Polymer and Organic Materials Commons^™

Hierarchical Structure And Material Integration For Electrocatalytic Co2 Reduction, Hamed Mehrabi

Graduate Theses and Dissertations

CO2 released by the combustion of fossil fuels is driving significant changes to the earth’sclimate. The natural cycle for removing CO2 from the atmosphere, namely photosynthesis, cannot keep up with the rate at which it is being added. Developing engineering approaches to remove CO2 from the atmosphere is becoming essential to reduce these effects. Removal leads to further issues of carbon sequestration and favorable CO2 reuse strategies, including the electrochemical transformation of recovered CO2 to useful products such as fuels and materials. Copper is an important electrocatalyst for the CO2 reduction reaction (CO2RR) because of its unique capability for producing …

Fabrication And Non-Covalent Functionalization And Characterization Of Graphene-Based Devices On Novel Substrate Cadmium Trithiophosphate (Iv) — Cdps, Abayomi Omotola Omolewu

Graduate Theses and Dissertations

With graphene at the center of several application areas such as sensing, circuits, high-frequency devices for communication systems, etc., it is crucial to understand how the intrinsic properties of devices made from graphene and other materials like platinum and palladium nanoparticles affect the performance of such devices for the specific application area. Many graphene-based devices for different application areas have focused mainly on the material composition of the graphene-based devices and how it affects performance parameters for the specific application. However, it would be insightful to understand how the intrinsic electrical properties of the graphene devices for different applications affect …

Synthesis Of Polyethylene Glycol-Based Hydrogels And Silver/Gold Nanostructures For Biomedical Applications, Isabelle Ishimwe Niyonshuti

Graduate Theses and Dissertations

This work focuses on the synthesis of biocompatible polyethylene glycol (PEG)-based hydrogels, silver nanoparticles (AgNPs), and silver-gold nanocages (Ag-AuNCs) for biomedical applications. The dissertation includes two parts with Part I on the work of PEG-based hydrogel for wound healing applications and Part II on the work of Ag/Au nanostructures for antimicrobial applications. Part I studies PEG-based hydrogel for the delivery of fibroblast growth factors (FGFs) for wound healing applications, aiming to overcome the challenge of designing hydrogels capable of the sustained release of bioactive FGFs. This research develops new biocompatible anionic injectable hydrogel formulations based on Poly (Oligo Ethylene Glycol …

Investigation Of Optical And Structural Properties Of Gesn Heterostructures, Oluwatobi Gabriel Olorunsola

Graduate Theses and Dissertations

Silicon (Si)-based optoelectronics have gained traction due to its primed versatility at developing light-based technologies. Si, however, features indirect bandgap characteristics and suffers relegated optical properties compared to its III-V counterparts. III-Vs have also been hybridized to Si platforms but the resulting technologies are expensive and incompatible with standard complementary-metal-oxide-semiconductor processes. Germanium (Ge), on the other hand, have been engineered to behave like direct bandgap material through tensile strain interventions but are well short of attaining extensive wavelength coverage. To create a competitive material that evades these challenges, transitional amounts of Sn can be incorporated into Ge matrix to form …

Tribological Studies Of Thick Polytetrafluoroethylene Coatings Enhanced By Polydopamine And Nanoparticles, Sujan Kumar Ghosh

Graduate Theses and Dissertations

Polytetrafluoroethylene (PTFE) is a popular low friction solid lubricant with high chemical and thermal stability. Thick PTFE coatings have the potential for many tribological applications, such as replacing Tin-based Babbitt materials in journal bearings. However, the weak bonding strength to the substrate and the high wear rate of PTFE coatings are current limiting factors. The lack of understanding of their tribological properties and wear mechanisms in oil-lubricated conditions and how coating thickness affects the tribological performance further hindered the use of PTFE coatings. In this dissertation, polydopamine (PDA), a bio-inspired adhesive, is used as an underlayer for or as a …

Phase-Field Modeling Of The Polymer Membrane Formation Process For Micro- And Ultra-Filtration, Michael Rosario Cervellere

Graduate Theses and Dissertations

Porous polymer membrane filters are widely used in separation and filtration process. Micro- and ultra-filtration membranes are commonly used in biopharmaceutical applications such as filtering viruses and separating proteins from a carrier solution. The formation of these membrane filters via phase inversion is a complex and interconnected process where varying casting conditions can have a wide variety of effects on the final membrane morphol- ogy. Tailoring membrane filters for specific performance characteristics is a tedious and time consuming process. The time and length scales of membrane formation make it extremely difficult to experimentally observe membrane formation. Modeling the membrane formation …

