Organizational Unit:

School of Chemical and Biomolecular Engineering

Permanent Link

https://hdl.handle.net/1853/70759

Parent Organization

Organizational Unit

College of Engineering

ArchiveSpace Name Record

https://finding-aids.library.gatech.edu/agents/corporate_entities/407

Full item page

Publication Search Results

Now showing 1 - 10 of 600

Analyzing Sorption Exclusion Effects for the CO2/CH4 Gas Pair Using Matrimid® CMS Dense Films

(Georgia Institute of Technology, 2023-07-31) Vessel, Taylor C.

This thesis uses the so-called dual-mode sorption model to analyze Matrimid® polyimide-derived carbon molecular (CMS) thin films. This model provides a useful framework to analyze and understand sorption in complex CMS morphology. The model is also helpful to connect morphology to the pyrolysis process used to create it. The dual mode model includes coexisting continuous and dispersed Langmuir terms. The model parameters related to these environments are reported and discussed in this work. CMS based membranes have been applied towards many different gas-pair separations. CMS thin films have appealing separation performance for key gas pairs; the carbon dioxide/methane pair, which is practically important, is the focus of this study. Previous measurements on CMS film sorption for this pair have been done. Surprisingly, applying the dual-mode sorption model to such thin films created from Matrimid® over a range of pyrolysis temperatures has not been done previously and is considered here. This thesis characterizes sorption properties of such CMS thin films for the CO2./CH4 pair and adds insights relevant to their separation. Suggestions for the next steps to extend this study are also provided.
Engineering Bovine Serum Albumin Nanoparticles For Improved Endosomal Escape And The Treatment Of Endometriosis

(Georgia Institute of Technology, 2022-12-09) Wimberley, Sydney C.

Endometriosis is an estrogen driven condition that affects about 10% of menstruating women. It causes severe pain and infertility, and limited treatment options are available. This work uses the anti-inflammatory protein, AvrA, an effector protein found in Salmonella that inhibits nuclear factor-kB (NF-kB) and mitogen-activated protein kinase (MAPK) signal cascades. However, this protein is highly insoluble and requires a carrier for delivery to the cytosol, and bovine serum albumin (BSA) nanoparticles are used to deliver AvrA. AvrA-BSA nanoparticles were delivered to End1/E6E7, an epithelial cell line derived from a woman’s endometrium with endometriosis. To measure functionality of AvrA-BSA nanoparticles, inflammatory cytokines were measured in this cell type under inflammatory conditions. AvrA-BSA nanoparticles are internalized by cells using endocytosis. Their delivery to the cytosol is highly inefficient and endosome contents are trapped and later destroyed or recycled out of the cell following fusion with lysosomes, this is phenomenon is called endosomal entrapment. To overcome this entrapment, BSA nanoparticles were modified by conjugating histidine to their hydroxyl groups. Histidine’s variable chain is imidazole, and it can act as a buffer in lower pH environments, such as endosomes. In an endosome at lower pH protons and ions will enter the endosome causing them to swell due to a concentration gradient and an increase in osmotic pressure, eventually causes rupture. Endosomal escape of nanoparticles was evaluated using a Galectin-8 assay, to quantify endosomal disruption events; and a functional readout, where nanoparticles are loaded with toxic proteins allowing cell death to be an indication of nanoparticle escape. Overall, imidazole conjugated BSA nanoparticles do increase endosomal disruption events, and are able to incur an increased cell death when nanoparticles are loaded with a toxic protein.
Cost-Effective, Aqueously Degradable Poly(Ethylene Terephthalate) Films Containing a Latent Metal Oxide Reagent

(Georgia Institute of Technology, 2022-12-08) Duprez, Natalie

The widespread use of plastics, combined with their durability and persistence in the environment, has created a tremendous environmental burden. Flexible packaging in particular, including films and polymer coatings, has a particularly low recycling rate. Substantial efforts have been made to replace these typically single-use materials with biodegradable options, but high costs, difficulties with processing, and unsuitable mechanical properties often prevent their widespread use. In this work, polyethylene terephthalate (PET), one of the most affordable and commonly used plastics available, is made to be degradable by the addition of CaO via melt-mixing. This allows the PET to undergo alkaline hydrolysis upon exposure to water, ultimately converting to ethylene glycol and calcium terephthalate (CaTP), a salt of terephthalic acid. Due to the inert nature of CaO relative to other alkaline reagents, it may be mixed into PET and processed without hydrolyzing the polymer chain, and the material undergoes degradation only in the presence of water. In this work, this latent hydrolysis reaction is studied via the full and partial degradation of PET/CaO composite films at different concentrations and temperatures. The films were seen to be able to hydrolyze completely in water, forming the expected CaTP product, given that there was adequate CaO to drive the reaction to completion. Identification and observation of intermediates in the series of degradation reactions validated the proposed mechanism for latent degradation. Based on the proposed mechanism, a kinetic model was developed to predict the conversion of PET depending on key system parameters. The observed trends could be explained logically and generally followed experimental results, indicating that the rate equations provide a good starting point for describing this system.
Mechanochemical depolymerization of poly(ethylene terephthalate)

