ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
Filtering by
- All Subjects: chemical engineering
- Creators: Green, Matthew
In this study, high quality graphene oxide membranes are synthesized on polyester track etch substrates by different deposition methods and characterized by XRD, SEM, AFM as well as single gas permeation and binary (H2/CO2) separation experiments. Membranes are made from large graphene oxide sheets of different sizes (33 and 17 micron) using vacuum filtration to shed more light on their transport mechanism. Membranes are made from dilute graphene oxide suspension by easily scalable spray coating technique to minimize extrinsic wrinkle formation. Finally, Brodie’s derived graphene oxide sheets were used to prepare membranes with narrow interlayer spacing to improve their (H2/CO2) separation performance.
An inter-sheet and inner-sheet two-pathway model is proposed to explain the permeation and separation results of graphene oxide membranes obtained in this study. At room temperature, large gas molecules (CH4, N2, and CO2) permeate through inter-sheet pathway of the membranes, exhibiting Knudsen like diffusion characteristics, with the permeance for the small sheet membrane about twice that for the large sheet membrane. The small gases (H2 and He) exhibit much higher permeance, showing significant flow through an inner-sheet pathway, in addition to the flow through the inter-sheet pathway. Membranes prepared by spray coating offer gas characteristics similar to those made by filtration, however using dilute graphene oxide suspension in spray coating will help reduce the formation of extrinsic wrinkles which result in reduction in the porosity of the inter-sheet pathway where the transport of large gas molecules dominates. Brodie’s derived graphene oxide membranes showed overall low permeability and significant improvement in in H2/CO2 selectivity compared to membranes made using Hummers’ derived sheets due to smaller interlayer space height of Brodie’s sheets (~3 Å).
DNA in mammalian cells was investigated. 3 plasmids, DH5-α, ER2925 and
GM272 were extracted and transformed from E. coli bacteria. DH5-α is the regular
methylated plasmid, however,ER2925 and GM272 lack Dam and Dcm enzymes which
methylate adenine and internal cytosine in prokaryotes respectively, hence they are
unmethylated. The 3 plasmids were delivered via different delivery vectors in two
cell lines, UMUC3 and MDA-MB-231 which are human bladder cancer cell line and
human triple negative breast cancer cell line, respectively.
Luciferase and BCA assay were carried out to quantify transgene expression to
compare the efficacy of gene delivery in three aforementioned plasmids. In addition,
hydrodynamic diameter and zeta potential was measured for all delivery vectors, to
correlate with other transgene expression data. The results show that methylated
plasmid has significantly higher transgene expression in mammalian cell lines. This
can be either a result of smaller size and more positive zeta potential that the methylated
plasmid had, or a result of having Dam and Dcm enzymes which enhance binding
of DNA and transcription factors and enhance gene expression. Having smaller size
and more positive zeta potential was proven to be the case for the methylated plasmid
in this study. However the latter hypothesis should be investigated furthermore.
The accelerated UV testing was performed in a UV chamber equipped with UV lights at an ambient temperature of 50°C, little or no humidity and total UV dosage of 400 kWh/m2. The mini-modules were maintained at three different temperatures through UV light heating by placing different thickness of thermal insulation sheets over the backsheet. Also, prior to thermal insulation sheet placement, the backsheet and laminate edges were fully covered with aluminum tape to prevent oxygen diffusion into the module and hence the photobleaching reaction.
The characterization results showed that mini-modules with UV-cut EVA suffered from discoloration while the modules with UV-pass EVA suffered from delamination. UVf imaging technique has the capability to identify the discoloration region in the UVC modules in the very early stage when the discoloration is not visible to the naked eyes, whereas Isc measurement is unable to measure the performance loss until the color becomes visibly darker. YI also provides the direct evidence of yellowing in the encapsulant. As expected, the extent of degradation due to discoloration increases with the increase in module temperature. The Isc loss is dictated by both the regions – discolored area at the center and non-discolored area at the cell edges, whereas the YI is only determined at the discolored region due to low probe area. This led to the limited correlation between Isc and YI in UVC modules.
In case of UVP modules, UV radiation has caused an adverse impact on the interfacial adhesion between the EVA and solar cell, which was detected from UVf images and severe Isc loss. No change in YI confirms that the reason for Isc loss is not due to yellowing but the delamination.
Further, the activation energy of encapsulant discoloration was estimated by using Arrhenius model on two types of data, %Isc drop and ΔYI. The Ea determined from the change in YI data for the EVA encapsulant discoloration reaction without the influence of oxygen and humidity is 0.61 eV. Based on the activation energy determined in this work and hourly weather data of any site, the degradation rate for the encaspulant browning mode can be estimated.
The first technique involves imbedding sorbent particles inside the fibers: forming particle-embedded fibers. It is demonstrated that particles will spontaneously coat themselves in the fibers at dilute loadings, but at higher loadings some get trapped on the fiber surface. A mathematical model is used to show that when these particles are embedded, the polymeric coating provided by the fibers may be designed to increase the kinetic selectivity and/or stability of the embedded sorbents. Two proof-of-concept studies are performed to validate this model including the increased selectivity of carbon dioxide over nitrogen when the MOF ZIF-8 is embedded in a poly(ethylene oxide) and Matrimid polymer blend; and that increased hydrothermal stability is realized when the water-sensitive MOF HKUST-1 is embedded in polystyrene fibers relative to pure HKUST-1 powder.
The second technique involves the creation of a pore network throughout the fiber to increase accessibility of embedded sorbent particles. It is demonstrated that the removal of a blended highly soluble polymer additive from the spun particle-containing fibers leaves a pore network behind without removing the embedded sorbent. The increased accessibility of embedded sorbents is validated by embedding a known direct air capture sorbent in porous electrospun fibers, and demonstrating that they have the fastest kinetic uptake of any direct air capture sorbent reported in literature to date, along with over 90% sorbent accessibility.
