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New function for Nobel compound

AmirResearchers have used Raijin to discover that nano-sized fragments of graphene can speed up the rate of chemical reactions.

Assistant Professor Amir Karton from the University of Western Australia said the finding suggested graphene – sheets of pure carbon – might have potential applications in catalysing chemical reactions of industrial and medical importance.

“Graphene is one of the most exciting materials to work with in nanotechnology because its 2D structure and unique chemical properties make it a promising candidate for new applications like nanodevices that can be used in mobile phones, health care devices and renewable energy,” Assistant Professor Karton said.

“Ever since the discovery of graphene in 2004, scientists have been searching for applications. We have discovered a new catalytic activity of graphene nanoflakes, which is very exciting.”

Graphene is remarkably strong for its weight – about 100 times stronger than steel – and conducts heat and electricity with great efficiency. The global market for graphene is reported to have reached US$9 million this year with most sales concentrated in the semiconductor, electronics, battery energy and composites.

“Graphene is a very hot topic at the moment,” says Assistant Professor Karton.

“Its discoverers earned a Nobel prize in 2010 just six years after its discovery. Most compounds of historical significance have been recognised with a Nobel prize 20 or even 30 years after discovery. That’s how amazing this material is.”

Assistant Professor Karton, who is supported by an ARC Discovery Early Career Researcher Award, used Raijin to show, for the first time, that graphene nanoflakes could efficiently catalyse a range of chemical reactions.

The sophisticated computational modelling they used had enormous compute and data requirements.

“Graphene nanoflakes are relatively large, as far as molecules go, which meant the compute requirements of the modelling increased exponentially with the size of the system. We required really large-scale calculations that we couldn’t do on any other cluster in Australia but Raijin.

“The two things that were really crucial for this project were very large RAM and very large and fast disks. We couldn’t have done it without the NCI facilities.”

The specific chemical reactions that graphene nanoflakes catalyse are called ‘inversion reactions’ of non-planar aromatic compounds such as the famous C60 carbon ‘buckyball’.

“C60 is highly symmetrical and you can break it down into two basic fragments,” Assistant Professor Karton explains. “These fragments are aromatic, bowl-shaped molecules which can convert from concave to convex.

“We found that graphene nanoflakes can catalyse this conversion through what we call ‘π–π interactions’.”

One of the two bowl-shaped molecules, corannulene, is a chiral molecule – that is, it can exist in two asymmetrical versions – and graphene nanoflakes can catalyse the conversion between these two forms.

Assistant Professor Karton says while it would be premature to say there are industrial applications for the discovery, he says it may be of interest to pharmaceutical companies.

“With most of the drugs we have that are chiral – that is, they can exist in asymmetrical versions – only one version will be biologically active. The ability to catalytically invert these chiral molecules might be helpful in understanding chiral inversions,” he says.

The team are also working with other computational groups at UWA to extend their work to graphene sheets, and with experimental groups, in order to test their computational predictions in real life.

“The next steps would be to extend the catalytic scope to other types of chemical reactions and extend the scope of the study to ‘infinite’ graphene sheets rather than graphene nanoflakes,” Assistant Professor Karton said.

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