Browsing by Author "Sambur, Justin, committee member"
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Item Embargo Advancing the utility of organic superbases in synthetic methodology(Colorado State University. Libraries, 2023) Sujansky, Stephen J., author; Bandar, Jeffrey, advisor; Miyake, Garret, committee member; Sambur, Justin, committee member; Cohen, Robert, committee memberDeprotonation is one of the most fundamental and important modes of molecular activation, making Brønsted bases a critical part of a synthetic chemist's toolbox. An exceptional class of Brønsted bases are organic superbases, which are finding increased use in modern synthetic methods due to their unique properties. This thesis describes the use of these unique properties to advance the synthetic utility of superbases in two ways; 1) improving superbase- catalyzed alkene hydrofunctionalization reactions; and 2) developing air-stable and convenient organic superbase prereagents. Chapter One describes organic superbases in detail to provide background and context for Chapters Two and Three. Within Chapter One, various classes of superbases are presented, as well as their unique properties, syntheses, and example applications. Finally, the limitations and challenges associated with the use of superbases are discussed. Chapter Two describes the Bandar Group's superbase-catalyzed alkene hydrofunctionalization methodology. Within this chapter mechanistic studies as well as computational modeling, done as part of a collaboration with the Paton Group, are presented. These mechanistic studies provided insight into the factors controlling the reaction equilibrium. This insight was then used to logically address the limitations associated with the original conditions reported by the Bandar Group in 2018. The results of this work help to improve reaction efficiency and to expanded substrate scope. This understanding also led to the development of a catalytic anti-Markovnikov aryl alkene hydration method that allows convenient access to β-aryl alcohols. Chapter Three describes the development of air-stable organic superbase precatalysts and prereagents. Superbase salts that decarboxylate were developed as a first strategy method to generate the neutral superbase in solution. This initial salt system then led to the discovery of stable superbase carboxylate salts that react with and open epoxide additives in situ to neutralize the superbase conjugate acid. This ring strain release strategy is shown to be effective at promoting a range of reactions including Michael-type addition, ester amidation, deoxyfluorination, SNAr and Pd-catalyzed cross coupling reactions. These superbase precatalysts and prereagents provide a means to access the unique properties of organic superbases from air-stable and easy-to-handle salts. Overall, Chapters Two and Three represent significant progress in advancing the utility of organic superbases in synthetic methodology. My work in Chapter Two, along with the Bandar's and Paton Group's efforts, meaningfully expanded the scope and usefulness of superbase- catalyzed alcohol addition reactions. Our new mechanistic understanding proved to be fundamental to a range of addition reactions and pushed the boundary of possible nucleophilic addition reactions. My efforts in Chapter Three, along with Garrett's significant contributions, have made organic superbase much more convenient to use, synthesize and store. This greater convenience and potentially lower cost can be expected to improve access to superbase chemistry and serve as the foundation for future discoveries. Additionally, the ability to control the concentration of superbase in solution will have many benefits in expanding substrate scopes and modulating reaction profiles where a strong base is required but is also detrimental to the overall process.Item Open Access Bioelectrochemical production of graphene oxide using bacteria as biocatalysts(Colorado State University. Libraries, 2019) Nunez Hernandez, Diana Marcela, author; De Long, Susan, advisor; Kipper, Matt, committee member; Sambur, Justin, committee memberThe demand for production of graphene oxide (GO), which is a precursor for large-scale production of graphene, has been increasing due to the broad array of uses of both nanomaterials. Due to the unique electrical and mechanical properties of these 2D nanomaterials, applications in composites have shown enhancements by contributing a tunable energetic band gap, high strength, and high transparency among other features. The tunable band gap of the graphene derivatives is one of the key properties of these nanomaterials. By varying the size of the energetic band gap (in eV) between the conduction and valence bands, resistance can be decreased to promote electron flow in the material lattice. A large energetic band gap (insulators) means more resistance for electron flow. Being able to control the band gap of a nanomaterial, allows for many applications in batteries, supercapacitors, and semiconductors being the most promising applications for these nanomaterials. Other applications include flexible electronics, renewable energy, drug delivery, contaminant removal, sensors, and more. Unfortunately, large-scale production of graphene using current methods is challenging due to low yield, impurities, high cost, high energy input, slow production rates and/or hazardous chemical reactants and wastes. For this study, the focus was on the bioelectrochemical production of GO (BEGO) as a novel technology for producing these nanomaterials with low energy input, inexpensive and non-hazardous reagents at standard conditions, and using microbes as biocatalysts. The BEGO process consists of a single-chamber microbial electrosynthesis cell (MES) that uses a graphite rod anode and a cathode (carbon cloth or stainless steel) to drive redox reactions. This MES can be operated at low voltage in a three-electrode (-0.8-1.4V vs. Ag/AgCl), or two-electrode system (~3.1V DC), with bacteria inoculated in a phosphate media solution. During this study, the BEGO process was investigated to advance understanding of the production process and the properties of the BEGO nanomaterial produced. To achieve this, the objectives established include: 1) developing methods for purifying and quantifying the nanomaterial during the production process in the complex aqueous-phase reactor matrix, 2) identifying key physical and chemical properties of the nanomaterial product using various spectroscopy and microscopy techniques, and 3) analyzing the microbial communities present in the reactors and in the graphite anode biofilm. To quantify the BEGO and estimate production rates, different spectrophotometric and gravimetric methods were used. Ultraviolet-visible spectroscopy (UV-Vis) at 229 nm was found to be the best method. This wavelength is specific to GO as it corresponds to the π → π * transitions of aromatic C-C bonds comprising the majority of the molecule, regardless of the oxidation state. Different centrifugation and filtration