Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Rice professor's nanotube theory confirmed: Air Force Research Laboratory experiment shows chirality of tube controls speed of growth

A single nanotube stretches out across a microscopic silicon pillar in the Air Force Research Laboratory experiment. (Credit: Rahul Rao/Air Force Research Laboratory)
A single nanotube stretches out across a microscopic silicon pillar in the Air Force Research Laboratory experiment.

(Credit: Rahul Rao/Air Force Research Laboratory)

Abstract:
The Air Force Research Laboratory in Dayton, Ohio, has experimentally confirmed a theory by Rice University Professor Boris Yakobson that foretold a pair of interesting properties about nanotube growth: That the chirality of a nanotube controls the speed of its growth, and that armchair nanotubes should grow the fastest.

Rice professor's nanotube theory confirmed: Air Force Research Laboratory experiment shows chirality of tube controls speed of growth

Houston, TX | Posted on January 30th, 2012

The work is a sure step toward defining all the mysteries inherent in what Yakobson calls the "DNA code of nanotubes," the parameters that determine their chirality -- or angle of growth -- and thus their electrical, optical and mechanical properties. Developing the ability to grow batches of nanotubes with specific characteristics is a critical goal of nanoscale research.

The new paper by Air Force senior researcher Benji Maruyama; former Air Force colleague Rahul Rao, now at the Honda Research Institute in Ohio; Yakobson and their co-authors appeared this week in the online version of the journal Nature Materials.

It's an interesting denouement in a saga that began with a 2009 paper by Yakobson and his collaborators. That paper, which presented the theoretical physicist's dislocation theory of chirality-controlled growth, described how nanotubes emerge as if single threads of atoms weave themselves into the now-familiar chicken-wire-like tubes. It also garnered a bit of controversy over what precisely the results meant.

"Boris caught some heat over it," Maruyama said. "The experimental work out there indicated his theory might be true, but they couldn't confirm it. The good part about our work is that it's fairly unambiguous."

Yakobson, Rice's Karl F. Hasselmann Professor of Mechanical Engineering and Materials Science and professor of chemistry, took it all in stride. "The criticism didn't affect anything; it was actually the best advertisement and motivation for further work," he said. "In fact, (nanotube pioneer Sumio) Iijima noted early that 'helicity may aid the growth.' We have transformed it into a verifiable equation."

Experimental confirmation of a theory is never final but always satisfying, he admitted, and the Air Force lab was uniquely equipped to prove the linkage between the speed of a nanotube's growth and its chiral angle.

The chirality of a single-walled nanotube is determined by the way its carbon atoms are "rolled." Yakobson has described it as similar to rolling up a newspaper; sometimes the type lines up, and sometimes it doesn't. That alignment determines the nanotubes' electrical properties. Metallic armchair nanotubes, so named for the shape of their uncapped edges, are particularly desirable because electrons pass through from tip to tip with no resistance, while semiconducting nanotubes are useful for electronics, among other applications.

Rao developed a technique in Maruyama's lab to measure the growth rates of individual nanotubes. "It's an impressive setup," Yakobson said. "They can grow individual tubes in very low density and identify their signatures - their chirality - and at the same time measure how rapidly they grow."

The technique involved mounting catalyst nanoparticles on microscopic silicon pillars and firing tightly controlled lasers at them. Heat from the laser triggered the nanotubes to grow through a standard technique called chemical vapor deposition, and at the same time, the researchers analyzed nanotube growths via Raman spectroscopy.

From the spectra, they could tell how fast a nanotube grew and at what point growth terminated. Subsequent electron microscope images confirmed the spectra were from individual single-walled nanotubes, while chiral angles were determined by comparing post-growth Raman spectra and nanotube diameters to the Kataura plot, which maps chirality based on band gap and diameter.

They noted in the paper that the results provide a basis for further research into growing specific types of nanotubes. "Now that we know what the growth rate is for a particular chirality nanotube, one could think about trying to achieve growth of that specific chirality by influencing growth conditions accordingly," Rao said. "So, basically, we now have another 'knob' to turn."



"This work is at a very early development stage, and it's all about post-nucleation," Yakobson said. "Nucleation sets what I think of as the genetic code - very primitive compared to biology - that determines the chirality and the speed of growth of a nanotube." He said it may be possible someday to dictate the form of a nanotube as it begins to bubble up from a catalyst, "but it will take a lot of ingenuity."



