title: DFT study of chemical mechanism of pre-SERS spectra in Pyrazine-metal complex and metal-Pyrazine-metal junction.
abstract: The chemical mechanism of Normal Raman Scattering (NRS) and pre-surface enhanced Raman scattering (pre-SERS) spectra for Pyrazine-Ag(2) complex, Ag(2)-Pyrazine-Ag(2) junction and Ag(2)-Pyrazine-Au(2) junction were investigated with density functional theory (DFT) and charge difference densities (CDDs) for the first time. The NRS intensities of the above three structures enhanced obviously relative to isolated Pyrazine and the enhancement mechanism was confirmed to be static chemical enhancement. The pre-SERS intensities of the above three structures enhanced evidently compared to corresponding NRS intensities, and the enhancement mechanism was confirmed to charge transfer (CT) resonance Raman enhancement. The largest enhanced orders of NRS and pre-SERS intensities among the three structures were up to 10(3) and 10(5), respectively. Compared the intensity of pre-SERS with corresponding intensity of NRS spectra, the enhancement effect of Pyrazine-Ag(2) complex was larger than the others. Intramolecular and intermolecular CT on resonant electronic transition were described by CDDs.
authors.affiliation: School of Physics & Optoelectronic Technology, School of Chemical Engineering and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116024, PR China.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Zhao
authors.forename: Shasha
authors.initials: S
authors.lastname: Liu
authors.forename: Yuanzuo
authors.initials: Y
authors.lastname: Li
authors.forename: Maodu
authors.initials: M
authors.lastname: Chen
mesh_terms: D006046:Gold / Q000737:chemistry* / Q000378:metabolism*; D053768:Metal Nanoparticles / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D011719:Pyrazines / Q000737:chemistry* / Q000378:metabolism*; D011789:Quantum Theory; D012834:Silver / Q000737:chemistry* / Q000378:metabolism*; D013059:Spectrum Analysis, Raman
chemical_list: D011719:Pyrazines; D012834:Silver; D006046:Gold