氢键调控实现超分子组装结构整体光响应的STM研究

Self-assembly is an effective method for preparing optical nanodevices. The performance of molecule-based devices depends greatly on the light response of organic molecules and the order of their assembly at interfacial regions. Introducing long alkyl groups to a photosensitive organic molecule can dramatically increase the order and stability of its assembled structure on surfaces. However, the light response of these species can only occur very locally due to the rigidity of C - C covalent bonds and the strong interaction between long alkyl chains and the substrate. This destroys the order of the assembled structure over a wider area and consequently decreases the efficiency of nanodevices. It remains a great challenge, though, one of the keys to improving the performance of nanodevices is to control the photo-response of assembled organic molecular structures over a large area or even the whole interfacial region. On the basis of the solid background in the field of hydrogen-bonded molecular self-assembly, the applicant proposes to study the construction of multifunctional organic molecular nanostructures with light response using hydrogen-bonded binary system instead of covalent-based single component system. Due to the flexibility of the hydrogen bonds, the assembly and the light response of molecular assemblies should become manipulable over large areas. The regulation of hydrogen bonding, and thus, the dynamics of self-assembly of the nanostructures by external trigger will be investigated by scanning tunneling microscope (STM), from the single molecule level up to the micron scale. From these results, and combining quantum mechanics and DFT theoretical modeling, we expect to reveal the mechanisms behind the self-assembly process itself and the mechanisms of hydrogen-bonding regulation in these nanostructures. The direct consequence of these mechanisms on the optical response of the assemblies will also be investigated. These studies will make an important contribution to the field of surfaces/interface engineering, and will provide experimental and theoretical guidance for the preparation of new optical nanodevices with high performance.

分子自组装是制备分子光学器件的有效方法。分子器件的性能与界面分子的光响应及其在界面排列的有序性密切相关。在光活性分子中引入长链烷烃可有效提高组装结构的稳定性，但由于C-C共价键的刚性及烷基链与基底间较强作用的限制，光响应只能发生在局部区域，破坏了组装结构的有序性，虽然部分实现了器件的功能，但远不能满足要求。因此，如何实现更大面积乃至整个区域的分子光响应，是提高纳米光学器件性能的关键。在基于氢键的分子自组装领域的研究基础上，申请人提出用氢键联接的双组分代替以共价键联接的单组分来构筑光响应纳米结构，利用氢键键长和键角的微观灵活性实现对组装结构大范围的光调控。利用STM技术探测氢键对光引发的自组装结构微观变化的调控作用，运用量子力学方法进行理论模拟和分析，揭示这类光活性纳米结构形成的微观机制及氢键在该体系中的调控机制，实现对该类功能纳米结构的可控构筑，为制备高性能纳米光学器件奠定实验和理论基础。

在基于氢键的分子自组装的研究基础上，申请人提出用氢键代替以共价键联接的单组分来构筑光响应纳米结构，利用氢键键长和键角的微观灵活性实现对组装结构大范围的光调控。利用STM 技术探测氢键对光引发的自组装结构微观变化的调控作用，实现对该类功能纳米结构的可控构筑，为制备高性能纳米光学器件奠定实验和理论基础。在本项目执行的三年时间内，我们重点围绕含有炔基或双键官能团的功能有机分子在固-液或气-固界面的组装行为及氢键对其光聚合反应的调控进行了一系列探索研究，取得了一些较有意义的结果。其中，（1）通过分子间氢键的调控实现了在表面获得大面积的炔烃光聚合产物。单根聚合物骨架长度可达100 nm以上，说明氢键键长和键角的灵活性可以满足由分子构象或分子间间距变化而带来的结构微调，从而提高了分子的光聚合效率；（2）而利用氢键调控二维模板内纳米组装体2(4,4'-bpe)2(iso-pa) 的光化学反应研究工作，则提供了一种获得烯烃大范围、高效率光聚合的有效途径。同时，该工作也更好的揭示了分子模板与表面吸附组分之间的协同作用，这也为分子模板对界面分子组装理论的发展提供了有价值的信息。以上这些工作具有重要的学术价值，为高性能光电器件的制备和应用提供了可靠地理论和实验依据。