Resonance Raman Spectroscopy and Scanning Probe Microscopy of Light-Harvesting Chromophore Aggregates

在这个由实验物理化学项目支持的项目中，Jeanne McHale教授和Ursula Mazur教授将进行光谱和扫描探针测量，以研究光收集聚集体（LHAs）的激发态特性与其超分子结构之间的联系。共振拉曼光谱、原子力显微镜和扫描隧道显微镜（STM）将解决以下问题：(1)分子结构的细节（非平面性、金属离子的存在、电荷等）如何影响LHA在纳米和介观长度尺度上的形态（纳米棒、纳米环、螺旋等）？(2)光学和电子性质如何取决于分子和超分子结构？(3)对于分形聚集体，子单元是如何组装的，它们之间的电子通信的性质是什么？(4) lha系综的结构非均质性程度如何，如何在光谱中反映出来？在这项合作研究中，McHale实验室将测量和分析LHAs的拉曼激发谱，以揭示激子耦合。对贵金属上lha的表面增强共振拉曼信号进行优化，以获得单个lha的拉曼光谱。Mazur实验室将获得由不同程度的非平面性分子组成的自组装聚集体的高分辨率STM图像，以探索其在指导闭合环形成方面的作用，类似于在光合生物中发现的那些。此外，他们将使用轨道介导的隧道光谱在分子和亚分子分辨率上成像与电子传递相关的离域轨道。在这项工作中感兴趣的lha在分子电子学，传感器和太阳能转换中有应用。对聚集体形态、分子结构和组装的光学和电子性质之间联系的基础研究将使这些性质能够针对特定应用进行调整，借鉴自然界的想法，优化lha的结构以收集和汇集太阳能到反应中心。除了像过去一样培养多样化的研究生和本科生外，PI和联合PI还将通过参与WSU的“提高数学和科学管道”，将拟议的研究作为向当地印第安人和西班牙裔学生推广的工具。这个项目让高风险的高中生参与植物科学和替代能源的研究项目。

In this project supported by the Experimental Physical Chemistry Program, Professors Jeanne McHale and Ursula Mazur will perform spectroscopic and scanning probe measurements to investigate the link between excited state properties of light harvesting aggregates (LHAs) and their supramolecular structures. Resonance Raman spectroscopy, atomic force microscopy, and scanning tunneling microscopy (STM) will address the following questions: (1) How do details of molecular structure (nonplanarity, presence of metal ions, charge, etc.) influence LHA morphology (nanorods, nanorings, helices, etc.) on nano- and meso-scopic length scales? (2) How do optical and electronic properties depend on molecular and supramolecular structure? (3) For fractal aggregates, how are the sub-units assembled and what is the nature of the electronic communication between them? (4) What is the extent of structural heterogeneity in the ensemble of LHAs and how is it reflected in the optical spectra? In this collaborative research, the McHale lab will measure and analyze Raman excitation profiles of LHAs to reveal excitonic coupling. The surface-enhanced resonance Raman signal of LHAs on noble metals will be optimized in order to obtain Raman spectra of individual LHAs. The Mazur lab will obtain high-resolution STM images of self-assembled aggregates composed of molecules with varying degrees of nonplanarity to probe its role in directing the formation of closed rings similar to those found in photosynthetic organisms. In addition, they will use orbital mediated tunneling spectroscopy to image the delocalized orbitals associated with electron transport at molecular and submolecular resolution. The LHAs of interest in this work have applications in molecular electronics, as sensors, and in solar energy conversion. Fundamental studies of the link between aggregate morphology, molecular structure, and optical and electronic properties of the assembly will enable these properties to be tuned for a particular application, borrowing ideas from nature where the structures of LHAs are optimized to collect and funnel solar energy to the reaction center. In addition to training diverse graduate and undergraduate students as they have in the past, the PI and co-PI will use the proposed research as a vehicle for outreach to area Native American and Hispanic students by participating in WSU's "Pumping up the Math and Science Pipeline". This program engages high-risk high school students in research projects in plant science and alternative energy.