Collaborative Research: Studies of Charge Transport in Designed Nanoscale Molecular Assemblies

德克萨斯农工大学的James D. Batteas教授和纽约市立大学研究基金会高级科学研究中心的Adam B. Braunschweig教授得到了化学系大分子、超分子和纳米化学项目的支持，以开发一种方法，使分子组装可以建立在扩展和纳米结构的金属表面上，以展示可预测的特性。分子组装在精确的纳米级几何形状的表面上，旨在以直接的方式捕获和传输电荷和能量。先进的成像和光学技术被用来检查所得到的结构，并确定结构如何控制电子通过分子的运动，或者它们如何与它们沉积的表面交换能量。该项目推进了改进的光收集和太阳能转换、便携式化学传感和量子计算的发展。在这项研究的过程中，来自不同背景的研究生，本科生和K-12学生准备加入先进的电子劳动力。他们在化学合成、材料化学和表面科学交叉领域的交叉研究中接受培训，在主要研究人员的实验室之间进行协调合作。设计能够捕获和传输电荷的分子组件，并通过有效的电子耦合以可预测和可指导的方式交换能量，对于实现从新型传感器到分子/有机电子学到染料敏化太阳能电池等设备的设计至关重要，其中分子组件是调制器件光电特性的组成部分。几个关键问题的解决，以促进这些和其他应用分子为基础的系统的合理设计，并指导他们的实施。这些问题包括定向分子相互作用（如范德华、氢键和局部交联）如何影响电子传递行为？研究人员还想知道分子组装如何在空间上受限，并在纳米级结中以精确的结构制造，以用于潜在的设备应用。研究小组提出了一个问题：空间限制和组件内部局部分子间相互作用的综合效应以及与表面的相互作用如何控制它们最终产生的光学和电子特性？探索了一系列自组装系统，包括卟啉类化合物、二维（2D）交联的二乙基硫醇和供体-受体染料分子，如苝、二氰萘和二酮吡咯衍生物。之所以选择这些材料，是因为它们可定制的光电特性使它们成为有机电子器件的合理目标。这些材料的纳米级组件被创建在扩展的金表面和图案金纳米结构上，以进一步探索激子-等离子体耦合对组装系统的光学和电荷输运行为的影响。通过一系列表面科学方法，包括STM、AFM、XPS、IR、荧光和拉曼光谱，详细测量了组装过程和光电性能。该项目弥合了理解单分子和扩展分子薄膜中电荷传导的差距，这是相对未被探索的。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Professors James D. Batteas of Texas A&M University and Adam B. Braunschweig of the Research Foundation CUNY - Advanced Science Research Center are supported by the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry to develop an understanding of methods whereby molecular assemblies can be built on extended and nanostructured metal surfaces to exhibit predictable properties. Molecular assemblies built with precise nanoscale geometries on surfaces are designed to trap and transport charge and energy in directable ways. Advanced imaging and optical techniques are used to examine the resulting structures and to determine how the structures control the movement of electrons through the molecules or how they exchange energy with the surfaces on which they are deposited. The project advances the development improved light harvesting and solar energy conversion, portable chemical sensing, and quantum computing. In the course of this research, graduate, undergraduate and K-12 students from diverse backgrounds are prepared to join the advanced electronics workforce. They are trained in cross-cutting research at the intersection of chemical synthesis, materials chemistry, and surface science in a coordinated collaborative environment between the laboratories of the principle investigators. Designing molecular assemblies that can trap and transport charge, and exchange energy in predictable and directable ways via efficient electronic coupling, is critical for enabling the design of devices ranging from novel sensors to molecular/organic based electronics, to dye sensitized solar cells, where molecular assemblies are integral components for modulating the optoelectronic properties of the devices. Several key questions are addressed to foster the rational design of molecular based systems for these and other applications, and to guide their implementation. These questions include how can directed molecular interactions (e.g. van der Waals, hydrogen bonding and local cross-linking) influence electron transport behavior? Researchers also want to know how molecular assemblies can be spatially confined and fabricated with precise architectures in nanoscopic junctions for potential device applications? The team asks how the combined effects of spatial confinement and local intermolecular interactions within the assemblies and with surfaces afford control over their final resulting optical and electronic properties? A series of self-assembled systems is explored, including porphryinoids, two-dimensional (2D) cross-linked diacetylenic thiols, and donor-acceptor dye molecules, such as perylene, dicyanonaphthalene and diketopyrrolopyrrole derivatives. These are selected because their tailorable optoelectronic properties make them reasonable targets as components for organic electronic devices. Nanoscale assemblies of these materials are created on extended gold surfaces, and patterned gold nanostructures, to further explore the effects of exciton-plasmon coupling on the resulting optical and charge transport behavior of the assembled systems. The assembly processes and optoelectronic properties are measured in detail via a host of surface science approaches including, STM, AFM, XPS, IR and fluorescence and Raman spectroscopies. The project bridges the gap between understanding charge conduction in single molecules and extended molecular thin films, which is relatively unexplored.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.