Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International

Wikipedia Affiliate Button

Home > Press > Oddball edge wins nanotube faceoff: Rice U. theory shows peculiar 'Janus' interface a common mechanism in carbon nanotube growth

Rice University researchers have determined that an odd, two-faced "Janus" edge is more common than previously thought for carbon nanotubes growing on a rigid catalyst. The conventional nanotube at left has facets that form a circle, allowing the nanotube to grow straight up from the catalyst. But they discovered the nanotube at right, with a tilted Janus edge that has segregated sections of zigzag and armchair configurations, is far more energetically favored when growing carbon nanotubes via chemical vapor deposition. (Credit: Illustration by Evgeni Penev/Rice University)
Rice University researchers have determined that an odd, two-faced "Janus" edge is more common than previously thought for carbon nanotubes growing on a rigid catalyst. The conventional nanotube at left has facets that form a circle, allowing the nanotube to grow straight up from the catalyst. But they discovered the nanotube at right, with a tilted Janus edge that has segregated sections of zigzag and armchair configurations, is far more energetically favored when growing carbon nanotubes via chemical vapor deposition. (Credit: Illustration by Evgeni Penev/Rice University)

Abstract:
When is a circle less stable than a jagged loop? Apparently when you're talking about carbon nanotubes.

Oddball edge wins nanotube faceoff: Rice U. theory shows peculiar 'Janus' interface a common mechanism in carbon nanotube growth

Houston, TX | Posted on July 29th, 2019

Rice University theoretical researchers have discovered that nanotubes with segregated sections of "zigzag" and "armchair" facets growing from a solid catalyst are far more energetically stable than a circular arrangement would be.

Under the right circumstances, they reported, the interface between a growing nanotube and its catalyst can reach its lowest-known energy state via the two-faced "Janus" configuration, with a half-circle of zigzags opposite six armchairs.

The terms refer to the shape of the nanotube's edge: A zigzag nanotube's end looks like a saw tooth, while an armchair is like a row of seats with armrests. They are the basic edge configurations of the two-dimensional honeycomb of carbon atoms known as graphene (as well as other 2D materials) and determine many of the materials' properties, especially electrical conductivity.

The Brown School of Engineering team of materials theorist Boris Yakobson, researcher and lead author Ksenia Bets and assistant research professor Evgeni Penev reported their results in the American Chemical Society journal ACS Nano.

The theory is a continuation of the team's discovery last year that Janus interfaces are likely to form on a catalyst of tungsten and cobalt, leading to a single chirality, called (12,6), that other labs had reported growing in 2014.

The Rice team now shows such structures aren't unique to a specific catalyst, but are a general characteristic of a number of rigid catalysts. That's because the atoms attaching themselves to the nanotube edge always seek their lowest energy states, and happen to find it in the Janus configuration they named A|Z.

"People have assumed in studies that the geometry of the edge is a circle," Penev said. "That's intuitive -- it's normal to assume that the shortest edge is the best. But we found for chiral tubes the slightly elongated Janus edge allows it to be in much better contact with solid catalysts. The energy for this edge can be quite low."

In the circle configuration, the flat armchair bottoms rest on the substrate, providing the maximum number of contacts between the catalyst and the nanotube, which grows straight up. (Janus edges force them to grow at an angle.)

Carbon nanotubes -- long, rolled-up tubes of graphene -- are difficult enough to see with an electron microscope. As yet there's no way to observe the base of a nanotube as it grows from the bottom up in a chemical vapor deposition furnace. But theoretical calculations of the atom-level energy that passes between the catalyst and the nanotube at the interface can tell researchers a lot about how they grow.

That's a path the Rice lab has pursued for more than a decade, pulling at the thread that reveals how minute adjustments in nanotube growth can change the kinetics, and ultimately how nanotubes can be used in applications.

"Generally, the insertion of new atoms at the nanotube edge requires breaking the interface between the nanotube and the substrate," Bets said. "If the interface is tight, it would cost too much energy. That is why the screw dislocation growth theory proposed by Professor Yakobson in 2009 was able to connect the growth rate with the presence of kinks, the sites on the nanotube edge that disrupt the tight carbon nanotube-substrate contact.

"Curiously, even though Janus edge configuration allows very tight contact with the substrate it still preserves a single kink that would allow continuous nanotube growth, as we demonstrated last year for the cobalt tungsten catalyst," Bets said.

Bets ran extensive computer simulations to model nanotubes growing on three rigid catalysts that showed evidence of Janus growth and one more “fluid” catalyst, tungsten carbide, that did not. "The surface of that catalyst is very mobile, so the atoms can move a lot," Penev said. "For that one, we did not observe a clear segregation."

