Browsing by Author "Kipper, Matthew, committee member"
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Item Open Access A selection of nitric oxide-releasing materials incorporating S-nitrosothiols(Colorado State University. Libraries, 2017) Lutzke, Alec, author; Reynolds, Melissa, advisor; Henry, Charles, committee member; Kennan, Alan, committee member; Kipper, Matthew, committee memberNitric oxide (NO) is a diatomic radical that occurs as a crucial component of mammalian biochemistry. As a signaling molecule, NO participates in the regulation of vascular tone and maintains the natural antithrombotic function of the healthy endothelium. Furthermore, NO is produced by phagocytes as part of the immune response, and exhibits both antimicrobial and wound-healing effects. In combination, these beneficial properties have led to the use of exogenous NO as a multifunctional therapeutic agent. However, the comparatively short half-life of NO under physiological conditions often renders systemic administration infeasible. This limitation is addressed by the use of NO-releasing polymeric materials, which permit the localized delivery of NO directly at the intended site of action. Such polymers have been utilized in the development of antithrombotic or antibacterial materials for biointerfacial applications, including tissue engineering and the fabrication of medical devices. NO release from polymers has most frequently been achieved through the incorporation of functional groups that are susceptible to NO-forming chemical decomposition in response to appropriate environmental stimuli. While numerous synthetic sources of NO are known, the S-nitrosothiol (RSNO) functional group occurs naturally in the form of S-nitrosocysteine residues in both proteins and small molecule species such as S-nitrosoglutathione. RSNOs are synthesized directly from thiol precursors, and their NO-forming decay has generally been established to produce the corresponding disulfide as a relatively benign organic byproduct. For these reasons, RSNOs have been conscripted as practical NO donors within a physiological environment. This dissertation describes the synthesis and characterization of RSNO-based NO-releasing polymers derived from the polysaccharides chitin and chitosan, as well as the development of amino acid ester-based NO-releasing biodegradable poly(organophosphazenes) (POPs). The broad use of chitin and chitosan in the development of materials for tissue engineering and wound treatment results in a significant overlap with the therapeutic properties of NO. NO-releasing derivatives of chitin and chitosan were prepared through partial substitution of the carbohydrate hydroxyl groups with the symmetrical dithiols 1,2-ethanedithiol, 1,3-propanedithiol, and 1,6-hexanedithiol, followed by S-nitrosation. Similarly, thiol-bearing polyphosphazenes were synthesized and used to produce NO-releasing variants. Polyphosphazenes are a unique polymer class possessing an inorganic backbone composed of alternating phosphorus and nitrogen atoms, and hydrolytically-sensitive POP derivatives with organic substituents have been prepared with distinctive physical and chemical properties. Although POPs have been evaluated as biomaterials, their potential as NO release platforms has not been previous explored. This work describes the development of NO-releasing biodegradable POPs derived from both the ethyl ester of L-cysteine and the 3-mercapto-3-methylbutyl ester of glycine. The NO release properties of all polymers were evaluated at physiological temperature and pH, and the results suggested potential suitability in future biomaterials applications.Item Open Access An economic and environmental assessment of guayule resin co-products for a US natural rubber industry(Colorado State University. Libraries, 2023) Silagy, Brooke, author; Reardon, Kenneth, advisor; Quinn, Jason C., advisor; Kipper, Matthew, committee member; Bradley, Thomas, committee memberGuayule (Parthenium argentatum) is a natural rubber producing desert shrub that has the potential to be grown in semi-arid areas with limited water resources. Numerous studies have examined the costs and environmental impacts associated with guayule rubber production. These studies identified the need for additional value from the rubber co-products, specifically the resin, for sustainable and commercial viability of the biorefinery concept. This study developed process models for resin-based essential oils, insect repellant, and adhesive co-products that are integrated with sustainability assessments to understand the commercial viability. A techno-economic analysis and cradle-to-gate life cycle assessment (LCA) of these three different co-product pathways assumed a facility processing 66 tonnes/day of resin (derived from the processing of 1428 tonnes per day of guayule biomass) and included resin separation through co-product formation. The evaluation outcomes were integrated into an established guayule rubber production model to assess the economic potential and environmental impact of the proposed guayule resin conversion concepts. The minimum selling price for rubber varied by co-product: $3.54 per kg for essential oil, $3.40 per kg for insect repellent, and $1.69 per kg for resin blend adhesive. The resin blend adhesive