protocols were compared to purify the BEGO out of the complex matrix. For quantification methods in solution, centrifugation at 10,000 x g for 15 minutes was found to be the most effective method for removal of large particles and biological material, with BEGO remaining in solution. For material characterization, various techniques were used to identify the functional groups present and the morphology of the BEGO sheets. It was found through Fourier transform infrared spectroscopy (FT-IR) and UV-Vis, that the nanomaterial contained less carboxyl/carbonyl groups than GO produced by the traditional Hummers' method. Raman spectroscopy and thermogravimetric analysis (TGA) showed high disorder and weight loss events consistent with known GO spectra. Microscopy analysis revealed the BEGO process yields sheet sizes of a few hundred nm to 1-2 µm in lateral dimensions. Transparency and Fast Fourier transform (FFT) images indicate the BEGO consists of only single-layered to few-layered structures, which are needed for downstream applications. The microbial analysis was done on bioreactors with different inocula sources. DNA and RNA were extracted from both the bulk liquid media and the rod biofilm. At the end of the operation period, microbial communities in the bioreactors had diverged from the inoculum source. Microbial communities in the BEGO producing reactors consisted of both aerobic and anaerobic microorganisms. The most abundant genera on the rod biofilm were the unknown Comamonadaceae (10-11%), Hydrogenophaga (9-21%), Methyloversatilis (15-22%), and Pseudomonas (11-36%) all from the Proteobacteria phylum. Thus, these microbial phylotypes may play a key role in catalyzing BEGO production, enabling this novel and sustainable approach to nanomaterial synthesis.Item Open Access Computational modeling of low-density ultracold plasmas(Colorado State University. Libraries, 2017) Witte, Craig, author; Roberts, Jacob L., advisor; Eykholt, Richard, committee member; Kruger, David, committee member; Sambur, Justin, committee memberIn this dissertation I describe a number of different computational investigations which I have undertaken during my time at Colorado State University. Perhaps the most significant of my accomplishments was the development of a general molecular dynamic model that simulates a wide variety of physical phenomena in ultracold plasmas (UCPs). This model formed the basis of most of the numerical investigations discussed in this thesis. The model utilized the massively parallel architecture of GPUs to achieve significant computing speed increases (up to 2 orders of magnitude) above traditional single core computing. This increased computing power allowed for each particle in an actual UCP experimental system to be explicitly modeled in simulations. By using this model, I was able to undertake a number of theoretical investigations into ultracold plasma systems. Chief among these was our lab's investigation of electron center-of-mass damping, in which the molecular dynamics model was an essential tool in interpreting the results of the experiment. Originally, it was assumed that this damping would solely be a function of electron-ion collisions. However, the model was able to identify an additional collisionless damping mechanism that was determined to be significant in the first iteration of our experiment. To mitigate this collisionless damping, the model was used to find a new parameter range where this mechanism was negligible. In this new parameter range, the model was an integral part in verifying the achievement of a record low measured UCP electron temperature of 1.57 ± 0.28K and a record high electron strong coupling parameter, Γ, of 0.35 ± 0.08. Additionally, the model, along with experimental measurements, was used to verify the breakdown of the standard weak coupling approximation for Coulomb collisions. The general molecular dynamics model was also used in other contexts. These included the modeling of both the formation process of ultracold plasmas and the thermalization of the electron component of an ultracold plasma. Our modeling of UCP formation is still in its infancy, and there is still much outstanding work. However, we have already discovered a previously unreported electron heating mechanism that arises from an external electric field being applied during UCP formation. Thermalization modeling showed that the ion density distribution plays a role in the thermalization of electrons in ultracold plasma, a consideration not typically included in plasma modeling. A Gaussian ion density distribution was shown to lead to a slightly faster electron thermalization rate than an equivalent uniform ion density distribution as a result of collisionless effects. Three distinct phases of UCP electron thermalization during formation were identified. Finally, the dissertation will describe additional computational investigations that preceded the general molecular dynamics model. These include simulations of ultracold plasma ion expansion driven by non-neutrality, as well as an investigation into electron evaporation. To test the effects of non-neutrality on ion expansion, a numerical model was developed that used the King model of the electron to describe the electron distribution for an arbitrary charge imbalance. The model found that increased non-neutrality of the plasma led to the rapid expansion of ions on the plasma exterior, which in turn led to a sharp ion cliff-like spatial structure. Additionally, this rapid expansion led to additional cooling of the electron component of the plasma. The evaporation modeling was used to test the underlying assumptions of previously developed analytical expression for charged particle evaporation. The model used Monte Carlo techniques to simulate the collisions and the evaporation process. The model found that neither of the underlying assumption of the charged particle evaporation expressions held true for typical ultracold plasma parameters and provides a route for computations in spite of the breakdown of these two typical assumptions.Item Open Access Corrosion testing of alloys for biomass cookstove combustors(Colorado State University. Libraries, 2017) Banta, Kelly, author; Marchese, Anthony, advisor; Mizia, John, committee member; Jathar, Shantanu, committee member; Sambur, Justin, committee memberWorldwide, over 3 billion people use biomass for cooking and heating. Many people cook over 3-stone fires or inefficient and highly polluting traditional cookstoves, presenting a large human health risk and significant climate impacts. One solution to this is the development of improved cookstoves, which can alleviate this burden by being more efficient and cleaner-burning. To be effective in their purpose, improved cookstoves must be long-lasting. Achieving longevity is challenging from a material corrosion perspective, particularly in the case of metallic combustors, because cookstove combustors must operate at high temperatures (> 600 deg. C) in environments with corrosive species released