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Item Characterizing excited state dynamics and carrier transport in hybrid organic-inorganic lead halide perovskites via ultrafast microscopy(Montana State University - Bozeman, The Graduate School, 2018) Hill, Andrew Hinson; Chairperson, Graduate Committee: Erik Grumstrup; Kori E. Smyser, Casey L. Kennedy, Eric S. Massaro and Erik M. Grumstrup were co-authors of the article, 'Ultrafast microscopy of methylammonium lead iodide perovskite thin films: heterogeneity of excited state spatial and temporal evolution' which is contained within this thesis.; Kori E. Smyser, Casey L. Kennedy, Eric S. Massaro and Erik M. Grumstrup were co-authors of the article, 'Screened charge carrier transport in methylammonium lead iodide perovskite thin films' in the journal 'Journal of physical chemistry letters' which is contained within this thesis.; Casey L. Kennedy, Eric S. Massaro and Erik M. Grumstrup were co-authors of the article, 'Perovskite carrier transport: disentangling the impacts of effective mass and scattering time through microscopic optical detection' in the journal 'Journal of physical chemistry letters' which is contained within this thesis.; Casey L. Kennedy and Erik M. Grumstrup were co-authors of the article, 'Determining the effects of A-site cation substitution on the optical response and transport properties of lead tri-bromide perovskites' submitted to the journal 'Journal of physical chemistry letters' which is contained within this thesis.Lead tri-halide perovskites have recently emerged as cost-effective alternatives to silicon for use in photovoltaic devices. A large contributor to their reduced cost compared to silicon is the simple solution processed techniques employed in their fabrication. While these methods can produce effective photovoltaic devices, heterogeneity endemic to solution processing makes characterization of tri-halide perovskites a challenging task. Most spectroscopic techniques use large sample interrogation volumes which often results in the indiscriminate sampling of grain boundaries and other heterogeneities which impact the spectroscopic observable. To circumvent this issue, pump-probe microscopy is used to dramatically shrink the sample volume, reducing the contributions from chemical and morphological heterogeneities and providing a more accurate measure of the sample's inherent properties. This work begins with a study of the recombination and transport dynamics methylammonium lead tri-iodide (MAPbI 3) perovskite. After identifying the main recombination pathways and contributions to the transient signal, experimental focus is shifted to the transport properties of MAPbI 3. The key contributing factors to the high diffusivities reported in MAPbI 3 are found to be strong electron-phonon coupling and a high static dielectric constant which serves to screen carriers from interactions with charged defects and other carriers. Then the development a new all-optical method capable of uniquely determining the two fundamental parameters that govern carrier transport (the mean scattering time and optical mass of photogenerated carriers) is reported. This method was applied to a series of different perovskite materials including MAPbI 3, cesium lead bromide di-iodide (CsPbBrI 2), methylammonium lead tri-bromide (MAPbBr 3), formamidinium lead tri-bromide (FAPbBr 3), and cesium lead tri-bromide (CsPbBr 3). The results of these experiments have led to the characterization of the role each perovskite constituent (namely, the identity of the organic cation and the halide stoichiometry) plays in determining the transport properties of the resulting material. The work presented in this dissertation characterizes the transport properties of lead halide perovskites. Measurements collected across multiple discrete and highly crystalline domains of multiple perovskite species have helped establish a relationship between the functionality and the local structure of these materials. Additionally, the design and first application of a new methodology to disentangle the effects of mean scattering time and the photogenerated carrier mass on carrier transport is reported. This technique will not only continue to aid in the characterization of lead-halide perovskites but will likely also see use on a host of other material systems to advance understanding of carrier transport in a variety of materials.Item The development of superresolution spectroscopic techniques and characterization of microscale exciton diffusion in organic semiconducting polymers(Montana State University - Bozeman, College of Letters & Science, 2018) Massaro, Eric Stephen; Chairperson, Graduate Committee: Erik Grumstrup; Andrew H. Hill and Erik M. Grumstrup were co-authors of the article, 'Superresolution structured pump-probe microscopy' in