(Georgia Institute of Technology, 2022-08-01) Osibo, Anuoluwatobi Arinola

Efficient chemical recycling of consumer plastics (i.e. depolymerization down to monomers) is a crucial step needed to achieve a circular materials economy. In this work, depolymerization poly(ethylene terephthalate) (PET) via mechanochemical hydrolysis with sodium hydroxide and acid catalyst is studied. When sodium hydroxide is used, complete depolymerization is achieved in 20 min. The stages of the depolymerization are investigated by monitoring monomer yields and the change in the PET molecular weight over the course of the reaction. The monomer yields initially increase linearly with milling time, up to a yield of roughly 40%. However, the molecular weights of the residual PET decrease concomitantly only slightly, suggesting a reaction scheme analogous to a shrinking core model. As the reaction progresses, a physical transition of the PET/NaOH from a powder to a homogenous wax and a simultaneous increase in the depolymerization rate is observed. The influence of ball-to-powder mass ratio (BPR) and milling frequency are studied to derive a kinetic rate expression. The linear relationship between BPR and monomer yield and the known relationship between milling frequency are validated for this system. In the case of acid catalysts, zeolite is observed to perform better and a monomer yield greater than 42% is seen with large pore zeolites. It is hypothesized that the reaction is occurring the pores of the zeolites and the confinement effect of this catalyst provides an advantage as compared to bulk material catalyst.
ICAM-1 Targeted Delivery and Biodistribution of Protein Nanoparticles

(Georgia Institute of Technology, 2022-07-20) Queen, Adaya

Inflammation is a regulated response to injury or infection that protects and repairs the body. When an inflammatory response is unregulated, hyper-inflammation can lead to organ damage and endothelium dysfunction. Recently, SARS-CoV-2 infections have been the cause of severe pneumonia, cardiovascular complications, and organ failures. Severe infections are accompanied by pulmonary hyper-inflammation and induced vascular endothelium damage. Protein nanoparticles can be modified to target and deliver anti-inflammatory cargo to the source of inflammation which is primarily among vascular endothelium cells. Specifically, this thesis explores the fabrication and optimization of protein nanoparticles with conjugated antibodies to specifically target endothelial cells. Protein nanoparticle targeting and uptake were confirmed in the cytoplasm of cultured Human Umbilical Vascular Endothelial Cells (HUVEC) using confocal microscopy and flow cytometry. Lastly, the biodistribution of these nanoparticles was assessed in healthy mice to understand the targeting of protein nanoparticles conjugated with targeting antibodies in vivo. Overall, this thesis demonstrates the impact that conjugated antibodies have on enhancing intracellular delivery and the biodistribution of these nanoparticles in vivo.
Partial Oxidation of Hydrocarbons Over Ceria Zirconia Catalysts

(Georgia Institute of Technology, 2022-02-10) Williams, Olivia

This thesis describes research along several avenues pertaining to oxidation reactions. First, the major conclusions are summarized from a perspective describing active oxygen species on catalyst surfaces. Some oxygen species are more selective than others and if these species were better understood, a catalyst surface could be tuned to produce those selective species instead of unselective ones. However, these species readily interconvert and there does not exist a single analytical method which can characterize—and differentiate—between all of the possible species. Due to this situation, analytical techniques are focused upon in that paper. The most promising analytical technique is isotope exchange coupled with infrared spectroscopy and an inline mass spectrometer. Next, methane partial oxidation over ceria zirconia catalysts is studied with infrared spectroscopy. Methane and oxygen concentrations are modulated to differentiate active and spectator species via modulation excitation spectroscopy. Aromatic and alkoxy surface species modulate in sync with each other, supporting the hypothesis that these species compete with each other in the partial oxidation of methane to methanol; formates are formed in all cases, and these species are associated with the complete combustion of methane to carbon dioxide and water. Chemical looping may be an appropriate reaction engineering method to increase the yield of selective oxidation products since the formate and alkoxy species were separated during the oxygen modulation experiment over nickel-copper on ceria zirconia. Finally, two reactions (water splitting and heptane partial oxidation) catalyzed under mechanical forces are explored. It was hypothesized that oxygen could be mechanically driven from the ceria lattice. Oxygen from water would then replenish the lattice, releasing hydrogen. Due to iron contamination from the steel vessel, this hypothesis cannot be confirmed. Ceria zirconia, when milled in the presence of heptane, exhibits infrared bands in the C-O stretching region, leading to the conclusion that some sort of oxidative reaction occurs during milling. Additional study needs be performed to describe this system fully.
Furthering the Resurgence of Zinc Batteries in the Age of Rechargeability Through Scalable Anode Material Synthesis

