Simple, Inexpensive Sensor Detects Shoe Bomb Chemical

(NASA)

University of Illinois chemists in Champaign, Illinois have developed a simple sensor to detect an explosive used in shoe bombs, with the potential to be built into inexpensive 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 bombing attempts. TATP is easy to prepare from readily available components and has been difficult to detect. It also defies most standard methods of chemical sensing; it doesn’t fluoresce, absorb ultraviolet light, or readily ionize.

Kenneth Suslick, professor of chemistry, and postdoctoral researcher Hengwei Lin developed a colorimetric sensor array that can quantitatively detect even very low levels of TATP vapor, down to a mere 2 parts per billion. To create the sensor array, the researchers printed a series of 16 tiny colored dots, each in a different pigment, on an inert plastic film.

A solid acid catalyst breaks down TATP into detectable components that cause the pigments to change color, like litmus paper. Each pigment then changes colors 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.

The sensor is uniquely attuned to TATP, and is unaffected by changes in humidity or exposure to other chemicals, such as personal hygiene products or laundry detergents. It also has a long shelf life, so airport security and other users can keep a supply on hand.

The researchers’ findings were published in an article published in the Journal of the American Chemical Society (paid subscription required). They also developed a functional prototype handheld device. The handheld sensor now is being commercialized by iSense, a sensor manufacturer based in Palo Alto, California.