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Now showing 1 - 10 of 13

The Use of Selective Polymerization of Poly(Methyl Methacrylate) for Area-Selective Masking of Nanoscale Semiconductors

(Georgia Institute of Technology, 2019-08) Weiss, Trent

Nanowire transistor research has intensified in the past two decades due to the need for a novel idea to improve upon shortcomings associated with the modern transistor. A prevailing shortcoming in conventional transistor fabrication is limited throughput due to top-down fabrication steps such as lithography. One solution of interest is the nanowire heterostructure transistor which is fabricated in a bottom-up approach and leverages selective surface chemistry to controllably mask specific segments of the structure. The purpose of this work is to use polymers for selective surface chemical treatment on semiconductors enabling selective deposition or annealing of a dielectric by masking specific substrate chemistries. This occurs in a bottom-up fabrication process. The dielectric will act as the gate oxide for a nanowire transistor. Prior research has indicated that polymers can prevent various molecules from reaching a substrate surface due to their dense network. In this study, atom transfer radical polymerization is utilized to create a soft mask that is selective to silicon. The polymer of interest, poly(methyl methacrylate), is grown on initiating groups anchored to a silicon surface to attain a desired thickness. The intermediate steps are optimized for the best possible performance. The polymer is then subjected to atomic layer deposition with aluminum oxide to determine the stability of the polymer and its practicality as a mask for oxide deposition. These experiments may elucidate a method for gate oxide formation on a nanowire heterostructure. Success could have significant impact on this field and would be the next step to attaining functioning nanowire transistors for use in everyday devices.
Use of recycled linear low-density polyethylene carbon in Li-ion anodes

(Georgia Institute of Technology, 2019-05) Mathur, Aarti

Lithium-ion batteries are commonly used in many small electronics around the world. Efforts to make components of Li-ion batteries more sustainable have ranged from use of a brown algae extract in Li-ion anodes to efforts to recycle lithium. Linear-low density polyethylene (LLDPE) has been shown to exhibit the strong conductive properties required of a conductive agent in a Li-ion anode and can be made from recycled waste plastics such as cling wrap and poly-gloves. Electrodes were fabricated using polyethylene glycol (PEG) coated magnetite as the active material, PPBT polymeric binder, and LLDPE Carbon. Electrodes made with 14.3 wt.% LLDPE did not cycle well and exhibited a poor morphology with a cracked surface and large aggregates. Simple conductivity testing using a 4-point probe and profilometry measurements showed that Super-P was orders of magnitude more conductive than LLDPE. Increasing the carbon loading to 33.3 wt.% LLDPE in the electrode drastically improved rate capabilities and capacity retention. SEM analysis showed that a higher carbon loading of LLDPE had a better morphology overall and demonstrated less cracking. However, when compared to Super-P, the electrode had larger aggregates and a higher density of clumping. EDX SEM imaging and elemental (Fe, O, C) image mapping confirmed the presence of Fe3O4 nanoparticles, carbon additives, and PPBT binder. XPS analysis after 100 cycles confirmed the presence of an SEI layer in the LLDPE electrode. XPS on electrode slurries showed the presence of satellite peaks which confirm interactions between the polymeric binder and active material surface, regardless of carbon used. EIS testing provided information on the charge transfer resistances of Super-P and LLDPE which was consistent with the cycling trends. Overall, use of LLDPE in Li-ion batteries has been shown to work in a half-cell assembly. The performance of LLDPE does not beat the current industry standard, Super-P, but demonstrates promise for use after further optimization and analysis.
Porous Matrimid Support Membranes for Organic Solvent Separations

(Georgia Institute of Technology, 2019-05) Moschella, Emily S.

