糠醛分子表面增强拉曼光谱的密度泛函理论研究

Study of Density Functional Theory for Surface-Enhanced Raman Spectra of Furfural

采用密度泛函理论(density functional theory,DFT),在B3LYP/6-31+G**(C,H,O)/LANL2DZ(Ag)水平上,对糠醛(furfural,FUR)分子进行了几何结构优化,并计算了FUR分子的常规拉曼散射(normal Raman scattering,NRS)光谱和FUR与Ag原子以及Ag2和Ag4团簇吸附的表面增强拉曼散射(surface-enhanced Raman scattering,SERS)光谱。结果表明,理论值与已有的实验值符合得较好,采用FUR-Ag4吸附构型的计算结果比FUR-Ag和FUR-Ag2吸附构型的计算结果更符合已有实验值。最后,通过Gauss View可视化软件,对FUR分子的振动频率进行了更为全面地归属。通过FUR分子SERS与NRS的比较,可得出FUR分子与Ag原子发生了相互作用,且被吸附的糠醛分子的杂五环是与银表面垂直的。

In the present paper,DFT method at the B3LYP/6-31＋G＊＊（C,H,O）/LANL2DZ（Ag） level was used to optimize molecular configurations of furfural.Based on the optimized structure,the normal Raman spectrum（NRS） of FUR and the surface-enhanced Raman spectrum（SERS） of FUR adsorbed on Ag,Ag2 and Ag4 were all calculated,which were compared with the experimental values.The calculation results indicated that a good conformity was found between the computed and the experimental results.The results of furfural adsorbed on Ag4 were more approximate to the ever reported experimental date than those of furfural adsorbed on Ag and Ag2.At the end,detailed analysis of the Raman spectrum and more comprehensive assignments of the vibration mode for furfural were studied by the software of GaussView.The data of the SERS by comparing with the one of NRS show that furfural molecule and Ag atoms interact with each other.And we suppose that the molecular plane with the ring of adsorbed furfural molecule is vertically orientated to the silver surface.The work in this paper offers a theory evidence for detection and trace analysis of drinks containing furfural.