Abstract
In a world focused on the development of cybersecurity, many densely populated areas and transportation hubs are still susceptible to terrorist attacks via improvised explosive devices (IEDs). These devices frequently employ a combination of peroxide based explosives as well as nitramines, nitrates, and nitroaromatics. Detection of these explosives can be challenging due to varying chemical composition and the extremely low vapor pressures exhibited by some explosive compounds. No electronic trace detection system currently exists that is capable of continuously monitoring both peroxide based explosives and certain nitrogen based explosives, or their precursors, in the vapor phase. Recently, we developed a thermodynamic sensor that can detect a multitude of explosives in the vapor phase at the parts-per-trillion (ppt) level. The sensors rely on the catalytic decomposition of the explosive and specific oxidation–reduction reactions between the energetic molecule and metal oxide catalyst; i.e. the heat effects associated with catalytic decomposition and redox reactions between the decomposition products and catalyst are measured. Improved sensor response and selectivity were achieved by fabricating free-standing, ultrathin film (1 µm thick) microheater sensors for this purpose. The fabrication method used here relies on the interdiffusion mechanics between a copper (Cu) adhesion layer and the palladium (Pd) microheater sensor. A detailed description of the fabrication process to produce a free-standing 1 µm thick sensor is presented.
Highlights
In a world focused on the development of cybersecurity, many densely populated areas and transportation hubs are still susceptible to terrorist attacks via improvised explosive devices (IEDs)
The thermodynamic sensor was constructed on ultrathin, 20 μm thick yttria-stabilized zirconia (YSZ) ribbons measuring 1.6 cm × 0.7 cm
A 400 Å thick layer of copper was sputter-deposited onto the substrate, which acted as an adhesion layer between the microheater and the yttriastabilized zirconia (YSZ)
Summary
In a world focused on the development of cybersecurity, many densely populated areas and transportation hubs are still susceptible to terrorist attacks via improvised explosive devices (IEDs). Densely populated venues and transportation hubs are patrolled by canines which are trained to selectively identify peroxide and nitrogen based IEDs2,3 By virtue of their highly sensitive noses, these dogs are capable of detecting explosives at remarkably low levels (< ppt) and employ directionality which leads to precise identification of an IED’s location[2]. These systems possess a large footprint relative to small-scale chemical sensors which limits their feasibility and functionality in a portable platform Other analytical methods such as, ion mobility spectroscopy (IMS)[15,16,17,18,19] and liquid c hromatography[20], require pretreatment of the analyte prior to analysis which severely increases the time required for sample processing and cannot be used for continuous, real-time detection. Trace detection of TATP has been displayed by a potentiostatic sensors with titania n anotubes[26] but were somewhat limited in traditional humid/ambient conditions
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