Tuning the Photo-physics of Organic Semi-conductors using Morphological and Plasmonic Effects

聚合物是由许多称为单体的小分子连接在一起形成的长分子链。通过改变单体的化学结构，化学家们可以创造出吸收光、发荧光和导电的聚合物，使它们在手机显示器、太阳能光电转换器甚至医学成像方面都很有用。 尽管有这些优点，但聚合物在暴露于氧气和光时会降解，并且当链聚集在一起形成用于设备的薄膜时，它们的荧光会降低。在化学结构，动力学和机制A以及化学系的大分子，超分子和纳米化学项目的支持下，麦基-梅隆大学的琳达·佩特亚努教授正在应对这些挑战。 她与她的学生一起工作，使用各种光谱工具来理解为什么聚合物链在放置在金属膜上时降解较少，以及为什么当链聚集在一起时它们的荧光会减少。 该团队的发现正在帮助化学家为消费电子应用创造改进的聚合物，这可能会产生重大的社会影响。 更广泛的教育影响在于培养具有光学和新成像方法专业知识的学生。 此外，对K-12学生和公众的宣传展示了光如何与物质相互作用。 作为该奖项的一部分，开发的推广活动和演示帮助年轻科学家可视化微观和宏观世界之间的联系，并帮助公众了解这种基本联系如何在他们日常生活中使用的许多产品的开发中发挥关键作用。 本论文主要研究共轭半导体低聚物、聚合物及其聚集体。 这些材料展示了在与分子尺度相比大的距离上传输能量和电荷的显着能力。这些性质，除了它们的发射率，是重要的应用范围从光电器件，如光致发光和发光二极管，化学传感器和生物标签。从基本的角度来看，扩展的或电子离域的结构，如这些聚合物和它们的聚集体，是令人感兴趣的，因为它们的电子性质位于小分子和扩展固体的电子性质之间的差距。 该项目的目标是双重的。 首先是利用各种光谱和成像工具，分子建模和合成修饰进行全面的调查，以了解发射光谱，动力学和产量是如何由基态构象和系统间交叉和内部转换的速率和效率控制的。 第二个是探索两个局部环境扰动，溶剂极性和等离子体场效应，对荧光产率和单线态-三线态弛豫，能量转移和电荷分离的速率和效率的影响。 这些数据可以更好地了解这类重要材料的结构、形态和局部环境如何优化，以满足现有和新型应用的需要，这些应用需要高发射率和有效的电荷传输。该奖项反映了NSF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。

Polymers are long molecular chains formed by linking together many small molecules, called monomers. By varying the monomer's chemical structure, chemists can create polymers that absorb light, fluoresce, and conduct electricity, making them useful for cell phone displays, solar photovoltaics, and even in medical imaging. Despite these advantages, polymers degrade upon exposure to oxygen and light, and their fluorescence decreases when the chains pack together to form the films used in devices. With support from the Chemical Structure, Dynamics, and Mechanism A and Macromolecular, Supramolecular, and Nanochemistry Programs in the Division of Chemistry, Professor Linda Peteanu of Carnegie-Mellon University is addressing these challenges. Working with her students, she is using a wide array of spectroscopic tools to understand why polymer chains degrade less when placed onto metal films, as well as why their fluorescence is reduced when the chains pack together. The team's discoveries are helping chemists to create improved polymers for consumer electronics applications, which could have significant societal broader impact. The educational broader impacts lie in the training of students with expertise in optics and novel imaging methods. In addition, outreach to K-12 students and to the public demonstrate how light interacts with matter. The outreach activities and demonstrations developed as part of this award help young scientists visualize the connections between the microscopic and macroscopic worlds and help the general public appreciate how this fundamental connection has been critical in the development of many of the products they use in their everyday lives. This research focuses on conjugated semi-conducting oligomers, polymers and their aggregates. These materials demonstrate the remarkable ability to transport energy and charge over distances that are large compared to molecular scales. These properties, in addition to their emissivity, are important to applications ranging from opto-electronic devices, such as photovoltaics and light emitting diodes, to chemical sensors and biological labels. From a fundamental perspective, extended or electronically-delocalized structures, such as these polymers and their aggregates, are of interest because their electronic properties lie in the gap between those of small molecules and extended solids. The goals of this project are two-fold. The first is to perform a comprehensive investigation utilizing a variety of spectroscopic and imaging tools, molecular modeling, and synthetic modification to understand how the emission spectra, dynamics and yields are controlled by ground-state conformation and by the rates and efficiencies of intersystem crossing and internal conversion. The second is to explore the effects of two local environmental perturbations, solvent polarity and plasmonic field effects, on the fluorescence yield and the rates and efficiencies of singlet-triplet relaxation, energy transfer and charge separation. These data may yield a better understanding of how the structure, morphology, and local environment of this important class of materials can be optimized for existing and novel applications that require high emissivity and efficient charge transport.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.