title: The mechanism of N-Ag bonding determined tunability of surface-enhanced Raman scattering of pyridine on MAg (M = Cu, Ag, Au) diatomic clusters.
abstract: Binary coinage metal clusters can show a significantly different enhancement in surface-enhanced Raman scattering (SERS) from that of pure element clusters, owing to their tunable surface plasmon resonance energies affected by the composition and atomic ordering. Yet, the tunability by composition requires a deep understanding in order to further optimize the SERS-based detection technique. Here, to fill this deficiency, we conducted detailed analyses of the SERS of pyridine adsorbed through N-Ag bonding on the homonuclear diatomic metal cluster Ag2 and heteronuclear diatomic metal clusters of AuAg and CuAg, as well as the involved charge transfer under an intracluster excitation, based on calculations using time-dependent density functional theory with a short-time approximation for the Raman cross-section. We find that although the SERS enhancements for all complexes can reach the order of 10(3)-10(4), the corresponding wavelengths used for SERS excitation are significantly different. Our molecular orbital analysis reveals that the complexes based on heteronuclear metal clusters can produce varied electronic transitions owing to the polarization between different metal atoms, which tune the SERS enhancements with altered optical properties. Our analyses are expected to provide a theoretical basis for exploring the multi-composition SERS substrates applicable for single molecular detection, nanostructure characterization, and biological molecular identification.
authors.affiliation: Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, College of Life Sciences, Jilin University, Changchun, 130012, China. lzq@jlu.edu.cn.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Yang
authors.initials: Y
authors.lastname: Gao
authors.forename: Haoran
authors.initials: H
authors.lastname: Xu
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Wang
authors.forename: Zhengqiang
authors.initials: Z
authors.lastname: Li
authors.forename: Rui-Qin
authors.initials: RQ
authors.lastname: Zhang
mesh_terms: D001665:Binding Sites; D003198:Computer Simulation; D008670:Metals / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D009584:Nitrogen / Q000737:chemistry*; D013059:Spectrum Analysis, Raman / Q000379:methods*; D020349:Surface Plasmon Resonance / Q000379:methods*
chemical_list: D008670:Metals; D009584:Nitrogen