Graphene, Graphene Oxide and Carbon Nanotubes in Raman Spectroscopy

In previous discussions we have considered the Raman spectra of specific carbon-based materials, such as diamond, graphite, and the biochar resulting from pyrolysis of biomass. We have shown how spectra can be decomposed, according to the intended number of components and the proper line shapes. Here, we approach the Raman spectra of graphene and graphene oxide, to understand how many components are required to interpret the related fingerprints. Besides graphene and graphene oxides, here we also review some literature about the Raman spectroscopy of carbon nanotubes, focusing especially on the line shapes. As shown by literature, the Raman spectra are able of giving information on the nature of nanotubes (metallic or semiconducting) and if they are single- or multi-walled structures. We will find that the Raman spectroscopy is able of investigating even a single nanotube. It will be stressed the role of curvature in breaking the symmetry of carbon layers, to produce the observed Raman bands. In particular, the existence of Breit-Wigner-Fano lines will be investigated.