Researchers at Queen Mary University of London have shown that graphene is 3D as well as 2D. Image: Yiwei Sun.
Researchers at Queen Mary University of London have shown that graphene is 3D as well as 2D. Image: Yiwei Sun.

Graphene is actually a three-dimensional (3D) material as well as a two-dimensional (2D) material, according to a new study from researchers at Queen Mary University of London in the UK. Realizing that graphene is a 3D material is important for understanding its mechanical properties and for developing novel graphene-based devices.

Often hailed as a 'wonder material', graphene has the highest known thermal and electrical conductivity and is stronger than steel, as well as being light, flexible and transparent. Its uses are wide-ranging and recently it was shown that it could even act as a barrier against mosquito bites (see New study shows graphene can prevent mosquito bites).

In this new study, reported in a paper in Physical Review Letters, the researchers asked two fundamental questions: to what extent is graphene graphite, and what is the true thickness of graphene?

To their surprise, they found that 2D graphene, which is a single flat layer of carbon atoms arranged in a honeycomb structure, has many of the same mechanical properties as 3D graphite, which is a naturally occurring form of carbon made up of a very weak stack of many layers of graphene. They further discovered that graphene has a similar resistance to compression as graphite and that it is significantly thicker than is widely believed.

If the thickness of a block of graphite 100 layers thick is measured, the thickness of a single graphene layer should simply be the thickness of the graphene block divided by 100. Therefore, it is reasonable to consider graphene to have a thickness of 0.34nm.

"Graphene owes its thickness to an array of chemical bonds sticking out above and below the 2D plane of carbon atoms," explained lead author Yiwei Sun from Queen Mary University of London. "Hence graphene is really a 3D material, albeit with a very small thickness.

"By applying conventional 3D theory, which has been used for around 400 years, to 2D materials such as graphene, which have been known for 15 years, we show that similar arguments apply to other so-called 2D materials, such as boron nitride and molybdenum disulphide. In that sense, 2D materials are actually all 3D."

Graphene is often called the world's first 2D material. It was discovered in 2004 by peeling off graphene flakes from bulk graphite (used in pencil leads and lubricants) with sticky tape. It is regarded as part of a new class of 2D materials and is currently modeled by scientists as a sheet of atoms with very little depth, hence the name 2D material.

This story is adapted from material from Queen Mary University of London, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.