from biomass combustion. A key part of this challenge is cost, since materials must be inexpensive to permit widespread adoption in the developing world; however, corrosion resistant materials are typically costlier. In this work, screening protocols for corrosion testing of cookstove combustor materials were developed and shown to be effective methods for accelerated corrosion testing, and a number of alloys were evaluated for corrosion performance. Additionally, a FeCrSi alloy was identified as a potentially low-cost material with high corrosion resistance in cookstove applications. This alloy is currently being patented.Item Open Access Developing and investigating copper and iron chalcogenide nanoparticle syntheses to elucidate the underlying processes of formation(Colorado State University. Libraries, 2021) Moloney, Lily June, author; Prieto, Amy L., advisor; Sambur, Justin, committee member; Krummel, Amber, committee member; Buchanan, Kristen, committee memberNanoparticle technology is rapidly growing field due to the unique, tunable properties of nanoparticles (NPs) as compared to their bulk counterparts, enabling a wide range of new applications. The key step, however, to applying NP systems to new areas is developing high quality syntheses. Specifically, solution-based methods for synthesizing NPs offer many synthetic handles for tuning structure/property relationships by controlling composition, size, morphology and capping agents. To effectively design syntheses to control the resulting properties, in depth investigation of the underlying fundamental processes are required. Elucidation of these processes would allow trends to be illuminated and a toolkit of synthesis methods could be built. However, a myriad of interactions (organic, inorganic, solid-state) occur during these reactions, and often these interactions are intertwined with each other. Therefore, careful examination of nanoparticle synthesis for various systems are necessary to advance the NP field. In Chapter 1, we review literature reports that exemplify the careful examination of underlying mechanisms and pathways required for developing synthesis methods that allow for control over composition, size, morphology. This chapter is split into two major sections; 1) balancing precursor reactivities and elucidating mechanisms and 2) understanding reaction pathways. The first section is split into anion and cation speciation/reactivity. The anion section focuses on the development of chalcogenide reactivity trends and how these trends have led to advanced nanoparticle control. The cation section considers the use of metal-amide complexes to increase and balance reactivities of cations to produce small, phase pure NPs. In depth mechanism studies of these metal-amide reactions in model unary and binary system led to the utilization of this reagent in more complex ternary systems. The second section focuses on investigation of reaction pathways, discussing how exploration of the reaction phase space as well as determination of intermediates is important for achieving a full picture. We end with a brief discussion on the importance of thorough characterization for describing these reaction mechanisms and pathways accurately. The importance of investigating the reaction pathway was inspiration for the research described in Chapter 2. Few solution-based techniques to synthesize Cu3Si, a material with applications in electronics, batteries, and photovoltaics, exist. This could stem from the limited number of Si precursors viable in solution-based techniques. This led us to explore the reaction between Mg2Si and CuCl2 in oleylamine, as a solution-based metathesis route to form Cu3Si particles. The reaction pathway and the role of the solvent were characterized and elucidated. It was found that the reaction proceeds through a two-step pathway, where a Si matrix, Cu particles, and MgCl2 initially form. Then, the Cu particles diffuse into the Si matrix to form Cu3Si particles encased in a Si matrix (Cu3Si@Si matrix). Additionally, various solvents are tested to understand the importance of the solvent for the reaction to proceed successfully. The coordinating ability of the solvent was important, where an overly non-coordinating or coordinating solvent limited the production of Cu3Si@Si matrix particles. Oleylamine was found to be a “goldy-locks” solvent as the coordination supported both steps of the reaction. In Chapter 3, the mechanistic metal-silylamide studies described in Chapter 1 offered inspiration. Specifically, Rebecca C. Miller in our group was recently able to synthesize Fe2GeS4 by utilizing lithium bis(trimethylsilyl)amide (LiHMDS). The increased understanding of the Fe-Ge-S phase space and the role of the LiHMDS gained from this previous study led to the research presented in Chapter 3. In this chapter, we report the first nanoparticle synthesis of Fe2GeSe4 and Fe2GeS4-xSex (x = 0.8 and 1) via a LiHMDS-assisted hot-injection method. This system allowed the role of LiHMDS in balancing not only the cationic but also anionic species to be investigated. This was done by exploring the synthesis parameters, the pre-injection chalcogen speciation, and the reaction pathways. Finally, in Chapter 4, synthesis methods attempted toward Cu2SiSe3 formation are described and a future direction for this project is proposed. Copper-based chalcogenides have gained much attention due to their exemplary intrinsic and structural properties. Cu2SiSe3 has been theorized to be a potential photovoltaic material, yet a NP synthesis of this material has not been realized. Exploration of hot injection, metathesis, and solvothermal solution phase methods are reported. However, all efforts resulted in binary Cu/Se phases over the formation of the desired ternary. A future direction for this project could be instead focusing on investigating reactivity trends of the group IV elements, Si, Ge, and Sn, using an amide-assisted synthesis of the Cu2IVSe3 materials.Item Open Access Expanding the medicinal chemistry toolbox: development of new pyridine and piperidine functionalization strategies(Colorado State University. Libraries, 2022) Greenwood, Jacob W., author; McNally, Andrew, advisor; Bandar, Jeffrey, committee member; Sambur, Justin, committee member; Chatterjee, Delphi, committee memberNitrogen-containing heterocycles, such as pyridine, are ubiquitous in pharmaceuticals, agrochemicals, ligands, and materials. Therefore, robust methods for their direct functionalization are highly desired. Chapter one focuses on the importance of pyridine-containing molecules, the reactivity of pyridine, and challenges associated with functionalization of such compounds. In chapter two, a method for bipyridine synthesis is discussed that uses pyridylphosphonium salts as radical precursors. Other radical precursors failed to provide the desired products, highlighting the unique reactivity imparted by the phosphonium group. In chapter three, pyridylphosphonium salts are explored as alternatives to cyanopyridines in