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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 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.
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]
The induced charge carriers of metal/graphene hybrid nanostructure could be up to 7 times higher than that of pristine graphene ones due to the plasmonic enhancement. So far, the graphene plasmonic effects have been demonstrated for different applications ranging from light modulation [15] [16] to biological/chemical sensing.
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.
A graphene helix, similar to the carbon nanotube, is a structure consisting of a two-dimensional sheet of graphene wrapped into a helix.These graphene sheets can have multiple layers, called multi-walled carbon structures, that add to these helices thus increasing their tensile strength but increasing the difficulty of manufacturing.
It was studied in detail by Kohlschütter and Haenni in 1918, who described the properties of graphite oxide paper. [9] Its structure was determined from single-crystal diffraction in 1924. [10] The theory of graphene was first explored by P. R. Wallace in 1947 as a starting point for understanding the electronic properties of 3D graphite.
In physics, Dirac cones are features that occur in some electronic band structures that describe unusual electron transport properties of materials like graphene and topological insulators. [ 1 ] [ 2 ] [ 3 ] In these materials, at energies near the Fermi level , the valence band and conduction band take the shape of the upper and lower halves ...