Nanotechnology Now

Our NanoNews Digest Sponsors



Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > ‘Two-Faced’ Bioacids Put a New Face on Carbon Nanotube Self-Assembly

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. Image, 70 micrometers wide, was taken using near-infrared fluorescent microscopy. (Color added for clarity.)

Credit: NIST
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. Image, 70 micrometers wide, was taken using near-infrared fluorescent microscopy. (Color added for clarity.)

Credit: NIST

Abstract:
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.

‘Two-Faced’ Bioacids Put a New Face on Carbon Nanotube Self-Assembly

GAITHERSBURG, MD | Posted on January 13th, 2009

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 (see, for example, "NIST's Stretching Exercises Shed New Light on Nanotubes," Tech Beat, Apr. 12, 2007), 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."

(For more on the purifying of carbon nanotubes, see "Spin Control: New Technique Sorts Nanotubes by Length," Tech Beat, May 13,2008.)

* E.K. Hobbie, J.A. Fagan, M.L. Becker, S.D. Hudson, N. Fakhri and M. Pasquali. Self-assembly of ordered nanowires in biological suspensions of single-wall carbon nanotubes. ACS Nano, published online Dec. 16, 2008.

** Sodium deoxycholate.

####

About NIST
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 Links

“Spin Control: New Technique Sorts Nanotubes by Length,” Tech Beat, May 13,2008.

Related News Press

News and information

Switching to spintronics: Berkeley Lab reports on electric field switching of ferromagnetism at room temp December 17th, 2014

ORNL microscopy pencils patterns in polymers at the nanoscale December 17th, 2014

Unraveling the light of fireflies December 17th, 2014

First Home-Made Edible Herbal Nanodrug Presented to Pharmacies across Iran December 17th, 2014

Self Assembly

Revealed: How bacteria drill into our cells and kill them December 2nd, 2014

Live Images from the Nano-cosmos: Researchers watch layers of football molecules grow November 5th, 2014

Outsmarting Thermodynamics in Self-assembly of Nanostructures: Berkeley Lab reports method for symmetry-breaking in feedback-driven self-assembly of optical metamaterials November 4th, 2014

NYU Researchers Break Nano Barrier to Engineer the First Protein Microfiber October 23rd, 2014

Nanotubes/Buckyballs

A sponge-like molecular cage for purification of fullerenes December 15th, 2014

'Trojan horse' proteins used to target hard-to-reach cancers: Scientists at Brunel University London have found a way of targeting hard-to-reach cancers and degenerative diseases using nanoparticles, but without causing the damaging side effects the treatment normally brings December 11th, 2014

Detecting gases wirelessly and cheaply: New sensor can transmit information on hazardous chemicals or food spoilage to a smartphone December 8th, 2014

Green meets nano: Scientists at TU Darmstadt create multifunctional nanotubes using nontoxic materials December 3rd, 2014

Discoveries

Switching to spintronics: Berkeley Lab reports on electric field switching of ferromagnetism at room temp December 17th, 2014

ORNL microscopy pencils patterns in polymers at the nanoscale December 17th, 2014

Unraveling the light of fireflies December 17th, 2014

Fraud-proof credit card possible because of quantum physics December 16th, 2014

Announcements

Switching to spintronics: Berkeley Lab reports on electric field switching of ferromagnetism at room temp December 17th, 2014

ORNL microscopy pencils patterns in polymers at the nanoscale December 17th, 2014

Unraveling the light of fireflies December 17th, 2014

First Home-Made Edible Herbal Nanodrug Presented to Pharmacies across Iran December 17th, 2014

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




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE