【作者】 麻鲁鲁；

【导师】 陶绪堂；

【作者基本信息】 山东大学 ， 材料物理与化学， 2012， 博士

【摘要】 自从Cram和Lehn提出超分子化学的概念以来,通过调节离子或分子间的非共价作用(如氢键作用,π-π堆积,亲疏溶剂作用以及表面效应)使其自组装成超分子结构以制备纳米材料,令器件的微型化的研究获得了重大的突破。在此基础上,引入多刺激响应的基团作为组装基元制备的能响应外部刺激的智能超分子材料,在传感器、分子电路、分子导线、数据存储及处理等领域具有巨大的潜在应用价值。基于此,本论文以传感、电导、存储与转换等功能为导向,利用具有优异的光和热化学稳定性的花二酰亚胺衍生物的刚性平面大π共轭结构及典型的n型半导体特性,以其为主体,分别在花环湾位置和端位置修饰上具有光刺激响应的光致变色基团——偶氮苯或二噻吩乙烯,通过特定波长的光的照射改变其分子结构,研究了其分子的动态自组装行为及其对光刺激的响应,从而实现了对其自组装过程有效的光调控,并在此基础上研究了其纳米超分子聚集体及微晶在电导光开关、荧光开关、高导电性材料等方面的应用。下面是具体的研究工作：1.偶氮苯取代的苝二酰亚胺类化合物由纳米带到纳米球的光控自组装及电导性能研究将具有光开关特性的偶氮苯基团(AZO)修饰到了典型的n-型有机半导体化合物花二酰亚胺(PDI)的湾位置.通过紫外可见吸收光谱(UV/vis spectroscopy)、扫描电镜(SEM)、透射电镜(TEM)、X-射线衍射(XRD)、原子力显微镜(AFM)等测试研究了其光控自组装行为及偶氮苯取代基的异构对其自组装纳米结构的影响。通过365nm紫外光的辐照诱导偶氮苯基团的异构化,成功实现了其自组装纳米结构由带到球的可控的形貌演变。所形成的纳米带具有高度有序的一维分子排列,而在纳米球中由于光异构化诱导的顺式分子构型的弯曲,纳米带的一维有序堆积被打乱,形成了排列相对疏松无序的三维球状纳米结构。在此基础上,我们研究了单根纳米带的导电性能。由于花二酰亚胺核(PDI)的一维长程有序的π-π堆积,纳米带表现出良好的半导体性质其在空气中的电导率约为2×10-5S·m-1。进一步地,其电导随紫外光的照射时间的增加明显降低。我们认为这主要是由其纳米结构中光诱导的无序结构的增加导致的。由此,得到了一种新颖的光诱导电导开关超分子体系。2.基于偶氮苯取代的苝二酰亚胺类化合物的高电导率一维单晶微米带在研究了AZO-PDI化合物在聚集态下相关性质的基础上,我们又通过溶液法生长得到了一种新型的基于化合物Azo-PDIs的单晶微米带,对其晶体结构和导电性质进行了深入研究。由于其独特的“H”型π-π紧密堆积,其中花核共轭基团最近的垂直距离为3.29A,单晶微米带表现出了很高的电导率即在0.04-0.5S·m-1数量级。另外,通过电导率的各向异性测试,初步研究了其晶体中优化的分子堆积与高电导率性质的关系,以期为具有优良性能的半导体材料的设计与合成提供有效的理论指导。3.二芳稀取代的苝二酰亚胺化合物的光致变色纳米结构设计合成了二芳烯取代的苝二酰亚胺光致变色化合物BTE-PDI,并通过再沉淀法研究了其自组装行为及其相应聚集体的纳米结构。由扫描电镜SEM与透射电镜图像TEM表征了其先自组装为零维纳米球而后进一步生长为一维纳米管结构。无论是纳米球还是纳米管都具有高度有序的壳层结构,表明在其自组装过程中存在分级组装现象。纳米球的荧光可通过紫外光的照射进行调控,表现出了这种聚集体的优良的光致变色开关性能。这些发现提供了一种简便的制备动态智能的纳米器件的方法即将具有多刺激响应的基团引入到构筑基元中而后通过自组装得到所需的纳米材料。这种先进的组装生长过程也为人工模拟自然界中某些生物的特征生长开辟了一条新途径。更多还原

