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