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David Bradley ISSUE #66
June 2007
Lengthy Nanobelts
Ling Zang

Think of nanotechnology and the first thing that strikes you is the amazingly small sizes involved. The building blocks of this fledgling technology are usually measured in billionths of a meter, with units linking together to make super-structures that barely measure up to the width of a human hair or the period at the end of this sentence. Now, scientists at Southern Illinois University have stretched the notion of nanotechnology to design and synthesize a range of nanoscopic belts that almost sound big. Their nanobelts are about one millimeter long, the thickness of a dime.

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So, why are Ling Zang and his students at SIUC expanding their nanobelts? In the June 13 issue of the Journal of the American Chemical Society, they explain that this feat will facilitate the construction of integrated nanoelectronic devices, such as gas sensors. Connecting the nanoscopic to the microscopic and then to the everyday world of the macroscopic is a major obstacle for the realization of nanotechnology. Relatively long lengths of "wire" could be crucial to bridging the gaps between nanoscopic sub-units, electrodes, and other electronic components.

Zang's nanobelts are composed of electrically conductive perylene tetracarboxylic diimide an organic molecule that the team has modified to enable a self-assembly process, in which one form of the material spontaneously links together to form the long nanobelts; all of uniform size. The researchers explain that with the nanobelts it would seem ideal for a broad range of electronic applications.

"The millimeter-long nanobelts we have successfully fabricated will enable the more convenient construction of integrated nanoelectronic devices, where deposition of a wire across multiple parallel electrodes is usually demanded," Zang told Reactive Reports. He points out that two-electrode devices that have already been employed in photonic and gas sensors using long nanowires will be improved by removing the need to fabricate electrodes with a submicrometer gap. This step requires sophisticated photolithographic methods. "We have demonstrated with the long PTCDI nanobelt that a pair of electrodes separated by as much as 80 micrometers can be used to construct a gas sensor device." Such a device would be less susceptible to the presence of tiny amounts of impurities or dust when detecting a target gas molecule, such as an industrial chemical leak, illicit drug smuggling, or even a chemical weapons agent.

J Am Chem Soc, 2007, 129, 7234-7235