Porous Matrimid® polymeric membranes were developed as supports for thin film composites (TFCs) of dense, selective polymers to target organic solvent separations. Selective polymers form dense membranes and must be thinly coated on porous supports to obtain high permeances (pressure-normalized fluxes) of target solvents. The goal of this work was to develop support membranes that demonstrated excellent stability in organic solvents and sufficient porosity to allow toluene permeances of 60-200 Lm-2h-1bar-1 such that a composite has permeance of 0.1-1Lm-2h-1bar-1. A final objective was to quantify the effects of production conditions on membrane morphology and performance. Polymer ‘dopes’ (homogeneous polymer solutions) of Matrimid® containing varying compositions of solvent and non solvent were cast using the phase inversion technique. The resulting flat membranes were then crosslinked to prevent dissolution in harsh solvents. The desired permeance was achieved with a precise control over the dope compositions and production conditions. The impact of several casting parameters such as co-solvent evaporation time, ambient humidity, and post-processing procedures were studied. Generally, a decrease in permeance was observed as the drying time prior to phase inversion was increased. Average permeance at the optimized dope composition was 76.4 Lm-2h-1bar-1, with a standard deviation of 62.5 Lm-2h-1bar-1. The effect of different crosslinkers on membrane swelling and permeability was quantified, with 1,6-hexanediamine emerging as the most suitable crosslinker. Gas porosimetry was used to determine surface pore size, which was found to generally increase with permeance.
CO2 Capture Using 3D Printed PIM-1 Incorporating Solid Adsorbents

(Georgia Institute of Technology, 2018-05) Sidhu, Nathan A.

Rising atmospheric CO2 concentration has exceeded nature’s carbon recycling capacity and caused severe environmental hazards. To capture CO2 from point sources and from atmospheric air, various solid CO2 adsorbents, including zeolites, metal organic frameworks (MOFs) and immobilized amines, have been developed. While this has been a promising development, the discrete nature of the solid adsorbents limits their applications without the use of a substrate. To reduce energy cost of direct air capture, it is important to develop a structured adsorbent with both high adsorbent efficiency and low gas pressure drop. In this work, we proposed a 3D-printing technique to manufacture a structured CO2 adsorbent, in which a solid adsorbent is supported by a highly permeable polymer with intrinsic microporosity (PIM-1). This method of adsorbent development allows for customizable substrate patterning and sizing, thereby allowing for the transport properties through the adsorbent to be tuned. Compared with existing 3D-printing techniques for structured adsorbent manufacture, our technique features mild activation conditions and low internal mass transfer resistance. The solid adsorbents selected for the study include Mg-MOF-74, HKUST-1, and Zeolite 13X. Rheological studies were performed to determine the optimal loading compositions for the polymer-adsorbent inks and these inks were successfully printed.
Effects of solution concentration on properties of P3HT films

(Georgia Institute of Technology, 2018-05) Keane, Daniel P

Past experiments have studied Poly(3-hexylthiophene-2,5-diyl) (P3HT) by examining the roles of parameters including molecular weight, aggregation methods, and dispersion method on device performance. However, the role of the P3HT solution concentration on the polymer’s properties are not fully understood. This research examined the role of polymer solution concentration on the properties of UV-treated P3HT. P3HT of two different molecular weights was examined, and three different concentrations each were examined for each weight. To characterize a given weight-concentration combination, electrical capabilities of the films were measured on FETs, UV-vis measurements were taken of solution and films, and films were examined under Atomic Force Microscopy (AFM). The results suggest that the long-range order of P3HT films is closely related to the solution concentration. For films created from higher solution concentrations, more fibers in films of P3HT are aligned in the same direction and a larger fraction of polymer in the solution is aggregated. Of the three solution concentrations tested, the middle concentrations performed the best electrically, suggesting that solubility factors, chain count, and viscosity strongly affect the resulting film’s properties.
Synthesis and Optimization of Poly(Nickel-Ethylenetetrathiolate) for High Performance n-Type Thermoelectric Polymers

