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 What the world's tiniest 'monster truck' reveals
23.08.2017 | American Chemical Society

nachricht Treating arthritis with algae
23.08.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

What the world's tiniest 'monster truck' reveals

23.08.2017 | Life Sciences

Treating arthritis with algae

23.08.2017 | Life Sciences

Witnessing turbulent motion in the atmosphere of a distant star

23.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>