Chemical Engineering Commons^™

Integrated Cellular Systems, Jason Carl Harper

Chemical and Biological Engineering ETDs

The generation of new three-dimensional (3D) matrices that enable integration of biomolecular components and whole cells into device architectures, without adversely altering their morphology or activity, continues to be an expanding and challenging field of research. This research is driven by the promise that encapsulated biomolecules and cells can significantly impact areas as diverse as biocatalysis, controlled delivery of therapeutics, environmental and industrial process monitoring, early warning of warfare agents, bioelectronics, photonics, smart prosthetics, advanced physiological sensors, portable medical diagnostic devices, and tissue/organ replacement. This work focuses on the development of a fundamental understanding of the biochemical and nanomaterial mechanisms …

Novel Routes For Synthesis Of Pd Nanoparticles And Faceted Zno Supports For Heterogeneous Catalysts, Patrick David Burton

Chemical and Biological Engineering ETDs

Alcohol steam reforming is a promising source of hydrogen as fuel, and could be improved by the use of an optimal catalyst. The methanol steam reforming reaction, CH3OH+H2O --> 3H2+CO2 frequently conducted by means of a Cu/ZnO catalyst. Unfortunately, this catalyst deactivates quickly and is pyrophoric. Pd catalysts are much more stable, but reactions using these catalyst follow the decomposition pathway, CH3OH --> 2H2+CO. PdZn alloys can achieve the desired selectivity, and have been noted to form under reaction conditions from Pd/ZnO heterogeneous catalysts. In the present work, careful synthesis techniques of specific support and nanoparticle surfaces have been developed …

Effects Of Non-Planar Distortions In Porphyrin Compounds On Their Properties And Functionality, Raid Haddad

Chemical and Biological Engineering ETDs

Porphyrins and related compounds are ubiquitous in nature, performing diverse functions including solar energy transduction, electron transport, molecular transport and storage, and catalysis. Due to their unique photophysical and chemical properties, they are excellent candidates for application as photosensitizers, catalysts, photocatalysts, molecular electronics and opto-electronics. Several properties of porphyrins are sensitive to small variations in their structure, and this dissertation investigates the effects of out-of-plane distortions of the macrocycle on optical properties, reactivity to axial ligands, and substituent rotation. The structure-functions relationships are examined using molecular simulations, UV-visible absorption spectroscopy, resonance Raman spectroscopy, and normal-coordinate structural decomposition (NSD) analysis of …

Polymerization In Emulsion Microdroplet Reactors, Nick J. Carroll

Chemical and Biological Engineering ETDs

The goal of this research project is to utilize emulsion droplets as chemical reactors for execution of complex polymerization chemistries to develop unique and functional particle materials. Emulsions are dispersions of immiscible fluids where one fluid usually exists in the form of drops. Not surprisingly, if a liquid-to-solid chemical reaction proceeds to completion within these drops, the resultant solid particles will possess the shape and relative size distribution of the drops. The two immiscible liquid phases required for emulsion polymerization provide unique and complex chemical and physical environments suitable for the engineering of novel materials. The development of novel non-ionic …

Development Of Novel Bio/Nano Interfaces For Materials Science And Biomedical Applications, Carlee Ashley

Chemical and Biological Engineering ETDs

Virus-like particles (VLPs) of MS2 bacteriophage possess a variety of characteristics that enable their use in biomedical and materials science applications. MS2 VLPs are perfectly monodisperse and possess a highly regular periodic structure. Their protein capsids can be modified in precise locations via chemical conjugation or genetic display of peptides, and their interior volumes can be readily loaded with a variety of non-genomic materials by taking advantage of their ability to self-assemble in the presence of RNA and RNA-modified cargos. Using peptides identified by filamentous phage display, I have demonstrated the utility of MS2 VLPs as targeted nanocarriers capable of …

Selective Epitaxial Growth Techniques To Integrate High-Quality Germanium On Silicon, Darin Leonhardt

Chemical and Biological Engineering ETDs

High-quality Ge-on-Si heterostructures have been actively pursued for many advanced applications, including near-infrared photodetectors, high-mobility field effect transistors, and virtual substrates for integrating III-V multijunction solar cells. However, growing epitaxial Ge on Si poses many engineering challenges, ranging from lattice mismatch, to thermal expansion coefficient mismatch, to non-planar morphological evolution. The lattice mismatch between Ge and Si often leads to a high density of threading dislocations. These dislocations, if not reduced, propagate through the subsequently grown GaAs layer, deteriorating its quality. To overcome these engineering challenges, we have developed three different approaches based on molecular beam epitaxy to significantly reduce, …