the journal 'ACS Photonics' which is contained within this thesis.; Andrew H. Hill, Casey L. Kennedy and Erik M. Grumstrup were co-authors of the article, 'Imaging theory of structured pump-probe microscopy' in the journal 'Optics Express' which is contained within this thesis.; Erik M. Grumstrup was a co-author of the article, 'Label-free saturated structured excitation microscopy' in the journal 'Photonics' which is contained within this thesis.; Erik M. Grumstrup was a co-author of the article, 'Exceptionally fast nanoscale exciton diffusion in donor-acceptor polymer thin films' which is contained within this thesis.; Erik M. Grumstrup was a co-author of the article, 'Toward direct imaging of sub-10 nm carrier diffusion lengths by differential detection pump-probe microscopy' which is contained within this thesis.Disordered semiconducting materials offer cost effective, solution processable alternatives to highly crystalline semiconducting materials for utilization in a variety of optoelectronic devices. However, characterization of these complex materials systems using bulk spectroscopic methods is heavily influenced by chemical and morphological heterogeneity inherent to the material. The experiments described in this thesis are designed to improve the fundamental understanding of the photophysical processes in disordered solution processed semiconducting materials by developing and utilizing high spatial resolution spectroscopic methods. Chapters 2-4 will outline the experimental and theoretical development of two superresolution spectroscopic techniques. First (chapters 2 & 3), structured pump-probe microscopy (SPPM) utilizes a structured excitation profile along with a diffraction limited probe pulse to achieve ~100 nm spatial resolution. Using SPPM it is also possible to collect time resolved spectroscopic data from a sub-diffraction limited volume. Second (chapter 4), label-free saturated structured excitation microscopy (LF-SSEM) is theoretically developed. LF-SSEM is experimentally similar to SPPM but exploits the saturation of the absorption process to achieve even greater resolution enhancement. Here, simulated LF-SSEM is shown to achieve ~33 nm spatial resolution. Chapter 5 demonstrates the utilization of PPM to investigate exciton transport in the organic semiconducting polymer (OSP), poly [N-9''-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT). Although OSPs have shown great promise for use in a variety of optoelectronic applications, much remains un-known about their excited state dynamics. The data reported here represents a significant contribution to the rapidly growing wealth of knowledge pertaining to OSP systems. Specifically, the microscale exciton diffusivity observed in PCDTBT thin films using PPM is found to reach 3.2 cm 2/s. Chapter 6 examines a technique in the early stages of development and optimization that is able to detect excited state carrier diffusion with increased sensitivity and accuracy compared to PPM. Differential detection pump-probe microscopy (DDPPM) uses two probe pulses to selectively eliminate the signal of carriers that have not diffused beyond the boundaries of the initial excitation. The experiments described within this dissertation are diverse, yet the common goal is to increase and improve the knowledge of photophysical properties in disordered semi-conducting materials. This goal takes two forms in the development of novel spectroscopic methodology and the characterization of complex materials using PPM. The singular result is the advancement of basic science pertaining to complex semiconducting materials systems.Item Organic enrichment at aqueous interfaces studied with non-linear spectroscopy: cooperative adsorption of soluble saccharides to lipid monolayers(Montana State University - Bozeman, College of Letters & Science, 2019) Link, Katie Ann; Chairperson, Graduate Committee: Robert Walker; Chia-Yun Hsieh, Aashish Tuladhar, Zizwe Chase, Zheming Wang, Hongfei Wang and Robert A. Walker were co-authors of the article, 'Vibrational studies of saccharide-induced lipid film reorganization at aqueous/vapor interfaces' in the journal 'Chemical physics' which is contained within this thesis.; Gabrielle N. Spurzem, Aashish Tuladhar, Zizwe Chase, Zheming Wang, Hongfei Wang and Robert A. Walker were co-authors of the article, 'Organic enrichment at aqueous interfaces: cooperative adsorption of glucuronic acid to DPPC monolayers studied with vibrational sum frequency generation' submitted to the journal 'Journal of physical chemistry B' which is contained within this thesis.; Gabrielle N. Spurzem, Aashish Tuladhar, Zizwe Chase, Zheming Wang, Hongfei Wang, and Robert A. Walker were co-authors of the article, 'Cooperative adsorption of trehalose to DPPC studied with vibrational sum frequency generation' which is contained