Tunable Generation and Adsorption of Energetic Compounds in the Vapor Phase at Trace Levels: A Tool for Testing and Developing Sensitive and Selective Substrates for Explosive Detection

摘要

Among various methods for landmine detection, as wellnas soil and water pollution monitoring, the detection ofnexplosive compounds in air is becoming an important andninevitable challenge for homeland security applications,ndue to the threatening increase in terrorist explosivenbombs used against civil populations. However, in the lastncase, there is a crucial need for the detection of vapornphase traces or subtraces (in the ppt range or even lower).nA novel and innovative generator for explosive tracenvapors was designed and developed. It allowed thengeneration of theoretical concentrations as low as 0.24nppq for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) innair according to Clapeyron equations. The accurate gen-neration of explosive concentrations at subppt levels wasnverified for RDX and 2,4,6-trinitrotoluene (TNT) using angas chromatograph coupled to an electron capture detec-ntor (GC-ECD). First, sensing material experiments werenconducted on a nanostructured tungsten oxide. Thensensing efficiency of this material determined as itsnadsorption capacity toward 54 ppb RDX was calculatednto be five times higher than the sensing efficiency of a 54nppb TNT vapor. The material sensing efficiency showednno dependence on the mass of material used. The resultsnshowed that the device allowed the calibration and dis-ncrimination between materials for highly sensitive andnaccurate sensing detection in air of low vapor pressurenexplosives such as TNT or RDX at subppb levels. Thendesigned device and method showed promising featuresnfor nanosensing applications in the field of ultratracenexplosive detection. The current perspectives are tondecrease the testing scale and the detection levels to pptnor subppt concentration of explosives in air.