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.


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.


DFT simulations


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