co-product pathway had the lowest greenhouse gas emissions. These findings show a pathway that supports the development of a biorefining concept based on resin-based adhesives that can catalyze a US based natural rubber industry.Item Embargo Design and fabrication of bioactive coatings to catalytically generate nitric oxide on the surfaces of extracorporeal circuits(Colorado State University. Libraries, 2022) Wick, Tracey V., author; Reynolds, Melissa M., advisor; Kipper, Matthew, committee member; Olver, Christine, committee memberBlood-contacting medical devices suffer from biofouling caused by proteins, platelets and other cells adhering to the surface which often leads to severe complications and eventual device failure. In particular, extracorporeal membrane oxygenation (ECMO) is a life support treatment that is highly prone to coagulation issues due to a large blood-contacting surface area and turbulent blood flow. The ECMO circuits are constructed from catheters, tubing, and an oxygenator which all come into contact with blood and have several connections that alter the blood flow. The standard therapy to decrease thrombotic complications is to administer a systemic anticoagulant, usually unfractionated heparin. While this reduces clotting, harmful and potentially fatal hemorrhagic complications arise. Researchers have looked to nitric oxide (NO), a common biomolecule produced by the endothelium, as an alternative to locally inhibit clotting. Previous work has shown a reduction in thrombotic activity using NO-releasing substances, but these substances only last for a short period of time. An approach explored herein takes advantage of a catalytic mechanism to generate NO from endogenous NO-donors, S-nitrosothiols (RSNOs). RSNOs have been shown to catalytically generate NO through copper catalysis and in particular, with a copper-based metal-organic framework, H3[(Cu4Cl)3(BTTri)8-(H2O)12]·72H2O where H3BTTri = 1,3,5-tris(1H-1,2,3-triazole-5-yl)benzene] (CuBTTri). Importantly, CuBTTri has been shown to be stable under biological conditions and compatible with human cells; therefore, it is a promising candidate for biomedical applications. This report explores the addition of CuBTTri on the surfaces of ECMO. In Chapter 2, a CuBTTri-doped composite is coated onto the extracorporeal circuitry tubing. The fabrication method to apply CuBTTri to the tubing is reported, and the coating was shown to actively generate NO when exposed to a RSNO and no adverse effects were noted during hemocompatibility testing. In Chapter 3, CuBTTri is immobilized on the surface of an ECMO oxygenator using polydopamine. The morphology of the coating was evaluated and the CuBTTri on the surface of the oxygenator was catalytically active, generating NO when exposed to a RSNO. The incorporation of CuBTTri on the surfaces of these components could improve the hemocompatibility of the device, providing a safer and more effective life support system.Item Open Access Developing tools to study the interaction between the lipopeptide surfactin and phospholipid bicelles with infrared spectroscopy(Colorado State University. Libraries, 2012) Blaser, Jennifer M., author; Krummel, Amber, advisor; Levinger, Nancy, committee member; Kipper, Matthew, committee memberSurfactin has been shown to have concentration-dependent effects on lipid membranes with proposed mechanisms of action including ion chelation, ion channel formation, and a detergent-like effect. The concentration ranges for these behaviors have not been established, the structure of surfactin in a membrane has not been determined, and information regarding the dynamics of the surfactin-lipid interaction is limited at best. Therefore, a tunable phospholipid bicelle system was created to study the surfactin-lipid interaction as a function of surfactin concentration using infrared (IR) spectroscopy which can provide both structural and dynamic information. But first, the direct interaction between surfactin and bicelles was confirmed with dynamic light scattering (DLS) measurements that suggest surfactin exhibits detergent-like effects above a 2.0 mM concentration. For surfactin in Tris buffer, the IR spectra displayed a significant concentration-dependent shift in the amide-I band and a distinct change in the amide-I to amide-II band intensity ratio. These data indicate that surfactin experiences a conformational transition over the concentration range studied. The conformational transition may occur due to the formation of surfactin micelles and higher order aggregates upon increasing concentration. Surfactin was also studied in the presence of phospholipid bicelles. At low surfactin concentrations in the presence of bicelles, the amide-I band exhibits nearly identical spectral features to those found for higher concentrations of surfactin in Tris buffer, and the amide-I to amide-II band intensity ratios showed similar trends. The results of these studies indicate that the conformation of surfactin may be similar in micelles, higher order aggregates, and bicelles with the bicelles limiting the conformational distribution of the surfactin molecules. Additional studies are necessary to determine surfactin's structure in these model membranes and obtain dynamic information to better understand the mechanism of the