A new and simple sensor to sniff out shoe bombs

WASHINGTON - Scientists have developed a simple sensor to detect an explosive used in shoe bombs.

This finding by the University of Illinois scientists could lead to inexpensive, easy-to-use devices for luggage and passenger screening at airports and elsewhere.

Triacetone triperoxide (TATP) is a high-powered explosive that in recent years has been used in several bombing attempts.

The few methods available to screen for TATP aren’t feasible for on-the-ground use in airports, as they require large, expensive equipment, extensive sample preparation, or relatively high concentrations of TATP in solid or liquid form.

Kenneth Suslick of the University of Illinois along with Hengwei Lin have developed a colorimetric sensor array that can quantitatively detect even very low levels of TATP vapour-down to a mere 2 parts per billion.

To create the sensor array, the researchers print a series of 16 tiny colored dots - each a different pigment - on an inert plastic film. A solid acid catalyst breaks down TATP into detectable components that cause the pigments to change colour, like litmus paper.

Each pigment changes colours depending on the concentration of TATP in the air. The array is digitally imaged with an ordinary flatbed scanner or an inexpensive electronic camera before and after exposure to the air.

“Imagine a polka-dotted postage stamp sensor that can sniff out the shoe-bomber explosive simply by using a digital camera to measure the changing colours of the sensor’s spots.

The pattern of the colour change is a unique molecular fingerprint for TATP at any given concentration and we can identify it in a matter of seconds,” said Suslick.

The array is uniquely sensitive to TATP.

In addition to demonstrating their sensing technique with an ordinary flatbed scanner, the researchers also developed a functional prototype hand-held device.

The portable instrument, designed to easily screen luggage or shoes, uses inexpensive white LED illumination and an ordinary digital camera similar to a cell-phone camera.

They findings were published in the Journal of the American Chemical Society. (ANI)