Investigation Of Membrane Based Processes For Biomedical Applications, Efecan Pakkaner

Graduate Theses and Dissertations

As substantial developments were achieved in nanotechnology and polymer engineering, especially in the last few decades, the use of membranes and membrane-based procedures was found to be expanding into more and more research and development areas; including biological engineering, life sciences and biomedical engineering. Not only have they been the main focus of meaningful research, but they have also been the main pieces of the solutions to very thorny problems encountered within a wide range of applications from microfluidics to water treatment, thanks to their versatility, cost-effectiveness and biocompatibility, when compared to conventional separation techniques. To celebrate and embrace these …

Oxone® Mediated Tempo-Oxidized Cellulose Nanomaterials: Material Characterization, Ultrafiltration Membrane Separations, And Thin Film Composite Gas Transport Analysis, John Phillips Moore

Graduate Theses and Dissertations

Cellulose nanomaterials (CNMs) are derived from plant matter and are comprised of nanoscopic cellulose crystals and fibers. They have a diverse set of applications, from cosmetics to oil recovery. This study focuses on the properties of Oxone® mediated TEMPO-oxidized cellulose nanomaterials (OTO-CNMs) and their use in controlling the transport properties of polymeric substrates. Synthesis and characterization of cellulosic nanoparticles have resulted in the creation of OTO-CNMs with properties that increase hydrophilicity. With added hydrophilicity, OTO-CNMs possess lower fouling propensity, making them ideal membrane additive for transport limited separations such as hemodialysis.

To utilize the material and unique properties thereof, this …

Biopolymeric Materials For Tissue Regeneration, Cell Manufacturing, And Drug Delivery, David Alfonso Castilla-Casadiego

Graduate Theses and Dissertations

The development of materials for tissue regeneration, cell manufacturing, and drug delivery is possible by the manipulation of polymer properties and the use of three different techniques including layer-by-layer, electrospinning, and molding technique.

By applying the layer-by-layer technique over biomaterials, it is possible to develop polymeric multilayers that promote a more favorable environment for cellular functionality, increasing the possibility of improving their acceptance in the area of implantation. IRVASE demonstrated being a powerful technique that allows for a reliable characterization of the physical-chemical and thermal properties of the fabricated surfaces. This opens the possibility to monitor the design of surfaces …

Peptoid-Based Microsphere Coatings For Biomaterial Applications, Jesse Leland Roberts

Graduate Theses and Dissertations

Peptoids are peptidomimetic oligomers that predominantly harness similarities to peptides for biomimetic functionality. The incorporation of chiral, aromatic side chains in the peptoid sequence allows for the formation of distinct secondary structures and self-assembly into supramolecular assemblies, including microspheres. Peptoid microspheres can be coated onto substrates for potential use in biosensor technologies, tissue engineering platforms, and drug-delivery systems. They have the potential for use in biomedical applications due to their resistance to proteolytic degradation and low immunogenicity. This dissertation focuses on the physical characteristics and robustness of the peptoid microsphere coatings in various physiological conditions, along with their ability to …

Development Of Biomaterials For Drug Delivery, Raquel De Castro

Graduate Theses and Dissertations

Drug delivery systems (DDS) have highly evolved in the last decades with the development of hydrogels and nanoparticles. However, high systemic uptake, side effects, low bioavailability, and encapsulation efficiency continue to be a major hurdle faced by such DDSs.

Nanoparticles and hydrogels can be specifically designed for targeted DDSs to mitigate some of the problems. This dissertation aimed to design two DDSs for ocular drug delivery and one for cancer treatment. The first project sought to develop chitosan nanoparticles (Cs-NP) using PEGDA as a copolymer to encapsulate gentamicin (GtS) for ocular drug delivery. Cs-NPs contain positive charges that can interact …

Characterization Of Gesn Semiconductors For Optoelectronic Devices, Hryhorii Stanchu