surfactin-lipid interaction.Item Open Access Elastic free-standing RTIL composite membranes for CO2/N2 separation based on sphere-forming triblock/diblock copolymer blends(Colorado State University. Libraries, 2016) Wijayasekara, Dilanji B., author; Bailey, Travis S., advisor; Fisk, John D., committee member; Kipper, Matthew, committee member; James, Susan, committee memberThe main focus of this dissertation was the development of a robust polymeric membrane material for separating CO2 from a gas mixture of CO2 and N2. Flu gas, which is mainly a mixture CO2 and N2, is the single largest form of anthropogenic CO2 emissions to the atmosphere. Capturing CO2 from flu gas is considered as a measure of controlling anthropogenic CO2 emissions. Existing CO2 capturing technologies for flu gas suffer from low efficiency and the low cost effectiveness. Adoption of membrane technology is comparatively the best route towards the economical separations. Challenges faced by existing CO2 separation membrane materials are the lack of high mechanical robustness and the processability required for fabrication of membrane units while maximizing their gas separation properties. We were able to form a novel membrane material that addresses each of these challenges. These novel membranes are based on highly swollen, self-standing films produced using sphere-forming PS-PEO diblock and PS-PEO-PS triblock copolymer blends. The intricate connectivity among spherical domains produced during melt-state assembly (prior to swelling), provides a framework that remains elastically tough even in the presence of large quantities of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTf2N) - a room temperature ionic liquid (RTIL) that has high selectivity for CO2 over N2. Further investigations on improving the robustness of these membranes and the gas separation properties were carried out based on two scenarios. First, potential of improving the thermal stability of these membranes by replacing the thermoplastic polystyrene with a thermoset moiety such as a chemically cross-linked polyisoprene (PI) was researched. Cross-linking chemistry utilized required a post-polymerization modification of PI and it was found that this oxidation modification of olefins on PI caused the decoupling of triblock copolymer in the blend and also substantially hindered melt-state self assembly. The membranes formed with this modification turned out to have inferior mechanical properties compared to the polystyrene based ones, most likely due to the above mentioned complications. Due to the time restrictions, this study was limited to just the identification of the existing challenges in the proposed strategy. Recommendations for addressing the challenges identified are also presented later in the dissertation. The second scenario for improving the performance of these membranes was to increase their productivity by improving both the CO2 permeability and maximizing the trans-membrane pressure differentials possible during operation. To accomplish this we focused on the development of an alternative matrix material (alternative for PEO) enriched with ionic groups. The goal was to increase matrix solubility in the RTIL (improved CO2 permeability) while simultaneously strengthening matrix-RTIL interactions for reduced leaching under higher pressure differentials. Synthetic routes to achieve this task involved a sequential polymerization of isoprene and ethoxy ethyl glycidyl ether (EEGE) monomers. Polymerization of EEGE to yield high molecular weight linear blocks proved to be extremely challenging due to the undesirable chain transfer reaction tendency of EEGE monomer. A great deal of research effort was spent characterizing various anionic reaction conditions and developing measures aimed at suppressing chain transfer. While ultimately unsuccessful, the results of these studies provide significant insight into the challenges of forming high molecular weight linear polyglycidols and will hopefully provide inspiration for the development of future synthetically successful strategies. A series of proof of concept experiments for transforming alcohol functionalities on this polymer system to imidazolium was also completed successfully. The dissertation concludes with a final project completed outside the main objective of the dissertation - a morphological characterization of a series of thermoplastic elastomers with unique molecular architectures. This work is reported separately in the appendix I.Item Open Access Engineering complex liver models for drug screening and infectious diseases: a biomaterials and co-culture perspective(Colorado State University. Libraries, 2018) Lin, Christine, author; Khetani, Salman R., advisor; Gustafson, Daniel, committee member; Kipper, Matthew, committee member; Pagliassotti, Michael, committee memberIn vitro liver models have many applications in disease modeling and drug screening. Micropatterned cocultures (MPCCs) of primary human hepatocytes (PHHs) and supportive stromal cells have been shown to display high hepatic functions for long-term drug and disease studies. However, MPCCs lack liver non-parenchymal cells (NPCs) and the proper microenvironmental cues that can play important roles in conditions such as drug-induced liver injury (DILI), which is the leading