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Proceedings Paper

Plasmonic near-field nano-imaging and spectroscopy
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Paper Abstract

We report on near-field Raman spectra of a single nanocrystal of adenine molecules using a silver-coated apertureless probe tip. Raman signal is amplified due to surface plasmon polaritons localized at the metallic tip by a factor of more than 2700 times compared with the far-field Raman signal. Plasmonic near-field Raman spectrum showed eight Raman bands assigned to the normal modes of adenine molecule based on the density functional theory calculations. Vibrational frequencies of some Raman bands are observed to have shifted to the values of the corresponding bands, observed using conventional surface enhanced Raman-scattering spectrum. We found that these frequency shifts are caused by the transient states of the adenine-silver complexes by analyzing vibration mode of the complexes; that is, the near-field Raman spectra of adenine agree with Raman spectra of the complexes which are calculated by reducing the bond distance between an adenine molecule and a silver atom. Repulsive forces calculated from reduction of the bond distance were equal to the atomic force applied to the adenine molecule in our Raman NSOM experiment. All results support that the active Raman shift occurs owing to the deformation of adenine molecules pressurized by the silver atoms of the tip.

Paper Details

Date Published: 19 October 2004
PDF: 12 pages
Proc. SPIE 5512, Plasmonics: Metallic Nanostructures and Their Optical Properties II, (19 October 2004); doi: 10.1117/12.564843
Show Author Affiliations
Satoshi Kawata, Osaka Univ. (Japan)
Hiroyuki Watanabe, Osaka Univ. (Japan)
Yasushi Inouye, Osaka Univ. (Japan)

Published in SPIE Proceedings Vol. 5512:
Plasmonics: Metallic Nanostructures and Their Optical Properties II
Naomi J. Halas; Thomas R. Huser, Editor(s)

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