Gold nanoparticle dimer plasmonics: Finite element method calculations of the electromagnetic enhancement to surface-enhanced raman spectroscopy

Jeffrey M. McMahon, Anne Isabelle Henry, Kristin L. Wustholz, Michael J. Natan, R. Griffith Freeman, Richard P. Van Duyne, George C. Schatz

Research output: Contribution to journalArticle

146 Citations (Scopus)

Abstract

Finite element method calculations were carried out to determine extinction spectra and the electromagnetic (EM) contributions to surface-enhanced Raman spectroscopy (SERS) for 90-nm Au nanoparticle dimers modeled after experimental nanotags. The calculations revealed that the EM properties depend significantly on the junction region, specifically the distance between the nanoparticles for spacings of less than 1 nm. For extinction spectra, spacings below 1 nm lead to maxima that are strongly red-shifted from the 600-nm plasmon maximum associated with an isolated nanoparticle. This result agrees qualitatively well with experimental transmission electron microscopy images and localized surface plasmon resonance spectra that are also presented. The calculations further revealed that spacings below 0.5 nm, and especially a slight fusing of the nanoparticles to give tiny crevices, leads to EM enhancements of 1010 or greater. Assuming a uniform coating of SERS molecules around both nanoparticles, we determined that regardless of the separation, the highest EM fields always dominate the SERS signal. In addition, we determined that for small separations less than 3% of the molecules always contribute to greater than 90% of the signal.

Original languageEnglish
Pages (from-to)1819-1825
Number of pages7
JournalAnalytical and Bioanalytical Chemistry
Volume394
Issue number7
DOIs
Publication statusPublished - Aug 1 2009

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Keywords

  • Electromagnetic field enhancement
  • Finite element method
  • Nanoparticle dimer
  • Surface-enhanced Raman spectroscopy

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry

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