Development and Application of Size and Charge Resolved NMR

北卡罗来纳大学教堂山分校的Charles Johnson在实验物理化学计划的支持下，继续开发基于分子大小和电荷的扩散有序和迁移率有序的核磁共振方法来解析分子。一个主要的努力将被指向实现高分辨率核磁共振结合扩散和流动成像的环形腔探测器(TCD)。实验和计算机模拟将被用来研究TCD图像和线形所独有的静电场不均匀、非共振效应、不完全弛豫和辐射衰减的表现。传统和TCD方法都将集中在两个合作应用上：(1)研究特殊设计的表面活性聚合物在液体和超临界二氧化碳中的相互作用；(2)研究最近合成的由硫普罗宁单分子膜保护的可分离、可溶于水的金团簇。第一组实验的动机是，液体/超临界二氧化碳作为聚合反应的溶剂系统越来越重要，这些聚合反应是由环境驱动的，需要逐步淘汰氯氟烃，避免挥发性有机化合物的排放，并减少含水废水的流动。第二组实验为电泳核磁共振方法提供了测试基础，并提供了对粒子的电动性质进行建模的机会，其中核心半径、配体的层厚度和多分散度可以改变。该项目涉及利用核磁共振光谱学开发新的实验，并将这些新技术应用于重大化学问题。环境友好型二氧化碳作为聚合物合成和清洁过程的溶剂越来越重要，该项目的成果将加强对液体和超临界二氧化碳有效实际使用所需的理解。由有机化合物单分子膜保护的金团簇在纳米电子器件、化学传感器和生物传感器中具有潜在的应用前景，本研究将为深入了解这些簇合物体系的性质提供依据。

Charles Johnson of the University of North Carolina at Chapel Hill is supported by the Experimental Physical Chemistry Program to continue the development of diffusion ordered and mobility ordered NMR methods for the resolution of molecules on the basis of molecular size and charge. A major effort will be directed toward implementing toroid cavity detectors (TCDs) for high resolution NMR combined with imaging of diffusion and flow. Experiments and computer simulations will be used to investigate manifestations of static field inhomogeneities, off-resonance effects, incomplete relaxation, and radiation damping that are unique to TCD images and line shapes. Both traditional and TCD methods will be focused on two collaborative applications: (1) studies of interactions of specially designed surface active polymers in liquid and supercritical carbon dioxide, and (2) studies of recently synthesized isolable, water soluble gold clusters protected by monolayers of tiopronin. The first set of experiments is motivated by the growing importance of liquid/supercritical carbon dioxide as a solvent system for polymerization reactions resulting from the environmentally driven needed to phase out chlorofluorocarbons, to avoid emission of volatile organic compounds, and to reduce aqueous waste streams. The second set of experiments provides a testing ground for electrophoretic NMR methods as well as the opportunity to model electrokinetic properties of particles in which core radius, layer thickness of ligands, and degree of polydispersity can be varied. This project involves the development of novel experiments using nuclear magnetic resonance spectroscopy, and the application of these new techniques to significant chemical problems. Environmentally benign carbon dioxide is growing in importance as a solvent for polymer synthesis and cleaning processes, and outcomes from this project will enhance the understanding needed for effective practical use of liquid and supercritical carbon dioxide. Gold clusters protected by monolayers of organic compounds have potential applications in nanoscale electronic devices, chemical sensors, and biosensors, and the present studies will provide insights into the properties of these cluster systems.