Spin-Dependent Charge Transport through Chiral Assemblies

加州大学洛杉矶分校的Paul S. Weiss教授得到了化学系大分子、超分子和纳米化学（MSN）项目的支持，研究有机手性（如螺旋）分子和组装体中的电荷传输。手性分子和分子组合被放置在磁性表面和纳米结构上。许多通用的光谱和显微测量和成像技术被用于探测通过附着在表面的分子和组件的超快电荷转移运动。研究成果对自旋电子学和磁学的一般研究领域具有重要的推动作用。更好地了解这些有机组件为它们作为当前自旋电子器件的补充或替代品铺平了道路，例如具有低功耗和高密度的计算机逻辑和存储器。在进行项目的过程中，学生将在包括国际合作在内的多学科环境中接受培训。此外，Weiss教授还通过国家公共广播电台（NPR）和高中学生和教师课程等不同的场所进行受欢迎的演讲。该项目旨在阐明在金属和半导体表面吸附的手性分子组件中，有助于自旋选择性电荷传输的分子、底物和界面性质。最终目标是了解所涉及的过程，并评估在器件架构中实现手性有机组件作为自旋滤波器的未来实用性。首先，确定了分子自旋轨道耦合对DNA单分子层电子自旋过滤的作用机制。重金属离子被纳入DNA分子中，以操纵和增强螺旋诱导的自旋-轨道耦合。在铁磁性衬底和GaN霍尔效应器件表面上形成了DNA单层，并使用自旋依赖电化学、光电子能谱和霍尔电压测量来探测汞化的影响。其次，研究了通过手性配体拴住的铁磁底物和量子点之间的耦合。利用手性分子功能化量子点阵列的荧光寿命成像，测量了手性分子功能化量子点的光致发光寿命作为手性和衬底磁化的函数。测试了量子点的手性特征、组成和几何形状，以及束缚分子的长度（以及与衬底的电子耦合）。最后，利用核孔时钟光谱测量了碳硫醚对映体与磁化基底之间的超快电荷转移。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。

Professor Paul S. Weiss of the University of California, Los Angeles is supported by the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program of the Division of Chemistry to study charge transport through organic chiral (e.g., helical) molecules and assemblies. The chiral molecules and molecular assemblies are placed on magnetic surfaces and nanostructures. A number of versatile spectroscopic and microscopic measurements and imaging techniques are used to probe the ultrafast charge transfer movements through molecules and assemblies that are attached to surfaces. The research results may advance the general fields of spintronics and magnetism. Better understanding of these organic assemblies paves the way for their use as complements or replacements for current spintronic devices, such as computer logic and memory with low power and high density. In the course of conducting the project, students are trained in a multidisciplinary environment, including international collaboration. In addition, Professor Weiss gives popular talks through different venues, such as National Public Radio (NPR) and courses for high school students and teachers. The project aims to elucidate the molecular, substrate, and interfacial properties that contribute to spin-selective charge transport in chiral molecular assemblies adsorbed on metal and semiconducting surfaces. The ultimate goal is to understand the processes involved and to assess the future practicality of implementing chiral organic assemblies as spin filters within device architectures. First, the mechanistic role of molecular spin-orbit coupling on electron spin filtering by DNA monolayers are determined. Heavy metal ions are incorporated within DNA molecules to manipulate and to enhance helix-induced spin-orbit-coupling. Monolayers of DNA are formed on ferromagnetic substrates and on the surfaces of GaN Hall effect devices, and the effects of mercuration are probed using spin-dependent electrochemistry, photoelectron spectroscopy, and Hall voltage measurements. Second, the coupling between ferromagnetic substrates and quantum dots tethered via chiral ligands is investigated. The dependence of photoluminescence lifetime of the chiral molecule-functionalized quantum dots are measured as a function of handedness and substrate magnetization using fluorescence lifetime imaging of patterned arrays of chiral quantum dots. The chiral signature, composition, and geometry of the quantum dots, as well as the lengths of tethering molecules (and thus the electronic coupling to the substrate) are tested. Finally, ultrafast charge transfer measurements between carboranethiolate enantiomers and magnetized substrates using core-hole clock spectroscopy are conducted.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.