Nanotubes spark gas detector

Researchers from Rensselaer Polytechnic Institute have found a way to use carbon nanotubes to make very small, sensitive gas detectors.

Carbon nanotubes are rolled-up sheets of carbon atoms. The researchers use multi-walled nanotubes that measure 25 to 30 nanometers in diameter. A nanometer is one millionth of a millimeter.

Ionization detectors identify gases by fingerprinting their distinct ionization, or break-down characteristics. Its usually takes large amounts of heat, light or voltage to ionize gas molecules. As a result, ionization detectors are relatively large machines. They also usually work in conjunction with gas chromatography equipment that separates components of a mixture.

The researchers found that the way the tip of a nanotube curves makes it possible to amplify an electric field by many orders of magnitude compared to typical electronics. This enabled them to use the voltage provided by off-the-shelf batteries to break down tiny amounts of gas. The researchers' prototype uses an array of multiwalled carbon nanotubes separated from an electrode by 25 microns, which is about five times the width of a red blood cell.

The sensor arrays could be used practically in one to two years, according to the researchers. The work appeared in the July 9, 2003 issue of Nature.