UF Researchers Shine Light On New Explosives Detection Method

October 7, 2004

Note: This press release was revised on Oct. 2, 2006.

GAINESVILLE, Fla. — A team of University of Florida researchers has invented a way to rapidly detect traces of TNT or other hidden explosives simply by shining a light on any potentially contaminated object, from a speck of dust in the air to the surface of a suitcase.

“We have to find explosives quickly, inexpensively and, particularly, reliably,” said Rolf Hummel, a UF professor emeritus of materials science and engineering who heads the lab where the method was invented.

The development provides instantaneous results, gives no false positives, can be used remotely and is portable — attributes he says will make it indispensable at all levels of law enforcement, from local police to homeland security.

The method uses differential reflection spectroscopy, a technique that casts ultraviolet light on a material and measures the range and intensity of the wavelengths of light the material produces in response. The wavelength of the reflected light varies depending on the chemical structure of the material.

Using differential reflection spectroscopy to reveal the presence of TNT is similar to how “black light” uses UV radiation to make white clothes glow, Hummel said. “Once you shine UV light at the sample, the material then reflects (it) at specific wavelengths that are different for each material — it’s a kind of a fingerprint.”

TNT’s fingerprint are sharp, distinct peaks at a specific wavelengths within the electromagnetic spectrum, the researchers discovered. The electromagnetic spectrum encompasses the entire range of electromagnetic waves, from long-wavelength radio waves to visible light to short-wavelength gamma rays.

The key to this common attribute, Hummel said, lies in the explosives’ chemical makeup — they all contain at least two “nitro groups,” molecules made up of one nitrogen atom bound to two oxygen atoms.

The UF discovery of TNT’s signal was prompted by a request from the U.S. Army Research Office that challenged universities to find a way to make inexpensive, quick and reliable explosive-detection systems.

Sample collection for explosives is familiar to anyone who has recently passed through an airport: a swab brushed across an object, such as a suitcase, clothing or even a person, or puffs of air blasted across a filter that can trap tiny amounts of airborne explosives. The advantage of differential reflection spectroscopy-based explosives detection is that it can be remotely applied, and requires neither time-consuming and expensive machines nor trained dogs, said Hummel, who has applied for a patent on the technique.

“My major aim is that I would like to help and make a contribution towards secure life, airports and transportation,” he said. “Just shine UV light on a car, ship or person and see if the specific wavelengths come back — that’s my goal.”