title: Re-radiation enhancement in polarized surface-enhanced resonant Raman scattering of randomly oriented molecules on self-organized gold nanowires.
abstract: We explore the effect of re-radiation in surface-enhanced Raman scattering (SERS) through polarization-sensitive experiments on self-organized gold nanowires on which randomly oriented Methylene Blue molecules are adsorbed. We provide the exact laws ruling the polarized, unpolarized, and parallel- and cross-polarized SERS intensity as a function of the field polarizations. We show that SERS is polarized along the wire-to-wire nanocavity axis, independently from the excitation polarization. This proves the selective enhancement of the Raman dipole component parallel to the nanocavity at the single molecule level. Introducing a field enhancement tensor to account for the anisotropic polarization response of the nanowires, we work out a model that correctly predicts the experimental results for any excitation/detection polarization and goes beyond the E(4) approximation. We also show how polarization-sensitive SERS experiments permit one to evaluate independently the excitation and the re-radiation enhancement factors accessing the orientation-averaged non-diagonal components of the molecular Raman polarizability tensor.
authors.affiliation: CNR IPCF Istituto per i Processi Chimico-Fisici, Viale F. Stagno D'Alcontres 37, I-98156, Messina, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Fazio
authors.forename: Cristiano
authors.initials: C
authors.lastname: D'Andrea
authors.forename: Francesco
authors.initials: F
authors.lastname: Bonaccorso
authors.forename: Alessia
authors.initials: A
authors.lastname: Irrera
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Calogero
authors.forename: Cirino
authors.initials: C
authors.lastname: Vasi
authors.forename: Pietro Giuseppe
authors.initials: PG
authors.lastname: Gucciardi
authors.forename: Maria
authors.initials: M
authors.lastname: Allegrini
authors.forename: Andrea
authors.initials: A
authors.lastname: Toma
authors.forename: Daniele
authors.initials: D
authors.lastname: Chiappe
authors.forename: Christian
authors.initials: C
authors.lastname: Martella
authors.forename: Francesco
authors.initials: F
authors.lastname: Buatier de Mongeot
mesh_terms: D000327:Adsorption; D016880:Anisotropy; D006046:Gold / Q000737:chemistry*; D008962:Models, Theoretical; D053770:Nanowires / Q000737:chemistry*; D011827:Radiation; D013059:Spectrum Analysis, Raman; D013499:Surface Properties
chemical_list: D006046:Gold