There is nothing as spectacular as being at the forefront of science. This is exactly where we are, when talking scientific developments within the chemistry of the material graphene. Graphene was discovered as recent as in 2004 – and only 6 years later, the scientists Andrew Geim and Konstantin Novoselov were awarded the Nobel Prize in physics for their discovery. This highlights how amazing the material graphene is.
What Is Graphene?
Graphene is essentially a single atom thin sheet of carbon atoms – the building blocks of a graphite crystal. What is amazing and surprising is that being only a single atom thin sheet, graphene is effectively a two-dimensional crystalline material – this was until 2004 believed to be theoretically impossible. However, graphene does indeed exist and it is an amazingly strong and stable material.
What Is It Good For?
The special structure of graphene results in a number of amazing properties. Because of the symmetric structure of the material and its special double bond structure, graphene is a conducting material. In fact, it is the best conducting material at room temperature ever found. Essentially, electrons in graphene travel through a perfect graphene crystal without any energy loss. Imagine using this in your computers – there would be no energy loss to heating, and no cooling needed! This is one of the dreams of graphene research.
Graphene Keeps Everything Out
Another property of graphene is that it is impermeable to all gasses, water vapor etc. This is a very interesting property for protecting other materials. In principle, covering a piece of metal in graphene would make a perfect protection against corrosion!
Strong Conducting Plastic!
Mixing graphene pieces into other materials could alter those materials properties completely. One of the most widely used type materials in the world is plastic – or polymers. These materials very often require a number of toxic chemical additives to improve their properties. Many of these additives are known to have some unwanted effects, such as degrading fertility, damaging our kid’s health etc. If we could find replacements for these, it would be amazing. For some materials, this could be graphene. Mixing graphene into the polymer will alter the properties of the final material.
As the atomically thin layers of Graphene are essentially the building blocks of graphite, graphite is an obvious starting material in the production of graphene. Graphite is readily available commercially in huge quantities at relatively low prices. Graphite was also the starting material for the first successful production of graphene in 2004 by Andrew Geim and Konstantin Novoselov in Manchester. It was simply done by peeling layer by layer of a graphite crystal using ordinary adhesive tape. Using this very inefficient method extremely small graphene flakes of very high quality can be produced. These are mainly used for research purposes, when probing the special electronic properties of graphene.
Since the first scientific paper on graphene in 2004, a wide range of methods have been developed to produce graphene. These methods are taking two completely different approaches.
- Exfoliation from graphite
- Synthesis of large areas of graphene
Exfoliation from Graphite
To produce high volumes of graphene, chemical and physical methods are developed to split graphite into single sheets of graphene. The most widely used method at the moment is through the oxidation of graphite into graphite oxide, which is easily separated into single sheets and suspended in water. However, the properties of the produced graphene oxide is very different from pristine graphene. It is an insulator and not a conductor, it is brownish and not black, it is not as strong as graphene etc.
In order to improve on this, a number of solutions for producing pristine graphene from graphite have been suggested. These use either ultrasound, high shear forces or electrochemical intercalation of charged compounds to separate graphene. The disadvantage of these solutions are that the yield is often very low and it is very difficult to obtain stable dispersions of graphene in almost any solvent.
In our group we work both with oxidation, ultrasound, shear forces and electrochemical methods to produce graphene for the different projects.
Synthesis of Large Areas of Graphene
There are a number of methods to produce larger flakes of graphene, however the most widely used and most developed method is chemical vapor deposition (CVD) of graphene on metal substrates. A metal substrate is used as a catalyst to form the very stable graphene structure. The metal is heated in the presence of a carbon containing gas such as methane and as the carbon adsorb on the metal, the graphene structure is formed. Using this method it has been possible to make up to 30 inch pieces of single layer graphene.
In order to use the graphene produced in this way to make products like touch screen sensors, graphene has to be moved from the metal and onto another type of substrate. This can be done either by etching away the metal or by lifting of the graphene using physical, chemical or electrochemical methods.
In our group we are routinely producing graphene using CVD methods, as well as transfer graphene using both etching and electrochemical lift off techniques.
The Challenges – And Why We Study Graphene!
Graphene is found and produced in a wide range of qualities and forms. These all have different properties and it is a big challenge to understand and control properties of such a 2D material – a challenge science has never faced before. If we can control these properties, we can realize a number of amazing applications of graphene such as extreme coating materials, high-speed flexible and transparent electronics, new safer and better plastic materials, fast electronic sensors for a number of diseases … and the list just continues.
However, all this require that we can obtain a perfect control of the chemistry of an atomically thin sheet of carbon atoms. An exciting challenge that we are part of through the two large research projects DA-GATE and NIAGRA.
DA-GATE – the Danish Alliance of Graphene Application Technology and Engineering – is a national project funded by the Danish Council for Strategic Research with a grant of 20 mio DKK, running up to a total budget of 37 mio DKK. DA-GATE started in February 2013 and will run until 2017.
There are three important goals of DA-GATE:
- Producing and being able to handle and transfer single crystalline graphene in wafer scale.
- Making strongly bound graphene coatings that are resistant towards abrasion and corrosion.
- Producing graphene from graphite and understand how to control and handle this material for making printed electronics.
Our contribution is primarily within developing electrochemical techniques for transferring graphene grown on a metal substrate to other materials for high-speed electronics and to develop new methods for binding graphene to other substrates for coating applications.
The DA-GATE project is a joined project together with DTU, KU, LEGO, Welltec, Mekoprint, SP Group, Grundfos, Fraunhofer, Techflow, DTI, Aixtron, and SOL Voltaics.
NIAGRA – the National Initiative for Advanced Graphene Coatings and Composites – is a project aimed at taking graphene technology all the way to commercial products together with a number of industrial partners. The project is funded by the Danish National Advanced Technology Foundation with a total budget of 46 mio DKK. The project was started in 2013 and runs until 2018.
In NIAGRA the primary focus is on graphene as coating material as well as making new plastic materials combined with graphene – so-called polymer composite materials. We develop new methods for chemical control of graphene in order to prepare it for mixing with other materials in polymer composites and coatings.
The NIAGRA project is a joined project together with DTU, KU, Welltec, Mekoprint, SP group, and LEGO.