双氰胺在金团簇上吸附的密度泛函理论和表面增强拉曼光谱研究

Density Functional Theory and Surface Enhanced Raman Spectroscopy Studies of Dicyandiamide Adsorbed on Au Clusters

双氰胺是氰胺的二聚体,具有亚氨式和氨式两种互变异构体.将表面增强拉曼光谱(SERS)与密度泛函理论(DFT)结合,研究了互变异构的双氰胺分子在金表面的吸附行为.通过理论计算获得了亚氨式和氨式双氰胺分子的能量、分子轨道和光谱信息,以及双氰胺分子吸附在金簇表面的SERS响应.计算结果表明两种异构化的双氰胺分子都与Au3簇形成较稳定的复合物,并且双氰胺分子中N2原子优先吸附在金簇表面.拉曼实验结果与计算结果较为吻合,进一步说明具有互变异构的双氰胺分子在金基底中共存,并通过N2原子垂直吸附到金表面,符合SERS电磁场增强机制.

Dicyandiamide is a dimer of cyanamide that generally isomerizes into imino and amino forms. The behaviors of tautomeric dicyandiamide adsorbed on gold surface were studied by the density functional theory method combined with surface enhanced Raman spectroscopy（SERS）. By using DFT method the energies,molecular orbital, vibration spectral information of imino and amino forms of dicyandiamide and the SERS spectra of tautomeric dicyandiamide adsorbed on Au clusters were given. The results show that both tautomeric dicyandiamides form stable complexes with Au3 clusters, and the N（2） atom preferentially adsorbs on Au clusters. The experimental results are consistent with the calculated results, which show that the tautomeric dicyandiamides coexist on the Au substrate, are adsorbed vertically on the gold surface through the N（2） atom, and the SERS enhancement factors conform to electromagnetic-field enhancement mechanism.