Yakobson compared Janus nanotubes to the Wulff shape of crystals. "It's somewhat surprising that our analysis suggests a restructured, faceted edge is energetically favored for chiral tubes," he said. "Assuming that the lowest energy edge must be a minimal-length circle is like assuming that a crystal shape must be a minimal-surface sphere but we know well that 3D shapes have facets and 2D shapes are polygons, as epitomized by the Wulff construction.

"Graphene has by necessity several 'sides,' but a nanotube cylinder has one rim, making the energy analysis different," he said. "This raises fundamentally interesting and practically important questions about the relevant structure of the nanotube edges."

The Rice researchers hope their discovery will advance them along the path toward those answers. "The immediate implication of this finding is a paradigm shift in our understanding of growth mechanisms," Yakobson said. "That may become important in how one practically designs the catalyst for efficient growth, especially of controlled nanotube symmetry type, for electronic and optical utility."

Yakobson is the Karl F. Hasselmann Professor of Materials Science and NanoEngineering and of Chemistry. The National Science Foundation (NSF) and the Air Force Office of Scientific Research supported the research.

Computing resources were provided by the Department of Defense Supercomputing Resource Center; the National Energy Research Scientific Computing Center, supported by the Department of Energy Office of Science; the NSF-supported XSEDE supercomputer; and the NSF-supported DAVinCI cluster at Rice, administered by the Center for Research Computing and procured in partnership with Rice’s Ken Kennedy Institute for Information Technology.

####

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 home to the Baker Institute for Public Policy. With 3,962 undergraduates and 3,027 graduate students, Rice’s undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 2 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance.

Follow Rice News and Media Relations via Twitter @RiceUNews.

For more information, please click here

Contacts:
Jeff Falk
713-348-6775


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:

Two-faced edge makes nanotubes obey:

Caps not the culprit in nanotube chirality:

Yakobson Research Group:

George R. Brown School of Engineering:

Department of Materials Science and NanoEngineering:

Related News Press

News and information

The lightest shielding material in the world: Protection against electromagnetic interference July 3rd, 2020

Spintronics: Faster data processing through ultrashort electric pulses July 3rd, 2020

A path to new nanofluidic devices applying spintronics technology: Substantial increase in the energy conversion efficiency of hydrodynamic power generation via spin currents July 3rd, 2020

Towards lasers powerful enough to investigate a new kind of physics: An international team of researchers has demonstrated an innovative technique for increasing the intensity of lasers July 3rd, 2020

Graphene/ Graphite

Charcoal a weapon to fight superoxide-induced disease, injury: Nanomaterials soak up radicals, could aid treatment of COVID-19 July 2nd, 2020

Researchers discover new boron-lanthanide nanostructure June 25th, 2020

Transparent graphene electrodes might lead to new generation of solar cells: New roll-to-roll production method could enable lightweight, flexible solar devices and a new generation of display screens June 8th, 2020

2 Dimensional Materials

Researchers discover new boron-lanthanide nanostructure June 25th, 2020

Excitons form superfluid in certain 2D combos: Rice University researchers find ‘paradox’ in ground-state bilayers June 15th, 2020

Transparent graphene electrodes might lead to new generation of solar cells: New roll-to-roll production method could enable lightweight, flexible solar devices and a new generation of display screens June 8th, 2020

Chemistry

Fluorocarbon bonds are no match for light-powered nanocatalyst: Rice U. lab unveils catalyst that can break problematic C-F bonds June 22nd, 2020

Govt.-Legislation/Regulation/Funding/Policy

Towards lasers powerful enough to investigate a new kind of physics: An international team of researchers has demonstrated an innovative technique for increasing the intensity of lasers July 3rd, 2020

Carbon-loving materials designed to reduce industrial emissions July 3rd, 2020

Charcoal a weapon to fight superoxide-induced disease, injury: Nanomaterials soak up radicals, could aid treatment of COVID-19 July 2nd, 2020

The nature of nuclear forces imprinted in photons June 30th, 2020

Possible Futures

Spintronics: Faster data processing through ultrashort electric pulses July 3rd, 2020

A path to new nanofluidic devices applying spintronics technology: Substantial increase in the energy conversion efficiency of hydrodynamic power generation via spin currents July 3rd, 2020

Towards lasers powerful enough to investigate a new kind of physics: An international team of researchers has demonstrated an innovative technique for increasing the intensity of lasers July 3rd, 2020

Crystal structure discovered almost 200 years ago could hold key to solar cell revolution July 3rd, 2020

Chip Technology

Spintronics: Faster data processing through ultrashort electric pulses July 3rd, 2020

