A tiny sensor that monitors electrical conductivity allows scientists to detect the presence of explosives. The sensor measures the conductivity of two different thin films, one made of a cobalt compound and another made of a copper compound. When reacting to most fumes, the two films respond in similar ways, but when exposed to hydrogen peroxide the films show a difference in electrical conductivity. When the sensor indicates this difference, that means that trace amounts of hydrogen peroxide are present, a common ingredient of explosives.
From terrorist bombings on the ground and in the air, TATP, a peroxide-based explosive has been used in many suicide bombings. There’s no easy way to detect the chemical in the field. But now, that is about to change.
In 2005 terrorists blew up subway trains in London using homemade bombs made of a peroxide called TATP. The same explosive shoe bomber Richard Reid tried to use to blow up an airliner in 2001.
But terrorists may soon find their bombs harder to hide. Inside a machine, a team of physicists and chemists built an electronic nose able to sniff out the explosive chemical.
No bigger than a penny, the sensor chip can detect the tiniest traces of hydrogen peroxide vapor. Normally, thin films of copper and cobalt phthalocyanine conduct the same level of electrical current when exposed to gas. But add hydrogen peroxide vapor … and copper’s current strength increases while cobalt’s decreases.
“This material that is absorbed on the chip is a peroxide,” Ivan Schuller, professor of physics at the University of California, San Diego in La Jolla, Calif., told Ivanhoe.
“About 50 or so molecules we, and others, have looked at it’s the only one that will give this opposite behavior,” William Trogler, professor of chemistry at UCSD said. Small and low-powered, it fits in a variety of packages for use by the military or homeland security.
… The chip can distinguish between types of peroxide, so your whitening toothpaste won’t raise alarms. And they’re cheap — once mass produced these sensors could be made for less than a dollar a chip. A small price to pay to save lives.
via Sniffing Out Bombs — Physicists Create Highly Sensitive Explosives Detector.