Using carbon nanotubes, MIT chemical engineers have built what they say is the most sensitive electronic detector yet for sensing deadly gases such as the nerve agent sarin. Sarin, which killed 12 people in a 1995 terrorist attack on the Tokyo subway, can kill at very low concentrations — in just parts per million — after 10 minutes, so highly sensitive detection is imperative to save lives. The new detector is far more sensitive than needed to detect lethal doses.

The technology, which can also be employed to detect mustard gas, ammonia and VX nerve agents, has the potential to be used as a low-cost, low-energy device that could be carried in a pocket or deployed inside a building to monitor hazardous chemicals.

"We think this could be applied to a variety of environmental and security applications," said Michael Strano, the Charles and Hilda Roddey Associate Professor of Chemical Engineering and senior author of a paper describing the work published this week in the online edition of "Angewandte Chemie."

To build their super-sensitive detector, Strano and his team used an array of carbon nanotubes aligned across microelectrodes. Each tube consists of a single-layer lattice of carbon atoms, rolled into a long cylinder with a diameter about 1/50,000 the width of a human hair, which acts as a molecular wire.

The nanotube sensors require very little power — about 0.3 milliwatt. One sensor could run virtually forever on a regular battery.

When a particular gas molecule binds to the carbon nanotube, the tube's electrical conductivity changes. Each gas affects conductivity differently, so gases can be identified by measuring the conductivity change after binding.

The work was funded by the Department of Homeland Security under contract to the Federal Aviation Administration and MIT's Institute of Soldier Nanotechnology.

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