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Researchers Develop Sensor to Detect Explosives

Technology to Improve Homeland Security

A female officer letting an officer dog stiff out for bombs.
The new optical sensor can help airport-security and customs officers sniff out explosives concealed in passenger luggage.

By Edwin L. Aguirre

On Christmas Day 2009, a 23-year-old Nigerian passenger aboard a Northwest Airlines flight from Amsterdam tried to ignite a homemade explosive devise hidden in his underwear as the plane was preparing to land in Detroit.

Fortunately, the plot was foiled before anyone was seriously hurt or killed. The incident, however, highlights the need for the United States to be ever more vigilant in the face of global terrorism.

A group of UMass Lowell researchers has developed a highly sensitive optical sensor that can rapidly detect even trace amounts of explosives in the air. Such a sensor could be used to screen passengers, luggage and cargos at airports across the country to help safeguard the nation’s aviation infrastructure.

“Explosives like TNT and PETN are very hard to detect because of their extremely low vapor pressure, typically only a few molecules per billion air molecules at room temperature,” says Abhishek Kumar, a physics graduate student involved in the project at the Center for Advanced Materials (CAM). “Our optical sensor can detect less than a picogram, or a trillionth of a gram, of explosive in vapor phase under room temperature in a matter of seconds.”

Physics professor and CAM Director Jayant Kumar led the sensor’s development. The group also includes Mukesh Pandey, a postdoctoral fellow at UMass Lowell who has been with Harvard Medical School since 2009.

“Our work has been funded by four-year grants from the National Science Foundation and the Army Research Lab totaling about $500,000,” says Abhishek Kumar.

Fluorescent Materials Sniff Out Explosives

To create the sensor, the team used organic fluorescent materials ߞ; such as certain kinds of dyes and semiconducting polymers ߞ; that respond to the trace elements of explosives in the air. A thin film of the organic solution is smeared on a flat surface, like a glass slide, and exposed to the air being tested. By shining ultraviolet light on the film’s surface and measuring the amount of fluorescent light emitted, it’s possible to quickly determine whether molecules of explosives have adhered to the surface.

“When exposed to TNT, for example, the intensity of the emitted light decreases. Based on the decrease in the intensity of fluorescence of the dye or polymer, one can infer the presence of this high explosive in the air sample,” says Abhishek Kumar.

The team will present its findings at the March meeting of the American Physical Society in Dallas.

Checking for Toxic Gases

Abhishek Kumar says the sensing technology can be used for other applications such as detecting toxic gases in mines, factories and accident sites.

“The fundamental concept is very versatile,” he says. “Based on the nature of the toxic gas, one can choose the appropriate film material to get a specific response.”

The group is investigating other polymeric materials and is planning to develop a small commercial device with multiple sensors that would help minimize the chances of false alarms.

“The polymer film can be mass-produced and distributed broadly at low cost, bringing enhanced explosives-detection capability to airports around the world,” he says.

Prof. Jayant Kumar, right, with graduate students Abhishek Kumar, center, and Mukesh Pandey.