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

聚合物是由许多小分子连接在一起形成的长分子链，称为单体。通过改变单体的化学结构，化学家可以创造出吸收光、荧光和导电的聚合物，使其用于手机显示器、太阳能光伏，甚至用于医学成像。尽管有这些优点，但聚合物在暴露在氧气和光线下时会降解，当链聚集在一起形成设备中使用的薄膜时，它们的荧光会减弱。在化学系化学结构、动力学和机理A以及大分子、超分子和纳米化学项目的支持下，卡内基梅隆大学的Linda Peteanu教授正在应对这些挑战。与她的学生合作，她使用了一系列的光谱工具来了解为什么聚合物链在放置在金属薄膜上时降解较少，以及为什么当链堆积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更好的聚合物，这可能会产生重大的社会影响。教育的更广泛影响在于培养具有光学专业知识和新颖成像方法的学生。此外，面向K-12学生和公众的外展展示了光如何与物质相互作用。作为该奖项的一部分，开展的外展活动和演示帮助年轻科学家直观地了解微观和宏观世界之间的联系，并帮助普通公众认识到这种基本联系在他们日常生活中使用的许多产品的开发中是多么关键。本论文主要研究共轭半导体齐聚物、聚合物及其聚集体。这些材料显示出非凡的能力，可以在比分子尺度更大的距离内传输能量和电荷。除了发射率外，这些特性对于从光伏和发光二极管等光电设备到化学传感器和生物标签的各种应用都很重要。从基本的角度来看，扩展的或电子离域的结构，如这些聚合物及其聚集体，是有意义的，因为它们的电子性质位于小分子和扩展的固体之间的间隙。这个项目的目标有两个。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、动力学和产率是如何由基态构象以及系统间交叉和内部转换的速度和效率控制的。二是研究了两种局部环境扰动--溶剂极性效应和等离子体场效应对荧光产额、单重态-三重态驰豫、能量转移和电荷分离的速率和效率的影响。这些数据可能会让我们更好地理解如何优化这类重要材料的结构、形态和局部环境，以适应需要高发射率和高效电荷传输的现有和新应用。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。

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.