Graduate Theses and Dissertations

Germanium-tin alloys with Sn compositions higher than 8 at. % to 10 at. % have recently attracted significant interest as a group IV semiconductor that is ideal for active photonics on a Si substrate. The interest is due to the fact that while at a few percent of Sn, GeSn is an indirect bandgap semiconductor, at about 8 to 10 at. % Sn, GeSn transitions to a direct bandgap semiconductor. This is at first surprising since the solid solubility of Sn in Ge under equilibrium growth conditions is limited to only about 1 at. %. However, under non-equilibrium growth conditions, …

Adhesion And Deformation Mechanisms Of Polydopamine And Polytetrafluoroethylene: A Multiscale Computational Study, Matthew Brownell

Graduate Theses and Dissertations

Polydopamine (PDA) has been shown to bond via covalent bonding, van der Waals forces, and hydrogen bonding and is known to adhere strongly to almost any material. The application of PDA between a substrate and a PTFE surface coating has resulted in low friction and a greatly reduced wear rate. Previous research probing the capabilities and limitations of PDA/PTFE films have studied the wear and mechanical properties of the film, but the overall adhesive and deformation mechanisms remain unclear.

In this research, we investigate the tribological properties of PDA and PTFE molecules and composites from the atomic to the microscale …

Growth And Characterization Of Semiconductor Materials And Devices For Extreme Environments Applications, Abbas Sabbar

Graduate Theses and Dissertations

Numerous industries require electronics to operate reliably in harsh environments, such as extreme high temperatures (HTs), low temperature (LT), radiation rich environments, multi-extreme, etc. This dissertation is focused on two harsh environments: HT and multi-extreme.

The first study is on HT optoelectronics for future high-density power module applications. In the power modules design, galvanic isolation is required to pass through the gate control signal, reject the transient noise, and break the ground loops. The optocoupler, which consists of a lighting emitting diode (LED) and photodetector (PD), is commonly used as the solution of galvanic isolation at room temperatures. There is …

Peptoid And Antibody-Based Gfp Sensors, Solomon Isu

Graduate Theses and Dissertations

In this work, we have made and characterized a pair of immunobiosensors for detecting the green fluorescent protein (GFP) in an aqueous matrix. An anti-GFP antibody-based biosensor was assembled to detect GFP, while a novel peptoid (N-substituted oligomers of glycine designated as IOS-1) biosensor was also assembled for GFP detection. A quartz crystal microbalance (QCM) gold sensor was used as the supporting substrate for self-assembly of the immunobiosensors. Gravimetric measurements of the QCM gold sensor during immunobiosensor construction and operation were available in real-time using a QCM instrument. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Fluorescence microscopy were used …

A Study Of Protein And Peptide-Directed Nanoparticle Synthesis For Catalytic Materials, Abdollah Mosleh

Graduate Theses and Dissertations

Nanoparticles have received much attentions due to their unique properties that makes them suitable candidates for a broad range of applications. As the size of particles decreases, their surface area-to-volume ratio would increase which is the main cause of much attention. In addition to the size, their morphologies and compositions may also play important roles for defining unique properties. Nanoparticle synthesis include both bottom-up and top-down strategies. To control the process of inorganic nanoparticles synthesis one could follow the bottom-up approach to have atom-level control over their compositions, morphologies, phases, and sizes which is the subject of this work. Due …

Investigation Of Critical Technologies Of Chemical Vapor Deposition For Advanced (Si)Gesn Materials, Joshua Matthew Grant

Graduate Theses and Dissertations

The development of new materials for efficient optoelectronic devices from Group IV elements is the heart of Group IV photonics. This has direct ties to modern technology as the foundation for the electronics industry is silicon. This has driven the development of silicon-based optoelectronics using these other Group IV materials as silicon is a poor optical material due to its indirect band gap when compared to the III-V semiconductors that are used by most of the optoelectronics industry. While efforts have been made to integrate III-V materials onto silicon substrates, the incompatibility with the complementary metal oxide semiconductor process has …

Effects Of Surface-Directed Spinodal Decomposition On Binary Thin-Film Morphology, Michael Brian Wise

Graduate Theses and Dissertations

Preferential wetting can have a significant impact on the kinetics of phase separation in certain systems. The depletion of the wetting component can simply alter domain growth rates or change the structure entirely. In this thesis, we employ a Cahn-Hilliard model to study the evolution of binary thin-films with symmetric surface wetting. Three possible morphologies were identified: discrete, bicontinuous, and a novel quasi-2D bicontinuous structure in which both phases retain continuity throughout the volume as well as on the center xy plane. Using a continuity factor, regions of film thickness versus blend composition were classified as producing a certain morphology. …

