Investigation On The Mechanism For The Catalytic Coupling Reaction Of 4-DEABT、4-NBT Adsorbed On The Silver Nano Surface

When the molecules adsorbed on the noble metal(Ag or Au) nanostructures, it would lead to the enhancement of noble metal Raman signal strength. This abnormal surface optical phenomenon is defined as the Surface-enhanced Raman Spectroscopy which is often used to study surface adsorption and identification of surface adsorbed species. Due to the structure of thiol aniline have double functional group and the two ends of the thiol aniline can be connected with the metal, the research of the single molecule surface enhanced Raman spectroscopy is a very important probe molecule.In recent years, researchers have found that the abnormal signal in the surface enhanced Raman spectrum, but the mechanism is not clear. A theoretical and experimental study of the catalytic coupling reaction about the adsorption of thiol-aniline and its derivatives on silver electrode was reported. The theoretical part is mainly about the spectrum, but there is little research on the micro mechanism. Therefore, the reaction mechanism of the catalytic coupling reaction, the adsorption on the nano silver surface of the thiol aniline derivatives, needs further study.In this paper, we have studied the mechanism for the catalytic coupling reaction of 4-DEABT、4-NBT adsorpted on the surface silver nano surface using the density functional theory(DFT) B3 LYP method on 6-311 + G ** basis set(Ag using the pseudopotential basis set LanL2dz). Concluded as follow:The first, when 4-DEABT was adsorbed on nano-silver surface, the visible light to a extent reduced the activation energy of the reaction. Whereby visible light can be obtained in the reaction system to remove the acetyl group played during the photo-assisted catalysis. On the other hand, under visible light irradiation, adsorption sulfhydryl side did not play a catalytic role to assist.The second, it may occur in different potential energy surface of the reaction channel crossover phenomenon. Because we found there were two key crossing points CP1, CP2. Through effective spin flip can lower the reaction barrier.The third, when 4-NBT adsorbed on nano-silver surface, the key response was to remove groups of two substituents on the amino terminus; in the case of visible light and anti-ends conditions, a lower activation energy required for the reaction. 4-NBT adsorbed on the surface of silver nanoparticles occurred catalyzed coupling reaction of 4,4-dimercapto-azobenzene(4,4’-DMAB).