A) Molecular structure of graphene (GR), graphene oxide (GO), and reduced graphene oxide (rGO). B) Comparison of various graphene production techniques according to quality and cost: (a) molecular beam epitaxy, (b) micromechanical exfoliation, (c) chemical vapor deposition, (d) epitaxial growth on SiC, (e) molecular assembly, (f) liquid-phase exfoliation, and (g) photoexfoliation. Adapted with permission from (Bonaccorso et al. 2012)