(Georgia Institute of Technology, 2022-01-18) Wilson, Evan Nathaniel

Herein, two separate zinc anode projects are combined into one work. The overarching theme of this work is the focus on zinc anodes and the constraint of affordable precursor materials and scalable material processing with the goal of achieving commercializable performance. The first project is a carbon-coated \ce{ZnO} anode material for use in Ni-Zn alkaline rechargeable batteries. To achieve the desired morphology and functionality of the carbon coating, a two step process with spray drying and annealing was selected as the synthesis approach after reviewing the literature on scalable production of core-shell battery materials. The precursors selected for the carbon coating and zinc oxide were thermoset water-based polymer and zinc oxide nanoparticles, based on a review of the literature as well as the constraints inherent to the spray drying and annealing synthesis approach. Two candidate carbon precursors were attempted, however both had problems when used to make an ion-sieving carbon coating for zinc anodes. The first carbon precursor, polyurethane, had a poor coating quality with a pore structure that was too open, with wide pores allowing dissolved zinc species to escape, and with a poor electrical contact to the contained zinc oxide, resulting in poor zinc utilization. The second carbon precursor, resol, catalyzed hydrogen evolution, resulting in inefficient battery charging as well as self-discharge and mechanical degredation of the anode, all of which led to rapid capacity loss upon full-cell cycling. A different carbon precursor is needed to enable this technology, perhaps with a change in materials processing associated with the constraints of future promising carbon precursor materials. The second project is a porous 3D host material for zinc anodes, which includes an alloy-seeding approach which uses a thermodynamic advantage to direct the nucleation of zinc and maintain electrode structure over long-term cycling. The material was successfully synthesized and early testing showed much promise in the reversibility of the anode material, however the full-cell platform of neutral zinc-air with fluoridated electrolyte is relatively new and the available commercial air electrodes were not designed for either the presence of zinc ions in solution at high concentration or the high current density which the alloy-seeding 3D zinc host is capable of cycling with, and so the performance of the full cell was artificially limited, calling for more research in the future with a better cathode pairing. While both projects were not successful in achieving their performance goals, both technologies may yet be successful with additional research due to the sound nature of their underlying concepts.
Electrode Modifications for Improved Anion Exchange Membrane Water Electrolyzer Durability

(Georgia Institute of Technology, 2021-12-14) Dobbs, Alexandra

Within this dissertation electrode modifications for improved anion exchange membrane (AEM) electrolyzer durability are investigated. Ionic and inert catalyst binders were analyzed during electrolysis and the relationships between material properties and electrode stabilization or degradation are discussed. Systematic analysis of electrode formulations illuminates different catalyst deactivation mechanisms and potential solutions.
Surface Engineering of Protein Nanoclusters to Overcome Mucus Barriers

(Georgia Institute of Technology, 2021-11-01) Pho, Thomas

Intranasal delivery of vaccines is a needle-free route that can induce mucosal antibodies and cellular responses to neutralize pathogens before entering systemic circulation, as well as systemic immunity. However, nasal secretions and mucosa are biological barriers that have been shown to inhibit delivery of antigens and nanoparticles to nasal-associated lymphoid tissue. Coatings and surface modifications on nanoparticles can alter transport and immune responses due to their interaction with biological barriers and cells. Protein nanoclusters (PNC) are one type of vaccine nanoparticle, made from protein antigens, that can be modified to change size, surface charge, and surface chemistry. Specifically, this thesis explores the interactions of mucus and model ovalbumin antigen PNC displaying different surface covalent modifications and non-covalent layer by layer coatings. Transport of the PNC in extracted mucus was characterized using bulk channel diffusion to visualize population distributions and multiple particle tracking for single particle behavior analysis. Lastly, the protein corona of these nanoparticles are identified in nasal fluids to understand their potential in vivo interaction during intranasal delivery. Overall, this thesis demonstrates the impact that surface modifications have on protein nanoparticle vaccines to overcome mucus barriers and, ultimately, improve cellular uptake and immunological processing.
ATOMISTIC SIMULATIONS OF ATACTIC POLYPROPYLENE: INITIAL GUESS OPTIMIZATION AND LONG-RANGE CORRECTION EVALUATION

(Georgia Institute of Technology, 2021-10-01) Trevino Garrido, Nohemi Dxandi

It was shown by this research, that after about 75% of initial guess chain polymerization, chains would began to collapse into compact conformations due to the self-avoiding nature of the chains. This resulted in structural inaccuracies in the initial guess that would not be ameliorated by energy minimization or molecular dynamics. Thus, the effect of density on the structural and energetic components of initial guess generation was investigated in this research. Findings showed significant asymmetry in chains generated with the present established initial guess method. Additionally, cohesive energy density, diffusivity, and entanglement of atomistic models of atactic polypropylene are strongly sensitive to density changes and were improved at densities that were even higher than the experimental density. However, there were only slight changes to structural properties such as mean square radius of gyration, the characteristic ratio, and chain symmetry as density was modified. Additional initial guess methods were developed such as integrating minimization into the polymerization process, filtration of initial guesses based on their structural properties, multi-step minimization, an expanding periodic boundary method, and optimization of forcefield parameters for initial guess generation. Additionally, a simple, rapid, and empirical method was developed for calculating energy and pressure long-range corrections. This method involved iteratively replicating the periodic lattice of the polymer system and matching the cutoff to the new size of the system. Thus, the potential energy is dependent on the number of cells in the lattice and the potential energy eventually converged to provide the long-range corrections. The cohesive energy also converged since the isolated energy of the chains is a constant value and could thus also be rapidly calculated.