Polaron and Spin Transport in Nanoscale Molecular Junctions

该奖项由化学部的高分子，超分子和纳米化学计划资助。 C教授明尼苏达大学双城分校的丹尼尔弗里斯比得到了支持，他开发了制作有机半导体薄膜（1 - 10 nm，宽度只有人类头发的一小部分）的技术，并使用原子力显微镜（AFM）灵敏地测量了它们的导电性能。有机膜以这样的方式制成，即分子取向被精确控制，使得在最有利的方向上测量导电性。这些方法通过提供有关电荷如何在定向分子中移动的新知识，推进了有机半导体科学的前沿，从而支撑了显示技术。 有机半导体属于一类新的功能分子材料，其在智能手机显示器和电视机中使用的有机发光器件（OLED）中取得了广泛的商业成功。了解这些分子半导体在微观“甚至纳米级”长度尺度上的导电特性对它们的持续改进至关重要。 将研究与教育相结合，为研究生和博士后研究人员提供研究机会，培养他们成为分子合成和表征，电导测量和纳米技术的下一代专家。 该计划利用PI和他的学生在过去15年中开发的独特实验方法，包括（i）进行探针原子力显微镜（CP-AFM）以形成金属-分子-金属结，以及（ii）寡亚胺点击化学用于构建表面锚定的π共轭线，单体对链结构进行单体控制。项目有四个目标：（1）使用同位素标记来理解π共轭分子线中极化子和极化子跳跃过渡态的性质;（2）研究极化子尺寸对跳跃输运的影响;（3）使用具有铁磁（FM）接触的CP-AFM自旋阀结来测量作为分子线长度和定制结构两者的函数的自旋输运;（4）演示电子结构控制和电流切换。 该团队与两个量子化学小组合作，为该项目提供理论和计算支持。总的来说，研究计划平衡了低风险的实验，这些实验肯定会产生重要的结果，而高风险的想法则会开辟新的方向。

This award is funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry. Professor C. Daniel Frisbie of the University of Minnesota-Twin Cities is supported to develops techniques both for making ultrathin films (1-10 nm, a tiny fraction of a human hair in width) of organic semiconductors and for sensitively measuring their conduction properties using an atomic force microscope (AFM). The organic films are made in such a way that molecular orientation is precisely controlled so that electrical conduction is measured in the most favorable direction. These methods advance the frontiers of organic semiconductor science that underpin display technology by providing new knowledge about how charges move in oriented molecules. Organic semiconductors belong to a new class of functional molecular materials that have achieved widespread commercial success in organic light emitting devices (OLEDs) employed in smart phone displays and televisions. Understanding the electrical conduction properties of these molecular semiconductors on microscopic "even nanoscopic" length scales is vital to their continued improvement. Integrating the research with education provides research opportunities for graduate students and postdoctoral researchers, training them to be the next generation of experts in molecular synthesis and characterization, electrical conductance measurements, and nanotechnology. The plan leverages unique experimental approaches developed by the PI and his students over the last 15 years including (i) conducting probe atomic force microscopy (CP-AFM) for forming metal-molecule-metal junctions and (ii) oligoimine click chemistry for building surface-anchored pi-conjugated wires with monomer-by-monomer control over chain architecture. There are four project goals: (1) to use isotopic labeling to understand the nature of polarons and polaron hopping transition states in pi-conjugated molecular wires; (2) to investigate polaron size effects on hopping transport; (3) to measure spin transport as a function of both molecular wire length and tailored architecture using CP-AFM spin valve junctions with ferromagnetic (FM) contacts; (4) to demonstrate electronic structure control and current switching. The team collaborates with two quantum chemistry groups that provide theoretical and computational support for the project. Overall, the research plan balances lower risk experiments that are certain to yield important results with higher risk ideas that open up new directions.