Environmental effects on photoluminescence of single-walled carbon nanotubes

Spectroscopy is a powerful technique to characterize single-walled carbon nanotubes (SWNTs). In particular, photoluminescence (PL) and the excitation spectroscopies have made a great advance in understanding the energy states and transition processes of excitons in SWNTs. The PL spectroscopy also has a potential to assign the chiral index (n,m) of a SWNT and to evaluate the abundance of (n,m) in bulk SWNTs. (Bachilo et al., 2002, Miyauchi et al., 2004). In order to establish the PL spectroscopy as a reliable standard technique to characterize SWNTs, it is necessary to understand not only the intrinsic physics of excitons, but also the effect of extrinsic factors, so-called environmental effects. (Fantini et al., 2004) The optical property of SWNTs is modified sensitively by the environmental condition around the SWNT, since excitons exist on the surface of the SWNT. In this chapter, we focus on the environmental effects on the optical properties of SWNTs. After fundamental physics of the optical transition and PL spectroscopy in SWNTs, various types of environmental effects are discussed with the practical examples.