photoredox-catalyzed radical coupling reactions. This work expands the scope of the reaction manifold to complex pyridine substrates where installation of the cyano group can be challenging. Chapter four introduces the value of piperidines and challenges associated with their synthesis. A strategy is described to address these limitations using isolable, cyclic iminium salts as a general platform to elaborate the piperidine scaffold with several medicinally relevant functional groups. An alternative piperidine synthesis is presented in chapter five, where the mild transformation of a range of pyridines into pyridinium salts is achieved, followed by mild hydrogenation to the desired piperidine products. This method operates under mild conditions and can tolerate substitution at the 2-position of the pyridine substrate. As a result, a large amount of pyridine starting materials can now be engaged to form piperidines that are challenging to make with other technologies.Item Open Access Exploring phase selectivity and morphological control in Cu-Sb-Se nanoparticle synthesis(Colorado State University. Libraries, 2023) Kale, Amanda R., author; Prieto, Amy L., advisor; Sambur, Justin, committee member; Krummel, Amber, committee member; Ma, Kaka, committee memberNanoparticles are used in a variety of applications, such as optoelectronics, medicine, and energy generation and storage. Different applications necessitate different nanoparticle compositions and morphologies. Thus, developing fine synthetic control over composition, phase, and morphology is of interest to the field. Solution-phase nanoparticle synthesis allows control over particle shape and size, though phase purity is often an issue in ternary syntheses. Often precursor reactivity must be balanced to avoid binary sinks; however, in the Cu-Sb-Se system, the ternaries compete with one another. In this dissertation we explore the knobs of a hot-injection synthesis in oleylamine that can be tuned to favor different Cu-Sb-Se ternary phases and control particle morphologies. In Chapter I we begin with a discussion of the term precursor reactivity and how we define it here. We also address the common frameworks used to explain reactivity, and the specific challenges of balancing reactivity in multinary chalcogenide syntheses. We also discuss how these challenges manifest in the Cu-Sb-Se system, and why the structures and phase space of this material are interesting to study. In Chapter II we discuss a guide for fitting X-ray diffraction data for complex nanomaterial systems, outlining important considerations when working on the nanoscale as well as our sequential approach to refinements and recommended best practices. We also discuss a case study on the refinements of anisotropic, multiphase systems, which we use for the following chapter. The main synthetic work follows in the next two chapters, focusing first in Chapter III on the decomposition of metastable Cu3SbSe3 to thermodynamic CuSbSe2. We investigate how this can be manipulated through the addition of an amide base. In Chapter IV, we explore tuning morphology and specifically nanosheet branching in CuSbSe2, in which we show that we can induce twinning in CuSbSe2 and initial characterization suggests that this occurs in a different manner than in the very similar sulfide system. Finally, in Chapter V we reflect on the considerations and next steps for this work, including preliminary results on the use of soft base ligands to complex Cu, as well as on promising directions of field of nanoparticle synthesis as a whole.Item Open Access Functional nanostructured ionic liquid-based block copolymer systems for energy applications(Colorado State University. Libraries, 2021) May, Alyssa Winter, author; Bailey, Travis S., advisor; Reynolds, Melissa, committee member; Sambur, Justin, committee member; Lear, Kevin, committee memberRoom-temperature ionic liquids (RTILs) are pure molten salts that have zero vapor pressure, a wide range of thermal stability, negligible flammability, and high ionic conductivity. These qualities make them desirable as electrolyte replacements for the more common lithium salt-doped carbonate solvents which are ubiquitous in current battery technology despite being exceptionally flammable. Use of liquid electrolytes, even non-flammable ones, has its drawbacks and challenges, like preventing leakage of the electrolyte and maintaining good contact with electrode surfaces, particularly when the battery electrodes or container become physically warped. With the emergence of flexible electronics technologies like foldable phones, bendable displays, and "wearables," interest has grown in developing solid electrolytes that are mechanically robust and sufficiently good ionic conductors, as they greatly expand the design possibilities for batteries. Block copolymers (BCPs) are an ideal platform from which to develop solid electrolyte materials as the variety of polymerizable blocks and physical properties that can be derived from them are nearly limitless. In this dissertation, we explore two methods for incorporating ionic liquid components into solid BCP materials, and thoroughly delve into their interesting chemical, physical, and mechanical properties to demonstrate their potential as functional materials. The first method is the direct, sequential polymerization of both ionic liquid-based and traditional monomers to create poly(ionic liquid) (PIL) BCPs that can microphase separate to form ordered nanostructures. We report on the synthesis of both cobalt-containing and imidazolium-based PIL BCPs and provide a comprehensive examination of their melt-state phase behavior, including the observation of all four equilibrium morphologies available to diblock copolymers: lamellae (Lam), bicontinuous gyroid (Gyr), hexagonally packed cylinders (Hex), and spheres (S). From the morphological phase behavior, we were able to build two phase diagrams and extract critical information about the materials, such as block density of the methyl-imidazolium PIL block. This is an essential parameter for BCP design that enables researchers to target specific morphologies when creating similar materials in the future. The morphology of solid-state conductive materials like PIL BCPs has direct implications on their transport properties, as only certain morphologies (Gyr, S) can have fully continuous domains in which ions can flow, so fully understanding the spectrum of phase behavior in a BCP material is incredibly important for creating truly functional materials from them. The second method is the integration of RTIL into amphiphilic, non-ionic BCPs as a selective swelling solvent to create ion gels, or gel polymer electrolytes (GPEs). We have designed these BCPs, based on melt-state phase separating blends of polystyrene-b-poly(ethylene oxide) (SO) and polystyrene-b-poly(ethylene oxide)-polystyrene (SOS) in which the hydrophilic O block is the majority component, to form hydrophobic spherical domains of S that form a tethered, physically crosslinked networked