Synchrotron X-ray studies on atomic structures of matter: self-assembled monolayers and environmental arsenic chemical speciation

点击翻译按钮获取中文摘要

This research proposal concerns with experimental studies on atomic structures of materials. Two classes of materials are of our interest. The first is called self-assembled monolayers, or SAMs. These are the films formed on solid substrates, with the thickness of a single molecule. They typcially consist of hydrocarbon molecule chains with one end chemically anchored on the solid substrate surface and the other end left free standing or can be further modified to have a variety of interesting macroscopic properties, such as wetting, corrosion resistivity, and etc. Our interest is at the formation mechanisms of such films and hence to be able to form the new types with targeted material properties following a knowledge-based design strategy rather than the traditional trial and error approach. The second class of material of our interest is the environmental arsenic species related to anthropogenic activities. The environmental impact of arsenic and its endemic and chronic poisoning effects have been documented all over the world. To develop effective environmental remediation strategies, the molecular level understanding of the arsenic species is necessary. Our approach to address aforementioned subjects is based on using X-rays generated by a kind of electron or positron accelerators called synchrotrons, for example the newly commissioned third generation synchrotron, the Canadian Light Source (Saskatoon, SK), will be one of the primary tools for this study. Other facilities to be used include the Advanced Photon Source (Argonne National Laborotary, Chicago IL) and the Synchrotron Radiation Center (Univ. Wisconsin-Madison). The synchrotron X-rays are much brighter than that from the conventional X-ray machines, also the synchrotron X-rays are tunable in their wavelengths, another property that common X-ray machines do not have. These properties make it possible to have very intense and highly collimated X-ray beams over a wide range of wavelength to be applied for materials science studies.