【作者】 朱二旷；

【导师】 徐波；

【作者基本信息】 燕山大学 ， 材料物理与化学， 2015， 硕士

【摘要】 分子自组装形成的超分子结构的有序性和稳定性对分子器件的功能和性能非常重要。在本文中,我们首先研究了恩羧酸分子(AnCA)在Ag(111)表面和C60在选定的AnCA模板上的结构有序性,并进一步研究了AnCA模板上C60结构的热稳定性。通过退火,我们发现两种具有更高稳定性的新颖C60有序结构。我们发现AnCA分子随着表面密度的变化,可以自发形成四种AnCA有序相和一种退火形成的有序相:平行的带状结构、Z字型双带结构、两种相对简单的二聚体结构和kagome网状结构。AnCA分子自组装结构的多样性来源于AnCA分子在金属表面上不同作用力的相互竞争,如分子间相互作用,分子—衬底相互作用以及高的表面分子密度空间排列的需要。以两种AnCA分子二聚体结构为模板,我们研究了C60在其上的自组装过程。我们发现AnCA模板的结构稳定性影响C60分子的生长模式。根据选择不同的AnCA模板,要么形成横向相分离的AnCA-C60较大区域的排列,要么形成“外延式”C60二聚物结构。我们实验结果提出了一种通过选择合适的模板控制分子纳米结构的方法。通过退火,我们研究了AnCA模板上C60结构的结构演化过程。100°C退火后,在Ag(111)衬底上AnCA模板化的C60结构转变为两个新颖的、具有更高稳定性的C60自组装结构:自承载的C60二聚体结构和线性C60链状结构。有趣的是,线性C60链状结构中,C60分子在跨越链方向上具有交替的构型:自由旋转或者以特定的取向被冻结(C60的6:6键固定在最上面)。我们的研究展示了从最初不稳定的模板结构获得具有新颖特征且不能通过其它途径来实现的新结构一种新途径。更多还原

【Abstract】 Ordering and stability of supramolecular structures from molecular self-assembly are very important to the function and performance of molecular devices. In this thesis, we investigated the structural ordering of 9-anthracene carboxylic acid(AnCA) on Ag(111)surface and C60 on selected AnCA templates. We also investigated the thermal stability of AnCA-templated C60 structures, and identified two interesting C60 ordered structures with enhanced thermal stability from annealing.Depending on the molecular surface density, four spontaneously formed and one annealed AnCA ordered phases were observed, namely a straight belt phase, a zigzag double-belt phase, two simpler dimer phases, and a kagome phase. This structural diversity stems from a complicated competition of different interactions of AnCA molecules on metal surface, including intermolecular and molecular-substrate interactions,as well as the steric demand from high molecular surface density.The self-assembly process of C60 molecules on two simpler dimer phases of AnCA as templates was then studied. We found the structural stability of the AnCA templates influence the growth modes of C60 molecules. Either laterally separated AnCA–C60elongated domain arrays or an “epitaxial” C60 dimer structure over AnCA can be formed depending on the selected AnCA template. Our experimental observations suggest a pathway of molecular nanostructure control through the choice of suitable template.The structure evolution of AnCA-templated C60 structures with annealing was investigated. After annealing at 100°C, the AnCA-templated C60 structures on Ag(111)transition into two novel structures, a “self-hosted” C60 dimer structure and a linear C60 chain structure, with increased thermal stability. Most interestingly, C60 molecules in the chain structure possess alternative configurations on the surface across the chains, either rotational free or frozen into specific azimuth with 6:6 bond as the topmost feature. The thermal instability of the originally templated structure provides a probability to form new structures with interesting features which cannot be accessed otherwise.更多还原