Graphene is a monolayer of carbon atoms arranged in a honeycomb pattern that is incredibly light, flexible, and strong. A new study published in the Proceedings of the National Academy of Sciences from senior author Puru Jena of Virginia Commonwealth University describes a new structural arrangement of carbon. Instead of carbon atoms arranged in hexagons, the pattern is made out of pentagons. Very aptly, the theoretical material is being called penta-graphene. In the future, this could have a wide range of implications.
"The three last important forms of carbon that have been discovered were fullerene, the nanotube and graphene. Each one of them has unique structure. Penta-graphene will belong in that category," Jena said in a press release.
Street tiles in Cairo are composed of pentagons, and a painting depicting that arrangement caught the eye of co-author Qian Wang while she was out eating dinner with her husband. Ever the scientist, she was immediately inspired by the pattern.
"I told my husband, "Come, see! This is a pattern composed only of pentagons,'" Wang recalled. "I took a picture and sent it to one of my students, and said, 'I think we can make this. It might be stable. But you must check it carefully.' He did, and it turned out that this structure is so beautiful yet also very simple.”
The penta-graphene was then synthesized with computer modeling. Analysis of the material revealed that it is very stable and will not rearrange without external manipulation, and that it is strong and can bear temperatures up to 1,000 Kelvin (1,340 °F).
There are also certain situations in which penta-graphene could outperform standard graphene. Graphene lacks a bandgap that allows it to act as a semiconductor without making structural changes that compromise its strength, but penta-graphene appears to function as a reliable semiconductor in multiple orientations.
"When you take graphene and roll it up, you make what is called a carbon nanotube which can be metallic or semiconducting," Jena explained. "Penta-graphene, when you roll it up, will also make a nanotube, but it is always semiconducting.”
While the computer modeling readily shows that this pattern has a number of desirable attributes, the next step isn’t going to be quite as easy. Taking a computerized pattern and synthesizing it into an actual material has not been attempted yet, and there isn’t a clear approach to take. However, the researchers are very optimistic about the potential of the design.
"Once you make it, it [will be] very stable. So the question becomes, how do you make it? In this paper, we have some ideas,” Jena explained. “Right now, the project is theoretical. It's based on computer modeling, but we believe in this prediction quite strongly. And once you make it, it will open up an entirely new branch of carbon science. Two-dimensional carbon made completely of pentagons has never been known.”