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Gas sensor uses nanotube parts

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1:36pm, July 15, 2003
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Ever since the discovery of carbon nanotubes in 1991, scientists have been trying to put the tiny cylinders to work. Now, researchers have incorporated them into a gas sensor for potential uses that range from environmental monitoring at chemical plants to the detection of chemical weapons.

The device includes an electrode made from an array of carbon nanotubes that produces a strong electric field. Gas molecules subject to this field become charged, or ionized.

The specific voltage needed to ionize a particular gas is an identifying signature, says Nikhil Koratkar of Rensselaer Polytechnic Institute in Troy, N.Y. By measuring the electric current produced during the gas' ionization, the device can also determine the amount of gas present.

In the July 10 Nature, Koratkar and his colleagues report that their sensor identified a number of gases, including ammonia, argon, nitrogen, oxygen, and carbon dioxide–even when a gas was mixed with air.

Previously, sensors that use an electric field to ionize gases haven't been practical. They're bulky and unsafe, requiring high voltages to produce sufficient fields, says Koratkar. In comparison, carbon nanotubes' sharp tips need little voltage to produce a very strong field. Sensors based on them could be battery powered, safe, fast, and portable, Koratkar says.

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