Integration Of Composite Nanomaterials Into Anode And Cathode Designs, Claudia Wuillma Narváez Villarrubia

Chemical and Biological Engineering ETDs

This research introduces the use of bucky' papers based on SWNTs as anode electrode materials for the oxidation of NADH and L-Malate oxidation by poly(methylengreen) and malate dehydrogenase respectively. SWNTs were used to create an electrode design consisting of high surface area-hierarchically ordered carbon nanomaterials with controlled surface chemistry. Additionally, this research introduces new cathodes designs based on buckeye and toray papers for air-breathing and liquid electrolyte modes. Buckeye and 0.11mm-thick toray papers are used to design the air-breathing cathode by immobilization of Laccase using a non-covalent linking agent. The liquid electrolyte cathode, designed to be applied in implantable devices, …

Assessment Of The Biocompatibility, Stability, And Suitability Of Novel Thermoresponsive Films For The Rapid Generation Of Cellular Constructs, Jamie Reed

Chemical and Biological Engineering ETDs

Stimuli responsive polymers (SRP) are of great interest in the bioengineering community due to their use in applications such as drug delivery and tissue engineering. One example of an SRP is poly(N-isopropyl acrylamide) or pNIPAM. This SRP has the capability of changing its conformation with a slight temperature change: adherent mammalian cells spontaneously release as a confluent cell sheet, which can be harvested for cell sheet engineering purposes. Since its initial use in 1968, many researchers have used pNIPAM to obtain a cell sheet composed of their cell type of interest. The differing protocols used for these diverse cell types, …

Synthesis And Characterization Of Tethered Poly(N-Isopropylacrylamide) For Quantitative Cell Adhesion Studies, Phanindhar J. Shivapooja

Chemical and Biological Engineering ETDs

Environmentally responsive (or smart') polymers represent a new approach for controlling biofouling release. Poly(N-isopropylacrylamide) (PNIPAAm) is a thermo responsive polymer that can potentially be used to control biofouling, as it exhibits a change in its relative hydrophobicity above and below its lower critical solution temperature (LCST ~ 32\uf0b0C). This thesis reports on grafted PNIPAAm brushes, synthesized using a relatively simple and rapid method which allows atom transfer radical polymerization (ATRP) in presence of air. In this study the structure, purity and thermally responsive behavior of grafted brushes have been characterized using X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectroscopy, Fourier …

Ionic Self-Assembly Of Porphyrin Micro-Nano Structures For Solar Hydrogen Evolution, Yongming Tian

Chemical and Biological Engineering ETDs

This research project develops self-assembled porphyrin micro-nano structures and their metal nanocomposites for efficient solar H2 evolution. The project is composed of three inter-related tasks. The first task is to develop the synthetic methods for preparing the binary porphyrin micro-nano structures by ionic self-assembly under various aqueous solution conditions. Although the porphyrin molecules have been widely studied in artificial photosynthesis, the porphyrin monomers absorb light in a limited range of the solar spectrum and are unstable in solution. In using ionic selfassembly of two oppositely charged porphyrin molecules, we successfully synthesized the more robust micro/nano clover-like structures to replace the …

Aerosol Synthesis And Electrochemical Analysis Of Niobium Mixed-Metal Oxides For The Ethanol Oxidation Reaction In Acid And Alkaline Electrolyte, Daniel Konopka

Chemical and Biological Engineering ETDs

Direct ethanol fuel cells are especially important among emerging electrochemical power systems with the potential to offset a great deal of the energy demand currently met through the use of fossil fuels. Ethanol can be refined from petroleum sources or attained from renewable biomass, and is more easily and safely stored and transported than hydrogen, methanol or gasoline. The full energy potential of ethanol in fuel cells can only be realized if the reaction follows a total oxidation pathway to produce CO2. This must be achieved by the development of advanced catalysts that are electrically conductive, stable in corrosive environments, …

