Storing energy in carbon nanotubes

Figure 1. Carbon single-walled nanotubes (SWNTs) can be imagined as rolled-up rectangular strips of graphene monolayers.
The width of the rectangle and its orientation with respect to the graphene lattice must be such that it folds around and produces a seamless tube
The tube’s symmetry, and hence the electronic properties, is determined by the orientation of the rectangle with respect to the hexagonal lattice.