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.

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