Featured Research

from universities, journals, and other organizations

'Two-faced' Bioacids Put A New Face On Carbon Nanotube Self-assembly

Date:
January 17, 2009
Source:
National Institute of Standards and Technology (NIST)
Summary:
Researchers have demonstrated an inexpensive way to induce carbon nanotubes to "self-assemble" in long, regular strands, a useful technique for studying nanotube properties and potentially a new way to assemble nanotube-based devices.

Single wall carbon nanotubes enclosed in bile acid shells self assembled into a sheaf of long ordered fibrils each composed of several nanotube rods. Treating the microscope slide with a hydrophobic compound causes the fibrils to cluster like this at specific sites, probably at defects in the hydrophobic surface.
Credit: NIST

Nanotubes, the tiny honeycomb cylinders of carbon atoms only a few nanometers wide, are perhaps the signature material of modern engineering research, but actually trying to organize the atomic scale rods is notoriously like herding cats. A new study from the National Institute of Standards and Technology (NIST) and Rice University, however, offers an inexpensive process that gets nanotubes to obediently line themselves up—that is, self-assemble—in neat rows, more like ducks.

A broad range of emerging electronic and materials technologies take advantage of the unique physical, optical and electrical properties of carbon nanotubes, but most of them—nanoscale conductors or “nanowires,” for instance—are predicated on the ability to efficiently line the nanotubes up in some organized arrangement. Unfortunately, just mixed in a solvent, the nanotubes will clump together in a black goo. They can be coated with another molecule to prevent clumping—DNA is sometimes used—but spread the mixture out and dry it and you get a random, tangled mat of nanotubes. There have been a variety of mechanical approaches to orienting carbon nanotubes on a surface, but a more elegant and attractive solution would be to get them to do it themselves—self assembly.

NIST researchers studying better ways to sort and purify carbon nanotubes to prepare standard samples of the material were using a bile acid* to coat the nanotubes to prevent clumping. “Bile acids,” says NIST research chemist Erik Hobbie, “are biological surfactants, and like most surfactants they have a part that likes water and a part that doesn’t. This is a slightly complex surfactant because instead of having a head and a tail, the usual geometry, it has two faces, one that likes water and one that doesn’t.” Mixed in water, such hydrophobic/hydrophilic molecules normally want to group together in hollow spheres with their hydrophobic “tails” sheltered on the inside, Hobbie explains, but the two-faced geometry of this bile acid makes it form hollow rod shapes instead. Conveniently, the hollow rods can house the rod-shaped nanotubes.

As it turns out, there’s a bonus. Over the course of about a day, the bile acid shells cause the nanotubes to begin lining up, end to end, in long strands, and then the strands begin to join together in twisted filaments, like a length of twisted copper wire. The discovery is a long way from a perfect solution for ordering nanotubes, Hobbie cautions, and a lot of development remains to be done. For one thing, ideally, the bile acid shells would be removed after the nanotubes are in their ordered positions, but this has proven difficult. And the surfactant is toxic to living cells, which precludes most biomedical applications unless it is removed. On the other hand, he says, it already is an easy and extremely inexpensive technique for researchers interested in studying, for example, optical properties of carbon nanotubes. “It gives a recipe for how to create ordered, aligned arrangements of individual carbon nanotubes. You don’t need to use any external magnetic or electrical fields, and you don’t need to dry the tubes out in a polymer and heat it up and stretch it. You can get fairly significant regions of very nice alignment just spontaneously through this self assembly.”

* Sodium deoxycholate.


Story Source:

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


Journal Reference:

  1. Hobbie et al. Self-Assembly of Ordered Nanowires in Biological Suspensions of Single-Wall Carbon Nanotubes. ACS Nano, 2008; 0 (0): 081219164213075 DOI: 10.1021/nn800609y

Cite This Page:

National Institute of Standards and Technology (NIST). "'Two-faced' Bioacids Put A New Face On Carbon Nanotube Self-assembly." ScienceDaily. ScienceDaily, 17 January 2009. <www.sciencedaily.com/releases/2009/01/090113174546.htm>.
National Institute of Standards and Technology (NIST). (2009, January 17). 'Two-faced' Bioacids Put A New Face On Carbon Nanotube Self-assembly. ScienceDaily. Retrieved April 21, 2014 from www.sciencedaily.com/releases/2009/01/090113174546.htm
National Institute of Standards and Technology (NIST). "'Two-faced' Bioacids Put A New Face On Carbon Nanotube Self-assembly." ScienceDaily. www.sciencedaily.com/releases/2009/01/090113174546.htm (accessed April 21, 2014).

Share This



More Matter & Energy News

Monday, April 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Why Did Nike Fire Most Of Its Nike FuelBand Team?

Why Did Nike Fire Most Of Its Nike FuelBand Team?

Newsy (Apr. 19, 2014) Nike fired most of its Digital Sport hardware team, the group behind Nike's FuelBand device. Could Apple or an overcrowded market be behind layoffs? Video provided by Newsy
Powered by NewsLook.com
Small Reactors Could Be Future of Nuclear Energy

Small Reactors Could Be Future of Nuclear Energy

AP (Apr. 17, 2014) After the Fukushima nuclear disaster, the industry fell under intense scrutiny. Now, small underground nuclear power plants are being considered as the possible future of the nuclear energy. (April 17) Video provided by AP
Powered by NewsLook.com
Horseless Carriage Introduced at NY Auto Show

Horseless Carriage Introduced at NY Auto Show

AP (Apr. 17, 2014) An electric car that proponents hope will replace horse-drawn carriages in New York City has also been revealed at the auto show. (Apr. 17) Video provided by AP
Powered by NewsLook.com
Honda's New ASIMO Robot, More Human-Like Than Ever

Honda's New ASIMO Robot, More Human-Like Than Ever

AFP (Apr. 17, 2014) It walks and runs, even up and down stairs. It can open a bottle and serve a drink, and politely tries to shake hands with a stranger. Meet the latest ASIMO, Honda's humanoid robot. Duration: 00:54 Video provided by AFP
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:
from the past week

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