Scientific Results

Re-radiation enhancement in polarized Surface-Enhanced Resonant Raman Scattering of randomly oriented molecules on self-organized gold nanowires

Year: 2011

Authors: Fazio B., D’Andrea C., Bonaccorso F., Irrera A., Calogero G., Vasi C., Gucciardi P.G., Allegrini M., Toma A., Chiappe D., Martella C., Buatier de Mongeot F.

Autors Affiliation: CNR IPCF Istituto per i Processi Chimico-Fisici, Viale F. Stagno D\’Alcontres 37, I-98156, Messina, Italy; Dipartimento di Fisica “Enrico Fermi”, Università di Pisa and INO-CNR Sezione di Pisa, Largo Bruno Pontecorvo 3, 56126 Pisa, Italy ;Dipartimento di Fisica, Università di Genova, and CNISM, Via Dodecaneso 33, I-16146 Genova, Italy

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.

Journal/Review: ACS NANO

Volume: 5 (7)      Pages from: 5945  to: 5956

More Information: We acknowledge support by MIUR under Project PRIN 2008J858Y7. B.F., C.D\’A., and P.G.G. acknowledge funding from the European Union Seventh Framework Programme (FP7/2007-2013) under Grant Agreement No. 241818 (FP7-HEALTH-F5-2009-241818-NANOANTENNA). F.B.dM. acknowledges support by CNISM under project Innesco, by MAE under program Italia-Polonia, by Fondazione CARIGE and by ENEA under contract MSE.
KeyWords: nanoantennas; nanowires; self-organization; surface-enhanced Raman spectroscopy; polarization effects
DOI: 10.1021/nn201730k

Citations: 79
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