Biofuel Cell Anode For Nad-Dependent Enzymes, Ovalles Rosalba Rincón

Chemical and Biological Engineering ETDs

Enzymatic biofuel cells are a very attractive young technology based on utilization of natural, renewable and plentiful resources that offer an alternative energy source. Most fuel cells run on hydrogen; but it is extremely expensive and difficult to obtain, which is why research has moved to target fuels that are already available in nature, avoiding high costs of production, both economically and environmentally. Several biofuels with very high energy densities are available to us in abundance, but the challenges to make use of them are plenty. These biofuels contain several carbon-to-carbon bonds which make their oxidation processes significantly more complex …

Printable Lithium Batteries, Kyle Fenton

Chemical and Biological Engineering ETDs

Printable lithium iron phosphate (LiFePO4) cathodes and porous aerogel / polymer separators have been designed, constructed, and tested. The cathodes consist of LiFePO4, PVDF binder, and conductive carbon which was developed for robocast deposition (printing) onto carbon coated aluminum substrates to form 60 \uf06dm thick cathodes. Electrochemical and physical evaluation of these printed cathodes was performed to determine capacity, rate capability, and lifetime performance of the printed cathodes. Cells were constructed using a standard 2032 coin cell to ensure uniform electrode size and pressure on the layers of the battery. Cathodes printed exhibited up to 115 mAh/g capacity with a …

Sintering Of Metal Nanoparticles On Model Substrates, Levi R. Houk

Chemical and Biological Engineering ETDs

The sintering of precious metal catalysts is an important problem for the automotive and chemical process industry. As these precious metal catalysts sinter, the metal nanoparticles grow, which in return causes a loss in the overall surface area from loss of the number of available reaction sites. At high temperatures, sintering as a thermally activated process occurs more rapidly and the energetics of the sample changes. In automotive catalysis, for the catalytic converter, the exhaust gases from automobiles contain carbon monoxide, nitrogen oxide compounds, and other hydrogen compounds, which are detrimental to the atmosphere, and a catalyst is required to …

Field-Structured Chemiresistors : Tunable Sensors For Chemical-Switch Arrays, Douglas Read

Chemical and Biological Engineering ETDs

We have developed a significantly improved composite material for applications to chemiresistors, which are resistance-based sensors for volatile organic compounds. This material is a polymer composite containing Au-coated magnetic particles organized into electrically conducting pathways by magnetic fields. This improved material overcomes the various problems inherent to conventional carbon-black chemiresistors, while achieving an unprecedented magnitude of response. When exposed to chemical vapors, the polymer swells only slightly, yet this is amplified into large, reversible resistance changes—as much as 9 decades at a swelling of only 1.5 %. These conductor-insulator transitions occur over such a narrow range of analyte vapor concentration …

Model Electrode Structures For Studies Of Electrocatalyst Degradation, Ronald Goeke

Chemical and Biological Engineering ETDs

Proton exchange membrane fuel cells (PEMFCs) are being extensively studied as power sources because of their technological advantages such as high energy efficiency, high energy and power densities, environmental friendliness, low noise, rapid refueling, and fuel flexibility. The most effective catalyst in these systems consists of nanoparticles of Pt or Pt-based alloys on carbon supports. Understanding the role of the nanoparticle size and structure on the catalytic activity and degradation is needed to optimize the fuel cell performance and reduce the noble metal loading. Electrocatalyst degradation is believed to occur by four mechanisms; particle sintering (Ostwald ripening and migration and …

Dna Translocation Through An Array Of Kinked Nanopores, Zh Chen

Chemical and Biological Engineering ETDs

Synthetic solid-state nanopores are being intensively investigated as single-molecule sensors for detection and characterization of DNA, RNA, and proteins. This field has been inspired by the exquisite selectivity and flux demonstrated by natural biological channels and the dream of emulating these behaviors in more robust synthetic materials that are more readily integrated into practical devices. To date, the guided etching of polymer films, focused ion beam sculpting, and electron-beam lithography and tuning of silicon nitride membranes have emerged as three promising approaches to define synthetic solid-state pores with sub-nanometer resolution. These procedures have in common the formation of nominally cylindrical …

Atomic-Level Investigation Of Surface Processes Governing Sige Wetting Layer Formation Using Stm/Sts, Kyle J. Solis