that acts like an elastic solid when swollen. We demonstrate that SOS BCPs swollen in the RTIL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, or [EMIM][TFSI], have exceptional ionic conductivity, elasticity, distensibility, recovery rates, bulk toughness, and fracture toughness. This rare combination of multiple excellent mechanical properties and high ionic conductivity makes SOS GPEs auspicious candidates as solid electrolytes in energy transport and storage applications.Item Open Access Hot injection synthesis and characterization of copper antimony selenide non-canonical nanomaterials toward earth-abundant renewable energy conversion(Colorado State University. Libraries, 2018) Agocs, Daniel B., author; Prieto, Amy L., advisor; Buchanan, Kristen, committee member; Sambur, Justin, committee member; Sites, James R., committee member; Van Orden, Alan, committee memberRenewable and carbon-free energy generation has become a critically important field as the global population continues to increase. Further, the ample supply afforded by natural resources such as sunlight and geothermal heat are attractive options that can be harnessed using technologies like photovoltaics and thermoelectrics. There is a growing interest in searching for novel materials that exhibit high efficiencies in these devices, ideally composed of earth abundant, non-toxic materials. This search is aided by theory, which has identified several families of compounds with interesting structure types that may exhibit properties amenable to incorporation in high efficiency devices. However, many of these materials have not yet been thoroughly evaluated for photovoltaics or thermoelectrics. This dissertation is focused on developing the synthesis and describing the basic characterization of nanoparticles of members of the compounds in the Cu-Sb-Se series, of which syntheses have been developed for Cu3SbSe4 and Cu3SbSe3 and are described in this dissertation. Herein, we describe a hot-injection route for the formation of Cu3SbSe4 and Cu3SbSe3 nanocrystals. In order to place this work in context, the first chapter of this dissertation provides a detailed summary of the literature investigating the Cu-Sb-Se family of compounds. Here, the highest thermoelectric efficiencies have been achieved for Cu3SbSe4 while Cu3SbSe3 is not yet comparable thermoelectrically to Cu3SbSe4 nor as efficient as the photovoltaic material CuSbSe2. The second chapter details the development of a hot injection synthesis of Cu3SbSe4 nanocrystals. In order for these materials to be applied as electronic materials in real devices, their stability and function under ambient conditions is of interest. Therefore, we studied the changes in electronic conductivity as a function of exposure to atmosphere. The conductivity increase was attributed to a hole mobility increase, and this was further correlated to structural oxidations. Chapter 3 details development of a synthesis for phase-pure Cu3SbSe3 nanodiscs. This material has become of interest recently for photovoltaic applications due to its acceptable band gap for solar absorption. While the synthesis of nanoscale Cu3SbSe3 has been reported, these results have not been reproduced, and property measurements among these limited works vary. Therefore, a robust synthesis was developed and initial optical and photoelectrochemical properties were measured and are reported in this dissertation that demonstrate photoactivity in thin films of the Cu3SbSe3 nanodiscs. In the fourth chapter, a more vigorous exploration of the nanodisc morphology observed in Cu3SbSe3 is reported. As a degree of self-assembly is observed in stacks of the nanodiscs, the morphology is investigated to understand how tuning nanocrystal morphology, size, and surface might affect the resulting particle interactions. To this end, a double injection synthesis was developed wherein the products exhibit optoelectronic properties similar to those of the original single injection reaction. Chapter 5 entails the electrochemical investigation of the copper antimony selenide nanostructures. Electrochemical measurements to experimentally elucidate the electronic structure are reported, and a photovoltaic architecture is proposed for a Cu3SbSe3-absorber layer device. Further, the presence of a thiol has been demonstrated to be critical to not only morphology within the Cu3SbSe3 synthesis but also the product phase formation. Therefore, initial measurements and challenges with in-situ electrochemical exploration of precursor reactivity are reported. Finally, chapter 6 briefly emphasizes the major findings within this dissertation. The experimental results for both Cu3SbSe4 and Cu3SbSe3 syntheses are reiterated. Further, additional directions for future work with this system are suggested. These primarily focus on fabrication of a Cu3SbSe3 photovoltaic cell to begin understanding photogenerated carrier transport. This can be extended through applying knowledge gained by understanding disc stacking to improve film deposition and electronic properties within Cu3SbSe3 materials. Finally, development of an electrochemical measurement system for use in oleylamine media would allow a new perspective on investigation of colloidal nanocrystalline formation. These proposed experiments would contribute to their respective fields in the broader context of expanding search criteria for novel photovoltaic materials, addressing the challenge of grain boundary recombination sites in photovoltaic nanocrystals, and providing tools for exploring nanoparticle synthesis.Item Open Access Investigating molecular interactions contributing to self-assembly on ultrafast time scales with two-dimensional infrared spectroscopy(Colorado State University. Libraries, 2019) Kuhs, Christopher Thomas, author; Krummel, Amber T., advisor; McCullagh, Martin, committee member; Sambur, Justin, committee member; Ross, Kathryn, committee memberMany chemical systems rely on π-π interactions to drive self-assembly. These systems range from peptides and proteins to polyaromatic hydrocarbons (PAH). There are a wide variety of chemical environments where π-π interactions are critically important. In such environments, factors such as sterics or the solvent surrounding these aromatic systems will affect the final aggregate. To elucidate the chemical structures and system dynamics that exist in these π stacking molecular structures, many researchers are turning their attention to examining molecular vibrations. Chemical vibrations are affected by molecular coupling, solvent environments, and aggregated state. By using infrared spectroscopy to monitor these vibrations, we can develop a molecular picture of these aggregated systems. Two-dimensional infrared (2D IR) spectroscopy provides additional information on the structure and dynamics of aggregated systems that cannot be gained from traditional linear infrared techniques. This thesis focuses on using 2D IR to study two aggregate systems. First, this thesis focuses on the self-assembly of phenylalanine based dipeptides. One of the primary goals of this work was to understand how the solvent interacts with the dipeptides, a factor critical for self-assembly. Using 2D IR and molecular dynamics simulations this work investigated how the primary structure of an aromatic dipeptide system, Val-Phe versus Phe-Val, affects the solvation dynamics around the dipeptide. It also explores the primary sequence influences hydrogen-bond dynamics. The second part of this work examines how the polarity of a solvent influences π-π stacking of PAH. Using 2D IR it was found that these solvent dependent structures have different degrees of vibrational energy delocalization. This suggests that the choice in solvent will influence the flow of energy though aggregated systems.Item Open Access Investigation of chiral porphyrin aggregates with heterodyne-detected vibrational sum frequency generation spectroscopy(Colorado State University. Libraries, 2018) Lindberg, Kathryn A., author; Krummel, Amber, advisor; Levinger, Nancy, committee member; Sambur, Justin, committee member; Gelfand, Martin, committee memberIn nature, photosynthetic organisms harvest and transport solar energy through the finely-tuned interplay between vibrational, electronic, and excitonic characteristics within photosynthetic reaction centers. These characteristics depend intimately on the precise arrangement of the reaction centers' molecular building blocks. Further knowledge of the relationship between structure and function in these natural systems is key to advancing synthetic solar technologies like dye-sensitized solar cells and artificial photosynthesis. Photosynthetic pigments, such as chlorophyll and bacteriochlorophyll, are of particular interest since their absorptive role is the first step in the solar harvesting process. Porphyrins, a group of macrocyclic organic compounds closely related to these pigments, have gained attention as simpler models for their more complicated natural counterparts. Tetra(4-sulfonatophenyl) porphyrin (TSPP), which closely resembles bacteriochlorophyll, is particularly valuable because it forms molecular aggregates analogous to the highly quantum-efficient light-harvesting "antennae" present in green sulfur bacteria chlorosomes. Imaging and spectroscopic studies indicate that the helical nanotubular TSPP aggregates are chiral and have distinct exciton contributions along different axes. However, the precise arrangement of TSPP monomers within the aggregate walls is still debated, prompting further, more detailed studies. Heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectroscopy is a phase-sensitive, second-order nonlinear technique which probes the vibrational characteristics of noncentrosymmetric molecular environments. HD-VSFG experiments can also probe excitonic and vibronic characteristics via experimental double resonance. By use of polarization conditions, theoretical modeling, and computational fitting, detailed information on the orientation of vibrational, vibronic, and excitonic transition dipoles can be extracted from HD-VSFG spectra. This work presents doubly-resonant HD-VSFG spectra of TSPP thin films drop-cast on gold, which demonstrates the technique's sensitivity to the relationship between complex phase and excitonic versus monomeric characteristics. HD-VSFG is then used to compare spectra of TSPP thin films prepared from racemic and chiral aqueous solutions. This comparison includes a polarization condition sensitive to only chiral environments, further demonstrating HD-VSFG as a valuable tool in the structural investigation of TSPP aggregates.Item Open Access Investigation on the structural, mechanical and optical properties of amorphous oxide thin films for gravitational wave detectors(Colorado State University. Libraries, 2024) Castro Lucas, Samuel, author; Menoni, Carmen, advisor; Rocca, Jorge, committee member; Sambur, Justin, committee memberAmorphous oxide thin films grown through physical vapor deposition methods like ion beam sputtering, play a crucial role in optical interference coatings for high finesse optical cavities, such as those used in gravitational wave detectors. The stability of these atomically disordered solids is significantly influenced by both deposition conditions and composition. Consequently, these enable the tuning of structural, mechanical, or optical properties. The sensitivity of current gravitational wave interferometric detectors at the frequency range of around 100 Hz is currently limited by a combination of quantum and coating thermal noise (CTN). CTN is associated with thermally driven random displacement fluctuations in the high reflectance amorphous oxide coatings of the end-test masses in the interferometer. These fluctuations cause internal friction, acting as an anelastic relaxation mechanism by dissipating elastic energy. The dissipated internal elastic energy can be quantified through the mechanical loss angle (Q-1). These unwanted fluctuations associated with mechanical loss can be reduced through modifications of the atomic network in the amorphous oxides. Specifically, the combination of two or more metal cations in a mixed amorphous thin film and post-deposition annealing are known to favorably impact the network organization and hence reduce internal friction. The first study of this thesis reports on the structural modifications between amorphous TiO2 with GeO2 and with SiO2. High-index materials for gravitational wave detectors such as amorphous TiO2:GeO2 (44% Ti), have been found to exhibit low mechanical loss post-annealing at 600°C. Reaffirming annealing to be a major contributor to reducing mechanical loss this thesis examines: a) cation interdiffusion between amorphous oxides of TiO2 with GeO2 and with SiO2 and b) the modifications to the structural properties, both after annealing. The annealing temperature, at which this interdiffusion mechanism occurs, is key for pinpointing structural rearrangements that are favorable for reducing internal friction. Furthermore, to determine whether diffusion occurs into SiO2 after annealing is also important, given that the multi-layer mirrors of gravitational wave detectors utilize SiO2 as a low-index layer. The study of cation interdiffusion used nanolaminates of TiO2, SiO2 and GeO2 to identify cation diffusion across the interface. The results show Ge and Ti cation interfacial diffusion, at temperatures above 500°C. Instead, Si cations diffuse into TiO2 at a temperature around 850°C and Ti into SiO2 at around 950°C. These temperatures correspond to an average of 0.8 of the glass transition temperature (Tg), with Tg=606°C for GeO2 and Tg=1187°C for SiO2. These findings support previous research by our group in amorphous GeO2, which showed that elevated temperature deposition and annealing at 0.8 Tg, leads to favorable organization of the atomic network which is associated with low mechanical loss. The second study of this thesis investigates the structural, mechanical, and optical properties of amorphous ternary oxide mixtures following