Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Chemists ID process to sort carbon nanotubes by electronic properties


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:

More articles from Life Sciences:

nachricht Biologists unravel another mystery of what makes DNA go 'loopy'
16.03.2018 | Emory Health Sciences

nachricht Scientists map the portal to the cell's nucleus
16.03.2018 | Rockefeller University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>