cause of the prelaunch attrition and post-market withdrawal of pharmaceuticals, or diseases such as viral hepatitis. Hepatitis B virus (HBV) and hepatitis C virus (HCV) infection are major health problems that affect >250 million and ~130-170 million people worldwide, respectively, and the development of therapeutics has been hindered due to the lack of models in which to study human response to virus and drugs. Thus, long-term in vitro models that can be used to study the progression of viral infection and drug pharmacodynamics are required to develop safe and efficacious therapeutics. These models must also be human-relevant due to the narrow host tropism of hepatitis B and C and differences in liver pathways across species. Thus, the goal of this dissertation is to augment the MPCC model to include the relevant substrates and cell types for the study of cell-cell interactions in diseases such as hepatitis and DILI. Biomaterials can present important microenvironmental factors that interact with cells. Chitosan and heparin polyelectrolyte multilayers (PEMs) were utilized as a substrate to present extracellular matrix (ECM) proteins and growth factors (GF) to hepatocyte cultures. Liver biomatrix (LBM) derived from human and porcine sources were also assessed as substrates since LBM contains both soluble and insoluble cues that are usually found in the liver in vivo. In addition to improving the MPCC substrate, liver NPCs, such as primary human Kupffer cells (KCs), were incorporated into the MPCC model since KCs play key roles in immune responses and inflammation. This work will be used to establish models that integrate multiple liver cell types on a physiologically-relevant substrate to study disease states such as hepatitis and DILI towards creating effective therapeutics.Item Open Access Influence of adipose-derived mesenchymal stromal cells on osteosarcoma minimal residual disease(Colorado State University. Libraries, 2015) Aanstoos-Ewen, Megan, author; Ehrhart, Nicole, advisor; Kipper, Matthew, committee member; Dow, Steven, committee member; Custis, James, committee memberIntroduction: Mesenchymal stromal cells (MSCs) have been shown to improve bone integration and healing in several preclinical studies and have therapeutic potential in limb salvage following massive bone loss due to tumor resection. However, MSCs have also been shown to promote primary and pulmonary metastatic tumor growth when injected in the presence of gross tumor or when co-injected with tumor cells in rodent models. While these results raise concerns about the safety of using MSCs in sarcoma patients, MSCs are unlikely to be utilized in a clinical setting when gross tumor is present. The objective of this dissertation project was to develop murine models of minimal residual osteosarcoma following primary tumor removal then to utilize these models to determine whether the administration of adipose-derived MSCs with or without chemotherapy treatment in a minimal residual disease setting would promote either pulmonary metastatic osteosarcoma progression or local disease recurrence. We hypothesized that surgical site or intravenous administration of MSCs will influence either osteosarcoma pulmonary metastatic burden or local disease recurrence in a minimal residual disease setting. Materials & Methods: Two syngeneic, orthotopic models of luciferase-expressing osteosarcoma were developed. In the first model, tumor-bearing mice underwent a coxofemoral amputation and were followed to assess development of pulmonary metastases. In the second model, a femorotibial amputation was performed in order to develop a model of consistent local tumor recurrence. In this model, all gross tumor was removed, however, microscopic tumor remained at the surgical margin. In this dissertation project, three principle projects were completed to test our hypothesis. The first project explored the use of MSCs delivered either to the surgical site or intravenously to ascertain their influence on pulmonary disease burden. A follow-on pilot explored concurrent MSC and chemotherapy treatment on development of pulmonary disease. The second project evaluated the use of MSCs delivered either to the surgical site or intravenously on local recurrence of osteosarcoma at the surgical site. Gross recurrent tumor size was measured for comparison between treatment groups. The third project examined the use of cisplatin and MSCs on survival of mice following removal of primary osteosarcoma. Data were expressed in mean +/- SD or median with 95% CI. ANOVA test, Kruskal-Wallis test, Fisher’s Exact test, Welch’s test, t-test, and Mann Whitney test were used for statistical analysis. Significance was set at p<0.05. Results: Mice treated with intravenous MSCs had a faster time to first pulmonary metastatic disease detection than mice treated with MSCs injected into the surgical site or control mice (no MSCs) (p=0.022). No treatment effect was seen between groups with respect to time to tumor recurrence or size of recurrent tumor in the second study. Survival curves were significantly different when comparing cisplatin, cisplatin and MSC treatment, MSC alone treatment and untreated mice (p<0.001) as well as in pairwise comparisons. Mice treated with MSCs had a 73% chance of earlier death than untreated