Deducing the Adsorption Geometry of Rhodamine 6G from the Surface-Induced Mode Renormalization in Surface-Enhanced Raman Spectroscopy

Colin Van Dyck, Bo Fu, Richard P. Van Duyne, George C Schatz, Mark A Ratner

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Surface-enhanced Raman spectroscopy probes adsorbates on a plasmonic substrate and offers high sensitivity with molecular identification capabilities. In this study, we present a refined methodology for considering the supporting substrate in the computation of the Raman spectra. The supporting substrate is taken into account by employing a periodic slab model when doing the geometry optimization and normal mode analysis, and then the Raman spectrum is calculated for the isolated molecule but with the normal modes from the surface structure. We find that the interaction with the surface induces internal distortion in the molecule, and spectral shifts in the computed Raman spectrum. By comparing a low temperature surface-enhanced Raman spectroscopy measurement of Rhodamine 6G (R6G) with the computed Raman spectra of a series of adsorption geometries, we propose that the binding state captured in the experiment tends to possess the least internal distortion. This binding state involves upward orientation of ethylamine on R6G, and our calculations indicate that this is the lowest energy adsorption structure. Following this route, it is possible to infer both a molecular orientation and an adsorption geometry of the molecule from its Raman spectrum. Importantly, we note that, if the substrate correction is established to play a role, we also discuss that this corrected approach still has several shortcomings that significantly limit its overall accuracy in comparison with experimental spectra.

Original languageEnglish
Pages (from-to)465-473
Number of pages9
JournalJournal of Physical Chemistry C
Volume122
Issue number1
DOIs
Publication statusPublished - Jan 11 2018

Fingerprint

rhodamine
Raman spectroscopy
Raman scattering
Raman spectra
Adsorption
adsorption
Geometry
geometry
Substrates
Molecules
molecules
Molecular orientation
Adsorbates
Surface structure
slabs
routes
rhodamine 6G
methodology
optimization
probes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Cite this

Deducing the Adsorption Geometry of Rhodamine 6G from the Surface-Induced Mode Renormalization in Surface-Enhanced Raman Spectroscopy. / Van Dyck, Colin; Fu, Bo; Van Duyne, Richard P.; Schatz, George C; Ratner, Mark A.

In: Journal of Physical Chemistry C, Vol. 122, No. 1, 11.01.2018, p. 465-473.

Research output: Contribution to journalArticle

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