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March
31, 2003 |
Carbon Nanotubes Prove Sensitive to the
Elements
Saroj Nayak is one of the few researchers in the
country studying how molecules affect the electrical conductivity
of single-walled carbon nanotubes. Understanding what molecules
increase or decrease nanotube conductivity is key in the development
of ultra-sensitive devices that could detect the slightest traces
of air-borne toxins such as anthrax or pollutants in drinking
water.
Nayak, assistant professor of physics, has found
that exposing nanotubes to minute traces of water substantially
decreases the nanotubes’ electrical current, while exposure
to oxygen increases the current.
Such research could lead to better sensors in
water monitors. The nanotubes in such a device, for instance,
would have few electrical properties in normal drinking water.
But when the sensor is exposed to a toxic element, an electrical
current would trigger an alarm.
On the other hand, such a sensor could depend
on a decrease of electrical current to operate. In that case,
a device could shut down a water-supply system if a biological
or chemical agent were present. Research is under way to study
how the nanotubes react with carbon monoxide and ammonia.
“Consider that billions of nanotubes could
fit inside a sensor the size of a fingertip,” Nayak says.
“That and the fact the nanotube conductivity is extremely
sensitive to foreign molecules makes such sensors hundreds of
times more sensitive than what is currently available.”
Nayak, still perfecting the simulations, says
the biggest challenge is distinguishing one molecule from another
based on a nanotube’s electrical current. For example, an
ammonia and a water molecule could both affect the nanotube’s
electrical current the same way.
Nayak’s findings were reported in the journal
of Applied Physics Letters and his research is supported
by the American Chemical Society. Pulickel Ajayan, professor of
materials science and engineering at Rensselaer, graduate student
Yiming Zhang, and postdoctoral associate Ranjit Pati are on Nayak’s
research team.
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