New features in the anti‐Stokes and Stokes Raman spectra of single‐walled carbon nanotubes that are highly separated into their semiconducting and metallic nanotube components

Surface‐enhanced Raman scattering studies were performed using nonresonant (514.5 nm) and resonant (676.4 nm) optical excitations on single‐walled carbon nanotubes thoroughly separated into semiconducting (pure 99%) and metallic (pure 98%) components. Regardless of the support (Au or Ag), the metallic nanotubes do not present an anomalous anti‐Stokes Raman emission. Regardless of whether an on‐resonant or off‐resonant optical excitation is used, only the semiconducting nanotubes produce an abnormal anti‐Stokes Raman emission that grows when increasing the excitation light intensity or temperature. The Raman studies under light polarized relative to the main nanotube axis demonstrate that only semiconducting nanotubes are sensitive toward changes in the polarization of the excitation light. Copyright © 2014 John Wiley & Sons, Ltd.