Chu Hui, Yang Haifeng, Huan Shuangyan, Shen Guoli, Yu Ruqin
State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China.
J Phys Chem B. 2006 Mar 23;110(11):5490-7. doi: 10.1021/jp053914m.
Self-assembled monolayers (SAMs) of 6-mercaptopurine (6MP) on a silver electrode in acid and alkaline media were investigated by a combination protocol of the SERS technique with Raman mapping, and it was found that the adsorption mode of 6MP SAMs changed with the pH value of the environment. Quantum calculations for the vibrational mode were performed by the BLYP/6-31G method. 6MP was adsorbed on the silver electrode with a tilted orientation via S, N1, and N7 atoms in acid medium, while the SAMs adopted head-on adsorption modes with the S atom and the N1 atom anchoring the silver surface in alkaline medium. However, 6MP SAMs turned to the same upright orientation on the electrode through the S and N7 atoms when either acid or basic solution was removed. Stability of 6MP SAMs was observed by in situ SERS spectroelectrochemical measurements. The results reveal that the desorption potentials of 6MP SAMs formed under acid and alkaline conditions from the Ag electrode were at ca. -1.3 V and -1.6 V vs SCE, respectively.
采用表面增强拉曼光谱(SERS)技术与拉曼映射相结合的方法,研究了酸性和碱性介质中银电极上6-巯基嘌呤(6MP)的自组装单分子层(SAMs),发现6MP SAMs的吸附模式随环境pH值的变化而改变。通过BLYP/6-31G方法对振动模式进行了量子计算。在酸性介质中,6MP通过S、N1和N7原子以倾斜取向吸附在银电极上,而在碱性介质中,SAMs采用头对头吸附模式,S原子和N1原子锚定在银表面。然而,当去除酸性或碱性溶液时,6MP SAMs通过S和N7原子在电极上转向相同的直立取向。通过原位SERS光谱电化学测量观察了6MP SAMs的稳定性。结果表明,在酸性和碱性条件下形成的6MP SAMs从银电极上的解吸电位分别约为-1.3 V和-1.6 V(相对于饱和甘汞电极(SCE))。