Excitonic transition energies in single-walled carbon nanotubes: Dependence on environmental dielectric constant

The dependence of optical transition energies in single-walled carbon nanotubes (SWNTs) on environmental dielectric constant (epsilon(env)) have been investigated in the range of epsilon(env) from 1.0 to 37, by immersing SWNTs bridged overtrenches in various organic solvents by means of photoluminescence (PL) and the excitation spectroscopies. With increasing epsilon(env), both E-11 and E22 exhibited a redshift by several tens meV and a tendency to saturate at a epsilon(env) similar to 5 without an indication of significant (n,m) dependence. The redshifts can be explained by dielectric screening of the repulsive electron-electron interaction. We have also investigated the time-resolved PL in air and in solvent, respectively, utilizing the excitation intensity correlation technique. When the sample was immersed in solvent, the correlation signal collapsed, and the decay time decrease as compared to in air. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.