Simply Turn Up The Heat To Raise The Pressure

Scientists in Japan have discovered that simply heating graphene oxide nanosheets can generate high amounts of pressure with very little effort.

AsianScientist (Oct. 12, 2017) – In a study published in the journal Scientific Reports, researchers in Japan have demonstrated that the pressure between layers of graphene oxide can be tuned by heat.

Graphene is a sheet of carbon that is only one atom thick, drawing worldwide attention as a new material. The 2010 Nobel Prize in Physics was awarded to two scientists, Professors Andre Geim and Konstantin Novoselov, for their groundbreaking graphene experiments. The material is very thin, strong, flexible, and has high electrical conductivity.

On the other hand, oxidized graphene nanosheets have many oxygen functional groups at the front and back of graphene. Previous research has shown that if several layers of oxidized graphene nanosheets are heat treated, the interlayer distance shrinks as oxygen functional groups are eliminated.

In this study, a research group from Kumamoto University, Japan has discovered that pressure can be generated by simply stacking graphene oxide nanosheets and reducing the interlayer distance through heat treatment. It is an innovative approach for applying high pressure without using an enormous amount of energy.

To measure pressure between nanosheets, they used molecular materials that change the electrical state of metal ions in response to pressure in what is known as the spin crossover phenomenon. They observed an electrical state change of iron nanoparticles by sandwiching the material and measuring the spin crossover phenomenon between graphene oxide nanosheets.

As the interlayer distance became smaller, the pressure between layers increased. This meant that the pressure value can be adjusted by the heat treatment temperature. The maximum pressure the researchers measured was 38 megapascals. Moreover, they found that pressure does not occur unless the nanosheets are properly stacked.

“There are several examples of special materials that cause compression by sandwiching or wrapping, similar to our results here,” said Assistant Professor Ryo Ohtani of Kumamoto University who led the study. “But as far as we know, this graphene nanosheet is the first example in the world with the ability to adjust applied pressure by simply changing the heat treatment temperature.”

“We expect that this ‘nano-compressor’ will lead to new developments from fields such as material chemistry or physics, particularly since this technique produces high pressures that normally cannot be obtained without adding a large amount of energy,” he added.



The article can be found at: Sekimoto et al. (2017) Tuneable Pressure Effects in Graphene Oxide Layers.

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Source: Kumamoto University; Photo: Shutterstock.
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