post-annealing. These mixtures consist of TiO2:GeO2 combined with SiO2 and ZrO2, as well as TiO2:SiO2 combined with ZrO2. Candidate high index layers, such as amorphous TiO2:GeO2 (44% Ti), and TiO2:SiO2 (69.5% Ti) exhibit low mechanical loss after post-annealing at 600°C, and 850°C, respectively. The inclusion of a third metal cation is shown to delay the onset of crystallization to temperatures around 800°C. The addition of a third metal cation also modifies the residual stress of the ternary compared to the binary materials. There is an indication of densification when annealing past 600°C. The reduction in residual tensile stress, combined with the higher crystallization temperature of the ternary mixtures, present attractive properties. These properties will expand the parameter space for post-deposition processing, mainly of the TiO2:GeO2 -based mixtures, to further reduce mechanical loss. This advancement paves the way for amorphous oxide coatings for gravitational wave detectors with lower mechanical loss, aligning with plans for future detectors.Item Embargo Navigating the thermodynamic landscape in search of synthetic routes to ternary nitrides(Colorado State University. Libraries, 2022) Rom, Christopher Linfield, author; Neilson, James R., advisor; Prieto, Amy L., advisor; Sambur, Justin, committee member; Szamel, Grzegorz, committee member; Buchanan, Kristen, committee memberTernary nitride materials—a class of ceramics composed of two different metals bound with anionic nitrogen (N3-) as a solid—are underexplored because they are difficult to make. Nitrides rarely occur in nature, as the oxygen in the air (O2) is more reactive towards metals than the nitrogen (N2). Consequently, oxide minerals dominate the earth's crust while nitride minerals are extremely rare. Almost all ternary nitrides that have been discovered have synthesized, usually with rigorously air-free conditions. Despite much effort in the past century, the number of known ternary nitrides (approximately 450) pales in comparison to that of ternary oxides (over 4,000). Yet there are world-changing materials within this small number of compounds, like the (In,Ga)N alloys that underpin efficient blue light emitting diodes. Fortunately, recent computational work has predicted a number of theoretically stable ternary nitrides, providing targets for synthesis. This dissertation focuses on the synthesis of new ternary nitrides. Guided by increasingly user-friendly computational tools, these chapters describe syntheses overcome the thermodynamic barriers that often inhibit the formation of new ternary nitrides. Along the way, several new materials are discovered and characterized for promising magnetic and semiconducting properties: MnSnN2, MgWN2 in two structure types, Mg3WN4, MgZrN2, CaZrN2, and CaHfN2. These adventures in synthesis not only report new compounds, but also highlight promising strategies for future explorations of uncharted nitride phase space.Item Open Access Protein crystals as nanotemplating materials(Colorado State University. Libraries, 2019) Kowalski, Ann, author; Snow, Christopher, advisor; Kipper, Matt, committee member; Peebles, Christie, committee member; Sambur, Justin, committee memberThe advancement of nanomaterial development depends on the reliable and scalable synthesis of three dimensional nanostructures and devices. Applications for these materials range from catalysis and energy storage to biomedicine and imaging. Towards the goals of shape-controlled immobilization and synthesis, templating is arising as a promising manufacturing method. With the rise of bionanotechnology, DNA and protein scaffolds can be designed, synthesized, and functionalized to coordinate nanoparticles, enzymes, and other guests in three dimensions, or act as molds for the synthesis of anisotropic nanostructures. Inherently, protein crystals are an attractive target, as they have nearly unlimited designability, intrinsic functionality for a variety of useful materials, and mild reaction conditions. The overarching goal of this work is to explore the feasibility of protein crystals as templates for the creation of biohybrid materials. We show that protein crystals with large solvent channels can strongly adsorb and immobilize gold nanoparticles by reversible metal affinity interactions and that these nanoparticles can serve as nucleation sites for the growth of nanorods within the pores of protein crystals by a variety of gold growth methods. We show that, depending on the method used, gold nanorod synthesis within the crystals can be dependent on the presence of a seed particle. Despite their stability, these crystals can be dissolved to release the gold structures, which can be analyzed by electron microscopy and elemental analysis. A variety of gold nanorod products are formed, from highly anisotropic individual rods, to interconnected rod bundles, to parallel rods embedded within a protein matrix. Additionally, we show that protein crystal pores can be used for the long-term capture of multiple enzymes and that these enzymes retain their activity within the crystal. Product can be separated by a simple washing step, and the immobilized two-enzyme pathway can be used for multiple cycles over several weeks. Rates of product formation are higher for enzymes immobilized within crystals of a high surface-to-volume ratio; thus, the use of micron-sized crystals minimizes transport limitations typically associated with enzyme immobilization. Preliminary work suggests the crystals may also impart significant thermal stability to the embedded enzymes. Porous protein crystals may provide a superior templating method for the development of nanomaterials. Here we further demonstrate the wide variety of applications for protein crystals by revealing their success as scaffolds for immobilization, synthesis, and catalysis.Item Open Access Sustainable recycling of metal machining swarf via spark plasma sintering(Colorado State University. Libraries, 2021) Sutherland, Alexandra E., author; Ma, Kaka, advisor; Sambur, Justin, committee member; Simske, Steve, committee memberIn general, extracting virgin metals from natural resources exerts a significant environmental and economic impact on our earth and society. Production of virgin stainless steels and titanium (Ti) alloys have particularly caused concerns because of the high demands of these two classes of metals across many industries, with low fractions of scraps (less than one-third for steels and one-fourth for Ti alloys) that are currently recirculated back into supply. In addition, the conventional recycling methods for metals require multiple steps and significant energy consumption. With the overarching goal of reducing energy consumption and streamlining recycling practices, the present research investigated the effectiveness of direct reuse of stainless steel swarf and Ti6Al-4V alloy swarf as feedstock for spark plasma sintering (SPS) to make solid bulk samples. The parts made from machining swarf were characterized to tackle material challenges associated with the metal swarf such as irregular shapes and a higher amount of oxygen content. The hypothesis was that while solid bulk parts made from metal swarf would contain undesired pores that degrade mechanical performance, some mechanical properties (e.g., hardness) can be comparable or even outperform the industrial standard counterparts made from virgin materials, because of cold working and grain refinement that occurred to the swarf during machining and the capability of SPS to retain ultrafine microstructures. 