Mesoscale Computational Studies Of Thin-Film Bijels, Joseph M. Carmack

Graduate Theses and Dissertations

Bijels are a relatively new class of soft materials that have many potential applications in the technology areas of energy, medicine, and environmental sustainability. They are formed by the arrest of binary liquid spinodal decomposition by a dispersion of solid colloidal nanoparticles. This dissertation presents an in-depth simulation study of Bijels constrained to thin-film geometries and in the presence of electric fields. We validate the computational model by comparing simulation results with previous computational modeling and experimental research. In the absence of suspended particles, we demonstrate that the model accurately captures the rich kinetics associated with diffusion-based surface-directed spinodal decomposition. …

Structure And Property Of Polymers And Biopolymers From Molecular Dynamic Simulations, Xiaoquan Sun

Graduate Theses and Dissertations

Natural and synthetic polymers and biopolymers have been studied for a variety of applications in food emulsion, biopharmaceutical purification, tissue engineering, and biosensor. The structure and property of polymers and biopolymers are critically important to determine their functions. Molecular dynamics (MD) simulations have a unique advantage to explore the structure and property of polymers and biopolymers from the molecular level. In the dissertation, MD simulations were conducted to study the mechanisms of various biological and chemical processes controlled by polymers and biopolymers based on real-world experimental results.

Seven heptapeptides have been screened from a peptide library in our earlier study …

Phase Transitions In Monochalcogenide Monolayers, Mehrshad Mehboudi

Graduate Theses and Dissertations

Since discovery of graphene in 2004 as a truly one-atom-thick material with extraordinary mechanical and electronic properties, researchers successfully predicted and synthesized many other two-dimensional materials such as transition metal dichalcogenides (TMDCs) and monochalcogenide monolayers (MMs). Graphene has a non-degenerate structural ground state that is key to its stability at room temperature. However, group IV monochalcogenides such as monolayers of SnSe, and GeSe have a fourfold degenerate ground state. This degeneracy in ground state can lead to structural instability, disorder, and phase transition in finite temperature. The energy that is required to overcome from one degenerate ground state to another …

Self-Assembled Barium Titanate Nanoscale Films By Molecular Beam Epitaxy, Timothy Allen Morgan

Graduate Theses and Dissertations

One challenge of investigating ferroelectrics at the nanoscale has been controlling the stoichiometry during growth. Historically, the growth of barium titanate (BaTiO3) by molecular beam epitaxy has relied on a growth technique called shuttered RHEED. Shuttered RHEED controls the stoichiometry of barium titanate through the precise deposition of alternating layers of BaO and TiO2. While this approach has achieved 1% control of stoichiometry, finding self-limiting mechanisms to lock-in stoichiometry has been the focus of the growth community. The Goldschmidt tolerance factor predicts an unstable perovskite when barium sits in the titanium lattice site. The BaO-TiO2 phase diagram predicts a low-solubility …

Membranes For Food And Bioproduct Processing, Alexandru Marius Avram

Graduate Theses and Dissertations

Modified membranes for process intensification in biomass hydrolysis

Production of biofuels and chemicals from lignocellulosic biomass is one of the leading candidates for replacement of petroleum based fuels and chemicals. However, conversion of lignocellulosic biomass into fuels and chemicals is not cost effective compared to the production of fuels and chemicals from crude oil reserves. Some novel and economically feasible approaches involve the use of ionic liquids as solvents or co-solvents, since these show improved solvation capability of cellulose over simple aqueous systems. Membranes offer unique opportunities for process intensification which involves fractionation of the resulting biomass hydrolysate leading to …

The Effect Of Process Parameters And Surface Condition On Bond Strength Between Additively Manufactured Components And Polymer Substrates, Bharat Bhushan Chivukula

Graduate Theses and Dissertations

Additive patching is a process in which printers with multiple axes deposit molten material onto a pre-defined surface to form a bond. Studying the effect of surface roughness and process parameters selected for printing auxiliary part on the bond helps in improving the strength of the final component. Particularly, the influence of surface roughness, as established by adhesion theory, has not been evaluated in the framework of additive manufacturing (AM). A full factorial design of experiments with five replications was conducted on two levels and three factors, viz., layer thickness, surface roughness, and raster angle to examine the underlying effects …

