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Graphene (/ ˈ ɡ r æ f iː n /) [1] is a carbon allotrope consisting of a single layer of atoms arranged in a honeycomb planar nanostructure. [2] [3] The name "graphene" is derived from "graphite" and the suffix -ene, indicating the presence of double bonds within the carbon structure.
Graphene is the only form of carbon (or solid material) in which every atom is available for chemical reaction from two sides (due to the 2D structure). Atoms at the edges of a graphene sheet have special chemical reactivity. Graphene has the highest ratio of edge atoms of any allotrope. Defects within a sheet increase its chemical reactivity. [1]
Graphene is a semimetal whose conduction and valence bands meet at the Dirac points, which are six locations in momentum space, the vertices of its hexagonal Brillouin zone, divided into two non-equivalent sets of three points. The two sets are labeled K and K′. The sets give graphene a valley degeneracy of gv = 2.
Iron shows the characteristic chemical properties of the transition metals, namely the ability to form variable oxidation states differing by steps of one and a very large coordination and organometallic chemistry: indeed, it was the discovery of an iron compound, ferrocene, that revolutionalized the latter field in the 1950s. [1]
Graphene has very promising electrical properties. [1] Carbon nanotubes are semimetals meaning they are either metallic or semiconducting along the helical axis, this can depend on the curvature of the graphene helix. On top of having both of these properties graphene has a unique and useful is that it is a "zero-overlap semimetal". [2]
[9] [10] The electrons at the metallic structure could transfer to the graphene conduction band. This is attributed to the zero bandgap property of graphene nanosheet. Graphene plasmons can also be decoupled from their environment and give rise to genuine Dirac plasmon at low-energy range where the wavelengths exceed the damping length.
Graphene-metal composites can be used in thermal interface materials. [194] Adding a layer of graphene to each side of a copper film increased the metal's heat-conducting properties up to 24%. This suggests the possibility of using them for semiconductor interconnects in computer chips.
Bilayer graphene displays the anomalous quantum Hall effect, a tunable band gap [3] and potential for excitonic condensation. [4] Bilayer graphene typically can be found either in twisted configurations where the two layers are rotated relative to each other or graphitic Bernal stacked configurations where half the atoms in one layer lie atop half the atoms in the other. [5]