Featured Research

from universities, journals, and other organizations

Spin Control: New Technique Sorts Nanotubes By Length

Date:
May 20, 2008
Source:
National Institute of Standards and Technology
Summary:
Researchers have reported a new technique to sort batches of carbon nanotubes by length using high-speed centrifuges. The technique should be easy to scale to industrial quantities for a variety of nanotube applications where length is an important factor.

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

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.

Related Articles


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.


Story Source:

The above story is based on materials provided by National Institute of Standards and Technology. Note: Materials may be edited for content and length.


Journal Reference:

  1. J.A. Fagan, M.L. Becker, J. Chun and E.K. Hobbie. . Advanced Materials. 2008. 20. 1609--1613. http://dx.doi.org/10.1002/adma.200702353 [link]

Cite This Page:

National Institute of Standards and Technology. "Spin Control: New Technique Sorts Nanotubes By Length." ScienceDaily. ScienceDaily, 20 May 2008. <www.sciencedaily.com/releases/2008/05/080516164819.htm>.
National Institute of Standards and Technology. (2008, May 20). Spin Control: New Technique Sorts Nanotubes By Length. ScienceDaily. Retrieved December 21, 2014 from www.sciencedaily.com/releases/2008/05/080516164819.htm
National Institute of Standards and Technology. "Spin Control: New Technique Sorts Nanotubes By Length." ScienceDaily. www.sciencedaily.com/releases/2008/05/080516164819.htm (accessed December 21, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Sunday, December 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Building Google Into Cars

Building Google Into Cars

Reuters - Business Video Online (Dec. 19, 2014) Google's next Android version could become the standard that'll power your vehicle's entertainment and navigation features, Reuters has learned. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
AP Review: Nikon D750 and GoPro Hero 4

AP Review: Nikon D750 and GoPro Hero 4

AP (Dec. 19, 2014) What to buy an experienced photographer or video shooter? There is some strong gear on the market from Nikon and GoPro. The AP's Ron Harris takes a closer look. (Dec. 19) Video provided by AP
Powered by NewsLook.com
Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Buzz60 (Dec. 19, 2014) A double-amputee makes history by becoming the first person to wear and operate two prosthetic arms using only his mind. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins