Development and Application of Size and Charge Resolved NMR

点击翻译按钮获取中文摘要

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.