二苯基乙二胺在银胶表面吸附的表面增强拉曼光谱研究

Adsorption of Diphenyl Ethanediamine(DPEDA) on Colloidal Silver Surface:A SERS Study

以银纳米粒子作为SERS活性基底,研究了二苯基乙二胺(DPEDA)在银表面的吸附行为,并研究了溶液的pH值和DPEDA的浓度对吸附构型的影响。对比DPEDA的Raman和SERS谱图,可以认为DPEDA是通过氮原子的孤对电子吸附在银胶表面。在酸性介质中DPEDA的氨基被质子化生成胺正离子,导致DPEDA不容易吸附到银胶表面,所以DPEDA的SERS信号强度随着溶液酸性的增加而减弱。DPEDA的浓度变化对其吸附构型中芳香环的取向影响不大,但是其C-N键与表面的角度会有一定的变化。从SERS光谱得到的信息可以加深我们对DPEDA修饰的金属催化剂的多相不对称催化机理的认识。

Using Ag nanoparticles as SERS substrate, we investigated the adsorption of diphenyl ethanediamine （DPEDA） on colloidal silver surface, and the influences of pH value of solution and concentration of DPEDA on the adsorption of DPEDA. It is deduced by comparing the Raman and SE＇RS spectra that DPEDA adsorbs on silver surface through two N atoms via lone pairs of electrons. In acid solution, the NH2 groups were protonated and changed to NH3^＋. This leads to the difficulty of adsorption of DPEDA on metal surface and the decrease in intensity of SERS signal. The influence of DPEDA concentration on the steric orientation of phenyl rings is small, but the direction of C- N bond changes with the decrease of DPEDA concentration. The information obtained from SERS spectra could help us to understand the heterogeneous asymmetric catalytic mechanism on transition metal catalyst modified with DPEDA.