within this thesis.Field measurements of sea spray aerosols have reported high concentrations of soluble organic material that are in excess of the concentration of soluble organics in the ocean. The studies described in this dissertation investigated a possible mechanism for this increase deemed cooperative adsorption. The cooperative adsorption mechanism describes an interaction between an insoluble Langmuir monolayer at the aqueous/vapor interface and soluble organic molecules that would not normally be enriched at the surface. In this model, the soluble organics are drawn to the surface through non-covalent interactions with the lipid surfactant. This mechanism was investigated with the surface specific nonlinear optical technique, vibrational sum frequency generation spectroscopy. These optical measurements were coupled with surface tension measurements and differential scanning calorimetry measurements. To study cooperative adsorption, model systems were used; these were composed of a phosphatidylcholine lipid surfactant, DPPC, and soluble saccharides including glucosamine, glucuronic acid, and trehalose. Glucosamine, in both a positive and neutral state, induced ordering in both expanded and condensed DPPC monolayers, supporting cooperative adsorption as a mechanism. Glucuronic acid, an anion, ordered lipid monolayers in the limits that the lipid DPPC was moderately packed and there were no competing ions in solution. Trehalose, a larger, uncharged saccharide showed, through ordering the DPPC monolayer, indications of cooperative adsorption in moderately packed DPPC when the trehalose concentration was sufficiently high. These results support cooperative adsorption as a mechanism for the accumulation of soluble organics in sea spray aerosols with some limitations.Item Spectroscopic investigations into the active site structure and the mechanisms of radical SAM enzymes(Montana State University - Bozeman, College of Letters & Science, 2016) Shisler, Krista Ann; Chairperson, Graduate Committee: Joan B. Broaderick; Joan B. Broderick was a co-author of the article, 'Emerging themes in radical SAM chemistry' in the journal 'Current opinion in structural biology' which is contained within this dissertation.; Joan B. Broderick was a co-author of the article, 'Glycyl radical activating enzymes: structure, mechanisms and substrate interactions' in the journal 'Archives of biochemistry and biophysics' which is contained within this dissertation.; Masaki Horitani, Brian M. Hoffman and Joan B. Broderick were co-authors of the article, 'EPR and ENDOR analysis of small molecules inducing valence localization in PFL-AE' submitted to the journal 'Journal of the American Chemical Society' which is contained within this dissertation.; Rachel U. Hutcheson, Kaitlin S. Duschene, Adam V. Crain, Ashley Rasmussen, Jian Yang, Jessica L. Vey and Joan B. Broderick were co-authors of the article, 'The activation of the radical SAM enzyme pyruvate formate lyase activating enzyme is stimulated by potassium' submitted to the journal 'Biochemistry' which is contained within this dissertation.; Masaki Horitani, Kaitlin Duschene, Rachel U. Hutcheson, Amy Marts, George Cutsail III, William Broderick, Brian M. Hoffman and Joan B. Broderick were co-authors of the article, 'A rapid freeze quench ENDOR study of an organometallic radical intermediate in PFL-AE' submitted to the journal 'Journal of the American Chemical Society' which is contained within this dissertation.; This dissertation contain one article of which Krista Ann Shisler is not the main author.The radical S-adenosyl-L-methionine (SAM) superfamily of enzymes carry out diverse and complex reactions through generation of a 5'-deoxyadenosyl (5'-dAdo·) radical followed by transfer to substrate. These enzymes contain a [4Fe-4S] cluster which binds and transfers an electron to SAM. The exact mechanism of 5-dAdo· generation is unknown and the studies herein provide further investigation into pyruvate formate lyase activating enzyme (PFL-AE) and lysine 2,3-aminomutase (LAM) pre and post SAM cleavage. To understand the active site of PFL-AE prior to SAM cleavage, cation and small molecule effects were examined by electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopies. Previously, PFL-AE had been observed to contain a valence localized cluster in the presence of small molecules and this work used EPR and ENDOR spectroscopy to further probe the effects of these molecules. These studies determined that these molecules do not directly bind the cluster but rather an H xO species occupies the unique Fe site. The crystal structure of PFL-AE revealed a cation site and to probe this site, EPR and ENDOR spectroscopies were employed. Monovalent cations stimulated PFL-AE activity, with the greatest activity in the presence of potassium. The identity