Li Z, Han B, Wan L J, Wandlowski Th
Institute of Thin Films and Interfaces, ISG 3, and Center of Nanoelectronic Systems for Information Technology, Research Center Jülich, D-52425 Jülich, Germany.
Langmuir. 2005 Jul 19;21(15):6915-28. doi: 10.1021/la0507737.
The potential-induced adsorption and self-assembly of 1,3,5-benzene-tricarboxylic acid (TMA) was investigated at the electrified Au(111)/0.05 M H2SO4 interface by in-situ scanning tunneling microscopy (STM) and surface enhanced infrared reflection absorption spectroscopy (SEIRAS) in combination with electrochemical techniques. Depending on the applied electric field, TMA forms five distinctly different, highly ordered supramolecular adlayers on Au(111) surfaces. We have elucidated their real-space structures at the molecular scale. In the potential range -0.25 V < E < 0.20 V, planar-oriented TMA molecules form a hexagonal open-ring honeycomb structure, Ia, a hydrogen-bonded ribbon-type phase, Ib, and a herringbone-type phase, Ic, stabilized by directional hydrogen bonding and weak substrate-adsorbate interactions. Interfacial water molecules are being replaced. In 0.20 V < or = E < 0.40 V, e.g., around the potential of zero charge, and at slightly higher coverages, a close-packed physisorbed adlayer of hydrogen-bonded TMA dimers, II, was observed. Further increase of the electrode potential to positive charge densities causes an orientation change from planar to upright. An initially disordered phase, IIIa, transforms into an ordered, stripelike chemisorbed adlayer, IIIb, of perpendicularly oriented TMA molecules. One carboxylate group per molecule is bound to the electrode surface, while the two other protonated carboxyl groups are directed toward the electrolyte and act as structure-determining components of a hydrogen-bonded two-dimensional ladder-type network. Structural transitions between the various types of ordered molecular adlayers are attributed to (hole) nucleation and growth processes.
通过原位扫描隧道显微镜（STM）和表面增强红外反射吸收光谱（SEIRAS）并结合电化学技术，研究了1,3,5-苯三甲酸（TMA）在带电的Au(111)/0.05 M H₂SO₄界面上的电位诱导吸附和自组装。根据所施加的电场，TMA在Au(111)表面形成了五种明显不同的、高度有序的超分子吸附层。我们已经在分子尺度上阐明了它们的实空间结构。在-0.25 V < E < 0.20 V的电位范围内，平面取向的TMA分子形成六边形开环蜂窝结构Ia、氢键带状相Ib和人字形相Ic，这些结构通过定向氢键和弱的基底 - 吸附质相互作用得以稳定。界面水分子被取代。例如，在0.20 V ≤ E < 0.40 V范围内，即在零电荷电位附近且覆盖度稍高时，观察到了氢键连接的TMA二聚体的紧密堆积物理吸附层II。将电极电位进一步提高到正电荷密度会导致取向从平面变为直立。最初无序的相IIIa转变为垂直取向的TMA分子的有序条纹状化学吸附层IIIb。每个分子的一个羧基与电极表面结合，而另外两个质子化的羧基指向电解质，并作为氢键二维梯型网络的结构决定组分。各种类型的有序分子吸附层之间的结构转变归因于（空穴）成核和生长过程。
