Graphene and carbon nanotubes are the allotropic form of carbon. Single basal plane or layer of graphite is considered as graphene. Graphite is consisting of Sp2 bonds and diamond is of sp3 bonds. Carbon has four spare electrons. In graphite structure, two of them make two single (sigma) bonds while the other pair form a double bond (consists of one sigma and one pi bond). All of the bonds in the hexagons that form graphite layers are aromatic bonds. Each atom contributes a single electron in a p orbital to bonding that happens above and below the plane. All of the pi bonds are conjugated, making a large aromatic system that causes the conductivity. Electrical conductivity comes from phi bonds in carbonaceous materials. So graphitization can be considered as the primary condition.

Graphene and carbon nanotubes are the allotropic form of carbon. Single basal plane or layer of graphite is considered as graphene. Graphite is consisting of Sp2 bonds and diamond is of sp3 bonds. Carbon has four spare electrons. In graphite structure, two of them make two single (sigma) bonds while the other pair form a double bond (consists of one sigma and one pi bond). All of the bonds in the hexagons that form graphite layers are aromatic bonds. Each atom contributes a single electron in a p orbital to bonding that happens above and below the plane. All of the pi bonds are conjugated, making a large aromatic system that causes the conductivity. Electrical conductivity comes from phi bonds in carbonaceous materials. So graphitization can be considered as the primary condition.

Thank you so much Prof. Jiban Podder for your insightful explanations....

• DOI: 10.1016/S0008-6223(02)00196-3

Thanks Vinay S P for your time, but the paper you shared didn't discuss anything about my core question....

yes, heat has a great influence upon electrical conductivity, but also the degree of graphitization is more important. Amorphous carbon can increase a bit its conductivity, but the lack in a graphene-like structure will keep it from being highly conductive.

Thank you so much Aarón Morelos-Gómez

To me the term "graphitization" is not really valid for graphene and CNTs, as graphitization is a measure of several parameters that are only found in actual graphite. This includes parameters such as the interlayer spacing (d), the stacking between the different layers (ABA or ABC) etc. The probability for graphite stacking of layers (called P1) is then often used as an estimate of the level of graphitization in a material. But this parameter simply has no meaning in a single layer of graphene or in a single walled CNT.

In order to discuss the level of "perfection" or "crystallinity" in graphene and CNTs, I think that it is better to talk about an effective crystallite size (La) within the graphene layer itself. This effective grain size will limit the mean free path of the electrons and hence affect the electrical conductance. The value of La can be quantified by using selective area diffraction in a TEM, and will provide an estimate of the level of crystallinity in the material.

Here is some of our work in this area, where we relate the crystallite size La to the mechanical behaviour of CNTs: Article Quantifying crystallinity in carbon nanotubes and its influe...

Thank you very much Prof. Krister Svensson for your thought which actually i was expecting such explanations...Regards...

I totally agree with Jiban Podder. But I have some further confusion that why the conductivity of Graphene is better than Graphite. Graphene exhibits the highest in-plane electrical conductivity among known materials. Except for the anisotropy, I am wondering if it is possible that the van der Waals forces between interlayers of graphite restricts the delocalization of conjugated π electrons to some extent.

@ Huanxin Li: I believe the issue of poor conductivity in graphite has been solved. See Article Thermal Modification of Graphite for Fast Electron Transport...