Strong optical coupling between mutually orthogonal plasmon oscillations in a silver nanosphere-nanowire joined system

Seongyong Kim, Kohei Imura, Minwoo Lee, Tetsuya Narushima, Hiromi Okamoto, Dae Hong Jeong

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

A top-to-bottom joined system consisting of a silver nanowire and nanospheres was fabricated by embedding silver nanospheres on a glass or silicon substrate on which 3-aminothiophenol as an analyte molecule was adsorbed, and then placing silver nanowires on the substrate to make gap sites between a nanowire and nanospheres. In the far-field Raman measurements, the sphere under the wire exhibited more than 60 times higher Raman enhancement than isolated spheres. The surface enhanced Raman scattering (SERS) spectra obtained by the 647.1 nm excitation showed highly polarized feature, exhibiting ca. 4 times higher SERS intensity for the electric field parallel to the wire axis than that perpendicular to the wire axis while those by the 514.5 nm excitation showed non-polarized feature against the incident electric field direction. The polarized feature by the 647.1 nm excitation is explained in terms of optical coupling in a vertical direction to the substrate plane, between the silver nanosphere and the longitudinal surface plasmon mode of the nanowire. The longitudinal plasmon of the nanowire functions as an antenna of the incident radiation field in this type of coupled plasmon mode, to yield the confined field. Near-field two-photon excitation imaging measurements as well as numerical calculations of the localized electric field around the system support this idea and indicate that the coupling between the surface plasmon of silver nanospheres and the longitudinal mode of silver nanowires is site-selective.

Original languageEnglish
Pages (from-to)4146-4153
Number of pages8
JournalPhysical Chemistry Chemical Physics
Volume15
Issue number12
DOIs
Publication statusPublished - 2013 Mar 28

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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