title: Density functional theory study on surface-enhanced Raman scattering of 4,4'-azopyridine on silver.
abstract: Surface-enhanced Raman scattering (SERS) of 4,4'-azopyridine (AZPY) on silver foil substrate was measured under 1064nm excitation lines. Density-functional theory (DFT) methods were used to calculate the structure and vibrational spectra of models such as Ag-AZPY, Ag(4)-AZPY and Ag(6)-AZPY complexes with B3LYP/6-31++G(d,p)(C,H,N)/Lanl2dz(Ag) basis set. The Raman bands of AZPY were identified on the ground of analog computation of potential energy distribution. The calculated spectra of Ag(4)-AZPY and Ag(6)-AZPY models were much approximated to the experimental results than that of Ag-AZPY model. The DFT results showed that the angles between two pyridyl rings keep 0 degrees from AZPY to Ag-AZPY, Ag(4)-AZPY and Ag(6)-AZPY model. The energy gaps between the HOMO and LUMO changed from 363 to 1140nm for AZPY-Ag complexes according to the DFT results. An conclusion was conceived that chemical enhancement mechanism may play an important role in the SERS of AZPY on silver substrate.
authors.affiliation: State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Zhuang
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Shang
authors.forename: Xu
authors.initials: X
authors.lastname: Wang
authors.forename: Weidong
authors.initials: W
authors.lastname: Ruan
authors.forename: Bing
authors.initials: B
authors.lastname: Zhao
mesh_terms: D015394:Molecular Structure; D011725:Pyridines / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D013059:Spectrum Analysis, Raman
chemical_list: D011725:Pyridines; D012834:Silver