Graphene: it's Uses and Applications
The properties of graphene, carbon sheets that are only one atom thick, have caused researchers and companies to consider using this material in several fields. The following survey of graphene applications introduces you to many of these uses.
A survey of graphene applications:
Electrodes with very high surface area and very low electrical resistance. Researchers at Rice University have developed electrodes made from carbonnanotubes grown on graphene. The researchers first grow graphene on a metal substrate then grow carbon nanotubes on the graphene sheet. Because the base of each nanotube is bonded, atom to atom, to the graphene sheet the nanotube-graphene structure is essentially one molecule with a huge surface area.
Components with higher strength to weight ratios. Researchers have found that adding graphene to epoxy composites may result in stronger/stiffer components than epoxy composites using a similar weight of carbon nanotubes. Graphene appears to bond better to the polymers in the epoxy, allowing a more effective coupling of the graphene into the structure of the composite. This property could result in the manufacture of components with high strength to weight ratio for such uses as windmill blades or aircraft components.
Lower cost solar cells: Researchers have built a solar cell that uses graphene as a electrode while using buckyballs and carbon nanotubes to absorb light and generate electrons; making a solar cell composed only of carbon. The intention is to eliminate the need for higher cost materials, and complicated manufacturing techniques needed for conventional solar cells.
Transistors that operate at higher frequency. The ability to build high frequency transistorswith graphene is possible because of the higher speed at which electrons in graphene move compared to electrons in silicon. Researchers are also developing lithography techniques that can be used to fabricate integrated circuits based on graphene.
Lower cost of display screens in mobile devices. Researchers have found that graphene can replace indium-based electrodes in organic light emitting diodes (OLED). These diodes are used in electronic device display screens which require low power consumption. The use of graphene instead of indium not only reduces the cost but eliminates the use of metals in the OLED, which may make devices easier to recycle.
Storing hydrogen for fuel cell powered cars. Researchers have prepared graphene layers to increase the binding energy of hydrogen to the graphene surface in a fuel tank, resulting in a higher amount of hydrogen storage and therefore a lighter weight fuel tank. This could help in the development of practical hydrogen fueled cars.
Sensors to diagnose diseases. These sensors are based upon graphene's large surface area and the fact that molecules that are sensitive to particular diseases can attach to the carbon atoms in graphene. For example, researchers have found that graphene, strands of DNA, and fluorescent molecules can be combined to diagnose diseases. A sensor is formed by attaching fluorescent molecules to single strand DNA and then attaching the DNA to graphene. When an identical single strand DNA combines with the strand on the graphene a double strand DNA if formed that floats off from the graphene, increasing the fluorescence level. This method results in a sensorthat can detect the same DNA for a particular disease in a sample.
Lithium-ion batteries that recharge faster. These batteries use graphene on the surface of the anode surface. Defects in the graphene sheet (introduced using a heat treatment) provide pathways for the lithium ions to attach to the anode substate. Studies have shown that the time needed to recharge a battery using the graphene anode is much shorter than with conventional lithium-ion batteries.
Ultracapacitors with better performance than batteries. These ultracapacitiors store electrons on graphene sheets, taking advantage of the large surface of graphene to provide increase the electrical power that can be stored in the capacitor. Researchers are projecting that theseultracapacitors will have as much electrical storage capacity as lithium ion batteries but will be able to be recharged in minutes instead of hours.
Membranes for more efficient separation of gases. These membranes are made from sheets ofgraphene in which nanoscale pores have been created. Because graphene is only one atom thick researchers believe that gas separation will require less energy than thicker membranes.
Chemical sensors effective at detecting explosives. These sensors contain sheets of graphene in the form of a foam which changes resistance when low levels of vapors from chemicals, such as ammonia, is present.
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