Sniffer dog on a chip: Highly sensitive TNT detection with nanowires

Sep 15, 2010

(PhysOrg.com) -- To thwart possible terrorist attacks and to detect contamination on sites of former military installations, researchers have been concentrating their efforts in recent years on methods for the detection and analysis of explosives.

Fernando Patolsky and his team at the University of Tel Aviv have now developed a novel that detects trinitrotoluene (TNT), as well as other explosive species, with high sensitivity and without a concentration step. As the Israeli researchers report in the journal Angewandte Chemie, their detector is superior to sniffer dogs and all other previous detection methods for this explosive.

The difficulty with the detection of explosives such as TNT is their extremely low volatility. Methods available for the analysis of air samples are expensive and time-consuming, and require large, bulky instruments, laborious sample preparation, and expert handling. “There is a need for an inexpensive, miniaturizable method that allows for quick, easy, and robust high-throughput analysis in the field,” says Patolsky.

The scientists built their sensor using the principle of a nanoscale field-effect transistor. In contrast to a current-controlled classical transistor, a field-effect transistor is switched by means of an electric field. At the core of the device are made of the semiconductor silicon. These were coated with a molecular layer made from special silicon compounds that contains amino groups (NH2). TNT molecules bind to these amino groups in the form of charge-transfer complexes. The binding process involves the transfer of electrons from the electron-rich amino groups to the electron-poor TNT. This change in the charge distribution on the surface of the nanowires modulates the electric field and leads to an abrupt change in the conductivity of the nanowires, which is easily measured.

To improve the signal-to-noise ratio and thus increase the sensitivity, the scientists equipped their chip with an array of about 200 individual sensors. “We are thus able to analyze liquid and gaseous samples without prior concentration or other sample preparation at previously unattainable sensitivities,” says Patolsky. “We were able to analyze concentrations down to 0.1 ppt (parts per trillion); that is, one molecule of TNT in 10 quadrillion other molecules.” The sensor can be quickly regenerated by washing and is selective for TNT; other related molecules do not react the same way.

“We are now creating a chip based on large arrays of nanosensors chemically modified with a large number of chemical receptors, with different binding capabilities, in order to detect a whole spectrum of explosive species in parallel,” says Patolsky.

Explore further: Space-tested fluid flow concept advances infectious disease diagnoses

More information: Fernando Patolsky, Supersensitive Detection of Explosives by Silicon Nanowire Arrays, Angewandte Chemie International Edition 2010, 49, No. 38, 6830-6835, dx.doi.org/10.1002/anie.201000847

Related Stories

New method for detecting explosives

Mar 13, 2009

A group of researchers in Tennessee and Denmark has discovered a way to sensitively detect explosives based on the physical properties of their vapors. Their technology, which is currently being developed into prototype devices ...

Scientists improve explosives detection

Apr 21, 2005

MIT researchers have announced a scientific breakthrough that could greatly improve explosives detection for military and civilian security applications. Scientists have developed a new polymer that greatly inc ...

Plastic laser detects tiny amounts of explosives

Jun 08, 2010

(PhysOrg.com) -- Detecting hidden explosives is a difficult task but now researchers in the UK have developed a completely new way of detecting them, with a laser sensor capable of detecting molecules of explosives ...

Recommended for you

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Sanescience
not rated yet Sep 16, 2010
Awesome. Its not real time x-ray molecular holographics but that's gonna take time as they figure out how to miniaturize the one (and only) they built at Stanford.

http://www.huffin...350.html

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...