A laser sensor could detect even the tiniest trace of explosives, giving bomb sniffing dogs some tough competition.
Researchers at University of California - Berkeley found a way to significantly increase the sensitivity of light-based plasma sensors in detecting small quantities of explosives.
The findings were published in the July 20 edition of the journal Nature Nanotechnology.
The research team put the sensor to the test with a number of explosives including 2,4-dinitrotoluene (DNT), ammonium nitrate and nitrobenzene. They found the device could detect these chemicals in the air in concentrations as small as "0.67 parts per billion, 0.4 parts per billion and 7.2 parts per million, respectively," the university reported. This is an impressive improvement to current optical sensors.
"Optical explosive sensors are very sensitive and compact," said study leader Xiang Zhang, UC Berkeley professor of mechanical engineering. "The ability to magnify such a small trace of an explosive to create a detectable signal is a major development in plasmonsensor technology, which is one of the most powerful tools we have today."
The new method could have advantages over current explosive-detection methods such as bomb sniffing dogs.
"Bomb-sniffing dogs are expensive to train, and they can become tired," said study co-lead author Ren-Min Ma, an assistant professor of physics at Peking University.. "The other thing we see at airports is the use of swabs to check for explosive residue, but those have relatively low-sensitivity and require physical contact. Our technology could lead to a bomb-detecting chip for a handheld device that can detect the tiny-trace vapor in the air of the explosive's small molecules."
The semiconductors are smaller than most commercial explosive detectors; they are made of a layer of cadmium sulfide along with a semiconductor and a sheet of silver and magnesium sulfide. The device works by detecting the increased intensity of light signals that occur when molecules in chemicals such as TNT react with defects on the surface of the semiconductor.
Because of these features the researchers hope the plasmon laser could detect pentaerythritol tetranitrate (PETN), which is an explosive believed to be favored by terrorists. This compound is made of plastic so it often escapes detection.
"PETN has more nitro functional groups and is more electron deficient than the DNT we detected in our experiments, so the sensitivity of our device should be even higher than with DNT," Ma said.
