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Researchers Developing Nanotube Devices to Detect Chemical Warfare Agents

Researchers at Rensselaer Polytechnic Institute in Troy, N.Y., have been awarded a $1.3 million Nanoscale Interdisciplinary Research Team (NIRT) grant from the National Science Foundation (NSF) to further develop nanoscale chemical sensors using carbon nanotubes designed to detect toxic gases and chemical warfare agents.

"Traditionally, it could take several days to get gas analysis results back from a lab, but first responders don't have that kind of time. They need answers immediately," said Nikhil Koratkar, assistant professor of mechanical, aerospace and nuclear engineering Rensselaer and principal investigator on the project. "We are working to develop a system that alerts them to dangers in real time at the site of an emergency using a device that is battery-powered and transportable, such as a coin-sized device worn on a uniform or on a vehicle."

In 2003, the team developed a prototype sensor that demonstrated definitive identification of contaminants in real time. This new NSF grant will support research to boost the sensitivity of the device from identifying gases at concentrations of parts per hundred, as in the prototype, to parts per million, according to Koratkar. To do this, his team will examine how the size, shape and density of the nanotubes and the overall geometry of the device affects the sensitivity levels.

In the prototype, billions of carbon nanotubes sit in a silicon substrate. The sharp tips of the tubes greatly amplify the surrounding electric field, inducing ionization and electrical breakdown of gases at low voltages. All gases are classified by their different breakdown voltages – essentially, a dictionary of gas fingerprints. Once the voltage fingerprint is known, the gas can be identified. By monitoring the discharge current, it is possible to determine the gas concentration, said Koratkar.

The prototype is a breakthrough from traditional electrical-conductivity-based gas detectors, in which molecules must adsorb, or cling, to a thin film surface, thereby changing the film's electrical properties.

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