Surface-enhanced Raman of Z-vibration mode in single-walled and multi-walled carbon nanotube

Normal Raman scattering (NRS) and surface-enhanced Raman scattering (SERS) have been performed on single-walled and multi-walled carbon nanotubes to observe fine vibrational structures at the low- and intermediate-frequency regions. Following surface enhancement with silver particles, it is observed that the radial breathing mode, tangential mode, the overtone phonon peaks and coupling phonon peaks are suppressed. In contrast, the Z-breathing phonons, which correspond to vibration along the nanotube axis, and which are usually weak or non-existent in NRS, become enhanced in the SERS of both SWNTs and MWNTs.