SERS Comparison from Au, Ag, and Au-Ag Alloys: Insights by the First Principles

11 April 2018, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Surface enhanced Raman scattering (SERS) is presented via a case study of 2,2’-bipyridyl
(22BPY) molecules adsorbed on pure Au and Ag as well as on Au-Ag alloy nanodiscs. Experimental
SERS spectra from Au and Ag nanodics show similar peaks, but those from Au-Ag alloy
reveal new spectral features. The physical enhancement factors due to surface nano-texture were
considered by numerical simulations of light intensity distribution for the nano-textured Au, Ag,
and Au-Ag alloy surfaces, but found to cause only minor differences. For the chemical insights of
enhancement, the density functional theory (DFT) calculations were performed using Au20, Ag20,
and Au10Ag10 clusters of a pyramidal structure for SERS modeling. Binding of 22BPY to the clusters
was simulated by considering possible arrangements of vertex and planar physical as well as
chemical adsorption models. A qualitative match with experimental SERS results for the pure Au
and Ag was obtained. DFT models showing spectral shifts of 22BPY SERS on the alloy nanodiscs
are presented.

Keywords

DFT simulations
plasmonics
SERS

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