Quantitative Analysis of Molecular Conductance in Molecular Junctions

C教授明尼苏达大学双城分校的丹尼尔弗里斯比得到化学系大分子、超分子和纳米化学（MSN）项目的支持，研究分子半导体在微小纳米长度尺度上的导电性，并开发可能导致纳米电子学新应用的分子开关器件。分子半导体被用于商业OLED（有机发光二极管）显示器中，但是它们在分子长度尺度上的导电性质还没有被很好地理解。该项目增加了基础知识基础，并推进了功能电子半导体器件广泛应用所需的分子电子原理。将研究与教育相结合，为从事实验工作的研究生提供了宝贵的化学，材料研究和纳米技术技能，并使他们获得国际研究经验。 该项目为不同背景的本科生提供暑期研究机会，特别关注女性和代表性不足的少数民族成员。 从技术的角度来看，该奖项的重点是在两个机制制度，即量子力学隧道和经典跳跃极限的分子结构电导关系。这些非常不同的传输机制由分子结构定义，其中隧穿机制通常与长度小于约5 nm的分子有关，并且取决于键合结构，对于长于该值的分子，跳跃持续存在。首席研究员和他的合作者已经证明，称为单能级模型（SLM）的分析理论准确地描述了隧道机制中某些基准分子结的电流-电压（I-V）特性。在这个项目中，研究小组探索了SLM的一般性，用于描述各种系统中的分子隧穿，特别关注分子间相互作用和表面附着化学的影响。在跳跃制度中，重点是理解π共轭低聚物中分子内电荷转移过渡态的精确性质，特别是过渡态能量（自由能垒的高度）和相关的键长和角度变形。为此，动力学同位素分析跳跃传导相结合的过渡态的量子化学计算。隧道和跳跃推力都利用了独特的合成，测量和分析策略，由主要研究者的实验室开发，并得到了NSF的支持。该奖项反映了NSF的法定使命，并被认为是值得支持的，通过使用基金会的智力价值和更广泛的影响审查标准进行评估。

Professor C. Daniel Frisbie of the University of Minnesota-Twin Cities is supported by the Macromolecular, Supramolecular and Nanochemistry (MSN) Program of the Division of Chemistry to investigate electrical conduction in molecular semiconductors over tiny nanometer length scales and to develop molecular switching devices that may lead to new applications in nanoelectronics. Molecular semiconductors are employed in commercial OLED (organic light emitting diode) displays but their conduction properties on molecular length scales are not well understood. The project adds to the fundamental knowledge base and advances the molecular electronic principles needed for a wide range of applications in functional electronic semiconductor devices. Integrating the research with education provides the graduate students who perform the experimental work with valuable chemistry, material research and nanotechnology skills and expose them to an international research experience. The project provides summer research opportunities for undergraduate students of diverse backgrounds with special attention to females and members of underrepresented minorities. From a technical standpoint, the focus of this award is on molecular structure-conductance relationships in two mechanistic regimes, namely the quantum mechanical tunneling and the classical hopping limits. These very different transport mechanisms are defined by molecular structure, with the tunneling mechanism generally pertaining to molecules less than ~5 nm in length, and hopping persisting for molecules longer than this value, depending on bonding architecture. The principal investigator and his collaborators have shown that analytical theory called the single level model (SLM) accurately describes the current-voltage (I-V) characteristics for certain benchmark molecular junctions in the tunneling regime. In this project, the research team probe the generality of the SLM for describing molecular tunneling in a variety of systems with particular attention to the impact of intermolecular interactions and surface attachment chemistry. In the hopping regime, the emphasis is on understanding the precise nature of the intramolecular charge-transfer transition states in pi-conjugated oligomers, particularly the transition state energy (height of the free energy barrier) and the associated bond length and angle deformations. For this purpose, kinetic isotope analysis of hopping conduction is combined with quantum chemical calculations of the transition state. Both the tunneling and hopping thrusts leverage unique synthesis, measurement, and analysis strategies developed by in the principal investigator's laboratory with prior NSF supportThis 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.