2022-2023 Senior Honors Theses
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This collection contains theses produced by Class of 2023 Honors students
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Browsing 2022-2023 Senior Honors Theses by Department "Chemical and Biomolecular Engineering, William A. Brookshire Department of"
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Item CO2 Open Metal Site Selectivity in MIL-100 (Cr): A Computational Study(2023-05-02) Fleming, KevinMetal-organic frameworks (MOFs) are porous organometallic compounds that are of high interest due to their capability to trap industrial greenhouse gases, such as CO2, that contribute to anthropogenic global warming. A promising MOF that has gained the attention of the research community in recent years is the CO2 adsorbent MIL-100 (Cr). This compound consists of two primary structural components: a set of Cr3-?3-oxo clusters referred to as secondary building units (SBU) and organic linkers derived from trimesic acid. Thermally activated SBUs possess coordinatively unsaturated sites Cr sites -- or open metal sites (OMS) -- that can have oxidation states of +2 or +3. Previous experimental work indicated that CO2 molecules bind more strongly to Cr2+ OMS than to Cr3+ OMS at low adsorptive pressures. In this thesis project, two central questions were addressed. Firstly, can the experimentally observed OMS selectivity be verified through density functional theory (DFT) simulations? Secondly, what electronic processes are responsible for OMS selectivity? DFT computations of the binding energy, enthalpy, and Gibbs free energy of CO2 adsorption onto Cr2+ and Cr3+ OMS verify that CO2 exhibits a significantly greater affinity for the +2 OMS. In addition, a comparison of the adsorption charge transfer and optimized binding geometries reveal that this selectivity arises from the energetically favorable chemisorption of CO2 onto +2 OMS – relative to the weaker physisorption of the greenhouse gas onto +3 OMS. The novel methodology utilized for this study -- which addresses the issue of charge delocalization in DFT simulations -- can be implemented in computational investigations of CO2 OMS selectivity for other promising MOFs being considered for carbon capture applications.Item Rate Enhancement Effects of Steam Reforming of Methane over Dynamic Ruthenium Catalysts(2023-05-07) Vempatti, Veera Venkata RamprajwalMethane (CH4) is the second-most abundant greenhouse gas with a warming potential 25 times as great as carbon dioxide. Short-term action plans directed toward diminishing the effects of global warming should therefore include the mitigation of methane emissions. The direct capture of distributed CH4 emitted by relatively intractable sources like livestock for subsequent large-scale industrial processing faces severe economic challenges. On-site treatment of CH4 via transition-metal catalyzed steam reforming (SMR) in mobile, dynamically operated modular reactors can overcome the economic barriers of capturing stranded CH4. Existing kinetic studies of SMR over transition metal surfaces identified two competing surface phenomena: CH4 activation and CO* formation. The coupled nature of these two surface reactions limits the maximum realizable activity from static catalysts to the Sabatier optimum. In this work, decoupling of the competing elementary reactions over stepped Ruthenium (Ru) is attempted by modulating the chemisorption energy of the surface carbon intermediate (ΔEC). Brönsted-Evans-Polanyi (BEP) and scaling relationships were used to model the energy dependence of transition states and other surface intermediates, respectively, on ΔEC. Catalytic dynamics were simulated with a lumped kinetic model. ΔEC was oscillated as a square wave about two Ru basis energies with amplitudes of 0.1 eV and 1 eV over a broad range of frequencies. A band of frequencies (105 Hz - 109 Hz) corresponding to maximum enhancement in the time-averaged rate of SMR is observed.Item Z-Ring Formation as a Biomarker in Bacterial Persisters(2023-04-22) Wagner, Iva J.Bacterial infections that persist despite antimicrobial treatment are a growing concern in the medical field. While much research is focused on antibiotic resistance, bacterial persistence is also a significant contributor to the problem. Persister cells are a subpopulation of bacteria that can temporarily survive antibiotics, and they can resuscitate after treatment is stopped, leading to chronic infections. To properly research resuscitation in these persistent cells, we must first identify which cells to study. One way to do this is by using biomarkers, such as the formation of Z-rings during the growth-inhibited state, which can help determine which persister cells are capable of resuscitation. In this study, E. coli pUA66-ftsZ-gfp cultures were subjected to antibiotics including Gentamicin, Streptomycin, Ampicillin, and Fosfomycin antibiotics. Following treatment, the cells were starved in PBS for two days to allow for Z-ring formation. The next step involved transferring the bacteria onto a microscope slide coated with Luria Bertani (LB) agar, which provides the necessary nutrients for resuscitation. Images of both phase contrast and green fluorescence protein (GFP) fluorescence were taken hourly to monitor growth and Z-ring formation. This approach successfully demonstrated that Z-rings are a reliable biomarker for identifying whether cells are recovering from persistence and returning to normal function.