Using Circularly Polarized Light to Probe Electronic Excitations in Organic Supramolecular Assemblies

使用圆偏振光探测有机超分子组装体中的电子激发

• 批准号: 0906464
• 负责人: Francis Spano
• 金额: $ 30.6万
• 依托单位: Temple University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2012-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0906464&HistoricalAwards=false
• 关键词: Using; Circularly; Polarized; Light; Probe

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).TECHNICAL ABSTRACTThis award is funded by the Division of Materials Research and the Chemistry Division. It supports theoretical research and education on how oligomer/polymer films interact with and emit light. The PI aims to investigate fundamental excitations in organic assemblies by focusing on chiral supramolecular structures which are amenable to circular dichroism and circularly polarized luminescence spectroscopies. Compared with their unpolarized counterparts, these spectroscopies are far more sensitive to extended intermolecular interactions as well as the structure of the fundamental electronic excitations. Of particular interest to this study are pi-stacked helical rod aggregates consisting of functionalized conjugated molecular chromophores which self-assemble in solution or with the aid of a DNA template. Specific goals include: 1. A detailed understanding of the excitonic signatures in the circularly polarized luminescence dissymmetry spectrum. The unusual demise of the spectrum with increasing wavelength observed in helical rod aggregates and chiral polymer films contains vital information on the anatomy of the emitting species. This spectrum is unique amongst spectral probes in its high sensitivity to the inner-sphere distortion field surrounding the core vibronic excitation. The objective is to understand how the polaron radius, the reorganization energy, and the coherence length impact the shape and magnitude of the circularly polarized luminescence dissymmetry spectrum. International collaboration with experimentalists will enable applications to oligothiophene nanofibers. 2. A rigorous analysis of intermolecular interactions in helical rod N-mers. Aggregates with a controllable number of chromophores are ideal systems with which to rigorously evaluate theoretical models for extended intermolecular interactions and disorder. The circularly polarized luminescence dissymmetry spectrum and its absorption analog are sensitive probes of long-range interactions even in strongly disordered systems where excitons are localized to only a few chromophores. The PI aims to perform a detailed theoretical analysis of the absorption spectrum to help resolve these issues. 3. An appreciation of the exciton Cotton effect in systems with strong exciton-phonon coupling. In assemblies with strong exciton-phonon coupling the circular dichroism spectrum is far more complex than the simple Cotton couplet found for weak coupling. The PI aims to develop a comprehensive theory for the circular dichroism response of excitonic polarons to understand how information regarding intermolecular interactions and the aggregate morphology can be extracted from the spectral line shape. Applications to the ubiquitous and biologically-important carotenoid aggregates will be made. The above analyses will be based on a Holstein Hamiltonian. Excitonic interactions, linear exciton-phonon coupling, and disorder will be treated on equal footing under the two-particle approximation, which reduces the basis set to a tractable size without sacrificing accuracy. The broader impact of the proposed activities will be felt primarily through an enhanced understanding of a technologically important class of materials, possibly resulting in novel design strategies for improved organic light-emitting diodes and solar cells. The commercial impact of soft electronic devices is expected to dramatically increase over the next several years, through products like flexible displays, electronic labels and solid-state lighting. In addition, the proposed activities will enhance research infrastructure through international collaborations. NONTECHNICAL ABSTRACTThis award is funded by the Division of Materials Research and the Chemistry Division. It supports theoretical research and education on how thin films composed of a class of long chain molecules, polymers, interact with and emit light. The research is focused on key issues that impede understanding of the mechanisms by which these films interact with light, how light is absorbed by these materials and the nature of the electronic states after absorbing light. A key feature of the PI?s approach is to account for the interaction of electronic charge with vibrations of the molecular chains. Thin films of particular kinds of polymers may be useful as active materials for organic-based electronic devices such as transistors, light emitting diodes, and solar cells. This research project contributes to the intellectual foundations that will enable the use of these materials for lighting, solar energy conversion, and other electronic devices. The commercial impact of soft electronic devices is expected to dramatically increase over the next several years, through products like flexible displays, electronic labels and solid-state lighting. In addition, the proposed activities will enhance research infrastructure through international collaborations.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。技术摘要：本奖项由材料研究部和化学部资助。它支持关于低聚物/聚合物薄膜如何与光相互作用和发光的理论研究和教育。PI的目的是研究有机组件的基本激发，重点关注可适应圆二色性和圆偏振发光光谱的手性超分子结构。与它们的非极化对应物相比，这些光谱对扩展的分子间相互作用以及基本电子激发的结构更加敏感。本研究特别感兴趣的是由功能化共轭分子发色团组成的pi堆叠螺旋棒聚集体，其在溶液中或在DNA模板的帮助下自组装。具体目标包括：圆偏振发光不对称光谱中激子特征的详细理解。在螺旋棒聚集体和手性聚合物薄膜中观察到的不寻常的随波长增加而消亡的光谱包含了发射物质解剖结构的重要信息。该光谱在光谱探针中是独一无二的，因为它对核心振动激发周围的球内畸变场具有很高的灵敏度。目的是了解极化子半径、重组能和相干长度如何影响圆极化发光不对称光谱的形状和大小。与实验家的国际合作将使低聚噻吩纳米纤维的应用成为可能。2. 螺旋棒状N-mers分子间相互作用的严格分析。具有可控数量的发色团的聚集体是严格评估扩展分子间相互作用和无序的理论模型的理想系统。圆偏振发光不对称光谱及其吸收类似物即使在激子仅局限于少数发色团的强无序系统中也是远程相互作用的敏感探针。PI旨在对吸收光谱进行详细的理论分析，以帮助解决这些问题。3. 强激子-声子耦合系统中激子棉花效应的评价。在强激子-声子耦合的组件中，圆二色光谱远比弱耦合的简单Cotton对偶复杂得多。PI旨在为激子极化子的圆二色性响应发展一个全面的理论，以了解如何从谱线形状中提取有关分子间相互作用和聚集体形态的信息。应用于无处不在和生物重要的类胡萝卜素聚集体将作出。上述分析将基于荷尔斯泰因哈密顿量。激子相互作用，线性激子-声子耦合和无序将在双粒子近似下平等地处理，这将基集减少到可处理的大小而不牺牲精度。拟议活动的更广泛影响将主要通过加强对技术上重要的一类材料的了解，可能导致改进有机发光二极管和太阳能电池的新设计策略。软电子设备的商业影响预计将在未来几年急剧增加，通过产品如柔性显示器，电子标签和固态照明。此外，拟议的活动将通过国际合作加强研究基础设施。本奖项由材料研究部和化学研究部资助。它支持理论研究和教育，研究由一类长链分子、聚合物组成的薄膜如何与光相互作用和发光。研究的重点是阻碍人们理解这些薄膜与光相互作用的机制、这些材料如何吸收光以及吸收光后电子状态的性质的关键问题。PI的关键特性是什么？S方法是考虑电子电荷与分子链振动的相互作用。特定种类聚合物的薄膜可以用作有机电子器件的活性材料，如晶体管、发光二极管和太阳能电池。该研究项目为这些材料在照明、太阳能转换和其他电子设备上的应用奠定了知识基础。软电子设备的商业影响预计将在未来几年急剧增加，通过产品如柔性显示器，电子标签和固态照明。此外，拟议的活动将通过国际合作加强研究基础设施。