Plasmon-enhanced Raman scattering of coaxial hybrid nanowires made with light-emitting polymer and gold

We report on the plasmon-enhanced Raman scattering of coaxial hybrid nanowires (NWs) made with light emitting poly(3-methylthiophene) (P3MT) and gold (Au) core or coating. Absorption spectra of coaxial hybrid NWs showed the absorption peaks because of localized surface plasmon (SP) excitation at ∼ 567 and ∼ 610 nm, in addition to the π-π* transition peaks of P3MT. Raman spectra of a single strand of coaxial hybrid NW and plain P3MT NW was obtained by using three different wavelengths of laser excitation of 514, 633, and 785 nm. We found that Raman intensities of hybrid coaxial NWs were enhanced by 4 to 15 times over those of plain P3MT NWs with the Raman excitation wavelengths close to the observed SP energies of coaxial NWs. We attributed the observed enhancement of the Raman signal to the resonance of the incident laser with the matching SP energies, rather than the possible doping level change, in hybrid coaxial NWs.