Construction of the single molecule electroluminescence devices using insulated conducting polymers

本项目的目标是构建由光学功能导电聚合物和绝缘分子组成的一维超分子结构，评估其作为单分子电致发光器件的潜在应用。探索了几种构建绝缘分子线的方法：由环状分子(如环糊精)和电致发光聚合物(如聚噻吩类)组成的绝缘分子线的合成，导电聚合物自组装成一维纳米线，以及用阳极氧化铝多孔模板和绝缘分子和导电聚合物的溶液润湿模板。我们得到了高3-4 nm，宽24-27 nm的矩形截面聚噻吩型纳米纤维。纳米纤维的长度大于几个微米，表明它们的长径比高达103量级。研究还表明，金属与一维超分子结构之间的界面对有机电子器件的构建非常重要，聚合物与金属的电接触对器件的电学和发光性能有很大影响。在这个项目中，我们发现了聚噻吩在金衬底上的化学吸附行为：当聚烷基噻吩环与金衬底在甲苯溶液中浸泡时，聚噻吩环打开并与金衬底自组装形成特异键。化学吸附大大降低了聚烷基噻吩膜的接触电阻，提高了其场效应管的性能。我们还成功地用硒醇对聚噻吩端进行了修饰，与金属形成了特定的键。将该分子应用于原子力显微镜的单分子力谱分析，在单分子尺度上揭示了导电聚合物的构象与光学性质之间的密切关系。

The goal of this project is to construct one-dimensional supramolecular structure consisting of optically functional conducting polymers and insulating molecules, evaluating the potential application as a single-molecular electroluminescence device.Several methods were explored to construct insulated molecular wires (IMW): Synthesis of IMW consisting of cyclic molecules (e. g. cyclodextrins) and electroluminescent conducting polymers (e. g. polythiophenes), self-assembly of conducting polymers into 1-D nanowires, and template wetting with anodic alumina porous template and solutions of insulating molecules and conducting polymers. We obtained polythiophene nanofibers with the rectangular cross section of height 3-4 nm and width 24-27 nm. The nanofiber length longer than several um indicates their high aspect ratio on the order of 10^3.This research also revealed that the interface between metal and 1-D supramolecular structure is so important for the construction of organic electronic devices that the electric contact of polymers with metals affects the device performance significantly in electrical and luminescent properties. In this project, we found the chemisorption behavior of polythiophene onto gold substrate: When poly (alkylthiophene) molecules are immersed with gold substrate in toluene solution, the rings of polythiophene open and form specific bond with gold substrate self-assemblingly. The chemisorption reduced the contact resistance and improved the FET performance of poly (alkylthiophene) considerably. We also succeeded in the end modification of polythiophenes with selenols, forming specific bonds with metals. As a result of applying this molecule to single molecule force spectroscopy (SMFS) using an atomic force microscope (AFM), a close relation between conformation and optical properties of conducting polymers was revealed in a single molecular scale.