CAREER: Soft Light-Harvesting Systems Based on inter-Conjugated Polyelectrolyte Complexes

自然光合作用有机体使用高度专业化的超结构，其中包含许多分子成分。这些组件协同工作，将阳光有效地转化为电池所需的化学燃料。这些成分的排列方式是，当太阳光被颜料(含颜色的化合物)吸收时，能量可以在能量损失之前从一个成分迅速转移到下一个成分。自然界利用捕光细胞器以惊人的效率完成能量转移。人工模拟这种复杂的结构可以形成轻质材料，其光合作用功能可以精确控制。然而，制造人工光合作用系统仍然是一个重大挑战。在美国国家科学基金会化学部高分子、超分子和纳米化学项目的支持下，加州大学圣克鲁斯分校(UCSC)的艾兹纳教授和他的学生正在基于聚合物等软分子材料建造人造捕光细胞器。这些聚合物可以自组装成更大的结构，可以在空间中快速传输激发态，从而模拟光合作用细胞器的基本方面。该项目正在为研究生提供培训机会。艾兹纳教授正在以能量收集为载体，向转学学生传授高级化学问题解决技能，从而帮助他们为在化学科学中取得持续成功做好准备。首先，要完成人工捕光细胞器的形成，需要为将高效的电子能量转移(EET)继电器与更大的结构支架组装和接口奠定基础。为此，艾兹纳教授正在将共轭聚电解质(CPE)合成并组装成给体/受体络合物，其结构和热力学可以通过电子和离子自由度之间的耦合来控制。该项目阐明了CPE的主干如何通过系统地调节平均聚电解质长度和化学结构来影响复合体内的EET效率。然后对CPE络合物的相分离行为和共存相中的EET进行了表征，以阐明过量离子对捕光的影响。然后，将复合体与自组装的囊泡型隔室连接，形成柔软的捕光超结构的基础。对所得组件的表征涉及结合时间分辨电子光谱、光子散射、显微镜和流变学测量。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Natural photosynthetic organisms use highly specialized super-structures that house many molecular components. These components work in concert to efficiently convert sunlight to chemical fuel for the cell. The components are arranged so that when sunlight is absorbed by the pigments (color-containing compounds), the energy can move quickly from one component to the next before the energy is lost. Nature accomplishes energy transfer with remarkable efficiency using light-harvesting organelles. Mimicking such a complex structure artificially could lead to formation of light-weight materials, whose photosynthetic function could be exquisitely controlled. However, making artificial photosynthetic systems remains a major challenge. With support from the Macromolecular, Supramolecular and Nanochemistry Program of the NSF Division of Chemistry, Professor Ayzner at the University of California, Santa Cruz (UCSC) and his students are building artificial light-harvesting organelles based on soft molecular materials, such as polymers. These polymers can self-assemble into larger structures that can rapidly transport excited states through space, thus mimicking the fundamental aspects of photosynthetic organelles. The project is providing training opportunities for graduate students. Professor Ayzner is using the topic of energy harvesting as the vehicle to teach advanced chemical problem-solving skills to transfer students, thereby helping to prepare them for sustained success in the chemical sciences. Accomplishing the formation of an artificial light-harvesting organelle first requires laying a foundation for assembling and interfacing an efficient electronic energy transfer (EET) relay with a larger structural scaffold. To this end, Professor Ayzner is synthesizing and assembling conjugated polyelectrolytes (CPE) into donor/acceptor complexes, whose structure and thermodynamics can be controlled via the coupling between electronic and ionic degrees of freedom. This project elucidates how the backbone of a CPE influences the EET efficiency within the complex by systematically tuning the mean polyelectrolyte length and chemical structure. The phase separation behavior and EET in co-existing phases of inter-CPE complexes is then characterized to elucidate the influence of excess ions on light-harvesting. Complexes are then interfaced with self-assembled vesicle-type compartments to form the foundation of a soft light-harvesting super-structure. Characterization of resulting assemblies involves combining time-resolved electronic spectroscopy, photon scattering, microscopy and rheological measurements.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.