controls. Discussion/Conclusion: Intravenous administration of MSCs in a minimal residual osteosarcoma environment resulted in a faster time to first detection of pulmonary disease and in a higher chance of earlier death compared to untreated mice. However, administration of MSCs locally in a surgical site following sarcoma excision appears to be safe, even in the setting of known residual microscopic disease. Further, the use of cisplatin treatment appeared to ameliorate the effects of intravenous MSCs on survival. Based on these results, further study is warranted to evaluate the influence of intravenously administered MSCs on minimal residual pulmonary metastatic disease.Item Open Access New methods to access functionalized N-heterocycles(Colorado State University. Libraries, 2021) Patel, Chirag, author; McNally, Andrew, advisor; Bandar, Jeffrey, committee member; Reynolds, Melissa, committee member; Kipper, Matthew, committee memberN-heterocycles are ubiquitous in pharmaceuticals and agrochemicals. Their prevalence is due to the unique properties they can impart to a molecule. Due to their ubiquity, it is vital that synthetic chemists be able to modify the structure of these valuable scaffolds. Despite a great deal of literature on the functionalization of these important motifs, challenges toward the functionalization of N-heterocycles remain. Chapter 1 will highlight the importance of azaarenes in pharmaceuticals and explain the properties that make these structures so prevalent in drugs. Classical and modern methods to functionalize pyridines and diazines will also be discussed. Chapter 2 will describe the development of the phosphonium salt chemistry in the McNally lab and the use of these reactive intermediates to aminate pyridines and diazines via the Staudinger reaction. Chapter 3 will introduce the concept of phosphorus ligand-coupling and briefly describe its previous application toward the synthesis of bis-heterobiaryls. This chapter will also cover the importance of fluoroalkyl groups in both the pharmaceutical and agrochemical industries. Current methods to fluoroalkylate azaarenes will be discussed, and the development of a novel fluoroalkylation strategy via a phosphorus ligand-coupling reaction will be explained. Finally, chapter 4 covers ongoing research into the synthesis of N-alkyl/aryl pyridiniums and their hydrogenation to N-substituted piperidines. The importance of N-substituted piperidines and the limitations to their synthesis are described.Item Open Access New strategies to synthesize complex pyridines and tetrahydropyridines using main group chemistry(Colorado State University. Libraries, 2021) Fricke, Patrick J., author; McNally, Andrew, advisor; Crans, Debbie, committee member; Chen, Eugene, committee member; Kipper, Matthew, committee memberPyridine and piperidine are important molecular scaffolds in small molecule drug development in medicinal chemistry research. Because of their importance, methods to synthesize complex pyridines and piperidines are highly desirable. Chapter one discusses the importance of these scaffolds in the pharmaceutical industry along with the history of pyridine and piperidine synthesis and the challenges that still remain. Chapter two discusses the switching strategies for selective installation of phosphonium salts on polyazines. The methods include an acylation, base-mediate, phosphine mediate, and order-of-reagent addition strategies. Additionally, we demonstrate how these methods can be applied to medicinal chemistry research during structure-activity relationship studies by derivatizing the phosphonium salts. Chapter three presents a new strategy for selective pyridine alkylation at the 4-position of the pyridine ring. Using a triazine chloride activating group allows for 4-selective phosphonium ylide formation inside the pyridine ring. A Wittig olefination-rearomatization sequence with an aldehyde then furnishes the alkylated pyridine. This method offers an alternative strategy to conventionally used metal-catalyzed cross coupling and Minisci-type reactions. Chapter four describes a stepwise reduction method for the synthesis of dihydropyridine and tetrahydropyridine. Using N-Tf activation allows for a selective hydride reduction to the dihydropyridine, which can subsequently undergo hydrogenation to the tetrahydropyridine.Item Unknown Nitric oxide generation from S-nitrosothiols via interactivity with polymer-supported metal-organic frameworks(Colorado State University. Libraries, 2018) Neufeld, Megan J., author; Reynolds, Melissa, advisor; Chen, Eugene, committee member; Finke, Richard, committee member; Kipper, Matthew, committee member; Ravishankara, A. R., committee memberCatheters, extracorporeal systems, stents, and artificial heart valves are all common blood-contacting medical devices. Due to the differences in the chemical and physical properties of the polymeric materials used to construct medical devices and biological tissues in the cardiovascular system, complications such as thrombus formation arise from the resulting incompatibilities. Introduction of foreign materials that lack critical biological cues can result in disruption of the delicate balance maintained within the circulatory system. This disruption of homeostasis initiates a complex cascade of