Doping strategy of carbon nanotubes with redox chemistry

The chemical doping of single-walled carbon nanotubes (SWCNTs) has been an important issue in tailoring the electronic structures of SWCNTs. This paper proposes a strategy for controlling the doping types and doping concentrations by choosing the reduction potential of a dopant relative to the redox potential of SWCNTs. For this purpose, the redox potential plot in terms of the chirality and diameter was generated based on theoretical calculations, which were in good agreement with the experimental data obtained from individually separated SWCNTs. The change in the electronic structures of the SWCNTs with the various dopants was clearly observed by absorption and Raman spectroscopy, and was explained well by the redox potential argument. This principle was tested further by fabricating transparent conducting films followed by doping. Doping with Au3+ resulted in a sheet resistance of 100 Ω sq−1 at 90% transmittance. This SWCNT doping strategy for both n-type and p-type materials can be generalized to a wide range of nanostructures, such as nanowires and nanoparticles.