Chemical and Biological Engineering ETDs

Upon sub-monolayer Ge deposition on the 2xn reconstructed SiGe alloy wetting layer at room temperature, the predominant adspecies observed are so-called addimer chain structures (ADCSs). Polarity-switching scanning tunneling microscopy (STM) is used to study ADCSs, as they only appear in empty-state images. ADCSs are dilute structures comprising type-C addimers that reside in neighboring troughs and extend along all equivalent < 130> directions of the surface, giving rise to a zigzagged morphology. ADCSs exhibit localized movements, wherein their rearrangements are strongly coupled with the structure of the underlying substrate dimers. At elevated temperatures, ADCSs are observed to transition to compact epitaxial segments of …

The Sintering And Stability Of Catalytic Nano-Particles, Andrew Delariva

Chemical and Biological Engineering ETDs

Studies were performed on three different catalysts in order to determine their stability and sintering behavior. Pd deposited on a flat single crystal substrate made of Al2O3 was characterized to determine if the mechanism of Ostwald ripening was solely dominated by vapor phase transport of metal atoms. The atoms emitted could be determined by the rate of evaporation and an attempt was then made in order to relate the rates of emission to sintering (instability of nanoparticles). It was found that the rates of emission did not fully reflect vapor phase transport (direct evaporation). The particle-support interaction was increasing the …

Long-Term Desorption Behavior Of Uranium And Neptunium In Heterogeneous Volcanic Tuff Materials, Dean Cynthia

Chemical and Biological Engineering ETDs

Uranium and neptunium desorption were studied in long-term laboratory experiments using four well-characterized volcanic tuff cores collected from southeast of Yucca Mountain, Nevada. The objectives of the experiments were to 1. Demonstrate a methodology aimed at characterizing distributions of sorption parameters (attributes of multiple sorption sites) that can be applied to moderately-sorbing species in heterogeneous systems to provide more realistic reactive transport parameters and a more realistic approach to modeling transport in heterogeneous systems. 2. Focus on uranium and neptunium because of their high solubility, relatively weak sorption, and high contributions to predicted dose in Yucca Mountain performance assessments. Also, …

Bioadhesion To Model Thermally Responsive Surfaces, Brett J. Andrzejewski

Chemical and Biological Engineering ETDs

This dissertation focuses on the characterization of two surfaces: mixed self-assembled monolayers (SAMs) of hexa(ethylene glycol) and alkyl thiolates (mixed SAM) and poly(N-isopropylacrylamide) (PNIPAAm). The synthesis of hexa(ethylene gylcol) alkyl thiol (C11EG6OH) is presented along with the mass spectrometry and nuclear magnetic resonance results. The mixed SAM surface was confirmed to be thermally responsive by contact angle goniometry, 35° at 28 °C and 55° at 40 °C. In addition, the mixed SAM surfaces were confirmed to be thermally responsive for various aqueous mediums by tensiometry. Factors such as oxygen, age, and surface mole fraction and how they affect the thermal …

Templated Growth Of Platinum Nanostructures, Robert Garcia

Chemical and Biological Engineering ETDs

Novel platinum nanostructures were synthesized by templating the growth of platinum on treated polymer surfaces and within disk-like aqueous bicellar assemblies. The growth mechanisms of all structures were examined in detail. Platinum hollow nanospheres with uniform shell thickness were prepared by the seeded growth of platinum on the surface of latex beads with an adsorbed porphyrin photocatalyst followed by core removal. Templating bicelles of a high yield were synthesized for the first time and verified by electron microscopy. Dendritic platinum nanowheels were obtained as a result of confined growth within the bicellar interior. Sintering experiments revealed an unusual stability of …

Unraveling The Intricacies Of Spatial Organization Of The Erbb Receptors And Downstream Signaling Pathways, Michelle Costa

Chemical and Biological Engineering ETDs

Faced with the complexity of diseases such as cancer which has 1012 mutations, altering gene expression, and disrupting regulatory networks, there has been a paradigm shift in the biological sciences and what has emerged is a much more quantitative field of biology. Mathematical modeling can aid in biological discovery with the development of predictive models that provide future direction for experimentalist. In this work, I have contributed to the development of novel computational approaches which explore mechanisms of receptor aggregation and predict the effects of downstream signaling. The coupled spatial non-spatial simulation algorithm, CSNSA is a tool that I took …

Reactivity Study Of Platinum Nanoparticles And Nanowires Inside The Channels Of Mesoporous Silica, Marcus R. Smith

