A new approach to finding and removing defects in graphene (w/ Video)

Jun 06, 2010
Engineering professor Vivek Shenoy (right) and graduate student Akbar Bagri have explored the atomic configuration of graphene oxide, showing how defects in graphene sheets can be located and treated. Credit: Mike Cohea, Brown University

Graphene, a carbon sheet that is one-atom thick, may be at the center of the next revolution in material science. These ultrathin sheets hold great potential for a variety of applications from replacing silicon in solar cells to cooling computer chips.

Despite its vast promise, and its derivatives "are materials people understand little about," said Vivek Shenoy, professor of engineering at Brown University. "The more we can understand their properties, the more (technological) possibilities that will be opened to us."

Shenoy and a team of U.S. researchers have gained new insights into these mysterious materials. The team, in a paper in Nature Chemistry, pinpoints the atomic configurations of noncarbon atoms that create defects when graphene is produced through a technique called graphene-oxide reduction. Building from that discovery, the researchers propose how to make that technique more efficient by outlining precisely how to apply hydrogen — rather than heat — to remove impurities in the sheets.

The sheets produced by graphene-oxide reduction are two-dimensional, honeycomb-looking planes of carbon. Most of the atoms in the are carbon, which is what scientists want. But interwoven in the structure are also oxygen and , which disrupt the uniformity of the sheet. Apply enough heat to the lattice, and some of those oxygen atoms bond with hydrogen atoms, which can be removed as water. But some oxygen atoms are more stubborn.

This video is not supported by your browser at this time.
Atoms of oxygen create distortions in a graphene sheet. The key to removing them is to apply hydrogen in exactly the right places. Credit: Shenoy Lab, Brown University

Shenoy, joined by Brown graduate student Akbar Bagri and colleagues from Rutgers University and the University of Texas-Dallas, used molecular dynamic simulations to observe the atomic configuration of the graphene lattice and figure out why the remaining oxygen atoms remained in the structure. They found that the holdout oxygen atoms had formed double bonds with , a very stable arrangement that produces irregular holes in the lattice.

The oxygen atoms that form double bonds with carbon "have very low energy," Shenoy said. "They're unreactive. It's hard to get them out."

Now that they understand the configuration of the resistant oxygen atoms in the graphene, the researchers say adding hydrogen atoms in prescribed amounts and at defined locations is the best way to further reduce the graphene oxide. One promising technique, they write in the paper, is to introduce hydrogen where the oxygen atoms have bonded with the carbon atoms and formed the larger holes. The oxygen and hydrogen should pair up (as hydroxyls) and leave the lattice, in essence "healing the hole," Shenoy said.

Another approach is to remove the oxygen impurities by focusing on the areas where carbonyls — carbon atoms that are double-bonded to oxygen atoms — have formed. By adding hydrogen, the researchers theorize, the can be peeled away in the form of water.

The researchers next plan to experiment with the hydrogen treatment techniques as well as to investigate the properties of graphene oxide "in its own right," Shenoy said.

Explore further: Solar cells made from polar nanocrystal inks show promising early performance

Related Stories

Doping graphene

Jun 01, 2010

An organic molecule that has been found to be effective in making silicon-based electronics may be viable for building electronics on sheets of carbon only a single molecule thick. Researchers at the Max Planck ...

Producing graphene layers using crystallization

Mar 02, 2010

(PhysOrg.com) -- Ever since it's relatively recent discovery, graphene has generated a great deal of interest. Graphene is extracted from graphite in many cases, and consists of a sheet of carbon atoms bound together in a ...

Highlight: Nanopatterning of Graphene

Mar 11, 2010

Center for Nanoscale Materials (CNM) at Argonne National Laboratory users from Politecnico di Milano in Italy, working collaboratively with researchers in the Electronic & Magnetic Materials & Devices Group, ...

Recommended for you

Shiny quantum dots brighten future of solar cells

Apr 14, 2014

(Phys.org) —A house window that doubles as a solar panel could be on the horizon, thanks to recent quantum-dot work by Los Alamos National Laboratory researchers in collaboration with scientists from University ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

muggins
not rated yet Jun 06, 2010
Great find but would'nt this be highly expensive to cover large sheets of carbon, not to mention time consuming seeing as they need to focus on areas with hydroxyls and carbonyls.

More news stories

Shiny quantum dots brighten future of solar cells

(Phys.org) —A house window that doubles as a solar panel could be on the horizon, thanks to recent quantum-dot work by Los Alamos National Laboratory researchers in collaboration with scientists from University ...

Polymer microparticles could help verify goods

Some 2 to 5 percent of all international trade involves counterfeit goods, according to a 2013 United Nations report. These illicit products—which include electronics, automotive and aircraft parts, pharmaceuticals, ...

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. That is the message from US tech giants seeking to spread the online gospel to hard-to-reach regions.

Wireless industry makes anti-theft commitment

A trade group for wireless providers said Tuesday that the biggest mobile device manufacturers and carriers will soon put anti-theft tools on the gadgets to try to deter rampant smartphone theft.