events such as platelet adhesion and protein deposition that ultimately result in thrombus formation. As such, the propensity of blood to clot upon contact with a foreign surface represents a challenge unique to devices intended for vascular applications. The current clinical use of devices such as vascular catheters includes the administration of anticoagulants, however their associated complications such as internal hemorrhaging renders this practice undesirable as a long-lasting solution. A general limitation of existing devices made from synthetic polymers is their inability to integrate with their environment through biological cues (natural regulators). Materials that lack this behavior are often described as passive towards their environment. In comparison, active materials that can simulate natural molecules used to maintain biological responses may result in enhanced integration of medical devices. In the natural, healthy endothelium, the prevention of thrombus formation occurs through the release of anticoagulants and platelet inhibitors such as gaseous nitric oxide (NO). While the use of NO for medicinal purposes began indirectly in the late 1800s, the significance of its endogenous production was not known until the 1970s. In particular, NO is a key factor in the prevention of thrombus formation. While its remedial potential has led to its use as an exogenous therapeutic agent, its high reactivity limits its applicability as a localized therapeutic. This limitation is addressed by mimicking the natural endothelium and using small molecules in the bloodstream known as S-nitrosothiols (RSNOs) to produce NO directly from this physiological source. Biological RSNOs are theorized to aid in the stabilization and transport of NO and undergo an NO-forming decomposition in the presence of heat, light, and certain metals such as copper. Prior strategies have evaluated exploiting the physiological supply of RSNOs through the incorporation of copper complexes into polymeric materials. While these copper-based materials demonstrate the production of NO from RSNO decomposition, limitations arise due to the gradual loss of the catalytic material and toxicity from copper leaching. In order for this type of approach to be feasible, the active metal species must remain immobilized within the structural framework. Metal–organic frameworks (MOFs) are a class of crystalline materials that consist of organic ligands coordinated to metal centers. Certain copper-based MOFs have demonstrated the ability to enhance the generation of NO from RSNOs without the gradual loss of the active species. Through integration of certain copper-based MOFs with medically relevant polymers, materials can be prepared that promote the localized generation of NO at their surfaces. However, the feasibility of utilizing copper-based MOFs for such applications depends on effective incorporation within a supporting polymeric matrix and the retention of useful activity thereafter. As such, it is necessary to assess different MOF/polymer composites for their ability to promote NO generation from RSNOs prior to use in medical applications. This dissertation investigates the incorporation of two distinct copper-based MOFs into a selection of medically-relevant polymeric materials including cotton, poly(vinyl chloride), chitosan, and poly(vinyl alcohol). These MOF/polymer materials were subsequently tested for their ability to promote NO generation from RSNOs in an effort to assess the impact of incorporation within a polymer matrix. Overall, this work demonstrates the potential for blood-contacting MOF-containing materials in biomedical settings by identifying ideal characteristics that MOF/polymer composites should exhibit for optimization and translation to a clinical setting.Item Unknown Oxidative quenching organic photocatalyst design, synthesis and application in dual nickel/photoredox-catalysis(Colorado State University. Libraries, 2023) Chrisman, Cameron Hayes, author; Miyake, Garret, advisor; Paton, Robert, committee member; Zadrozny, Joseph, committee member; Kipper, Matthew, committee memberThe work described in this dissertation focuses on the development of a new class of organic photocatalysts and the application of oxidative quenching photocatalysts in dual nickel/photoredox-catalysis. The design of new organic photocatalysts is crucial for eliminating the need to use rare/expensive ruthenium and iridium that have dominated the field of photoredox catalysis. Additionally, the majority of the catalysts describe here-in operate through an oxidative quenching mechanism that remains underexplored in the field of dual nickel/photoredox catalysis. The first detailed mechanistic study on oxidative quenching in this field is reported and applied in a broad range of couplings.Item Unknown Stormwater treatment strategy for the degradation of aircraft deicing fluid at the Joint Base Elmendorf-Richardson in Anchorage, Alaska(Colorado State University. Libraries, 2017) Hernandez, Martha Liliana Nunez, author; Carlson, Kenneth, advisor; Sharvelle, Sybil, committee member; Kipper, Matthew, committee memberDue to the large volumes of aircraft deicing fluids (ADF) applied by U.S. commercial airports during winter months, stricter pollution control by regulatory agencies has been