This work presents a theoretical detailed analysis of the surface-enhanced Raman spectroscopy (SERS) of the pyridine− M 10 N 10 (M, N = Ag, Cu) tetrahedral (Td) clusters considering two binding positions: vertex (V) and surface (S). In addition to the wellknown monometallic Td structure, we added two different bimetallic Ag−Cu compositions, named Td1 and Td2 geometries. Density functional methodology with the use of BP86 and CAM-B3LYP exchange-correlation functionals (XCs) and LANL2DZ pseudopotential has been employed for analyzing the electronic structure and geometries, the chemical static (CHEM), and resonant Raman mechanisms (RR): charge transfer RR−CT and intracluster excitation RR−CR. The static CHEM mechanism shows an increase in the enhancement factors (EFs) of Py−V concerning Py−S positions, which can also be distinguished by the averaged adsorption energies and bond polarizabilities. The static SERS response for Cu−Py−V junction is from 5 to 10 times greater than Ag−Py−V EFs and up to 28 times greater than Py−S complexes. For the static Raman, we found that the analyses of ν 8a and ν 1 normal modes are related to the EF changes and allow us to distinguish V from S complexes. The TDDFT calculations show striking differences between BP86 and CAM-B3LYP XCs analyzed spectra, and CAM-B3LYP granted a clear distinction between V and S for the location of CT-type transitions. In addition, important differences were obtained from the analysis of the charge transfer excitations between both XCs. Resonant Raman calculations evidenced significant enhancements for RR−CT and RR−CR as compared to the static enhancements, and RR−CT can be distinguished from the RR−CR mechanism, while specific normal modes help to differentiate the vertex from the surface Py-junction. Bimetallic Ag−Cu nanostructures represent promising choices for SERS substrates, showing EFs higher than those of monometallic Ag.
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