(Georgia Institute of Technology, 2017-05) Eng, Arnold Jesse

Thermoelectric generators directly convert heat into electricity via the Seebeck effect, which creates a voltage in response to an applied temperature gradient. Thermoelectric generators have been limited to niche applications due to their high system costs. Electrically conducting polymers are an attractive class of materials, particularly for low-grade waste heat recovery applications. Furthermore, they are inexpensive owing to their abundance and potential to process from solution via printing techniques, and they have an inherently low thermal conductivity. Thermoelectric polymers are often compared by their power factor, which is a function of the electrical conductivity and the Seebeck coefficient. In this work, I investigate the thermoelectric properties of metallo-organic poly[Kx(Ni-ett)], which is one of the highest performing organic n-type TE materials. However, it is produced as a powder that is insoluble in common solvents such as methanol and water; previous attempts to solution process the material have resulted in significantly reduced thermoelectric properties. In this work, we optimize the synthesis of this polymer and fabricate a composite film by suspending poly[Kx(Ni-ett)] in a polymer matrix. This is achieved by optimizing the air exposure time and reducing the amount of polyvinylidene fluoride matrix needed to form a film. The obtained thin-film properties show a room temperature power factor that is several times higher than that of films reported in literature and shows excellent stability in air. Additionally, alternative polymer matrices are investigated to further improve thermoelectric properties.
Protein Nanocarrier for Targeted Intracellular Delivery of Functional Antibodies

(Georgia Institute of Technology, 2017-05) Lukianov, Cyril Igorevich

The cell membrane remains a formidable barrier for antibody-based therapies, and efficient intracellular delivery of functional antibodies may be critical for modulating intracellular signaling mechanisms and protein-protein interactions involved in various disorders. This study utilized protein engineering techniques to develop a novel nanocarrier that is capable of delivering functional antibodies to the intracellular environment. Each nanocarrier contains six SPAB antibody-binding domains, and is therefore capable of delivering up to six antibodies. The interaction between the SPAB domain of the nanocarrier and the heavy chain constant region of the antibody is noncovalent, thus allowing the nanocarrier to bind different functional antibodies with the same affinity. Three iRGD domains were integrated into the nanocarrier structure to allow for selective targeting of integrin-overexpressing cells. We successfully expressed the protein monomers, assembled the functional nanocarrier, and investigated its antibody-binding properties. Results of cellular uptake studies involving HeLa, MCF-7, as well as SK-BR-3 cancer cell lines indicate significant cellular uptake of antibody-loaded nanocarrier as compared to soluble antibody control. Without any modification of the carrier, we also used HER2 targeting antibodies to direct the carriers preferentially into HER2-positive SK-BR-3 cells. In addition to efficient cellular uptake, the highly biocompatible and modular nature of our nanocarrier makes it ideal for expanding the scope of antibody-based therapeutics to the intracellular environment.
Investigating Doped Mesoporous ZSM-5 for Cascade Catalysis

