Explosive detectionNano sensor detects minute traces of plastic explosives

Working in collaboration with the RhineMain Polytechnic, materials scientists at the Technische Unversität Darmstadt have developed an extremely sensitive explosives sensor that is capable of detecting even slight traces of the high-explosive chemical compound pentaerythritol tetranitrate (PETN). Terrorists had employed PETN in several attacks on commercial aircraft.

A Technische Unversität Darmstadt release reports that to date, the high-explosive chemical compound PETN could be detected exclusively by means of wipe tests and an ion-mobility spectrometer.

Since conducting such tests involves considerable time and effort, however, it is employed at airports for spot-checking only. Airport scanners and dogs trained to sniff out explosives have a hard time detecting PETN, since PETN is only slightly volatile and therefore liberates only small numbers of molecules into the ambient air. PETN is also a high explosive. Just a few grams are enough to totally destroy a medium-sized passenger car. Thanks to those properties, PETN has recently been frequently employed by terrorists. PETN was found in the package bombs that were intended to blow up cargo planes late last year and was also employed by the “underpants bomber” in his attempted attack on a passenger plane in December 2009.

Scientists at the TU Darmstadt have recently developed a nanosensor capable of detecting a single PETN molecule among ten billion air molecules.

Explaining the new type of explosive detector’s operation, Dipl. Ing. Mario Boehme stated that, “If a PETN molecule enters the sensor’s nanotube, the nitro groups characteristic of PETN adhere to its surface and change its electrical conductivity, and that change may be detected by electronic instrumentation.”

Checking for explosives without spending more time in the process

In order to detect PETN using the new sensor, all that is necessary is conducting ambient air across the sensor. Boehme added that, “One possibility would be equipping the conventional metal detectors and X ray machines employed at airport security checkpoints with the new sensor and a device for inducting air.” That approach would allow discreetly checking all passengers and their luggage for explosives without spending more time in the process. He went on to state that, “However, another possibility would be utilizing a hand-held device similar to a table vacuum cleaner that would allow checking individual passengers.” Since the sensors are extremely small and inexpensive to manufacture, he can also envision employing them at sports events or in other types of security checks. He and his research associates are currently seeking industrial collaboration partners.