Graphene is a form of carbon which has recently been receiving a great deal of attention. Some have come to call it “the wonder material” due to its many extraordinary properties. Although isolated in 2004, graphene's properties had been calculated decades earlier. It consists of a single layer of carbon atoms arranged in a hexagonal lattice. A single sheet of graphene is stronger than steel and yet remains very flexible, retaining all of its properties despite being bent and unbent multiple times. It is able to sustain extremely high electric current densities, is impermeable to all gasses, has a thermal conductivity double that of diamond and a very high electron mobility at room temperature. It is also easily chemically functionalized, allowing its properties to be increased or modified depending on the method with which it is made, or if it has metal ions within it.
Thanks to these many properties, graphene's potential is almost limitless. Its high electrical properties and impermeability to gasses make it excellent for use in ultracapacitors and fuel cells. Since it is carbon based, it is capable of working well with biological systems, making it ideal for bioapplications. Its thin sheets can be rolled into tubes for nanoelectronics. Its high optical absorption gives it a potential in phototonics, and it can be chemically modified to make it more suitable for each application.
What is Graphene?
There is often a lot of confusion as to what graphene really is. Graphene is defined as a single layer of carbon atoms arranged in a hexagonal lattice. However, there a number of materials often described as graphene, despite not matching this description. This is often called “pristine graphene.” The only a few ways to obtain such graphene. However, it is possible to create materials that are very similar to graphene.
Graphite oxide is an essential component of most methods of making this almost-graphene. As the name implies, it is graphite which has been oxidized, the most common method being Hummers' method. Graphene oxide is exfoliated graphite oxide. From there, graphene oxide can be reduced, making reduced graphene oxide, or r-GO.
r-GO is most commonly referred to as graphene, and it is the subject of most studies done on graphene. It is the most similar to pristine graphene, and its only difference from pristine graphene is that it sill has some oxygens and hydrogens left over from the graphite oxide. Despite these defects, pristine graphene's and r-GO's properties are still very similar. (Dreyer et al. 2010)
Epitaxial graphene is another common type. Epitaxial materials consist of a crystalline substance on top of another crystalline substrate. The most common form of epitaxial graphene is a single layer of graphene over a substrate of single-crystal silicon carbide. Silicon carbide itself has a high electrical properties and is currently used in many electronics. Combining it with graphene increases its electrical properties.