Abstract
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.
Highlights
Warning systems for risk prevention of terrorist attacks based on explosive detection at neuralgic public locations and infrastructures, such as airports, logistic centers, or governmental departments, are very important components of security management
The experimental setup included a tunable distributed feedback (DFB) laser diode with central wavelength at 1.552 μm and a spectral line width of 1 MHz, which was connected to the micro-ring chip via a single-mode fiber
Thin layers of sol-gel-imprinted polymers imprinted for TNT adsorption were deposited on top of highly sensitive photonic micro-ring chips
Summary
Warning systems for risk prevention of terrorist attacks based on explosive detection at neuralgic public locations and infrastructures, such as airports, logistic centers, or governmental departments, are very important components of security management. Fast detection of explosives in the gas-phase, stemming from contaminations at clothes or luggage, would be a significant enhancement for the recognition of explosives or other harmful chemicals used by terrorists. One of the current challenges for the detection of trace gas concentrations of explosives is the required sensitivity in the ppb range due to the low vapor pressures of most explosive substances. A variety of methods have been reported for detecting trinitrotoluene (TNT) in the gas-phase based on ion mobility spectrometry [1,2], surface acoustic wave devices [3], photoluminescence [4], electrochemistry [5,6], microcantilevers [7], and fluorescent polymers [8]
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