Effect of charge of a matrix polymer on the electronic states of single-walled carbon nanotubes

The determination of electronic states of single-walled carbon nanotubes (SWNTs) has been a central issue in science and nanotechnology of carbon nanotubes. Previously, we reported the electronic states of (n,m)SWNTs that were embedded in an anionic polymer, carboxymethylcellulose sodium salt (CMC). It is important to reveal how the electronic properties of individual (n,m)SWNTs are affected by the surrounding microenvironment. In this study, we focused on the effect of charge of the SWNT solubilizers. We used a cationic polymer, hydroxyethylcellulose ethoxylate (quaternized) (HEQ) as the SWNT solubilizer in place of CMC, and the isolated (n,m)SWNTs were embedded in a film of HEQ (matrix polymer) on an electrode. We found that the charge of HEQ virtually does not affect the electronic parameters, i.e., oxidation/reduction potentials, Fermi levels, and band gaps of the (n,m)SWNTs, indicating that the presented electronic parameters are the parameters of the intrinsic (n,m)SWNTs.