implemented. Agencies such as the Environmental Protection Agency (EPA), have made several attempts to improve stormwater management practices in airports which has resulted in a decrease of the discharge volumes of ADF contaminated water. However, many U.S. airports continue to explore and develop new strategies to reduce contaminant concentrations to meet the benchmark concentrations required to comply with discharge permits. One of the airports that has not complied with all EPA permits is the Air Force/Army military base Joint Base Elmendorf-Richardson (JBER) located in Anchorage, Alaska. The extremely low temperatures and high average yearly precipitation in Anchorage requires that JBER use a large volume of ADF solution to allow proper aircraft operations. The hundreds of thousand gallons of fluid that are applied during deicing season generates large volumes of contaminated stormwater runoff that is discharged into a nearby water body. Joint Base Elmendorf-Richardson has made several attempts to manage ADF usage on site, but the chemical oxygen demand (COD) and biological oxygen demand (BOD) limits have not been reduced to the standards set by regulatory agencies. To address this issue, JBER contacted the Energy and Water Sustainability Laboratory at Colorado State University (CSU) to determine possible stormwater treatment strategies to be applied on the military base. After considering all treatment technologies currently used at North America airports, the CSU team concluded that biological degradation by subsurface flow constructed wetlands (SFCW) was the most practical option for JBER. The final selection and recommendation was based on extensive literature review and analysis of design criteria, construction, O&M, and maintenance cost, as well as, information of various technologies used in cities with comparable climate conditions to Anchorage. The CSU team developed a series of bench scale experiments that simulated biological degradation in batch SFCWs under ambient and operational conditions relevant to JBERs case. Degradation data was obtained by measuring daily COD concentrations over a 30-day period. A total of 14 experiments at different conditions were performed. Parameters including temperature (5°C vs. 20°C), aeration (aerated vs. non-aerated), ADF composition (all ADF types used by JBER vs. propylene glycol only), and nutrient addition (with nutrients vs. without nutrients) were varied to determine their effect on degradation rates (k), and lag phase in the system. All kinetic parameters were determined and calculated based on first order degradation kinetics in a biological system. Numerical, graphical, and design of experiment (DOE) analyses suggested that the temperature in the system had the highest effect on degradation rates and lag-phases. Analysis of results suggested that the ADFs in stormwater can be treated with the SFCW technology under certain conditions. During winter months, sufficient aeration, nutrient addition and low propylene glycol content are necessary to achieve optimal degradation rates (k=0.11 day-1). However, during warmer months (May-August), it is possible to treat the stormwater under low oxygen, and low nutrient conditions reducing the energy costs of the system. If a stormwater strategy for treatment during warmer months is developed, the stormwater treatment can be optimized in the most economic manner.Item Unknown The dynamic nature of ligand layers on gold nanoclusters(Colorado State University. Libraries, 2020) Hosier, Christopher Allen, author; Ackerson, Christopher J., advisor; Kennan, Alan J., committee member; Henry, Chuck, committee member; Kipper, Matthew, committee memberGold nanoclusters have been heavily investigated over the last few decades for their potential use in sensing, imaging, energy conversion, and catalytic applications. The development of methodology that allows for controlled functionalization of the surface ligand layer in these compounds is of particular interest due to the role of ligands in determining a large number of cluster properties. One of the fundamental ways of tailoring the ligand layer is the use of ligand exchange reactions. Despite the synthetic utility that ligand exchange reactions afford, a significant number of unanswered challenges currently limits the scope and control that can be obtained with these reactions. While a large variety of ligand types have been used to protect nanocluster surfaces, the majority of reported ligand exchange reactions revolve around chalcogenate-for-chalcogenate exchange. Site-selectivity in these reactions is limited to kinetic phenomenon, and the role of intercluster exchange largely remains a mystery. Additionally, recent works suggest that changes in ligand orientation can impact bulk material properties. In this thesis, we seek to address these challenges by reporting new exchange methodology, probing the evolution of exchanged ligand layers over time, investigating the stability of ligand layers in reaction conditions, and exploring the impact of ligand orientation on nanocluster behavior and reactivity. By addressing these questions and challenges, we seek to move closer to the goal of developing methodology that can be easily and reliably used to tailor gold nanoclusters for directed applications.