Home > Press > Graphene 'onion rings' have delicious potential: Rice University lab grows 'bottom-up' nanoribbons for the first time
 |
| An electron microscope image of graphene "onion rings" shows the concentric, dark ribbons through the overlying sheet of graphene. The ribbons follow the form of the growing graphene sheet, which takes the shape of a hexagon. Credit: Tour Group/Rice University |
Abstract:
Concentric hexagons of graphene grown in a furnace at Rice University represent the first time anyone has synthesized graphene nanoribbons on metal from the bottom up -- atom by atom.
As seen under a microscope, the layers brought onions to mind, said Rice chemist James Tour, until a colleague suggested flat graphene could never be like an onion.
"So I said, ?OK, these are onion rings,'" Tour quipped.
The name stuck, and the remarkable rings that chemists marveled were even possible are described in a new paper in the Journal of the American Chemical Society.
The challenge was to figure out how such a thing could grow, Tour said. Usually, graphene grown in a hot furnace by chemical vapor deposition starts on a seed -- a speck of dust or a bump on a copper or other metallic surface. One carbon atom latches onto the seed in a process called nucleation and others follow to form the familiar chicken-wire grid.
Experiments in Tour's lab to see how graphene grows under high pressure and in a hydrogen-rich environment produced the first rings. Under those conditions, Tour, Rice theoretical physicist Boris Yakobson and their teams found that the entire edge of a fast-growing sheet of graphene becomes a nucleation site when hydrogenated. The edge lets carbon atoms get under the graphene skin, where they start a new sheet.
But because the top graphene grows so fast, it eventually halts the flow of carbon atoms to the new sheet underneath. The bottom stops growing, leaving a graphene ring. Then the process repeats.
"The mechanism relies on that top layer to stop carbon from reaching the bottom so easily," Tour said. "What we get are a multiple of single crystals growing one on top of the other."
The Tour lab pioneered the bulk manufacture of single-atom-thick graphene nanoribbons in 2009 with the discovery that carbon nanotubes could be chemically "unzipped" into long, thin sheets. Nanoribbons are being studied for use in batteries and advanced electronics and as heat sinks.
"Usually you make a ribbon by taking a large thing and cutting it down," Tour said. "But if you can grow a ribbon from the bottom up, you could have control of the edges." The atomic configuration at the edge helps determine graphene's electrical properties. The edges of hexagonal graphene onion rings are zigzags, which make the rings metallic.
"The big news here," he said, "is that we can change relative pressures of the growth environment of hydrogen versus carbon and get entirely new structures. This is dramatically different from regular graphene."
Graduate student Zheng Yan, a member of Tour's lab and lead author of the paper, discovered the new route to nanoribbons while experimenting with graphene growth under hydrogen pressurized to varying degrees. The sweet spot for rings was at 500 Torr, he said.
Further testing found the microscopic rings formed underneath and not on top of the sheet, and Yakobson's lab confirmed the growth mechanism through first-principle calculations. Yan also determined the top sheet of graphene could be stripped away with argon plasma, leaving stand-alone rings.
The width of the rings, which ranged from 10 to 450 nanometers, also affects their electronic properties, so finding a way to control it will be one focus of continued research, Tour said. "If we can consistently make 10-nanometer ribbons, we can begin to gate them and turn them into low-voltage transistors," he said. They may also be suitable for lithium storage for advanced lithium ion batteries, he said.
Co-authors of the paper are Rice graduate students Yuanyue Liu, Zhiwei Peng, Changsheng Xiang, Abdul-Rahman Raji and Errol Samuel; postdoctoral researchers Jian Lin, Gunuk Wang and Haiqing Zhou; Rice alumna Elvira Pembroke; and Professor Ting Yu of Nanyang Technological University. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science at Rice. Yakobson is the Karl F. Hasselmann Professor of Mechanical Engineering and Materials Science and professor of chemistry.
The Singapore National Research Foundation, the Office of Naval Research, the Lockheed Martin LANCER IV program and the Air Force Office of Scientific Research supported the work. Calculations were performed on the National Science Foundation-supported DaVinCI supercomputer at Rice, the National Institute for Computational Sciences' Kraken and the National Energy Research Scientific Computing Center's Hopper.