of the cation perturbed the EPR signal of PFL-AE which was more pronounced in the presence of SAM. ENDOR spectroscopy determined that SAM coordination differed depending on the monovalent cation. Due to its high reactivity, 5'-dAdo· has never been spectroscopically observed. In order to examine any intermediate states, a SAM analog and rapid freeze quench (RFQ) techniques were employed in conjunction with EPR and ENDOR spectroscopies. LAM can cleave the SAM analog, S-3',4'-anhydroadenosyl-L-methionine, to produce a stable allylic radical which was coupled with isotopically labeled lysine for ENDOR analysis. It was determined that radical generation is highly controlled with little movement towards its substrate upon 5'-dAdo· production. During RFQ techniques on PFL-AE, an organometallic intermediate species was observed. To probe this intermediate, isotopically labeled SAM and an 57Fe labeled cluster were coupled with the unknown paramagnetic species. It was determined that this intermediate was an unprecedented organometallic Fe-adenosyl bound species post SAM cleavage.Item Spectroscopic studies of noncovalent interactions at interfaces and their effects on interfacial structure, organization, and association(Montana State University - Bozeman, College of Letters & Science, 2015) Gobrogge, Eric Andrew; Chairperson, Graduate Committee: Robert Walker; B. Lauren Woods was an author and Robert A. Walker was a co-author of the article, 'Liquid organization at polar solid/liquid interfaces' in the journal 'Faraday discussions' which is contained within this thesis.; Jessica H. Ennist was an author and Kristian H. Schlick, Robert A. Walker and Mary J. Cloninger were co-authors of the article, 'Cyclodextrin-functionalized chromatographic materials tailored for reversible adsorption' in the journal 'ACS applied materials & interfaces' which is contained within this thesis.; Robert A. Walker was a co-author of the article, 'Partitioning of binary solvents at solid/liquid and solid/vapor interfaces' in the journal 'Journal of physical chemistry letters' which is contained within this thesis.Studies described in this dissertation used linear and nonlinear optical methods to examine the effects of noncovalent forces on molecular structure, organization and reactivity at solid/liquid, solid/vapor and liquid/vapor interfaces. These studies address three general questions: 1) Solvent structure at solid/liquid interfaces; 2) Solute adsorption to chemically tailored solid and liquid interfaces; and 3) Partitioning of binary solvents at solid/liquid and solid/vapor interfaces. 1) Solvent structure at solid/liquid interfaces. Vibrational sum frequency spectroscopy (VSFS) was used to study the interfacial organization of different alkanes and alcohols at the silica/liquid interface. Results showed that solvent organization depended sensitively on both interactions with the interface and on the solvent's molecular structure. Silica/methanol and silica/ethanol interfaces were also compared in order to determine why ethanol gives a VSFG spectrum but methanol does not. 2) Solute adsorption to chemically tailored interfaces. VSFS and fluorescence spectroscopy were used to characterize and analyze the effectiveness of silica substrates functionalized specifically to promote adsorption of organic analytes in aqueous solutions through catch and release chemistry. VSFS has also been used to study cooperative adsorption at aqueous/vapor interfaces to explore how insoluble surfactants can increase near-surface concentrations of soluble species. 3) Binary solvent partitioning at solid/liquid and solid/vapor interfaces. VSFS was used to study molecular organization at silica/binary solvent interfaces where the binary solvent consisted of acetonitrile and methanol in varying mole fractions. The vibrational spectra indicated that while methanol adsorbed ideally at the silica/vapor interface, acetonitrile accumulated in excess relative to the vapor phase composition. At the silica/liquid interface, methanol appeared to remain strongly associated with the surface until an acetonitrile mole fraction of 0.85 was reached. At higher mole fractions, interfacial acetonitrile adopts an antiparallel bilayer organization. This binary mixture was also compared to various other binary mixtures at the silica/vapor and silica/liquid interfaces.Item Mechanistic implications from 'in operando' optical and electrochemical studies of bio-related fuel chemistry in solid oxide fuel cells(Montana State University - Bozeman, College of Letters & Science, 2015) Kirtley, John David; Chairperson, Graduate Committee: Robert Walker; Bryan C. Eigenbrodt and Robert A. Walker were co-authors of the article, 'In situ optical studies of oxidation kinetics of NI/YSZ cermet anodes' in the journal 'ECS transactions' which is contained within