Band structure changes of single-wall carbon nanotubes by the presence of an ionic shell

We report the change of the band structure of two types of carbon nanotubes due to the presence of an isolated, non-conducting, uniformly charged shell held at a fixed distance above their surfaces. We find that, depending on the chirality of the nanotube, the strain on the lattice causes the dispersion relationships to change. This change can result in a modification of the band structure which can induce a metal--semiconductor transition. We consider these effects as a mechanism for heavy-metal ion sensing by functionalized carbon nanotubes.