Featured Research

from universities, journals, and other organizations

Simulations May Explain Nanoparticles 'Pinned' To Graphene

Date:
May 1, 2008
Source:
Sandia National Laboratories
Summary:
It was hard to understand how a graphene sheet -- a featureless, flat sheet of carbon atoms -- lying on an equally featureless iridium surface, somehow converted itself into a kind of muffin tin that formed "muffins" made from newly arrived iridium atoms. The muffins were equally spaced and of equal size. Graphene flakes are notoriously difficult to work with. Still, they are stronger than diamond, better heat-shedders and conductors than silicon, and thought to have great potential in the worlds of microelectronics and sensors. If only they could be tamed.

Graphene has proven a difficult material for researchers to tame. Peter Feibelman 's computational simulation suggests an explanation for why iridium atoms (colored green) nest regularly atop a base of graphene (dark-colored atoms) grown over an iridium substrate. Peter's image of the orderly nanoscopic metallic arrangement may provide insights to other scientists. His paper on the work was published in Physical Review B online.
Credit: Randy Montoya

It was hard to understand how a graphene sheet — a featureless, flat sheet of carbon atoms — lying on an equally featureless iridium surface, somehow converted itself into a kind of muffin tin that formed “muffins” made from newly arrived iridium atoms. The muffins were equally spaced and of equal size.

Graphene flakes are notoriously difficult to work with. Still, they are stronger than diamond, better heat-shedders and conductors than silicon, and thought to have great potential in the worlds of microelectronics and sensors. If only they could be tamed.

Imagining a whole new set of possible applications, people wanted to know why the orderly metallic array self-created itself.

“At the outset,” writes Sandia researcher Peter Feibelman, who created the explanatory simulation published last week in Physical Review B, “this seemed quite a mystery.”

The mystery started in 2005, when a German team discovered the new wrinkle in the battle to harness graphene but had difficulty in explaining the reaction.

A graphene flake lying atop an iridium crystal unexpectedly caused new iridium atoms, deposited atop the flake, to arrange themselves into cluster arrays, stable even as its temperature reached 400 to 500 kelvin.

Sherlock Holmes himself, looking for clues to why the iridium quantum dots so mysteriously attached, would have found little to go on.

The iridium support layer was flat as could be. The same was true of the graphene layer that formed on top of it, which sported neither hooks nor ports for nanoparticle docking.

Graphite itself — merely a group of sheets of graphene — is so slippery it can be used as a lubricant. Why would nanodots attach to the completed graphene layer instead of just sliding away?

Even granted an attachment mechanism, why would newly introduced iridium atoms form a moiré — a regular, ordered array — atop the graphene instead of a planar second surface — a sandwich where the iridium was the bread and graphene the meat?

The explanation for the template effect would be almost impossible to see by direct examination.

But Feibelman’s computational simulations produced a plausible explanation.

The simulation suggest that in regions where half the graphene flake’s carbon atoms sit directly above iridium atoms of the underlying crystal, iridium atoms added on top of the graphene flake make it buckle. These regions do not occur randomly, and in fact form the regular array needed to explain the nanodot moiré.

The buckling weakens tight links between the graphene’s neighboring carbon atoms, freeing them to attach to the added iridium atoms. Furthermore, buckling not only allows the carbon atoms that buckle upward to capture deposited iridium atoms, but also causes the carbon atoms that buckle down to attach firmly to the metal below, explaining the remarkable thermal stability of the nanodot arrays.

This orderly nanoscopic arrangement appeals to scientists trying to understand aspects of catalysis, Feibelman says. The atoms that make up tiny nanodots are expected to be in direct contact with inserted materials, important for speeding up desirable chemical reactions. The regular arrangement of the nanodots makes the science relatively simple, because every catalyst particle is the same and sits in the same environment.

“The rigorous periodicity of the nanodot arrays is a huge advantage compared to amorphous or ‘glassy’ arrangements where everything has to be described statistically,” says Feibelman.

Similar quantum dot arrangements on electrically insulating graphene could keep information packets separate and “addressable” for data storage, or provide superior conditions for quantum computing.


Story Source:

The above story is based on materials provided by Sandia National Laboratories. Note: Materials may be edited for content and length.


Cite This Page:

Sandia National Laboratories. "Simulations May Explain Nanoparticles 'Pinned' To Graphene." ScienceDaily. ScienceDaily, 1 May 2008. <www.sciencedaily.com/releases/2008/04/080428203354.htm>.
Sandia National Laboratories. (2008, May 1). Simulations May Explain Nanoparticles 'Pinned' To Graphene. ScienceDaily. Retrieved October 1, 2014 from www.sciencedaily.com/releases/2008/04/080428203354.htm
Sandia National Laboratories. "Simulations May Explain Nanoparticles 'Pinned' To Graphene." ScienceDaily. www.sciencedaily.com/releases/2008/04/080428203354.htm (accessed October 1, 2014).

Share This



More Matter & Energy News

Wednesday, October 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Japan Looks To Faster Future As Bullet Train Turns 50

Japan Looks To Faster Future As Bullet Train Turns 50

Newsy (Oct. 1, 2014) — Japan's bullet train turns 50 Wednesday. Here's a look at how it's changed over half a century — and the changes it's inspired globally. Video provided by Newsy
Powered by NewsLook.com
US Police Put Body Cameras to the Test

US Police Put Body Cameras to the Test

AFP (Oct. 1, 2014) — Police body cameras are gradually being rolled out across the US, with interest surging after the fatal police shooting in August of an unarmed black teenager. Duration: 02:18 Video provided by AFP
Powered by NewsLook.com
Raw: Japan Celebrates 'bullet Train' Anniversary

Raw: Japan Celebrates 'bullet Train' Anniversary

AP (Oct. 1, 2014) — A ceremony marking 50 years since Japan launched its Shinkansen bullet train was held on Wednesday in Tokyo. The latest model can travel from Tokyo to Osaka, a distance of 319 miles, in two hours and 25 minutes. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Robotic Hair Restoration

Robotic Hair Restoration

Ivanhoe (Oct. 1, 2014) — A new robotic procedure is changing the way we transplant hair. The ARTAS robot leaves no linear scarring and provides more natural results. Video provided by Ivanhoe
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:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

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