Yakobson revealed a formula last year that defined the nucleation probability through the edge energies for graphene, which is basically a cut-and-flattened nanotube. But the earlier and related dislocation theory applies to the following growth, and if confirmed further may turn out to be his masterwork.

"The dislocation theory of growth is elegant and simple," Rao said. "It's still too early to say that it is the only growth mechanism, but Boris should be given plenty of credit for proposing this bold idea in the first place."

Co-authors are former Rice graduate student Tonya Leeuw Cherukuri and David Liptak, both researchers at the Air Force lab.

The Air Force Office of Scientific Research and the National Research Council funded the work.

####

About Rice University
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is known for its "unconventional wisdom." With 3,708 undergraduates and 2,374 graduate students, Rice's undergraduate student-to-faculty ratio is less than 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice has been ranked No. 1 for best quality of life multiple times by the Princeton Review and No. 4 for "best value" among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to www.rice.edu/nationalmedia/Rice.pdf.

For more information, please click here

Contacts:
David Ruth
713-348-6327


Mike Williams
713-348-6728

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 Links

Read the abstract at:

Related News Press

News and information

Haydale Secures Exclusive Development and Supply Agreement with Tantec A/S: New reactors to be built and commissioned by Tantec A/S represent another step forward towards the commercialisation of graphene October 24th, 2014

QuantumWise guides the semiconductor industry towards the atomic scale October 24th, 2014

MEMS & Sensors Technology Showcase: Finalists Announced for MEMS Executive Congress US 2014 October 23rd, 2014

Nanoparticle technology triples the production of biogas October 23rd, 2014

Laboratories

National Synchrotron Light Source II Achieves 'First Light' October 23rd, 2014

Novel Rocket Design Flight Tested: New Rocket Propellant and Motor Design Offers High Performance and Safety October 23rd, 2014

Govt.-Legislation/Regulation/Funding/Policy

Novel Rocket Design Flight Tested: New Rocket Propellant and Motor Design Offers High Performance and Safety October 23rd, 2014

Strengthening thin-film bonds with ultrafast data collection October 23rd, 2014

Brookhaven Lab Launches Computational Science Initiative:Leveraging computational science expertise and investments across the Laboratory to tackle "big data" challenges October 22nd, 2014

Bipolar Disorder Discovery at the Nano Level: Tiny structures found in brain synapses help scientists better understand disorder October 22nd, 2014

Nanotubes/Buckyballs

Materials for the next generation of electronics and photovoltaics: MacArthur Fellow develops new uses for carbon nanotubes October 21st, 2014

Special UO microscope captures defects in nanotubes: University of Oregon chemists provide a detailed view of traps that disrupt energy flow, possibly pointing toward improved charge-carrying devices October 21st, 2014

Imaging electric charge propagating along microbial nanowires October 20th, 2014

Beyond LEDs: Brighter, new energy-saving flat panel lights based on carbon nanotubes - Planar light source using a phosphor screen with highly crystalline single-walled carbon nanotubes (SWCNTs) as field emitters demonstrates its potential for energy-efficient lighting device October 14th, 2014

Discoveries

QuantumWise guides the semiconductor industry towards the atomic scale October 24th, 2014

Iranian, Malaysian Scientists Study Nanophotocatalysts for Water Purification October 23rd, 2014

Nanoparticle technology triples the production of biogas October 23rd, 2014

Strengthening thin-film bonds with ultrafast data collection October 23rd, 2014

Announcements

Haydale Secures Exclusive Development and Supply Agreement with Tantec A/S: New reactors to be built and commissioned by Tantec A/S represent another step forward towards the commercialisation of graphene October 24th, 2014

QuantumWise guides the semiconductor industry towards the atomic scale October 24th, 2014

Advancing thin film research with nanostructured AZO: Innovnano’s unique and cost-effective AZO sputtering targets for the production of transparent conducting oxides October 23rd, 2014

Strengthening thin-film bonds with ultrafast data collection October 23rd, 2014

Military

NanoTechnology for Defense (NT4D) October 22nd, 2014

Crystallizing the DNA nanotechnology dream: Scientists have designed the first large DNA crystals with precisely prescribed depths and complex 3D features, which could create revolutionary nanodevices October 20th, 2014

Imaging electric charge propagating along microbial nanowires October 20th, 2014

1980s aircraft helps quantum technology take flight October 20th, 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