carbon chemistry
Researchers from the US and China have discovered a structural variant of carbon called ‘penta-graphene’ - a very thin sheet of pure carbon that resembles the pentagonal pattern of the tiles which pave the streets of Cairo.
U The authors of the paper include Puru Jena, a distinguished professor in VCU’s Department of Physics; Qian Wang, a professor at Peking University and an adjunct professor at VCU; and Jian Zhou, a postdoctoral researcher at VCU.
and mechanically stable, but also can withstand temperatures as high as 1000 K”, the authors said. “You know the saying ‘diamonds are forever’?”
nlike most forms of carbon, which
said senior author Puru Jena from VCU. “That’s
are made of hexagonal building blocks and sometimes
because it takes a lot of energy to convert diamond
interspersed with pentagons, carbon structures
back into graphite. This will be similar.”
composed only of pentagons were, until now,
Penta-graphene’s mechanical strength is derived
unknown. Writing in the journal Proceedings of the
from a rare property known as negative Poisson’s
National Academy of Sciences, the researchers ask,
ratio, said the researchers, as a result of its unique
“Is it possible to have materials made exclusively of
atomic configuration. The way the material stretches
carbon pentagons and if so will they be stable and have
is particularly unusual, with Wang noting, “If you
unusual properties?”
stretch graphene, it will expand along the direction
Qian Wang, a professor at Peking University
it is stretched but contract along the perpendicular
and an adjunct professor at Virginia Commonwealth
direction. However, if you stretch penta-graphene,
University (VCU), explained that she was dining
it will expand in both directions.”
in a restaurant with her husband when she noticed
And while graphene is a conductor of electricity,
artwork on the wall depicting pentagon tiles from
penta-graphene is a semiconductor. Jena explained,
the streets of Cairo.
“When you take graphene and roll it up, you make
“I took a picture and sent it to one of my students,
what is called a carbon nanotube, which can be
and said, ‘I think we can make this. It might be stable.
metallic or semiconducting. Penta-graphene, when
But you must check it carefully,’” she recalled. “He
you roll it up, will also make a nanotube, but it is
did, and it turned out that this structure is so beautiful
always semiconducting.” Although penta-graphene is currently only
yet also very simple.”
36 | LAB+LIFE SCIENTIST - March 2015
The researchers simulated the synthesis of
theoretical, Jena believes the eventual synthesis of
penta-graphene - a two-dimensional carbon allotrope
the material will “open up an entirely new branch of
composed entirely of pentagons - using computer
carbon science”. The versatility of the penta-graphene
modelling. According to their calculations, “the
and its derivatives is expected to have applications in
new carbon polymorph is not only dynamically
electronics, biomedicine, nanotechnology and more.
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New structural variant of carbon made of pentagons