The present invention is directed to methods of separating carbon nanotubes (CNTs) by their electronic type (e.g., metallic, semi-metallic, and semiconducting). Perhaps most generally, in some embodiments, the present invention is directed to methods of separating CNTs by bandgap, wherein such separation is effected by interacting the CNTs with a surface such that the surface interacts differentially with the CNTs on the basis of their bandgap, or lack thereof. In some embodiments, such methods can allow for such separations to be carried out in bulk quantities.