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, graphene 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 lattice are carbon, which is what scientists want. But interwoven in the structure are also oxygen and hydrogen atoms, 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.
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 carbon atoms, 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 oxygen atoms 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.
The research was funded by the National Science Foundation and the Semiconductor Research Corporation’s Nanotechnology Research Initiative. Other authors on the paper include Cecilia Mattevi and Manish Chhowalla from Rutgers (both now at Imperial College in London), Muge Acik and Yves Chabal from the University of Texas–Dallas.
Richard Lewis | EurekAlert!
OU-led team discovers rare, newborn tri-star system using ALMA
27.10.2016 | University of Oklahoma
First results of NSTX-U research operations
26.10.2016 | DOE/Princeton Plasma Physics Laboratory
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
27.10.2016 | Materials Sciences
27.10.2016 | Physics and Astronomy
27.10.2016 | Life Sciences