Resonant, Plasmonic Raman Enhancement of α-6T Molecules Encapsulated in Carbon Nanotubes

Surface-enhanced Raman scattering (SERS) and resonant Raman scattering are
widely used techniques to enhance the Raman intensity of molecules and nanomaterials by several orders of magnitude. In surface-enhanced Raman scattering typically molecules are investigated and their intrinsic resonance is often ignored while discussing the plasmonic enhancement. Here, we study α-sexithiophenes encapsulated in carbon nanotubes placed in the center of a nanodimer. By dielectrophoretic deposition we place the nanotubes precisely in the center of a plasmonic gold nanodimer and observe SERS enhancement from individual tube bundles. The encapsulated molecules are not subjected to chemical enhancement due to the protective character of the nanotube. Polarization dependent Raman measurements confirm the alignment of the molecules within the CNT and reveal the influence of the plasmonic near-field on the molecule’s Raman intensity. We investigate the encapsulated molecules in small CNT bundles with and without plasmonic enhancement and determine the molecular and plasmonic resonance by tuning the excitation wavelength. We observe a strong redshift of the maximum Raman intensity under plasmonic enhancement towards the plasmon resonance.