Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Spin Control: New Technique Sorts Nanotubes by Length

In a schematic of NIST's length separation technique for carbon nanotubes (l.), the nanotubes start at the bottom of a dense fluid. When spun in a centrifuge, the nanotubes begin to migrate through the fluid driven by their buoyancy, but the longer ones move faster, spreading them out by length. Photos (r.) shows a typical sample at the start and after 94 hours of spinning at 1257 radians per second (roughly 12,000 RPM).

Credit: NIST
In a schematic of NIST's length separation technique for carbon nanotubes (l.), the nanotubes start at the bottom of a dense fluid. When spun in a centrifuge, the nanotubes begin to migrate through the fluid driven by their buoyancy, but the longer ones move faster, spreading them out by length. Photos (r.) shows a typical sample at the start and after 94 hours of spinning at 1257 radians per second (roughly 12,000 RPM).

Credit: NIST

Abstract:
Researchers at the National Institute of Standards and Technology (NIST) have reported* a new technique to sort batches of carbon nanotubes by length using high-speed centrifuges. Many potential applications for carbon nanotubes depend on the lengths of these microscopic cylinders, and one of the most important features of the new technique, say the scientists, is that it should be easily scalable to produce industrial quantities of high-quality nanotubes.

Spin Control: New Technique Sorts Nanotubes by Length

GAITHERSBURG, MD | Posted on May 13th, 2008

So-called single wall carbon nanotubes (SWCNTs) are essentially sheets of carbon atoms only one atom thick that have rolled themselves into tubes with a diameter of approximately one nanometer. They have unique combinations of thermal, mechanical, optical and electronic properties that suggest a wide variety of uses, including circuit elements in molecular electronics, fluorescent tags for diagnostic and therapeutic applications in medicine and light sources for compact, efficient flat-panel displays, among many others.

Unfortunately, the methods for manufacturing carbon nanotubes always create a large percentage of nanojunk in the mix—clumps of carbon, ordinary soot, particles of metal used as a catalyst—and nanotubes come in an enormous range of lengths, from a few tens or hundreds, up to thousands of nanometers. Refining the lot is essential for most uses. For many potential applications, nanotubes need to be separated by length. In biomedical applications, for example, it has been shown that whether or not nanotubes are taken up in cells depends critically on length (see "Study: Cells Selectively Absorb Short Nanotubes.") Nanotubes used as components in future microcircuits obviously need to fit in place, and in optical applications, a nanotube's length determines how strongly it will absorb or emit light (see "Longer is Better for Nanotube Optical Properties.")

In 2006, researchers found that you could separate nanotubes by "chirality" (a measure of the twist in the carbon atom sheet) by spinning them in a dense fluid in an ultracentrifuge tube because of a relationship between chirality and buoyancy. In this new work, a team of NIST researchers demonstrated that a variation of the same technique can separate nanotubes by length. They showed that while the nanotubes ultimately will move to a point of equilibrium in the centrifuge tube dictated by their buoyancy, due to friction they will move at different rates depending on their lengths.

"When we spin the centrifuge, it turns out that the longer ones move faster. We basically just run a race and the longer ones move farther in the same amount of time," says researcher Jeffrey Fagan, "Eventually they get separated enough in position that we can just pull off layers and get different lengths."

What's particularly exciting, they say, is that while other techniques have been shown to sort nanotubes by length, this is the first approach that could be scaled up to produce commercially important quantities of nanotubes in a given length range. The process also removes much of unwanted junk—particularly metal particles—from the batch. NIST has applied for a patent on the process.

* J.A. Fagan, M.L. Becker, J. Chun and E.K. Hobbie. Length fractionation of carbon nanotubes using centrifugation. Advanced Materials. 2008. 20. 1609-1613.

####

About NIST
From automated teller machines and atomic clocks to mammograms and semiconductors, innumerable products and services rely in some way on technology, measurement, and standards provided by the National Institute of Standards and Technology.

Founded in 1901, NIST is a non-regulatory federal agency within the U.S. Department of Commerce. NIST's mission is to promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.

For more information, please click here

Contacts:
Michael Baum

(301) 975-2763

Copyright © NIST

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

Collaboration yields discovery of 12-sided silica cages June 20th, 2018

JPK talks with Dr Frank Lafont, Director of the BioImaging Center Lille (BICeL) about the use of the NanoWizard® AFM together with fluorescence microscopy in the study of living cells June 19th, 2018

Powering the 21st Century with Integrated Photonics: UCSB-Led Team Selected for Demonstration of a Novel Waveguide Platform Which is Transparent Throughout the MWIR and LWIR Spectral Bands June 19th, 2018

Executives Explore Key Megatrends and Innovations in MEMS, Sensors, Imaging Tech at SEMI-MSIG European Summits: Speakers to share developments in smart automotive, smart cities, smart industrial, biomedical, consumer and IoT, September 19-21, 2018 in Grenoble, France June 19th, 2018

Nanotubes/Buckyballs/Fullerenes/Nanorods

Nano-saturn: Supramolecular complex formation: Anthracene macrocycle and C60 fullerene June 8th, 2018

Unzipping graphene nanotubes into nanoribbons: New study shows elegant mathematical solution to understand how the flow of electrons changes when carbon nanotubes turn into zigzag nanoribbons June 6th, 2018

Making carbon nanotubes as usable as common plastics: Researchers discover that cresols disperse carbon nanotubes at unprecedentedly high concentrations May 15th, 2018

'Exceptional' research points way toward quantum discoveries: Rice University scientists make tunable light-matter couplings in nanotube films April 30th, 2018

Discoveries

Collaboration yields discovery of 12-sided silica cages June 20th, 2018

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Camouflaged nanoparticles used to deliver killer protein to cancer June 17th, 2018

Squeezing light at the nanoscale: Ultra-confined light could detect harmful molecules June 17th, 2018

Announcements

Collaboration yields discovery of 12-sided silica cages June 20th, 2018

JPK talks with Dr Frank Lafont, Director of the BioImaging Center Lille (BICeL) about the use of the NanoWizard® AFM together with fluorescence microscopy in the study of living cells June 19th, 2018

Powering the 21st Century with Integrated Photonics: UCSB-Led Team Selected for Demonstration of a Novel Waveguide Platform Which is Transparent Throughout the MWIR and LWIR Spectral Bands June 19th, 2018

Executives Explore Key Megatrends and Innovations in MEMS, Sensors, Imaging Tech at SEMI-MSIG European Summits: Speakers to share developments in smart automotive, smart cities, smart industrial, biomedical, consumer and IoT, September 19-21, 2018 in Grenoble, France June 19th, 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