A path to new nanofluidic devices applying spintronics technology: Substantial increase in the energy conversion efficiency of hydrodynamic power generation via spin currents July 3rd, 2020

Extensive review of spin-gapless semiconductors: Next-generation spintronics candidates: spin-gapless semiconductors (SGSs) bridge the zero-gap materials and half-metals June 26th, 2020

Process for 'two-faced' nanomaterials may aid energy, information tech June 26th, 2020

Nanotubes/Buckyballs/Fullerenes/Nanorods

Flexible material shows potential for use in fabrics to heat, cool July 3rd, 2020

Prodigiosin-based solution has selective activity against cancer cells: A new nanoformulation was described by Kazan University's Bionanotechnology Lab in Frontiers in Bioengineering and Biotechnology June 12th, 2020

Exotic nanotubes move in less-mysterious ways: Rice scientists, engineers show boron nitride’s promise for composites, biomedical applications June 2nd, 2020

Oil & gas and automotive sectors will benefit from durable polymers with graphene nanotubes May 14th, 2020

Optical computing/Photonic computing

A Tremendous Recognition’ Engineer Jonathan Klamkin earns prestigious award from DARPA June 23rd, 2020

Polymers can fine-tune attractions between suspended nanocubes: Interactions between hollow silica nanocubes suspended in a solution can be adjusted by varying the concentration of polymer molecules added to the mixture. June 19th, 2020

Printed perovskite LEDs: An innovative technique towards a new standard process of electronics manufacturing June 12th, 2020

Configurable circuit technology poised to expand silicon photonic applications: Chips can be programmed after fabrication for use in communication, computing or biomedical applications May 29th, 2020

Discoveries

The lightest shielding material in the world: Protection against electromagnetic interference July 3rd, 2020

Spintronics: Faster data processing through ultrashort electric pulses July 3rd, 2020

A path to new nanofluidic devices applying spintronics technology: Substantial increase in the energy conversion efficiency of hydrodynamic power generation via spin currents July 3rd, 2020

Towards lasers powerful enough to investigate a new kind of physics: An international team of researchers has demonstrated an innovative technique for increasing the intensity of lasers July 3rd, 2020

Materials/Metamaterials

Cellulose for manufacturing advanced materials: A review of the scientific literature made at the University of the Basque Country (UPV/EHU) highlights the potential of hybrid materials based on cellulose nanocrystals June 26th, 2020

Macroscopic quantum interference in an ultra-pure metal June 26th, 2020

Process for 'two-faced' nanomaterials may aid energy, information tech June 26th, 2020

Researchers discover new boron-lanthanide nanostructure June 25th, 2020

Announcements

Towards lasers powerful enough to investigate a new kind of physics: An international team of researchers has demonstrated an innovative technique for increasing the intensity of lasers July 3rd, 2020

Crystal structure discovered almost 200 years ago could hold key to solar cell revolution July 3rd, 2020

Flexible material shows potential for use in fabrics to heat, cool July 3rd, 2020

Carbon-loving materials designed to reduce industrial emissions July 3rd, 2020

Military

A Tremendous Recognition’ Engineer Jonathan Klamkin earns prestigious award from DARPA June 23rd, 2020

Fluorocarbon bonds are no match for light-powered nanocatalyst: Rice U. lab unveils catalyst that can break problematic C-F bonds June 22nd, 2020

Teaching physics to neural networks removes 'chaos blindness' June 19th, 2020

Is teleportation possible? Yes, in the quantum world: Quantum teleportation is an important step in improving quantum computing June 19th, 2020

Grants/Sponsored Research/Awards/Scholarships/Gifts/Contests/Honors/Records

Towards lasers powerful enough to investigate a new kind of physics: An international team of researchers has demonstrated an innovative technique for increasing the intensity of lasers July 3rd, 2020

Charcoal a weapon to fight superoxide-induced disease, injury: Nanomaterials soak up radicals, could aid treatment of COVID-19 July 2nd, 2020

The nature of nuclear forces imprinted in photons June 30th, 2020

A Tremendous Recognition’ Engineer Jonathan Klamkin earns prestigious award from DARPA June 23rd, 2020

Photonics/Optics/Lasers

Towards lasers powerful enough to investigate a new kind of physics: An international team of researchers has demonstrated an innovative technique for increasing the intensity of lasers July 3rd, 2020

Researchers discover new boron-lanthanide nanostructure June 25th, 2020

A Tremendous Recognition’ Engineer Jonathan Klamkin earns prestigious award from DARPA June 23rd, 2020

Polymers can fine-tune attractions between suspended nanocubes: Interactions between hollow silica nanocubes suspended in a solution can be adjusted by varying the concentration of polymer molecules added to the mixture. June 19th, 2020

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