Infrared-active phonons in carbon nanotubes

The aim of the present paper is to identify the main infrared vibrational features of carbon nanotubes. In this goal, infrared experiments have been performed on different well-characterized single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) as well as graphite and carbon aerogel. The comparison between the experimental spectra measured on these different samples allows us to identify the infrared-active modes of carbon nanotubes. In SWCNTs, the tangential modes are located around 1590 cm(-1) and the radial mode around 860 cm(-1). This latter mode vanishes in the infrared spectrum of DWCNTs. Finally, in the infrared spectra of all the carbon nanotubes investigated, a band around 1200 cm(-1) is evidenced and assigned to the D-band (disorder-induced band).