Chemical Mechanism and Tunability of Surface-Enhanced Raman Scattering of Pyridine on Heteronuclear Coinage Metal Diatomic Clusters: A Density Functional Study

As surface-enhanced Raman scattering (SERS) substrates, coinage bimetallic clusters offer high SERS enhancement and potential for applications in precision molecule detection. Here, we elucidate the chemical mechanism and reveal the tunability of the SERS of a pyridine molecule (Py) on coinage bimetallic substrate by investigating various possible heteronuclear coinage metal diatomic clusters (HCMDCs) interacting with the pyridine molecule. We obtain the Raman spectra, molecular orbital, and binding property of each HCMDC–Py system using density functional theory. We find that the Raman characteristic peaks, adsorption energy, charge transfer, geometry parameters, and molecular orbital distribution are all closely related to the compositions and binding sites of the HCMDC. The results show that the synergistic effect of different coinage metal atoms in the HCMDC plays an important role in SERS enhancement, which varies with the component and adsorption site of the HCMDC, thus providing the possibility of optimizing the SERS substrate by tuning the bimetallic cluster composition and adsorption site.