Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Chemists ID process to sort carbon nanotubes by electronic properties

12.09.2003


Rice, UIUC researchers find way to separate metallic, non-metallic nanotubes



Researchers at Rice University and the University of Illinois at Urbana-Champaign have discovered the first method to chemically select and separate carbon nanotubes based on their electronic structure. The new process, described in the Sept. 12 issue of Science magazine, represents a fundamental shift in the way scientists think about the chemistry of carbon nanotubes.

"Other than low-cost mass production, there’s no bigger hurdle to overcome in carbon nanotechnology than finding a reliable, affordable means of sorting single-walled carbon nanotubes," said Richard Smalley, University Professor and director of Rice’s Carbon Nanotechnology Laboratory. "If we can develop new technology based on electronic sorting and reliably separate metallic nanotubes from semi-metallic and semi-conducting varieties, we’ll have a terrific tool for nanoscience."


James Tour, Chao Professor of Chemistry, said, "The utility of specific carbon nanotubes, based upon their precise electronic characteristics, could be an enormous advance in molecular electronics. Until now, everyone had to use mixtures of nanotubes, and by process of elimination, select the desired device characteristics afforded from a myriad of choices. This could now all change since there is the possibility of generating homogeneous devices."

All single-walled carbon nanotubes are not created equal. There are 56 varieties, which have subtle differences in diameter or physical structure. Slight as they are, these physical differences lead to marked differences in electrical, optical and chemical properties. For example, about one-third are metals, and the rest are semiconductors.

Although carbon nanotubes have been proposed for myriad applications -- from miniature motors and chemical sensors to molecule-size electronic circuits -- their actual uses have been severely limited, in part because scientists have struggled to separate and sort the knotted assortment of nanotubes that result from all methods of production.

As a post-doctoral researcher in Smalley’s laboratory, Michael Strano, now a professor of chemical and biomolecular engineering at Illinois, developed a technique for breaking up bundles of nanotubes and dispersing them in soapy water. In the present work, Strano and his graduate students, Monica Usrey and Paul Barone, teamed up with Tour and his postdoctoral researcher Christopher Dyke to apply reaction chemistry to the surfaces of nanotubes in order to select metallic tubes over semiconductors.

To control nanotube chemistry, the researchers added water-soluble diazonium salts to nanotubes suspended in an aqueous solution. The diazonium reagent extracts an electric charge and chemically bonds to the nanotubes under certain controlled conditions.

By adding a functional group to the end of the reagent, the researchers can create a "handle" that they can then use to selectively manipulate the nanotubes. There are different techniques for pulling on the handles, including chemical deposition and capillary electrophoresis.

"The electronic properties of nanotubes are determined by their structure, so we have a way of grabbing hold of different nanotubes by utilizing the differences in this electronic structure," Strano said. "Because metals give up an electron faster than semiconductors, the diazonium reagent can be used to separate metallic nanotubes from semiconducting nanotubes."

The chemistry is reversible. After manipulating the nanotubes, the scientists can remove the chemical handles by applying heat. The thermal treatment also restores the pristine electronic structure of the nanotubes.

"Until now, the consensus has been that the chemistry of a nanotube is dependent only on its diameter, with smaller tubes being less stable and more reactive," Strano said. "But that’s clearly not the case here. Our reaction pathways are based on the electronic properties of the nanotube, not strictly on its geometric structure. This represents a new paradigm in the solution phase chemistry of carbon nanotubes."


###
The research was funded by the National Science Foundation, NASA, the Air Force Office of Scientific Research, and the Office of Naval Research.

The paper, titled, "Selectivity of Electronic Structure in the Functionalization of Single Walled Carbon Nanotubes," appears in this week’s issue of Science. Strano and Dyke co-wrote the paper with Smalley, Tour, Usrey, Barone, Rice undergraduate Mathew J. Allen, Research Assistant Hongwei Shan, Research Scientist Carter Kittrell, and Senior Faculty Fellow Robert H. Hauge.

Jade Boyd | EurekAlert!
Further information:
http://chico.rice.edu/

More articles from Life Sciences:

nachricht Polymers Based on Boron?
18.01.2018 | Julius-Maximilians-Universität Würzburg

nachricht Bioengineered soft microfibers improve T-cell production
18.01.2018 | Columbia University School of Engineering and Applied Science

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Polymers Based on Boron?

18.01.2018 | Life Sciences

Bioengineered soft microfibers improve T-cell production

18.01.2018 | Life Sciences

World’s oldest known oxygen oasis discovered

18.01.2018 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>