(Georgia Institute of Technology, 2017-05) Umo, David Ebung

With the recent innovations and progress in the nanotechnology industry, a family of microporous catalysts and adsorbents known as zeolites were developed in the mid 20th century. Zeolites have a wide-range of applications in energy utilization, so scientists have been carrying out research on this material with a focus on solving the world’s global warming and energy crisis. One Zeolite--commonly referred to as Zeolite Socony Mobil-5 (ZSM-5)--has shown a significant promise especially regarding potential applications in the petrochemical industry. The petrochemical industry is a major contributor towards the emission of greenhouse gases which cause global warming. The petrochemical industry also suffers from inefficient energy consumption in processes such as fractional distillation, hydrocracking etc. Scientists have carried out extensive research on zeolites’ application in post combustion CO2 capture to reduce the emission of CO2 and, in turn, reduce the effects of global warming. Similarly, scientists have also considered altering the acidity and basicity of the ZSM-5 to increase its catalytic efficiency for other industrial applications. Currently, the petrochemical Industry resorts to energetically intensive and inefficient processes to convert larger hydrocarbons to lighter, more valuable hydrocarbons and using ZSM-5 is a huge step towards solving this crisis. This study plans on addressing this energy crisis by analyzing the catalytic efficiency of the ZSM-5 in carbon-carbon bond forming/breaking reactions like the aldol condensation reaction and the one-pot deacetlyation Knoevenagel cascade reaction. In this research, I will start by varying the acidity of the ZSM-5 by synthesizing various forms of the ZSM-5 and substituting silica atoms for heteroatoms like Tin, Aluminum and Boron. The acid sites act as the catalyst for the first step of the Knoevenagel reaction I will then introduce mesopores into the ZSM-5s through a mesopore forming agent known as Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPOAC). The mesopores will serve to allow grafting of a fixed amount of organo-silanes on the surface of the ZSM-5. The fixed amount of organo-silanes in turn serves as a basic functional group and ensures the basicity of each ZSM-5 is roughly equal. The basic sites act as the catalyst for the second step of the Knoevenagel reaction. The bi-functional catalyst (acidic and basic) will be analyzed using X-ray diffraction and Thermogravimetric analysis to ensure the desired structural goal is achieved. Subsequently, the various bi-functional catalytic ZSM-5s will be analyzed for their respective catalytic efficiency in the one-pot deacetylation knoevenagel cascade reaction with the non-catalyzed reaction serving as a control experiment. The results of each experiment will be analyzed using gas chromatography and the catalytic efficiency will be determined through the measured conversion of each reactant. I hypothesize that the Tin, Aluminum, Boron and All-Silica ZSM-5s will have a decreasing order of acidity and in turn a decreasing order of catalytic efficiency in the cascade reaction. This is because the density functional theory suggests the level of acidity to be in that order and the first step of the cascade reaction is the rate determining step and is also acid-catalyzed. Conclusively, the results from this research could highlight the catalytic efficiency of the ZSM-5 and highlight its effectiveness in solving the world’s energy crisis. With the current move towards sustainable energy and energy efficiency globally, it is imperative that the Petrochemical Industry solves its energy crisis, to not be left behind in the energy race
Optimizing the thermal stability of influenza vaccine for microneedle delivery

(Georgia Institute of Technology, 2016-07-18) Desai, Miraj Nishil

The purpose of this study was to create a thermally stable formulation of influenza vaccine that can be delivered transdermally using a microneedle patch. By altering drying conditions, storage conditions, and formulation components, vaccine activity can be preserved at room temperature for several months in a dried state. Delivery via a soluble, biodegradable polymer microneedle patch is the method of choice in this study because it allows for self-administration of the drug, creates no sharps waste, is pain free, has high bioavailability, and shows potential for removing influenza vaccine from cold chain dependency. By optimizing the combination of stabilizing techniques previously studied, preliminary results have shown that excipient solutions made up of sucrose, trehalose, and arginine, to name a few, in an ammonium acetate buffer are able to preserve close to 100% of vaccine activity for at least six months at room temperature when patches are loaded with a full human dose. These results show much promise for the eventual removal of many vaccine and drug formulations from cold chain dependency.
Protracted Colored Noise Dynamics Applied to Nanoscale Studies of Block Copolymers

(Georgia Institute of Technology, 2015-06-30) Nicoloso, Daniel L.

Coarse-grained molecular dynamics is an accurate and versatile tool for understanding the dynamic behavior of molecules at a wide variety of length and time scales. This especially useful for understanding the kinetics of self-assembly processes in block copolymers, as these systems are difficult and expensive to study experimentally. One of the current limitations of molecular dynamics simulations is that when molecules in the system must overcome a large activation energy barrier, the computing speed decreases by several orders of magnitude. Protracted colored noise dynamics is a variation of molecular dynamics, which was developed to address the issue by incorporating stochastic colored noise into force calculations in simulation. Hypothetically, this should improve phase space sampling efficiency in molecular dynamics simulations and force kinetically inhibited systems to an equilibrium state more quickly. The purpose of this study was to apply protracted colored noise dynamics to simulations of block copolymers, including systems with kinetic limitations. The first goal of this study was to investigate potential computational speed up due to overcoming kinetic limitations with protracted colored noise dynamics. The results were very promising, showing an order of magnitude reduction in computational time for high activation energy simulations. The second goal was investigate the effect of random forces on the equilibrium structure of block copolymers in simulation. The results show that for sufficiently strong random forces, the block copolymers are highly disordered at equilibrium. In the course of this study, a threshold parameter space for protracted colored noise dynamics was developed to understand the limitations on noise strength.