Turmeric can be a 'cheap sensor for explosives'

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 spectroscopy" is already employed in a wide array of sensing and analysis techniques.

Illuminating some chemicals causes them to re-emit light of a different colour, sometimes for extended periods -- an effect exploited in, for example, glow-in-the-dark materials.
The intensity of this re-emitted light can change if different molecules bind to the fluorescent 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 throughout 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 was 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.

But curcumin's helpful optical properties only worked when it was dissolved in a liquid; when evaporated to a solid, it clumped together and the fluorescence stopped.
The researchers then hit on the idea of using a polymer called polydimethylsiloxane, which is thick and viscous at room temperature, 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.

In tests, the films can currently detect explosive levels down to 80 parts per billion, but the researchers said that for hgh-sensitivity applications like mine detection, they needed to increase the sensitivity further, by adjusting the chemical groups attached to curcumin.
The team is in talks with a firm to develop the technique into a portable detector device.