Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Magnets trump metallics

Rice University Professor Junichiro Kono, standing, and graduate student Thomas Searles set out to study interactions between magnetic fields and electrically charged particles and found that strong magnets can stop the flow of electrons through metallic single-walled carbon nanotubes. (Credit Jeff Fitlow/Rice University)
Rice University Professor Junichiro Kono, standing, and graduate student Thomas Searles set out to study interactions between magnetic fields and electrically charged particles and found that strong magnets can stop the flow of electrons through metallic single-walled carbon nanotubes. (Credit Jeff Fitlow/Rice University)

Abstract:
Magnetic fields can block conductivity of carbon nanotubes

Magnets trump metallics

Houston, TX | Posted on July 8th, 2010

Metallic carbon nanotubes show great promise for applications from microelectronics to power lines because of their ballistic transmission of electrons. But who knew magnets could stop those electrons in their tracks?

Rice physicist Junichiro Kono and his team have been studying the Aharonov-Bohm effect -- the interaction between electrically charged particles and magnetic fields -- and how it relates to carbon nanotubes. While doing so, they came to the unexpected conclusion that magnetic fields can turn highly conductive nanotubes into semiconductors.

Their findings are published online this month in Physical Review Letters.

"When you apply a magnetic field, a band gap opens up and it becomes an insulator," said Kono, a Rice professor in electrical and computer engineering and in physics and astronomy. "You are changing a conductor into a semiconductor, and you can switch between the two. So this experiment explores both an important aspect of the results of the Aharonov-Bohm effect and the novel magnetic properties of carbon nanotubes."

Kono, graduate student Thomas Searles and their colleagues at the National Institute of Standards and Technology (NIST) and in Japan successfully measured the magnetic susceptibility of a variety of nanotubes for the first time; they confirmed that metallics are far more susceptible to magnetic fields than semiconducting nanotubes, depending upon the orientation and strength of the field.

Single-walled nanotubes (SWNTs) -- rolled-up sheets of graphene -- would all look the same to the naked eye if one could see them. But a closer look reveals nanotubes come in many forms, or chiralities, depending on how they're rolled. Some are semiconducting; some are highly conductive metallics. The gold standard for conductivity is the armchair nanotube, so-called because the open ends form a pattern that looks like armchairs.

Not just any magnet would do for their experiments. Kono and Searles traveled to the Tsukuba Magnet Laboratory at the National Institute for Materials Science (NIMS) in Japan, where the world's second-largest electromagnet was used to tease a refined ensemble of 10 chiralities of SWNTs, some metallic and some semiconducting, into giving up their secrets.

By ramping the big magnet up to 35 tesla, they found that the nanotubes would begin to align themselves in parallel and that the metallics reacted far more strongly than the semiconductors. (For comparison, the average MRI machine for medical imaging has electromagnets rated at 0.5 to 3 tesla.) Spectroscopic analysis confirmed the metallics, particularly armchair nanotubes, were two to four times more susceptible to the magnetic field than semiconductors and that each chirality reacted differently.

The nanotubes were all about 0.7 to 0.8 nanometers (or billionths of a meter) wide and 500 nanometers long, so variations in size were not a factor in results by Searles. He spent a week last fall running experiments at the Tsukuba facility's "hybrid," a large-bore superconducting magnet that contains a water-cooled resistive magnet.

Kono said the work would continue on purified batches of nanotubes produced by ultracentrifugation at Rice. That should yield more specific information about their susceptibility to magnetic fields, though he suspects the effect should be even stronger in longer metallics. "This work clearly shows that metallic tubes and semiconducting tubes are different, but now that we have metallic-enriched samples, we can compare different chiralities within the metallic family," he said.

Co-authors of the paper include Yasutaka Imanaka and Tadashi Takamasu of NIMS, Tsukuba, Japan; Hiroshi Ajiki of the Photon Pioneers Center at Osaka University, Japan; and Jeffrey Fagan and Erik Hobbie, researchers at NIST, Gaithersburg, Md.

