Polymers may lead the way to detecting explosives more easily, claim researchers in the US.

Luminescent polymers could be used as sensors for trinitrotoluene (TNT), an explosive often used in bombs, according to William Trogler and Sarah Toal from the University of California in San Diego, US.

When a molecule of an explosive, such as TNT, binds to a polymer it can 'turn off' the luminescence of the polymer. This change can be used to sense very low concentrations of explosives. For example, Trogler has made a silicon-containing polymer that glows blue or green under illumination with a UV light, and dims in the presence of TNT. This could be used to detect trace explosives left by the fingerprints of a bomb maker, he said.

Timothy Swager, a chemical sensors expert from Massachusetts Institute of Technology, US said 'the amplifying properties of electronic polymers enable a number of new methods for explosive detection, the most significant of which is ultra-trace vapor detection of low volatility materials.  Electronic polymers are now delivering new capabilities for military and homeland security that were presently only possible through the use of trained canines.'

Before these sensors can be made into a useable device, more work is needed to reduce the cost and increase its sensitivity, said Trogler. 'We are looking at ways to incorporate specific reactive groups into the sensing polymer to distinguish different classes of explosives. It is humbling for researchers that the dog remains the most versatile sensing system. I'd swear that my golden retriever can selectively detect a single cheese molecule at 100 feet!'

Ruth Needham