The Analytical and Surface Chemistry (ASC) program will support the research project of Prof. Steven Sibener of the Department of Chemistry at the University of Chicago. Prof. Sibener and his students will elucidate how the reactivity of adsorbed species on a surface is influenced by the local structure and ensemble configuration of adsorbates. Prof. Sibener and his students will couple variable-temperature UHV-STM instruments that have been developed in the Sibener laboratory with supersonic and hypersonic molecular beams in order to systematically explore heterogeneous reaction mechanisms at the molecular level. This ambitious program will significantly advance our understanding of interfacial and molecular reactivity, generating fundamental knowledge for refining our understanding of mechanistic chemistry. The project will provide excellent training opportunities to undergraduate students, graduate students and postdoctoral fellows who wish to develop greater understanding of heterogeneous chemical systems. Prof. Sibener and his students will promote the understanding of fundamental chemistry in K-12 students and focus their efforts on students from under represented groups.
This program explored the efficacy of using molecular level imaging in conjunction with supersonic molecular beams and in situ spectroscopy to expand substantially our understanding of chemical processes occurring on well-characterized interfaces. Such fundamental studies are important for real-world applications in the development of new materials as well as new processes for the transformation and production of useful chemicals for society. This project elucidated how the reactivity of adsorbed molecules is influenced by the local, atomic-level geometrical structure and ensemble configuration of adsorbates, utilizing geometrically-restricted reactions to determine mechanistic details of chemical reactivity at the most fundamental level. A major effort was devoted to new instrumentation development whereby materials modification and interfacial chemical processes could be viewed in time and space as they occur using in situ scanning tunneling microscopy as well as infrared and x-ray spectroscopic characterization of reacting interfaces. These instruments were coupled with supersonic and hypersonic molecular beams in order to systematically explore heterogeneous reaction mechanisms at the molecular level. This approach allowed for the examination of interfacial chemistry where incident reactants and the interface were not at the same initial temperature, leading to new opportunities for uncovering pathways for interfacial reactivity under non-equilibrium conditions. Another key advantage was to examine, in situ, the local atomic structure of interfaces under specific reaction conditions, advancing our understanding of how interfaces geometrically change due to the presence of reactive intermediates on the surface – especially in the limit of local nanoscale ensembles and reconstructing interfaces where adsorption energetics can strongly influence local geometry, and hence the local quantum mechanical electronic energy landscape for reaction. Finally, using surface-oriented molecules as reactive targets, we explored steric effects at the most fundamental level of reactive encounters. Here geometrically-oriented end-groups were presented to reactants incident with well-defined energy and polar/azimuthal angles of attack with respect to the molecular framework. This ambitious program significantly advanced our understanding of interfacial and molecular reactivity, generating fundamental knowledge for refining our understanding of mechanistic chemistry. Primary outcomes included publications on the reactivity of molecular films with atomic oxygen, the formation and growth of highly ordered molecular films, precision measurements on the sticking and scattering dynamics of water from ice surfaces, as well as the design, construction and utilization of novel surface chemistry instrumentation for examining time and space resolved interfacial chemical processes at the molecular level. The Broader Impact and Educational activities occurred in many directions. Under the auspices of this project we sought to educate and inspire the next generation of scientific talent, and emphasized the critical role that they will play in the future development of our society. Group members participated in outreach to the local minority community, including Charter School, local public and private schools, and museum science outreach activities that have substantial representation from Hispanic and African-American South Side Chicago populations. A particularly successful primary outcome was our interaction with Chicago’s Museum of Science and Industry, where the Sibener Group helped with the development of an Interactive Periodic Table, which is now the museum’s leading exhibit in the chemical sciences. A majority of the members of the Sibener Group, including the PI, participated in at least one of these activities. The PI and group were also active in mentoring undergraduate as well as promising high school researchers. Participating high school, undergrad, graduate, and postdoctoral researchers were trained in forefront areas of the chemical sciences. Graduates have taken up positions as university and collegiate faculty, staff scientists in national labs, and high-tech/bio-tech researchers. Undergrads have gone on to doctoral programs at leading universities. Moreover, the PI was involved in curriculum reform, serving on the science advisory committee for the Laboratory School, a local K-12 private school with substantial minority enrollment. During this project the Sibener Group was also notable for its gender and ethnic composition, including approximately 50% representation by women. The PI fully recognizes that the future vitality of the science enterprise depends on the successful involvement of women and underrepresented minorities at all levels of training, as well as scientific outreach to the non-technical population of the country. The PI was also active in national scientific efforts, having served in various leadership positions in scientific societies, and served on advisory committees for the government, national laboratories, and NSF-sponsored centers.
