Event Description
Paola Barbara, PhD, associate professor, Department of Physics, Georgetown University
Single-walled carbon nanotubes are seamless molecular cylinders that are either metallic or semiconducting nanowires. The conductance of a semiconducting nanotube can be tuned by applying a voltage to a nearby gate electrode, providing a one-dimensional field-effect transistor at the nanometer scale.
These transistors are very sensitive detectors: Their electrical properties vary strongly when they are exposed to chemicals. After the first experiments about 14 years ago, where high sensitivity to NH3 (monitored in farms and industries) and NO2 (an air pollutant from motor vehicle exhaust and other combustion sources) was discovered [1], a strong sensitivity to many other molecules, including oxygen, methane, alcohol vapor and proteins, has also been reported.
The cause of the change in electrical properties is still unclear. One possibility is that molecules bind to the surface of the nanotubes and charge transfer occurs between the nanotube and the molecules. A second possibility is a change of the barriers for electrical transport at the interface between the nanotube and the electrical contacts. Understanding the mechanism that causes the response of devices made with single nanotubes or nanotube networks is an essential step for the design of efficient sensors.
Barbara will discuss experimental methods they recently developed to determine the gas sensing mechanism [2,3].
References:
[1] J. Kong, N. R. Franklin, C. Zhou, M. G. Chapline, S. Peng, K. Cho, and H. Dai, Science 287, 622 (2000).
[2] J. Zhang, A. Boyd, A. Tselev, M. Paranjape, and P. Barbara, Appl. Phys. Lett. 88, 123112 (2006).
[3] A. K. Boyd, I. Dube, G. Fedorov, M. Paranjape, and P. Barbara, Carbon (in press). |