May 10, 2011

MIT Nanosensor Can Detect Explosives

Researchers at MIT have created a new type of sensor that could bring homeland security to a new level.

The researchers, lead by Charles and Hilda Roddey Career Development Associate Professor of Chemical Engineer Michael Strano, developed a detector that is capable of picking up a single molecule of an explosive material.

Chemical engineers used one-atom-thick hollow cylinders made of pure carbon to create the sensors. 

These detectors are more sensitive than explosive sensors currently being used in commercial devices.  The devices used by airport security analyzed charged particles as they move through the air.

"Ion mobility spectrometers are widely deployed because they are inexpensive and very reliable. However, this next generation of nanosensors can improve upon this by having the ultimate detection limit, [detecting] single molecules of explosives at room temperature and atmospheric pressure," Strano said in a press release.

Strano's new technology uses protein fragments called bombolitins.

"Scientists have studied these peptides, but as far as we know, they've never been shown to have an affinity for and recognize explosive molecules in any way," he says.

His lab has developed carbon-nanotube sensors in recent years, including nitric oxide, hydrogen peroxide and toxic agents like nerve gas sarin. 

The team had to build a new type of microscope in order to read the sensor. 

"For a fluorescent sensor, using the intensity of the fluorescent light to read the signal is more error-prone and noisier than measuring a wavelength," Strano said in a statement.

Each nanotube-peptide combination reacts differently to different nitro-aromatic compounds.  The researchers are able to identify a unique "fingerprint" for each explosive they wish to detect by using several different nanotubes coated in different bombolitins.

"Compounds such as TNT decompose in the environment, creating other molecule types, and those derivatives could also be identified with this type of sensor," Strano said. "Because molecules in the environment are constantly changing into other chemicals, we need sensor platforms that can detect the entire network and classes of chemicals, instead of just one type."

University of California physics professor Philip Collins said the new sensor is a novel extension of Strano's previous work on carbon-nanotube sensors. 

"It's nice what they've done "” combined a couple of different things that are not sensitive to explosives, and shown that the combination is sensitive," Collins, who was not involved in this research, said in a statement.

The Institute for Soldier Nanotechnologies at MIT helped to fund the research.


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