Sunday, March 27, 2011

Spice can be a cheap sensor for explosives

Turmeric, one of the most popular spices, contains a chemical that could be the basis for cheap explosives detectors, a new study has claimed.

A team led by an Indian scientist found that the curcumin molecule, which is known for its anti-cancer and anti-oxidant properties, could replace more complex solutions to spot explosives like TNT, the BBC News reported.

Dr Abhishek Kumar of the University of Massachusetts and his colleagues, who presented their findings at the American Physical Society meeting, said the light-emitting properties of the curry ingredient changes when it gathers molecules of explosive material in air. This "fluorescence apectroscopy" is already employed in a wide array of sensing and analysis techniques.

Illuminating some chemicals causes them to re-emit light of a different color, sometimes for extended periods. The intensity of this re-emitted light can change if different molecules bind to the fluoorescent ones, and that is how sensing techniques can exploit the effect, Kumar said.

"If you have a gram of TNT and you sample a billion air molecules from anywhere in the room, you'll find four or five molecules of TNT - that's the reason they're so hard to detect," Kumar told the conference. "And, the US State Department estimates there are about 60 to 70 million land mines througout the the world; we need a very portable, field-deployable sensing device which is cheap, very sensitive,and easy to handle."

A curcumin-based mine detector could outperform the animal version, he claimed.

Kumar and his team were investigating the use of curcumin for biological applications, trying to make it easily dissolve in water, when they hit on the idea of making use of its optical properties. The team's first trick was to use a chemical reaction to attach "side groups" to the curcumin that preferentially bind to explosive molecules.

The researchers then hit on the idea of using a polymer called polydimethylsiloxane, spinning the mixture on glass plates to make extremely thin films. The idea would be to use an inexpensive light source - the team uses LEDs - shone on to the thin films, detecting the light they then put off. In the presence of explosives, the light would dim.

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