Graphene has extraordinary properties which will lead to a revolution in many technology areas. We have some examples here.
The outstanding properties of graphene make it attractive for applications in flexible electronics. Byung Hee Hong, Jong-Hyun Ahn and co-workers have demonstrated roll-to-roll production and wet chemical doping of mostly monolayer graphene films grown by chemical vapour deposition onto flexible copper substrates. They also used layer-by-layer stacking to fabricate a doped four-layer film with properties superior to those of commercial transparent electrodes such as indium tin oxides. The photograph on the cover shows a flexible touch-screen device containing graphene electrodes.
Graphene is flexible, absorbs only 2.3% of light and conducts electricity very well. A layer of liquid crystals is sandwiched between two flexible electrodes comprised of graphene and transparent polymer.
When there is no applied bias between the electrodes, liquid crystals scatter light and the smart window is opaque. When a bias is applied, the voltage aligns them, allowing light to pass through and the smart window turns transparent.
Graphene is one of the strongest and stiffest known materials and is also very light weight. These properties mean that graphene can be mixed with plastics such as epoxy to make composites which have good specific physical properties (i.e. strength per unit mass). Such graphene-plastic composites could be used to replace metals in the manufacture of aircraft and cars, making them lighter and more fuel efficient. Graphene is also electrically conductive which means it can be added to plastics to make them conductive as well. Conductive plastics are needed to protect carbon fibre aircraft wings against lightning strikes and prevent sparks from static electricity in the fuel lines and tanks of vehicles.
Given the great versatility of graphene’s properties and especially the ability to control many of its characteristics by external electric field (gate voltage), graphene has a potential to become an excellent material for spintronics. Our current efforts concentrate on ‘making graphene magnetic’ by introducing point defects, such as vacancies or adatoms. We have already demonstrated that vacancies in graphene act as individual magnetic moments and lead to pronounced paramagnetism. The effect of fluorine adatoms is even greater. Our study also revealed significant limitations on defect-induced magnetism in graphene: it appears to be impossible to make graphene ferromagnetic in this way, because adatoms attached to neighbouring carbon atoms effectively cancel each other’s magnetism, while high densities of vacancies destroy graphene’s crystal structure and its essential properties. Nevertheless, even the achieved weak magnetism makes it an exciting potential candidate for spin-based devices. The next step is to learn how to reversibly control this magnetism by electric field.
Conventional electronic devices are made up of silicon semiconductors, metal contacts, doped junctions or barrier structures, etc. Each of these components must be added vertically on top of one another. In contrast, we have recently developed novel concepts of nano-diodes and transistors that are based on single-layered device architecture. By using nano-scale electronic channels and tailoring the geometrical symmetry, the new devices have been demonstrated to have extremely high speed up to 1.5THz (1,500GHz), making them by far the fastest nanodevices to date. The single-layered device structures are particularly ideal for the unique, single-atom-layer graphene materials, with much greater performance envisaged. The immediate applications include high-speed electronics for next generation of computations and communications, far-infrared THz detection and emission, ultra-high sensitive chemical sensors, etc.
Contact: Prof. Aimin Song
Graphene plasmonics: extraordinary electronic properties of graphene combined with extraordinary optical properties of plasmonic metamaterials promise new exciting applications.
There are two main directions in developing graphene plasmonics:
- Plasmons can be used to modify the optoelectronic properties of graphene with possible application in graphene photovoltaics. This could lead to extremely fast photo-detectors and effective photocells.
- Graphene can be used to modify and electrically govern the optical properties of plasmonic systems. This could lead to the development of inexpensive, fast and small active optical elements.
Contact: Dr. Sasha Grigoriencko
There is enormous current interest in electrochemical energy conversion and storage. Developing efficient electrochemical methods and materials is a high research priority. Graphene is the ideal electrode material: it is conducting, relatively inert, light, strong, flexible and has maximum surface area - essential because electrochemical conversion processes are interfacial by definition, so depend on the amount of surface available. Consequently, there is huge effort here in Manchester in developing batteries, fuel cells, photovoltaic cells and supercapacitors based on graphene. Electrochemical methods can also contribute to the synthesis of graphene: to ensure that the supply of this fascinating material does not become a bottleneck in technological development.
Our philosophy is that the properties of graphene should be understood on a fundamental level, which would then allow their use in electrochemical devices to be optimised. Carbon based materials (graphites, amorphous carbons and nanotubes) are the basis of many electrochemical technologies, however the properties of the electrodes are dependent on the type/morphology of the carbon: it is important to see where graphene fits into the overall electrochemical "carbon spectrum".
Contact: Prof. Rob Dryfe
University of Manchester scientists were the first to demonstrate single-atom sensitivity in graphene Hall-bar devices. The most sensitive electronic detection is achieved by constructing a Hall-bar with graphene. Measurements are performed under the influence of a magnetic field, which deflects the electrons in the transverse direction to the applied electric field, generating a Hall voltage which is measured. This transverse Hall resistivity is very sensitive to changes in carrier concentration. The binding event between the graphene sensor and analyte leads to the donation or withdrawal of an electron from the graphene, which changes its electrical conductivity which can be measured. When a device is fabricated with a graphene sheet suspended in free space between two electrodes, it has a resonance frequency of vibration proportional to its mass. When an analyte interacts with such a graphene sensor, it changes the mass of the sensor. Some examples of sensor applications being pursued at Manchester include Genome-based graphene biosensor for detection of plant-to-plant and plant-to-pest signaling pathways in e-Agri and low-cost photonic sensors for environmental/health monitoring.
- Integrated circuits and nano-electronics
- Saturable Absorber for Ultrafast Pulsed Lasers
- Single Molecule Sensors
- Solar Cells