this thesis.; David M. Halat, Melissa M. McIntyre, Bryan C. Eigenbrodt and Robert A. Walker were co-authors of the article, 'High temperature 'spectrochronopotentiometry': correlating electrochemical performance with in situ raman spectroscopy in solid oxide fuel cells' in the journal 'Analytical chemistry' which is contained within this thesis.; Melissa M. McIntyre, David M. Halat and Robert A. Walker were co-authors of the article, 'Insights into SOFC NI/YSZ anode degradation using in situ spectrochronopotentiometry' submitted to the journal 'ECS transactions' which is contained within this thesis.; Anand Singh, David Halat, Thomas Oswell, Josephine M. Hill and Robert A. Walker were co-authors of the article, 'In situ raman studies of carbon removal from high temperature NI-YSZ cermet anodes by gas phase reforming agents' submitted to the journal 'Journal of physical chemistry C' which is contained within this thesis.; Daniel A. Steinhurst, Jeffrey C. Owrutsky, Michael B. Pomfret and Robert A. Walker were co-authors of the article, 'In situ optical studies of methane and simulated biogas oxidation on high temperature solid oxide fuel cells' in the journal 'Physical chemistry chemical physics' which is contained within this thesis.; Daniel A. Steinhurst, Jeffrey C. Owrutsky, Michael B. Pomfret and Robert A. Walker were co-authors of the article, 'Towards a working mechanism of fuel oxidation in SOFCS: in situ optical studies of simulated biogas and methane' submitted to the journal 'Journal of physical chemistry C' which is contained within this thesis.Solid oxide fuel cells using bio-renewable fuels promise efficient, sustainable, and clean electricity production, and are becoming more attractive sources of electrical power as global consumption of non-renewables accelerates. The excellent efficiencies of solid oxide fuel cells as solid state electrochemical devices arise mainly from the direct conversion of chemical to electrical energy--through oxygen reduction at the cathode, oxide diffusion through the electrolyte, and fuel oxidation at the anode. Some of these processes possess high activation energies, requiring high operational temperatures (generally > 650 °C). These conditions can hasten deleterious carbon accumulation and anode deterioration. These high operating temperatures also pose significant challenges in directly observing chemical reactions responsible for electrochemical oxidation and materials degradation. Yet, these observations are needed to understand fundamental mechanisms responsible for these processes--an understanding necessary to improve the performance, durability and versatility of SOFCs, especially as these devices are required to operate with complex fuels and fuel mixtures. In this work, solid oxide fuel cells constructed with traditional Ni/yttrium stabilized zirconia ceramic-metallic (or cermet) anodes are studied in operando and in situ with several novel optical techniques (Raman vibrational spectroscopy, near infrared thermal imaging and fourier-transform infrared emission spectroscopy) and electrochemical measurements that provide vital insights into mechanisms surrounding bio-related fuel electrochemistry. The first study demonstrated that Ni oxidation is slower than reduction at the anode. The second study quantified electrochemically accessible anode carbon accumulation under methane fuel, while detailing deleterious mechanisms and microstructural changes that accompany cell polarization in the absence of gas phase fuels. The third study explored the kinetics of carbon removal from Ni-based anodes by CO 2, H 2O, and O 2 and detailed mechanistically why they may be different. The fourth study revealed mechanisms associated with carbon formation and current generation from biogas and methane as a function of operational condition. Collectively, these studies have begun to provide the direct, molecularly specific information necessary to empirically evaluate mechanistic descriptions of biorelated fuel electrochemistry and anode degradation.Item Effect of sampling parameters on analysis by tandem cell gas phase coulometry(Montana State University - Bozeman, College of Letters & Science, 1985) Crawford, Robert JerryItem Some spectral and chemical interferences on the determination of dysprosium, holmium and erbium by atomic absorption spectrophotometry(Montana State University - Bozeman, College of Letters & Science, 1964) Claassen, Hans ChristianItem Solid state and solution NMR studies of model systems for parts of membrane proteins(Montana State University - Bozeman, College of Letters & Science, 1994) Adams, Earle RaymondItem Electrodeposition on a filament with subsequent thermal atomization followed by excitation for spectroscopic analysis(Montana State University - Bozeman, College of Letters & Science, 1969) Siemer, Darryl Duane