304L stainless steel and Ti-6Al-4V (Ti64) alloy swarf were collected directly from machining processes, cleaned, and then consolidated to bulk samples by SPS with or without addition of gas atomized powder. Nanoindentation and Vickers indentation were utilized to evaluate the hardness at two length scales. Ball milling was performed on Ti64 to assess the energy consumption required to effectively convert swarf to varied morphologies. In addition, to provide insight into the macroscale mechanical behavior of the materials made by SPS of recycled swarf, finite element modeling (FEM) was used to predict tensile stress-strain curves and the corresponding stress distributions in the samples. The key findings from my research proved that reuse of austenitic stainless steel chips and Ti64 alloy swarf as feedstock for SPS is an effective and energy efficient approach to recycle metal scraps, compared to the production and use of virgin gas atomized powders, or conventional metal recycling routes. The mechanical performance of the samples made from metal swarf outperformed the relevant industrial standard materials in terms of hardness while the ductility remains a concern due to the presence of pores. Therefore, future work is proposed to continue to address the challenges associated with mechanical performance, including but not limited to, tuning the SPS processing parameters, quantifying an appropriate amount of addition of powder as a sintering aid, and refining the morphology of the swarf by ball milling. It is critical for the health of our planet to always consider the tradeoff between energy consumption and materials performance.Item Open Access Synthetic and biosynthetic studies of okaramine and hapalindole natural products(Colorado State University. Libraries, 2018) Bair, Nathan Alexander, author; Williams, Robert M., advisor; McNaughton, Brian, committee member; Thamm, Doug, committee member; Sambur, Justin, committee memberThis dissertation is a report on the first total syntheses of hapalindoles C and D, natural products of a few cyanobacteria. Additionally, we report on our collaborative investigations on the biosynthesis of the hapalindole family of natural products. Lastly our efforts toward the total synthesis of okaramines R and B and attempts to synthesize a novel indoloazetidine ring are enclosed.Item Embargo Tuning antimony anodes through electrodeposition to inform on the reaction and degradation mechanisms in sodium-ion batteries(Colorado State University. Libraries, 2023) Nieto, Kelly, author; Prieto, Amy L., advisor; Sambur, Justin, committee member; Krummel, Amber, committee member; Bandhauer, Todd, committee memberElectrification of portable devices, transportation, and large grid-level storage necessitate a portfolio of energy storage devices tailored to specific applications. Sodium-ion batteries are a naturally abundant alternative to lithium, but high performing anodes must be developed in order to reach widespread commercialization. Alloy-based anodes such as antimony (Sb) are attractive targets for their high theoretical capacities. However, the electrochemical performance of Sb is poor, and the reaction mechanism is poorly understood. Herein, antimony-based anodes for sodium-ion batteries are explored to elucidate sodiation pathways and investigate the role of electrode fabrication, electrolyte composition, and architecture on the reaction and degradation mechanism. Chapter I describes our research methodology and consists of our synthetic method of electrodeposition, materials characterization, battery assembly, and electrochemical characterization. Through this process, we can develop a better understanding of the electrochemical performance of alloy-based anode materials. The tunability of electrodeposition as a synthetic technique for the fabrication of Sb-based anodes is exploited in Chapter II. The effects of solution additives in the electrodeposition of Sb anodes are investigated and provide insight into how the morphology and crystallinity of the deposited anodes can be tuned. It was revealed that CTAB and SPS could significantly tune the electrodeposition of Sb films by altering the deposition by causing structural changes that either improved cycle life or rate capabilities. In Chapter III, electrodeposited and slurry cast Sb anodes were compared through differential capacity analysis, and it was demonstrated that electrode fabrication can significantly impact the sodiation/desodiation reaction pathway. Additionally, electrodeposited Sb anodes provided valuable insight into the mechanism without having to deconvolute the influences of binders and additives necessary in slurry casting. Chapter IV describes preliminary studies on how electrolyte composition can influence sodiation/desodiation reactions during Sb anode cycling. Traditional battery electrolytes are composed of carbonate species and salts, which are reduced onto the anode surface to form the solid electrolyte interphase (SEI). Due to the inherent volume expansion of Sb anodes when sodiated/desodiated, the SEI is hypothesized to continuously form and affect the cyclability of these anodes. In this investigation, we have found that electrolyte composition can influence the cycle life and sodiation/desodiation pathway, and we describe additional studies to probe how the SEI could hinder sodium ion transport. Chapter V builds upon Chapter II and explores how electrodeposition can be employed to develop three-dimensional (3D) electrodes to enhance the energy and power density of Sb-based anodes. Although we show that experimental parameters can be tuned to obtain uniform coverage, significant challenges in achieving conformal coverage of the current collector while maintaining high active material loading remain. The final chapter, Chapter VI, concludes the dissertation by describing further directions required to deepen the understanding of the degradation mechanism for Sb. We have begun to develop a 3D-printed optical, electrochemical cell that can couple operando optical studies with electrochemical studies to understand how electrode composition, structure, and electrolyte composition affect mechanical stability and ionic/electronic diffusivity in these electrodes. Understanding these fundamental processes and developing tools and characterization techniques to study alloy-based anode materials will lay the foundation for creating earth-abundant energy storage systems with high energy densities and long cycle life.