Zhao Xiongce, Leng Yongsheng, Cummings Peter T
Nanomaterials Theory Institute, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Langmuir. 2006 Apr 25;22(9):4116-24. doi: 10.1021/la0532252.
We report a Monte Carlo simulation study of the self-assembly of 1,4-benzenedithiolate (BDT), tetrahydrofuran (THF), and their mixtures on a Au (111) surface. We use the grand canonical Monte Carlo method to obtain the equilibrium adsorption coverage. Canonical ensemble (NVT) simulation is then used to explore further the structural information of the equilibrated systems. Our results indicate that BDT molecules adsorb onto the Au (111) surface with one of the sulfur atoms bonded to Au atoms. THF molecules form clusters on the surface. For BDT-THF mixtures, BDT can selectively adsorb on Au (111) to form a monolayer, whereas the solvent THF molecules either float above BDT monolayer or occupy vacancies on the surface that are not covered by BDT molecules. BDT molecules adsorb on a Au (111) surface with an average tilt angle of about 18-35 degrees to the surface normal. The tilting angle decreases as the coverage increases. In addition, the BDT monolayer constitutes an ordered herringbone structure on the Au (111) surface, and the ordering pattern is insensitive to the BDT coverage. In comparison, the THF molecules exhibit amorphous structure on the Au surface. Interestingly, simulations indicate that the bonding behavior of BDT molecules on Au (111) is coverage-dependent. BDT bonds preferably on the Au top site when the surface coverage is low. As coverage increases, most BDT molecules bond on the bridge and fcc hollow sites.
我们报告了一项关于1,4 - 苯二硫醇盐（BDT）、四氢呋喃（THF）及其混合物在金（111）表面自组装的蒙特卡罗模拟研究。我们使用巨正则蒙特卡罗方法来获得平衡吸附覆盖率。然后使用正则系综（NVT）模拟进一步探索平衡体系的结构信息。我们的结果表明，BDT分子以其中一个硫原子与金原子键合的方式吸附在金（111）表面。THF分子在表面形成团簇。对于BDT - THF混合物，BDT可以选择性地吸附在金（111）上形成单分子层，而溶剂THF分子要么漂浮在BDT单分子层上方，要么占据表面上未被BDT分子覆盖的空位。BDT分子以相对于表面法线约18 - 35度的平均倾斜角吸附在金（111）表面。倾斜角随着覆盖率的增加而减小。此外，BDT单分子层在金（111）表面构成有序的人字形结构，并且这种有序模式对BDT覆盖率不敏感。相比之下，THF分子在金表面呈现无定形结构。有趣的是，模拟表明BDT分子在金（111）上的键合行为取决于覆盖率。当表面覆盖率较低时，BDT优先键合在金的顶位。随着覆盖率增加，大多数BDT分子键合在桥位和面心立方空位上。
