Graphene is widely regarded as one of the most exciting materials in the world of materials science. Graphene has leapt to relative fame in the 21st century with a number of high profile experiments and discoveries. In particular, Prof Andre Geim and Prof Kostya Novoselov of the University of Manchester were awarded the Noble Prize in Physics for their ground-breaking research into this intriguing two-dimensional material. Since then, Graphene has been linked with all sorts of technology and potential applications. But, what is it?
Put simply, Graphene is an allotrope of Carbon (Like Diamond) but arranged in a very thin (one atom thick) planar sheet of bonded carbon atoms densely packed in a honeycomb lattice structure.
A great way of thinking about Graphene is to start with a standard pencil and draw a line on a piece of paper. Most pencils are made using Graphite for their core and nearly every one of us has drawn a line on paper with a pencil. Therefore, we have all experienced and ‘made’ an extremely thin layer of Graphite on the paper – and a single layer of one-Atom thick Graphite sheet is in fact Graphene.
Graphene: unexpected science in a pencil line
Graphene: Unexpected Science in a Pencil. Video credit: University of Manchester, Run Time 1:47 mins
When was Graphene Discovered?
Scientists have known about the distinct layers that make up Graphite (Graphene) since the invention of X-ray Crystallography but the first reference to the name ‘Graphene’ is said to have been made by S. Mouras et al in 1987 to describe the graphite layers forming Graphite Intercallation Compounds or GIC’s. Previously, Graphene may have been described as graphite layers, carbon layers or carbon sheets. However, these terms would imply that the material was 3D and this is now recognised as not being the case for Graphene which is the only 2D Crystal known to man.
It was originally thought that Graphene was ‘unstable’ in its free state but once isolated for the first time by Andre Geim and Kostya Novoselov at the University of Manchester in 2003, it proved to be quite the opposite.
What Makes Graphene Special?
First, we must understand what Allotropes are; different structural forms of the same element with unique material characteristics, physical properties and chemical behaviours. For example, Diamonds and Graphene are made entirely of the same element (Carbon) but, the atoms are arranged in a different way, resulting in a completely different material.
Because Graphene is an isolated atomic plane of Carbon atoms tightly packed in a Honeycomb lattice (just one Carbon Atom thick) it is regarded as a 2 dimensional ‘building-block’ of Graphite. Hence, Graphite, in its simplest form may be described as lots of layers of graphene arranged on top of each other to make a 3 dimensional structure.
Graphene is special for a number of reasons but the principle reason for its notoriety is that it is the thinnest material known to man and yet it is also one of the strongest. As a conductor of heat it outperforms all known materials while being able to conduct electricity as efficiently (if not more efficiently) as Copper.
Graphene is also nearly transparent, yet still very dense: not even the smallest atom can pass through its densely packed honeycomb structure.
Introducing The Unique Properties of Graphene
Video Credit: University of Manchester. Run Time: 2:48mins
Key Material Properties of Graphene
Graphene may be just 1 Carbon Atom thick but it has some extremely exciting mechanical, optical, thermal, chemical and electronic properties:
- The Atomic Structure of Graphene is: sp2-bonded Carbon Atoms
- A Carbon-Carbon Bond Length of 0.142 Nanometres (nm)
- Thinnest Material Known to Man – 0.33nm (1millionth the thickness of human hair)
- The Lightest Material Known
- Extremely Strong (Harder than Diamond and 300x Harder than Steel)
- High Tensile Strength (>1TPa)
- Extremely Dense
- High Thermal Conductivity (> 5000 W/m/K)
- Highly Efficient Electrical Conductivity – More Efficient than Copper
- No Band Gap - Absorbing Photons T Any Energy Frequency
- Massless Charge Carriers - Quantum Hall effect - the 1st Material found to Exhibit this at Room Temperature
- Optical Transparency
- Elastic / Stretchable (u to 20% of Original Length - Unique for a Material this Strong)
- High Surface Area to Mass Ratio
- High Light Absorption – 2.3%
Since first being isolated in its ‘free-form’ and proved to be stable in 2003, Graphene has been linked with many fascinating and exciting applications in both material science and wider industry. Including but not limited to:
- Graphene Sensors – Extremely Fast Single Molecule Sensor Cells
- LCD (Liquid Crystal Displays)
- Organic Photovoltaic Cells
- Organic Light Emitting Diodes (OLEDs)
- Integrated Circuits
- Ballistic Transistors
- Single Layer Nano-diodes
- Flexible Electronics
However, with existing manufacturing processes Graphene is extremely challenging to mass produce which could prove to be a limiting factor in its commercial use. Therefore for many of the applications we highlight here, the Size of Graphene sheets required are currently just not feasible to produce economically. Much of the current research into Graphene is focusing on ‘growing’ the Carbon crystals in sheets big enough for commercial use but this method in itself has it’s commercial downsides.
The future for Graphene…
The future for Graphene is incredibly diverse but some principle, high-ranking future applications are listed below:
- Rapid DNA Sequencing
- Flexible Touch-screens
- LCD ‘Smart Windows’
- Terahertz Electronics
- Graphene Plasmonics – Extremely Fast Photo-Detectors / Photocells
- Single molecule Sensors
- Ultra Fast Pulsed Lasers
- Electrochemical Energy Conversion and Storage
However, Graphene research does not end here, the world of materials science is particularly focused on two ‘siblings’ of Graphene (which share a similar structure): Carbon Nano-tubes and fullerenes (often referred to as bucky-balls), regarded as 1-dimensional and 0-dimensional respectively. Although still at a very experimental stage, these materials may well revolutionise Electronics and Industrial Lubricants.