主-客体效应诱导分子三维自组装结构

The construction of three-dimensional ordered structure and the regulation of its performance are the primary tasks of the development of molecular devices. Recently, adopting the bottom-up molecular self-assembly method, people have conducted extensive research on the two-dimensional molecular self-assembly, which laid a solid foundation for the building of the controlled assembly of three-dimensional surface functional molecules and molecular recognition nanodevices. In this project, our ultimate aim is to use layer-by-layer self-assembled method to build out the three-dimensional ordered self-assembled structures with different different features. In one layer, the molecules are self-assembled into an organized structure, which is considered as a host template. Then through the host-guest molecular recognition, another layer is built through inter-layer interactions such as metal coordination, π-π stacking interaction and even weaker dispersion force. Through adopting the self-assembled monolayer of phthalocyanine as host molecular template and selecting the metal ions, nanoclusters, organic molecules as guest objects, the prepared three-dimensional architectures are expected to possess special optical and electronic performance. In the experiments we will apply scanning tunneling microscopy (STM), ultra-high vacuum scanning tunneling microscopy (UHV-STM) to characterize morphologies of the self-assembled products and the scanning tunneling spectrum (STS), absorption/fluorescence/Raman spectrum will be performed to explore their electronic and optical properties. Combining the density function theory (DFT) with non-equilibrium Green's functions (NEGF), we will carry out the high-performance calculation to understand the host-guest assembled mechanism and the effects on the optical properties and the electronic transport process on the surface and interface. In addition, some other factors, such as solvent polarity, experimental temperature, etc will be explored to study the influence on the morphology of the assembled structures and properties. This work will shed light on comprehending the the physical and chemical mechanisms of the surface molecules adsorption and provide important experimental methods and theoretical basis for achieving a three-dimensional self-assembly of ordered structures of the molecular layer and conducting performance regulation.

三维有序结构的构筑与性能调控是分子器件研制的首要任务。近来，人们采用"自下而上"的分子自组装方法，对二维分子自组装进行了大量的研究。这些研究为三维功能分子表面可控组装、分子识别等纳米器件的构筑奠定了坚实的基础。本项目以酞菁二维自组装分子层为主体分子模板，金属离子、纳米团簇、有机分子等为客体分子，通过基于金属配位、π-π等弱相互作用的主－客体识别效应，层－层构建出不同功能特性的三维有序自组装结构。利用STM、UHV-STM、STS、吸收/荧光/Raman光谱等手段，研究自组装三维结构的形貌、光电性能、以及外部环境如溶剂、温度等对三维结构的影响。结合密度泛函理论和非平衡态格林函数的高精度模拟计算，剖析主客体分子相互作用及电子传输机理。为深入揭示表面分子吸附的物理化学机制提供重要的实验手段和理论依据，最终实现三维自组装分子层有序结构的构筑及功能调控。

本项旨在通过分子间非共价键相互作用构筑具有高度有序结构的分子模板，以金属离子、纳米团簇、有机分子等为客体分子来构建不同功能特性的三维有序自组装结构。开展的研究内容主要包括：（1）一元体系的自组装行为研究 以具有刚性平面结构的芳香族化合物为自组装单元研究氢键和范德华力对分子自组装结构的影响；同时，探究了氢键与卤键两类重要非共价键作用在分子自组装结构形成过程中的竞争效应；（2）二元体系的自组装行为 分别选择三聚氰胺、硬脂酸两种为主体分子，DNA碱基（胸腺嘧啶，鸟嘌呤，腺嘌呤）为客体分子来探究主客体效应下二元自组装结构的形成机理；（3）分子相互作用机制的理论模拟 以蒙特卡罗、从头算方法等方法确定复杂分子的稳定构型，并以氢键相互作用为依据建立了树步计算法来准确快速得到分子稳定构型及相关物化特性。在整个研究中，我们由浅入深地对选择的体系从实验和理论两方面入手，对构筑分子自组装结构以及理解分子与分子，分子与基底等相互作用取得了一系列研究成果，发展出了一套针对生物分子结构模拟的方法，为深入揭示表面分子吸附的物理化学机制提供重要的实验手段和理论依据，推进了三维分子自组装有序结构的构筑及功能调控的相关研究。