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

June 6, 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.

The video will load shortly
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: From graphene to graphane, now the possibilities are endless

Related Stories

Doping graphene

June 1, 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 Institute ...

Producing graphene layers using crystallization

March 2, 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

March 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, have demonstrated ...

Recommended for you

Chemists create 3-D printed graphene foam

June 21, 2017

Nanotechnologists from Rice University and China's Tianjin University have used 3-D laser printing to fabricate centimeter-sized objects of atomically thin graphene.

Plant inspiration could lead to flexible electronics

June 21, 2017

Versatile, light-weight materials that are both strong and resilient are crucial for the development of flexible electronics, such as bendable tablets and wearable sensors. Aerogels are good candidates for such applications, ...

Neuron transistor behaves like a brain neuron

June 20, 2017

(Phys.org)—Researchers have built a new type of "neuron transistor"—a transistor that behaves like a neuron in a living brain. These devices could form the building blocks of neuromorphic hardware that may offer unprecedented ...

1 comment

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.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.