物理化学学报2017，Vol.33Issue(3)：530-538,9.DOI:10.3866/PKU.WHXB201611211
密度泛函理论研究银上吸附对巯基吡啶的SERS化学增强效应
Density Functional Theoretical Study on SERS Chemical Enhancement Mechanism of 4-Mercaptopyridine Adsorbed on Silver
摘要
Abstract
Surface-enhanced Raman spectroscopy (SERS) is one of the most powerful techniques for obtaining fingerprint information on molecules adsorbed on coinage metal surfaces.Its detection sensitivity has reached the single-molecule level.On the basis of density functional theoretical (DFT) calculations and Raman scattering theory,we investigated the normal Raman spectra of two isomers and surface-enhanced Raman scattering (SERS) spectra of 4-mercaptopyddine (4MPY) adsorbed on silver.The results aided us in uncovering the relationships between normal Raman spectra and SERS spectra and adsorption configuration,tautomedzation,protonation,and hydrogen bonding interactions as well as low-lying excited states.First,we compared the relative stability and normal Raman spectra of two isomers of 4MPY in the gas phase and aqueous solution with a solvent model similar to the solvation model of density (SMD).We then studied the Raman spectra of 4MPY interacting with silver clusters.Our results indicate that the Raman spectra were not dependent on the size of the silver clusters,owing to the formation of strong Ag-S bonds.We also considered two cases of Nend interaction in the 4MPY-Ag5 complex.(1) For the hydrogen bond interaction between the nitrogen in 4MPY and water clusters or hydrated proton clusters,the theoretical results indicated that the vibrational frequencies of the pyridine ring increase.(2) For the interaction of the 4MPY-Ag5 complex with a silver cluster Ag4 through the lone-paired orbital in nitrogen of the pyridine ring,the theoretical results further revealed that the vibrational frequency shift is in good agreement with SERS peaks reported in the literature.Finally,our calculated results focused on the relationship between the Raman spectra and the charge transfer mechanism when the excitation photonic energy matches the transition energy of low-lying excited states in single-end and double-end adsorption configuration.Particularly for the case of the double-end adsorption configuration,the charge transfer states from the excitation from the silver cluster binding to the pyridine ring not only enhance the Raman signals of v12,v1,and v8a modes,but also selectively enhance the Raman signal of the V9a mode associated with the symmetric C-H in-plane bending vibration.关键词
表面增强拉曼光谱/密度泛函理论/电荷转移机理/对巯基吡啶/银Key words
Surface-enhanced Raman spectroscopy/Density functional theory/Charge transfer mechanism/4-Mercaptopyridine/Silver分类
化学化工引用本文复制引用
吴元菲,李明雪,周剑章,吴德印,田中群..密度泛函理论研究银上吸附对巯基吡啶的SERS化学增强效应[J].物理化学学报,2017,33(3):530-538,9.基金项目
The project was supported by the National Natural Science Foundation of China (21273182,21533006,21373172).国家自然科学基金(21273182,21533006,21373172)资助项目 （21273182,21533006,21373172）
