Diminished Band-Gap Transitions of Single-Walled Carbon Nanotubes in\nComplexation with Aromatic Molecules

Abstract

The near-IR absorption spectrum of semiconducting single-walled carbon nanotubes is characterized by the transitions associated with the first (S₁₁) and second (S₂₂) pairs of van Hove singularities in the electronic density of states. We report that a significant effect on the transitions can be caused by non-covalent complexation of the nanotube with planar aromatic molecules such as pyrenes in solution, resulting in the absence of S₁₁ and S₂₂ bands in the near-IR absorption spectrum. Since the complexation is reversible, the characteristic absorption bands can be turned on and off with the complexation in a reversible fashion.