####
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 3,708 undergraduates and 2,374 graduate students, Rice's undergraduate student-to-faculty ratio is 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. 2 for "best value" among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to tinyurl.com/AboutRiceU.
Follow Rice News and Media Relations via Twitter @RiceUNews
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:
Read the abstract at:
Tour Group at Rice:
Yakobson Group at Rice:
News and information
Integrated Nanotechnology for Sustainable Future and Smart Living - Dr. Muhammad Mustafa Hussain - King Abdullah University of Science and Technology, Thuwal, Saudi Arabia July 19th, 2013
Desktop printing at the nano level: Northwestern researchers create state-of-the-art desktop nanofabrication tool July 19th, 2013
Injectable ?Smart Sponge? Holds Promise for Controlled Drug Delivery July 18th, 2013
Milikelvins drive droplet evaporation July 18th, 2013
Graphene
A new form of carbon: Grossly warped 'nanographene': Bucking planarity, contorted sheets of graphene alter physical, optical and electronic properties of new material July 15th, 2013
Air Force support for a new generation of lithium-ion batteries: New graphene technique can significantly increase the storage capacity of lithium ion by combining graphene nanoribbons with tin oxide July 15th, 2013
Miracle material graphene could deliver internet one hundred times faster July 14th, 2013
Jagged graphene can slice into cell membranes July 10th, 2013
Govt.-Legislation/Regulation/Funding/Policy
Milikelvins drive droplet evaporation July 18th, 2013
Nano Drug Crosses Blood-Brain Tumor Barrier, Targets Brain Tumor Cells and Blood Vessels July 18th, 2013
Origins and uses of wrinkles, creases, folds July 18th, 2013
NASA Engineer Achieves Another Milestone in Emerging Nanotechnology July 18th, 2013
Discoveries
Desktop printing at the nano level: Northwestern researchers create state-of-the-art desktop nanofabrication tool July 19th, 2013
Injectable ?Smart Sponge? Holds Promise for Controlled Drug Delivery July 18th, 2013
Milikelvins drive droplet evaporation July 18th, 2013
Stanford scientists break record for thinnest light-absorber July 18th, 2013
Announcements
Integrated Nanotechnology for Sustainable Future and Smart Living - Dr. Muhammad Mustafa Hussain - King Abdullah University of Science and Technology, Thuwal, Saudi Arabia July 19th, 2013
Desktop printing at the nano level: Northwestern researchers create state-of-the-art desktop nanofabrication tool July 19th, 2013
Origins and uses of wrinkles, creases, folds July 18th, 2013
Registration for 5th Int'l Conference on Nanostructures Starts on Kish Island July 18th, 2013
Interviews/Book Reviews/Essays/Reports/Podcasts/Journals
Desktop printing at the nano level: Northwestern researchers create state-of-the-art desktop nanofabrication tool July 19th, 2013
Injectable ?Smart Sponge? Holds Promise for Controlled Drug Delivery July 18th, 2013
Origins and uses of wrinkles, creases, folds July 18th, 2013
Artificial organelles transform free radicals into water and oxygen July 16th, 2013
Military
New nanoscale imaging method finds application in plasmonics July 16th, 2013
Broadband photodetector for polarized light: Rice, Sandia team uses carbon nanotubes for polarized-light detection July 16th, 2013
Air Force support for a new generation of lithium-ion batteries: New graphene technique can significantly increase the storage capacity of lithium ion by combining graphene nanoribbons with tin oxide July 15th, 2013
Silicon oxide memories transcend a hurdle: Embedded diodes boost Rice University invention?s potential as robust, roomy memory July 9th, 2013
Research partnerships
Stanford scientists break record for thinnest light-absorber July 18th, 2013
Nano Drug Crosses Blood-Brain Tumor Barrier, Targets Brain Tumor Cells and Blood Vessels July 18th, 2013
Origins and uses of wrinkles, creases, folds July 18th, 2013
NASA Engineer Achieves Another Milestone in Emerging Nanotechnology July 18th, 2013
Source: http://www.nanotech-now.com/news.cgi?story_id=47840
nfl draft picks 2012 space shuttle enterprise ryan leaf ryan leaf luke kuechly brad miller chandler jones
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.