 An inexpensive sensor detects peroxide-based explosives.
What’s no bigger than a penny, but capable of sniffing out the most common form of homemade explosives? A new sensor chip developed at UC San Diego.
The inexpensive sensor detects trace amounts of hydrogen peroxide, a chemical used in the most common form of homemade explosives, and could have widespread applications in monitoring the toxic hydrogen peroxide vapors from bleached pulp and other products to which factory workers are exposed. It can detect hydrogen peroxide vapor in the parts-per-billion range from peroxide-based explosives, such as those used in the 2005 bombing of the London transit system.
“The detection capability of this tiny electronic sensor is comparable to current instruments, which are large, bulky and cost thousands of dollars each,” says William Trogler, a professor of chemistry and biochemistry at UCSD and one of its inventors. “If this device were mass produced, it’s not inconceivable that it could be made for less than a dollar.”
The device was invented by a team led by Trogler; Andrew Kummel, a professor of chemistry and biochemistry; and Ivan Schuller, a professor of physics. Much of the research to develop the sensor was done by UCSD chemistry and physics graduate students Forest Bohrer, Corneliu Colesniuc and Jeongwon Park. The invention and operation of the sensor is detailed in a recent issue of the <I>Journal of the American Chemical Society<I>.
- Kim McDonald
Terrorist Traces
UC San Diego chemists have discovered how to catch bombers on film. Professor William Trogler and graduate student Jason Sanchez have shown that dark shadows on a glowing film can reveal traces of dangerous explosives. They have developed fluorescent polymers that emit blue light when placed under an ultraviolet lamp, and demonstrated that nitrogen-based explosives quench that glow, leaving tell-tale marks where the film has been touched by contaminated fingers.
Because the films fluoresce brightly, no special instruments are needed to read the results, which emerge within 30 seconds, as soon as the solvents dry. Even a very thin film sprayed on a suspect surface can detect the presence of minute amounts of some explosives, as little as a few trillionths of a gram. Handling explosives can leave 1,000 times that quantity or more stuck to fingers or vehicles.
Exposure to ultraviolet light for an extra minute or two alters one of the films so that traces of one class of explosives called nitrate esters begin to glow green, a property that could provide evidence to help solve a crime, or prevent one.
The spray-on films will be the basis of devices that can be used with little training to quickly detect dangerous chemicals in the field. UCSD has licenced the technology RedXDefense, a security systems company, which has developed a portable kit based on the idea.
- Susan Brown
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