Department of Chemistry, University of Minnesota, 207 Pleasant St SE, Minneapolis, Minnesota 55455, USA.
Langmuir. 2010 May 18;26(10):7133-7. doi: 10.1021/la904182p.
Self-assembled monolayers of 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP) were formed by equilibrium adsorption from a perchloric acid solution onto Au(111) using an interposed adlayer of bromide. The passivating bromide adlayer was generated by addition of 150 microM KBr to the electrochemical cell and allowed monolayer ordering at positive potentials where a disordered TPyP monolayer would be found on a bare Au(111) surface. The TPyP monolayers were characterized in situ with electrochemical scanning tunneling microscopy (EC-STM) and cyclic voltammetry. They were successfully observed at working electrode potentials between 0.0 and +1.3 V vs Ag/AgCl. This wide potential window of usability for the bromide adlayer extends to potentials more positive than what has been achieved for similar observations using iodide-modified Au(111). Within the TPyP monolayers, isolated domains with differing geometries could be distinguished, suggesting dynamic monolayer rearrangements. These results demonstrate that the presence of a passivating bromide adlayer is conducive to the formation of highly ordered organic monolayers. Indeed, bromide is not only one of the few anions that are suitable for this purpose, but it may be superior to the more frequently used iodide.
5,10,15,20-四(4-吡啶基)卟啉(TPyP)的自组装单层通过平衡吸附从高氯酸溶液中在 Au(111)上形成，使用溴化物的插入夹层。钝化溴化物夹层通过向电化学电池中添加 150 μM 的 KBr 生成，并允许在正电势下进行单层有序化，在裸露的 Au(111)表面上会发现无序的 TPyP 单层。TPyP 单层通过电化学扫描隧道显微镜(EC-STM)和循环伏安法进行原位表征。它们在工作电极电势为 0.0 至+1.3 V 与 Ag/AgCl 之间成功观察到。这种溴化物夹层的宽可用性电位窗口扩展到比使用碘化物修饰的 Au(111)进行类似观察时更正的电位。在 TPyP 单层内，可以区分具有不同几何形状的孤立域，表明单层的动态重排。这些结果表明，钝化溴化物夹层的存在有利于形成高度有序的有机单层。事实上，溴化物不仅是适合这种目的的少数阴离子之一，而且可能优于更常用的碘化物。