First, a logical categorization of potential adsorptive separation mechanisms in MOFs is outlined by comparing existing data with previously studied materials. Size-selective adsorptive separation is investigated for both gas systems using molecular simulations. A correlation between size-selective equilibrium adsorptive separation capabilities and pore diameter is established in materials with complex pore distributions. A method of generating mobile extra-framework cations which drastically increase adsorptive selectivity toward nitrogen over oxygen via electrostatic interactions is explored through experiments and simulations. Finally, deposition of redox-active ferrocene molecules into systematically generated defects is shown to be an effective method of increasing selectivity towards oxygen.
This work compares EVA encapsulant degradation in glass/backsheet and glass/glass field-aged PV modules. EVA was extracted from three field-aged modules (two glass/backsheet and one glass/glass modules) from three different manufacturers from various regions (cell edges, cell centers, and non-cell region) from each module based on their visual and UV Fluorescence images. Characterization techniques such as I-V measurements, Colorimetry, Different Scanning Calorimetry, Thermogravimetric Analysis, Raman spectroscopy, and Fourier Transform Infrared Spectroscopy were performed on EVA samples.
The intensity of EVA discoloration was quantified using colorimetric measurements. Module performance parameters like Isc and Pmax degradation rates were calculated from I-V measurements. Properties such as degree of crystallinity, vinyl acetate content and degree of crosslinking were calculated from DSC, TGA, and Raman measurements, respectively. Polyenes responsible for EVA browning were identified in FTIR spectra.
The results from the characterization techniques confirmed that when EVA undergoes degradation, crosslinking in EVA increases beyond 90% causing a decrease in the degree of crystallinity and an increase in vinyl acetate content of EVA. Presence of polyenes in FTIR spectra of degraded EVA confirmed the occurrence of Norrish II reaction. However, photobleaching occurred in glass/backsheet modules due to the breathable backsheet whereas no photobleaching occurred in glass/glass modules because they were hermetically sealed. Hence, the yellowness index along with the Isc and Pmax degradation rates of EVA in glass/glass module is higher than that in glass/backsheet modules.
The results implied that more acetic acid was produced in the non-cell region due to its double layer of EVA compared to the front EVA from cell region. But, since glass/glass module is hermetically sealed, acetic acid gets entrapped inside the module further accelerating EVA degradation whereas it diffuses out through backsheet in glass/backsheet modules. Hence, it can be said that EVA might be a good encapsulant for glass/backsheet modules, but the same cannot be said for glass/glass modules.
This dissertation bridges the food industry, material sciences, device fabrication, and biomedical engineering by demonstrating edible supercapacitors and electronic components and devices such as pH sensor.
Edible supercapacitors were fabricated using food materials from grocery store. 5 of them were connected in series to power a snake camera. Tests result showed that the current generated by supercapacitor have the ability to kill bacteria. Next more food, processed food and non-toxic level electronic materials were investigated. A “preferred food kit” was created for component fabrication based on the investigation. Some edible electronic components, such as wires, resistor, inductor, etc., were developed and characterized utilizing the preferred food kit. These components make it possible to fabricate edible electronic/device in the future work. Some edible electronic components were integrated into an edible electronic system/device. Then edible pH sensor was introduced and fabricated. This edible pH sensor can be swallowed and test pH of gastric fluid. PH can be read in a phone within seconds after the pH sensor was swallowed. As a side project, an edible double network gel electrolyte was synthesized for the edible supercapacitor.
In this thesis, a series of silicone surfactant graft copolymers were synthesized via hydrosilylation reaction. Poly(ethylene glycol) (PEG) of different chain length was grafted to a hydrophobic Poly(methylhydrosiloxane) (PMHS) backbone to improve the final hydrophilicity. Also, a positively charged quaternary ammonium salt (allyltriethylammonium bromide) was grafted to the PMHS backbone. The objective of this thesis was to synthesize polymers in predefined ratios of the above mentioned side groups and utilize these polymers to-
1) Study the effect of PEG chain length and its composition on the hydrophilicity of the polymer.
2) Study the effect of PEG: ammonium salt ratio on the surface tension of aqueous systems.
Analysis of FT-IR and 1H NMR spectra of the polymers confirmed the predicted structure. The absence of characteristic Si-H absorbance peak at 2160 cm-1 in FT-IR spectra indicates consumption of silane groups along the polymer backbone. The actual moles of the side chain grafted on the backbone are calculated by 1H NMR peak integration. The results of contact angle studies indicated an increase in hydrophilicity with an increase in the composition of PEG in molecule. A 2*2 factorial DOE analysis reported that the fraction of Si-H bonds converted to PEG grafts was the critical factor towards increasing the hydrophilicity (p value of 0.015). Surface tension studies report that the air-water interfacial tension of the synthesized polymers is between 28mN/m – 45mN/m. The amount of Si-H was concluded to be the deciding factor in lowering the surface tension.
In this work, a number of kinase enzymes have been identified by inhibition to be targets for enhancing polymer-mediated transgene expression (chapter 2), including the lead target which appears to affect intracellular trafficking of delivered nucleic acid cargo. The subsequent sections (chapters 3 and 4) of this work focus on targeting epigenetic modifying enzymes to enhance polymer-mediated transgene expression, and a number of candidate enzymes have been identified. Some mechanistic evaluation of these targets have been carried out and discussion of ongoing experiments and future directions to better understand the mechanistic descriptions behind the phenomena are discussed. The overall goal is to enhance non-viral (polymer-mediated) transgene expression by modulating cellular behavior for general gene delivery applications.