Interactive Physics And Characteristics Of Photons And Photoelectrons In Hyperbranched Zinc Oxide Nanostructures, Garrett Edward Torix

Graduate Theses and Dissertations

As is commonly known, the world is full of technological wonders, where a multitude of electronic devices and instruments continuously help push the boundaries of scientific knowledge and discovery. These new devices and instruments of science must be utilized at peak efficiency in order to benefit humanity with the most advanced scientific knowledge. In order to attain this level of efficiency, the materials which make up these electronics, or possibly more important, the fundamental characteristics of these materials, must be fully understood. The following research attempted to uncover the properties and characteristics of a selected family of materials. Herein, zinc …

Metal Assisted Nanowire Growth For Silicon Nanowire/Amorphous Silicon Composite Solar Cell, Asmaa Ali Sadoon

Graduate Theses and Dissertations

Solar cells are photovoltaic devices that convert the energy of light to electricity by the photovoltaic effect. Crystalline silicon-based solar cells are the most dominant solar cells in the market today due to the high efficiency and relatively low cost. However, the cost of such solar cell is still high due to the large amount of material that is consumed in fabricating such a device. Polycrystalline/amorphous thin films and nanomaterial technologies have emerged to reduce the high cost of c-Si based solar cells and increase the efficiency. In this research, we combined these two technologies to propose and fabricate silicon …

Wear Resistant Polydopamine/Ptfe Nanoparticle Composite Coating For Dry Lubrication Applications, Samuel George Beckford

Graduate Theses and Dissertations

This dissertation presents an investigation into the effect of nanoparticle fillers and a polydopamine adhesive primer on the tribological performance of thin PTFE films. The principal objective of this investigation was to reduce wear in PTFE films, an issue which precludes the use of PTFE films in tribological applications requiring high durability. The friction and wear of the composite films were evaluated using a ball-on-flat configuration in linear reciprocating motion. It was found that the use of a polydopamine adhesive primer reduces the wear of PTFE films more than 600 times. X-ray photoelectron spectroscopy (XPS) results show that a tenacious …

Phase Transformation In Monolayer Molybdenum Disulphide With And Without Defects Under Tension Predicted By Atomistic Simulations, Khanh Quoc Dang

Graduate Theses and Dissertations

In addition to its use as a solid lubricant, molybdenum disulphide (MoS2) has gained recent attention as a possible substitute for silicon as it is increasingly difficult to keep shrinking down electronic devices made of silicon, the conventional electronic material. When thinned down to atomic thickness, monolayer MoS2 possesses very unique and promising electronic and electrical properties. Unlike electronic and electrical properties, knowledge of the mechanical properties and role of structural defects on these properties of monolayer MoS2 is unexplored. For this thesis, the two main objectives are (1) to gain insight about the failure mechanism of monolayer MoS2 by …

Friction And Wear Of Polytetrafluoroethylene/Graphene Oxide Composite Thin Films, Justin Kyle Carter

Graduate Theses and Dissertations

Polytetrafluoroethylene (PTFE) is a commonly used solid lubricant due to its low coefficient of friction and chemical inertness. As a polymer, PTFE suffers from high wear and low adhesion to substrates limiting its use as a thin film. Thin PTFE films are ideal candidates for solid lubrication in micro-machines and bearing applications. The main goal of this work is to enhance the durability of thin PTFE films through the addition of few layered graphene oxide (GO) as filler. In order to address adhesion issues, the addition of an adhesive layer of polydopamine (PDA) between stainless steel substrates and thin PTFE …

Crack Growth Behavior Under Creep-Fatigue Conditions Using Compact And Double Edge Notch Tension-Compression Specimens, Santosh B. Narasimha Chary

Graduate Theses and Dissertations

The American Society for Testing and Materials (ASTM) has recently developed a new standard for creep-fatigue crack growth testing, E 2760-10, that supports testing compact specimens, C(T), under load controlled conditions. C(T) specimens are commonly used for fatigue and creep-fatigue crack growth testing under constant-load-amplitude conditions. The use of these specimens is limited to positive load ratios. They are also limited in the amount of crack growth data that can be developed at high stress intensity values due to accumulation of plastic and/or creep strains leading to ratcheting in the specimen. Testing under displacement control can potentially address these shortcomings …