A sensor for trinitrotoluene (TNT) detection was developed by using a combination of optical micro-ring technology and a receptor coating based on molecularly imprinted sol-gel layers. Two techniques for deposition of receptor layers were compared: Airbrush technology and electrospray ionization. A concentration of less than 5 ppb for TNT in the gas-phase, using electrospray deposition of the receptor layer, was detected. The cross-sensitivities to organic substances and further nitro-based explosives were compared. As a result, the sensitivity to TNT is about one order of magnitude higher in comparison to the explosives 2,4-dinitrotoluene (DNT) or 1,3-dinitrobenzene (DNB) and about four orders of magnitude higher than the organic substances phenol, ethanol, and acetone. The signal response of the sensor is fast, and the compact sensor design enables the deposition of different receptor layers on multiple optical micro-rings on one chip, which allows a more precise analysis and reduction of side effects and false alarms.
Both TATP and HMTD could be phlegmatized by coprecipitation with active charcoal resulting in mixtures with a nominal content of 40 wt-% (d40-TATP) and 10 wt-% (d10-HMTD), respectively. In terms of impact and friction sensitivity for both peroxides a content of 40 wt-% resulted in > 30 Nm impact sensitivity and > 360 N friction sensitivity. Both phlegmatized peroxides passed the Koenen Tube and Thermal Stability Test according to the UN recommendation on the transport of dangerous goods test manual. Investigations with a process mass spectrometer indicate that d40-TATP can produce a saturated TATP headspace at least in the same time as the same amount of pure TATP. Measurements with the transpiration method demonstrated that the vapor pressure p sat at 298.15 K of d40-TATP (2.3 Pa) and d32.7-TATP (0.9 Pa) is lower than that of pure TATP (6.7 Pa). Headspace SPME-GC/MS measurements revealed that the active charcoal does not contribute to the vapor profile of the training aid. Both d40-TATP and d10-HMTD were tested as training aids for explosive detection dog teams (EDD). In both differentiation track and realistic environment scenarios a detection rate of 100 % could be achieved by German Federal Police EDD with a false positive rate of solely 3 %.
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