【Abstract】 Since Cram and Lehn promulgated the concept of supramolecular chemistry, adjusting the non-covalent interactions between the ions or molecules (such as hydrogen bonding, π-π stacking, hydrophilic-hydrophobic interaction and surface effect) to self-assemble molecules to supramolecular nanomaterials has made miniaturization of device a significant breakthrough. Moreover, the fabrication of smart supramolecular materials that are responsive to external stimuli by the introduction of stimuli-responsive groups into building blocks is believed to have significant potential applications in the field of sensors, molecular circuits, data storage and processing etc.Aiming at the functionality such as sensor, conductivity, storage and conversion etc, we developed perylene diimide derivatives with excellent thermal and photochemical stability, π conjugated rigid plane and the typical n-type semiconductor characteristics as the backbone, and modified with photoresponsive photochromic groups---azobenzene or dithienyl ethylene at the bay position or end position of perylene diimide respectively. Through changing molecular structure by irradiation with specific lignt, we have investigated the dynamics of the molecular self-assembly behavior and its response to light stimulation and realized effective light modulation of its self-assembly process initially. In addition, the applications of nano-supramolecular aggregates and microcrystals as the light-induced conductive switch, fluorescent switch, high conductivity materials have been studied. The detailed research work in this paper is as follows:1. Light-controlled self-assembly and conductance:from nanoribbons to nanospheres based on azobenzene substituted perylene diimidePhotoswitchable azobenzene (AZO) chromophores were introduced to the bay-position of the traditional n-type perylene diimide (PDI). Photocontrolled self-assembly behaviours and the influence of the azobenzene substitution on the assembly structure were investigated by UV/vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). Controlled morphological evolution of the nanostructures from ribbons to spheres was facilely realized by driving the azobenzene switching unit with365nm light irradiation. The nanoribbons demonstrated highly ordered structures while the order of the molecular arrangement was destroyed in the nanospheres, as a result of the curved molecular conformation induced by photoisomerization. In addition, the conductivity of the single nanoribbon was investigated. Thanks to the one-dimensional long-range ordered π-π stacking of the PDI cores, the nanoribbon showed good semiconducting properties with a conductance in the range of2×10-5Sm-1in air. Furthermore, the conductivity decreased with UV light irradiation, mainly due to the increased randomness within the nanostructures, representing the light-induced switching of conductance in the supramolecular systems that is extremely interesting for molecular devices.2. Highly conductive organic single-crystal micro-ribbons formed by a solution process based on azobenzene substituted perylene diimideA novel single-crystal microribbon of Azo-PDIs formed through a solution process as a n-channel semiconductor has been achieved and characterized. Due to the distinctive "H" like close π-π stacking with the shortest vertical contact distance of3.29A, high conductance is determined in the range of0.04-0.5S·m-1. Furthermore, based on the results of conductivity anisotropy, a direct relationship between the maximized conductivity and the optimized molecular stacking is primarily discussed. And it will provide significant guidance on the design of new semiconductor materials with excellent performance.3. Photochromic nanostructures based on diarylethenes with perylene diimideA bisthienylethene-functionalized perylene diimide (BTE-PDI) photochromic dye was synthesized for self-assembly into1-D nanotubes by a reprecipitation method. SEM and TEM observations showed that the nanotubes were formed from their0-D precursors of hollow nanospheres. HR-TEM images revealed that both the nanospheres and the nanotubes have highly ordered lamellar structure, indicating the hierarchical process during assembly. The IR and XRD results revealed that DAE-PDI molecules were connected through intermolecular hydrogen bonds to form building blocks that self-assembled into nanostructures. Electronic absorption and fluorescence spectroscopic results indicated the H-aggregate nature of the self-assembled nanostructures. Competition and cooperation between the dipole-dipole interaction, intermolecular π-π stacking, and hydrophilic/hydrophobic interaction are suggested to result in nanostructures. Reconstruction was found to happen during the morphology transition progress from the0-D nanospheres to the1-D nanotubes, which was driven by donor-acceptor dipole-dipole interactions. Green emission at520nm originating from the DAE subunit was observed for the aggregates of vesicles and nanotubes, which could be regulated by photoirradiation with365nm light, suggesting the nanoaggregates to be photochromic switches.更多还原