Density of Graphene

The unit hexagonal cell of graphene contains two carbon atoms and has an area of0.052 nm. We can thus calculate its density as being 0.77 mg/m.  

A hypothetical hammock measuring 1 m made from graphene would thus weigh 0.77 mg. 

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The delocalized electronic density of graphene is highly sensitive to moieties adsorbed on the surface, allowing the development of sensors [38] and transducers [39] using the vibronics scenario. It has been demonstrated that information can be coded and processed using molecular electrostatic potentials, and we would like to amplify these signals to be readable in the conventional microelectronics. 

Closely related to the ID dispersion relations for the carbon nanotubes is the ID density of states shown in Fig. 20 for (a) a semiconducting (10,0) zigzag carbon nanotube, and (b) a metallic (9,0) zigzag carbon nanotube. The results show that the metallic nanotubes have a small, but non-vanishing 1D density of states, whereas for a 2D graphene sheet (dashed curve) the density of states... 

Fig. 20. Electronic 1D density of states per unit cell of a 2D graphene sheet for two (n, 0) zigzag nanotubes (a) the (10,0) nanotube which has semiconducting behavior, (b) the (9, 0) nanotube which has metallic behavior. Also shown in the figure is the density of states for the 2D graphene sheet (dotted line) [178].

It has been known that the basal graphite plane (graphene hexagon) is chemically inert. However, CNTs are susceptive to some chemical reactions due to the it-orbital mismatch in the curvature structures. Oxidation studies have revealed that the tips (caps) of CNTs are more reactive than the cylindrical parts [8, 20], Ab initio calculations indicate that the average charge density of a pentagon (at the tips) is 3 4 times larger... 

While electron microscopy is an invaluable tool for characterization of graphene, it is a costly and often time-consuming technique. In contrast, Raman spectroscopy is a quick and easy method to obtain a wide range of properties of graphene, including flake size, layer number, defect density, and doping levels amongst others [118]. 

A.A. Green, M.C. Hersam, Solution phase production of graphene with controlled thickness via density differentiation, Nano Fetters, 9 (2009) 4031-4036. 

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