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Item Excited state processes in ruthenium(II) polypyridyl complexes and cerium oxide nanoparticles(Montana State University - Bozeman, College of Letters & Science, 2016) Stark, Charles William; Chairperson, Graduate Committee: Patrik R. Callis; Wolfgang J. Schreier, Janice Lucon, Ethan Edwards, Trevor Douglas and Bern Kohler were co-authors of the article, 'Interligand electron transfer in heteroleptic ruthenium(II) complexes occurs on multiple time scales' in the journal 'The journal of physical chemistry A ' which is contained within this thesis.Solar driven hydrogen production from water is a sustainable alternative to fossil fuels, but suffers greatly from the large energy cost associated with splitting water. This report uses ultrafast transient absorption and other spectroscopic techniques to analyze several components that show potential for this photocatalysis, in particular observing the excited state dynamics of electron separation and recombination. In ruthenium(II) polypyridyl systems, the rate of interligand electron transfer (ILET) was found to change with time, initially behaving as an ultrafast barrierless process, but transforming into a much slower activated process as excess energy is vibrationally released over 100 ps following excitation. The change in ILET rates lead to changes in the population of localized 3 MLCT states distributed among each ligand, which are initially randomized, but favor the lower energy bipyridine ligands at longer times. Three analogous ruthenium complexes were then linked via a triazole bridge to a cobalt(II) polypyridyl center known to catalyze the formation of H 2, observing the electron transfer from ruthenium to cobalt using emission decay signals of the ruthenium complex. The electron transfer decay pathway was slower and relatively minor compared to similar ruthenium(II)-cobalt(II) systems; however, this reduced efficiency can potentially be explained by localizations on peripheral ligands, as well as a possible energy barrier on the 5-position of phenanthroline. Finally, citrate coated CeO 2 nanoparticles displayed ultrafast trapping of holes upon excitation with UV light, forming significantly deeper traps than has been observed in other metal oxides. Transient absorption signals of the excited holes decayed over hundreds of picoseconds, with lifetimes dependent on the pH of the solution, indicating that the trapping sites are influenced by the surface of the nanoparticle. The corresponding electrons appear to form long lived Ce 3+ sites, observable on timescales of minutes. The fate of these Ce 3+ sites is also pH dependent, indicating that CeO 2 may be an effective water-splitting photocatalyst under basic conditions.Item Characterization of the [FeFe]-hydrogenase : toward understanding and implementing biohydrogen production(Montana State University - Bozeman, College of Letters & Science, 2014) Swanson, Kevin Daniel; Chairperson, Graduate Committee: John W. PetersHydrogen may provide an avenue for a clean renewable fuel source, yet the methods to produce hydrogen are either extremely energy intensive, rely on fossil fuels, or require expensive noble metal catalysts. Biology may hold the keys necessary to unlocking new technologies that could change how hydrogen is produced. Microbial processes also produce hydrogen and harbor enzymes that carryout the reversible reduction of protons to hydrogen gas. These enzymes are capable of producing hydrogen at high rates comparable to platinum catalysts, but biological hydrogen catalysts can produce hydrogen using abundant elements carbon, oxygen, nitrogen, sulfur, iron, nickel and selenium. Biological hydrogen catalysts are termed hydrogenases, and though hydrogenases use abundant elements they are extraordinarily complex. This has made it difficult to construct model complexes using inorganic synthesis that can replicate the activities of their biological counterparts. One way to circumvent this problem is to use microbial hydrogen production and let microbes produce and maintain these enzymes inside a cell. Microbial hydrogen production also has the added benefit that hydrogen production could be engineered to connect with other metabolic processes such as photosynthesis and fermentation. Engineering microbes for hydrogen production could eventually allow for the production of hydrogen using inexpensive energy inputs such as solar energy or waste materials. Yet, there are many barriers that need to be overcome in order to engineer a robust microbial organism. One of the primary difficulties of developing this technology has been the oxygen sensitivity of hydrogenases. Hydrogenases when exposed to atmospheric concentrations of oxygen either completely inactivate or their rates are significantly slowed. To engineer a hydrogenase that is more amenable for microbial hydrogen production, the optimization of expressing and purifying hydrogenase enzymes has been developed. Methodologies have been developed to characterize how oxygen inactivates hydrogenase enzymes, and a new methodology has been explored to help find novel hydrogenase gene sequences that may help in engineering oxygen tolerant enzymes.Item Insights into key barriers in the implementation of renewable biofuel technologies(Montana State University - Bozeman, College of Letters & Science, 2013) Therien, Jesse Beau; Chairperson, Graduate Committee: John W. Peters; Keith E. Cooksey, Matthew C. Posewitz, and John W. Peters were co-authors of the article, 'Extended hydrogen production by alginate-immobilized, sulfur-deprived Chlamydomonas reinhardtii' submitted to the journal 'International journal of hydrogen energy' which is contained within this thesis.; Oleg A. Zadvornyy and John W. Peters were co-authors of the article, 'Phototroph co-culturing for the optimal production of biofuels' submitted to the journal 'Biotechnology for biofuels' which is contained within this thesis.; Trinity L. Hamilton, Donald A. Bryant, Zhenfeng Liu, Seth M. Noone, Paul W. King, and John W. Peters were co-authors of the article, 'Genome of Clostridium pasteurianum, transcriptional analysis and structural determinants of its hydrogenases' submitted to the journal 'Journal of bacteriology' which is contained within this thesis.Bioenergy can be defined as renewable energy derived from biological sources. As world energy consumption increases and fossil fuel supplies are depleted, national and international energy requirements will become more diverse and more complicated. Clearly, the niche that alternative and renewable energy sources occupy in the energy portfolio will continue to increase over time. Currently, bioenergy in the form of biofuel production including alcohols, lipids, and hydrogen represent working technologies that are in large part only economically limited where large scale production is currently too costly to compete with fossil fuels. As a result, there has been a significant investment in basic science research to make these technologies more robust and more amenable to scale up. This includes large scale cultures of model biofuel producing organisms, consortia of organisms, and even mimetic systems in which components derived from biological sources are incorporated into materials. The success of future biofuel technologies is dependent on advancing these technologies by overcoming some of the key barriers that decrease the practicality of wide scale implementation. A key to the large scale production of biofuels in the form of alcohols, lipids, or hydrogen is to develop mechanisms to limit the costs associated with culturing organisms and harvesting fuels. A technique used to facilitate the production of bio-hydrogen from eukaryotic algae is described and shows promise as a way to reduce costs associated with handling microorganisms used in bioreactors. Immobilization the hydrogen producing alga Chlamydomonas reinhardtii in calcium alginate facilitates manipulation of culture conditions during biofuel production and their subsequent harvest. The design of tailored microbial consortia or co-culturing multiple organisms provides a means of simplifying and reducing costs of media components required for biofuel production by providing key media components metabolically. Finally, genomic and gene expression studies have provided clues into structural determinants responsible for superior hydrogen production by certain enzymes that can be incorporated into model hydrogen producing organisms or merged into biomaterials. Together, these studies have contributed to the progression and knowledge of bioenergy promoting an increasing and long lasting presence of renewable fuels in the global energy portfolio.