Searles conducted the majority of the research during a visit to NIMS supported in part by a National Science Foundation Partnerships for International Research and Education grant to Kono and his co-principal investigators. Other funding came from the Department of Energy Office of Basic Energy Sciences, the Robert A. Welch Foundation and the Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

Read the abstract here: prl.aps.org/abstract/PRL/v105/i1/e017403

####

For more information, please click here

Contacts:
David Ruth
Director of National Media Relations
Rice University
Houston, Texas
(W) 713-348-6327
(C) 612-702-9473

Copyright © Rice University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Basque researchers turn light upside down February 23rd, 2018

Stiffness matters February 23rd, 2018

Imaging individual flexible DNA 'building blocks' in 3-D: Berkeley Lab researchers generate first images of 129 DNA structures February 22nd, 2018

'Memtransistor' brings world closer to brain-like computing: Combined memristor and transistor can process information and store memory with one device February 22nd, 2018

Govt.-Legislation/Regulation/Funding/Policy

Imaging individual flexible DNA 'building blocks' in 3-D: Berkeley Lab researchers generate first images of 129 DNA structures February 22nd, 2018

'Memtransistor' brings world closer to brain-like computing: Combined memristor and transistor can process information and store memory with one device February 22nd, 2018

Arrowhead Receives Regulatory Clearance to Begin Phase 1 Study of ARO-AAT for Treatment of Alpha-1 Liver Disease February 22nd, 2018

Computers aid discovery of new, inexpensive material to make LEDs with high color quality February 20th, 2018

Academic/Education

Luleň University of Technology is using the Deben CT5000TEC stage to perform x-ray microtomography experiments with the ZEISS Xradia 510 Versa to understand deformation and strain inside inhomogeneous materials November 7th, 2017

Park Systems Announces the Grand Opening of the Park NanoScience Center at SUNY Polytechnic Institute November 3rd, 2017

Two Scientists Receive Grants to Develop New Materials: Chad Mirkin and Monica Olvera de la Cruz recognized by Sherman Fairchild Foundation August 16th, 2017

Moving at the Speed of Light: University of Arizona selected for high-impact, industrial demonstration of new integrated photonic cryogenic datalink for focal plane arrays: Program is major milestone for AIM Photonics August 10th, 2017

Nanotubes/Buckyballs/Fullerenes/Nanorods

Nanotube fibers in a jiffy: Rice University lab makes short nanotube samples by hand to dramatically cut production time January 11th, 2018

Touchy nanotubes work better when clean: Rice, Swansea scientists show that decontaminating nanotubes can simplify nanoscale devices January 4th, 2018

Paving the way for a non-electric battery to store solar energy: UMass Amherst scientists say a polymer chain organized like a string of Christmas lights assists energy storage December 22nd, 2017

Nanotubes go with the flow to penetrate brain tissue: Rice University scientists, engineers develop microfluidic devices, microelectrodes for gentle implantation December 19th, 2017

Discoveries

Basque researchers turn light upside down February 23rd, 2018

Histology in 3-D: New staining method enables Nano-CT imaging of tissue samples February 22nd, 2018

Developing reliable quantum computers February 22nd, 2018

Imaging individual flexible DNA 'building blocks' in 3-D: Berkeley Lab researchers generate first images of 129 DNA structures February 22nd, 2018

Announcements

Basque researchers turn light upside down February 23rd, 2018

Stiffness matters February 23rd, 2018

Histology in 3-D: New staining method enables Nano-CT imaging of tissue samples February 22nd, 2018

Developing reliable quantum computers February 22nd, 2018

Research partnerships

Basque researchers turn light upside down February 23rd, 2018

Computers aid discovery of new, inexpensive material to make LEDs with high color quality February 20th, 2018

Rutgers-Led Innovation Could Spur Faster, Cheaper, Nano-Based Manufacturing: Scalable and cost-effective manufacturing of thin film devices February 14th, 2018

Understanding brain functions using upconversion nanoparticles: Researchers can now send light deep into the brain to study neural activities February 14th, 2018

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project