Chemical and Biological Engineering ETDs

Pt metal nanowires and nanoparticles were prepared using mesoporous silica as the template. Mesoporous silica with straight 1-dimensional, tortuous 1-dimensional and 3-dimensional channels was used. The experimental techniques included CO oxidation, Chemisorption, XRD, and STEM. CO oxidation and chemisorption provided the data to calculate the intrinsic reactivity, known as turn over frequency (TOF). Powder XRD was used to measure line broadening. The FWHM of the XRD line broadening was used with the Scherrer formula to determine Pt metal crystallite size. STEM images permitted for the measurement of the particle diameters, and the determination of morphology.

Two commercially available reference samples …

Infrared Diode Laser Absorption Spectroscopy Measurement Of Gas Phase Radicals In C₄F Discharges For Plasma Model Validation, Karla Waters

Chemical and Biological Engineering ETDs

The etching characteristics of oxide and photoresist thin films in C₄F₈ discharges in an inductively coupled GEC Reference cell have been determined. Infrared diode laser absorption spectroscopy (IR-DLAS) measured absolute concentrations of CF_x radicals in C₄F₈ discharges and correlated their behavior to the oxide etch process. Additionally, Langmuir probe and OES data were collected to aid in characterizing the plasma and the oxide/photoresist etch processes.

A central composite design of experiment was employed. The factors were source power, chuck bias power, and total pressure. The source power varied from 200 to 500 W, …

Activation Of Precipitated Iron Fischer-Tropsch Catalysts, Mehul D. Shroff

Chemical and Biological Engineering ETDs

The Fischer-Tropsch Synthesis (FTS) is an important step in the manufacture of synthetic fuels from coal. The use of iron catalysts for FTS, though desirable from the standpoint of process economy, is hampered by problems relating to catalyst attrition and carbon buildup. In addition, from a research perspective, there has been a long-standing controversy in the literature with regard to the nature of the active phase.

The effect of activation and reaction treatments on the resulting phase transformations in a commercial, precipitated and spray-dried, Fe₂O₃ - CuO - K₂O Fischer-Tropsch catalyst have been studied. Different …

X-Ray Induced Electron Emission, Charles A. Aeby

Chemical and Biological Engineering ETDs

An experimental technique has been developed and successfully used in the measurement of X-Ray induced electron emission from a variety of materials including a group of significance to satellite applications. A database has been established which extends measure emission characteristics to an order of magnitude lower energies than previously available.

Separations Of Dilute Solutions By The Smooth Deposit Approach Of The In-Situ Indirect Freezing Process, Jeng-Hung Lue

Chemical and Biological Engineering ETDs

The main objective of the present study is to demonstrate experimentally the feasibility of applying the smooth deposit ap­proach of the in-situ indirect freezing process to the separations of both dilute organic mixtures and aqueous mixtures. The in-situ indirect freezing process with in-situ washing and melting opera­tions was first introduced by C. Y. Cheng and S. W. Cheng [1].

Assessment Of Corrosion And Scaling In A Low Temperature Geothermal System, David Bruce Orrell

Chemical and Biological Engineering ETDs

The feasibility of a low temperature geothermal system to be located in the area immediately surrounding Albuquerque, New Mexico, was assessed with respect to corrosion and scaling. Theories of corrosion and scaling were explored and an extensive literature survey was performed to predict trends and apply design criteria and guidelines regarding corrosion and scaling from other geothermal environments to the proposed geothermal installation in Albuquerque. A recirculating corrosion test loop was built, and fifteen metals were tested for general corrosion resistance in seawater at 190° F and 3 ft/sec flow velocity. Results show this test procedure to be viable and …

Deep Penetration Of Electrons Into Homogeneous Media By The Method Of Condensed Collisions, Joseph Francis Janni

Chemical and Biological Engineering ETDs

The objective of this dissertation was to develop an accurate and efficient alternative to presently available methods of calculating the steady state penetration of electrons deep into homogeneous materials. A thorough solution must include scalar fluxes, net currents, angular distributions, and differential energy spectra. This research has successfully developed the method of condensed collisions, which provides an alternative to methods now in use for the solution of the electron transport problem. The condensed collsion method is general, but has been applied specifically to deep penetration electron transport to demonstrate its utility. The present aplication was for electrons having incident energies …