sensor signature provides redundancy in the sensor response, which helps mitigate false positives. The orthogonal sensor response is linear when plotted as a function of target molecule concentration. XPS was employed to confirm the oxidation state of metal oxides used as catalysts, which were a function of deposition and post deposition heat treatments.