The focus of this dissertation research involves surface charge manipulation of functionalized monolayers. Application of potential to acid or base terminated organic films immobilized on electrodes results in the ionization of the terminal groups. The ionization of these groups using applied potential provides conditions favorable the control of polyelectrolyte deposition to the monolayer surface. Research is presented that asserts that the interfacial pH of acid or base terminated monolayers responds to applied potential as a result of the accumulation of phosphate counterions to the monolayer-solution interface. Results obtained from applied potential modulation of surface charge endeavors strongly suggest that manipulation of terminal group ionization with applied potential “turns on“ or “turns off“ the charge of the monolayer. Switching on the surface charge of functionalized monolayers using applied potential yields conditions that make it possible for the promotion or inhibition of electrostatic attachment of polyelectrolyte to the monolayer surface. Electrostatic interactions between immobilized polyelectrolytes and redox probes result in changes in electron transfer that can be monitored with electrochemical impedance measurements. Impedance measurements provide a qualitative assessment of the degree of potential-driven polyelectrolyte self assembly. The electrostatic interactions between the redox probe in solution and the terminal region of monolayers directly affects the extent of charge-transfer between the electrode and the redox probe in solution. For this reason, impedance measurements are able to provide an indication of whether or not potential drives to electrostatic deposition to the terminal region of a functionalized monolayer. Unlike impedance measurements, quartz crystal microbalance measurements provide quantitative mass assessments that confirm polyelectrolyte deposition of inhibition under the direction of applied potential. Application of appropriate potentials is shown to induce variations in the electrostatic interactions between redox probes in solution and terminal groups of monolayers. Variations in the electrostatic interactions between the modified electrode and the redox probe modulate electron transfer that produces varying current. Since scanning electrochemical microscopy (SECM) relies on modulation of feedback current underneath a ten-micrometer platinum tip, SECM provides a means for monitoring of potential-driven surface charge modulation. Experiments presented in this dissertation will show that in addition to monitoring the effect of applied potential on the charge of ionizable surface groups, SECM can also be used to selectively deposit a polyelectrolyte to the surface of a carboxylic acid terminated monolayer. The SECM tip was rastered over the surface of a functionalized monolayer in the form of a simple pattern while the electrode was immersed in a dilute polyelectrolyte solution. As the SECM tip was moved and potential stepped more positive than the PZC, ionization was confined ionization to one spot encouraging localized ionic self assembly. / Ph. D.

Silicate melt inclusions are ubiquitous in quartz phenocrysts, yet there are few studies of such inclusions from porphyry copper systems. A melt inclusion forms when magma is trapped in a growing phenocryst. If a phenocryst is able to preserve the original parent magma, then accurate information can be obtained for ancient volcanic systems. In recent igneous systems, melt inclusions are commonly preserved as optically clear homogeneous glass representative of magma stored at depth before eruption. Melt inclusions are difficult to recognize in quartz phenocrysts from porphyry copper system because they are crystalline and hidden by exsolved magmatic volatiles. The inclusions range in size from less than 5 to over 150 μm. In order to evaluate the magmatic contribution to economic mineralization, we conducted three separate studies to determine whether or not crystallized melt inclusions preserve representative samples of magma. The first study modeled the phase relationships that occur during equilibrium crystallization and melting of haplogranite magma trapped in quartz. Results from the model are similar to observations made during the heating of crystallized melt inclusions from porphyry copper systems. It is necessary to re-melt the crystal and volatile phases before chemical analysis. Micro-explosions caused by heating resulted in the loss of important chemical components. Our second study evaluated several microthermometric heating procedures using synthetic melt inclusions trapped at conditions similar to those inferred for porphyry copper systems. A synthetic hydrous melt was saturated with saline hydrothermal solutions allowing both melt and aqueous fluids to be trapped in quartz. Based on microthermometric measurements from these coeval melt and aqueous fluid inclusions we were able to predict the known trapping temperature and pressure of formation. This technique can be applied to natural samples to constrain trapping pressures and temperatures. It was found that slower heating rates could be used to avoid overheating and that heating under a confining pressure greatly minimizes the decrepitation of inclusions. The third study examined the copper concentrations in melt inclusions from the Red Mountain, Arizona porphyry copper system. Older andesite magma contains pyroxene with melt inclusions of higher copper concentrations compared to melt inclusions in quartz from quartz latite. The higher water concentrations in crystallized melt inclusions in the quartz, and abundant aqueous fluid inclusions indicates that the exsolution of water from the magma occurred prior to the trapping of melt inclusions in quartz. The lower water concentrations and the absence of aqueous fluid inclusions indicates that the andesite never reached the stage of water exsolution. The results obtained here are consistent with models that suggest that copper is extracted from the melt by saline magmatic fluids, producing a metal-charged hydrothermal solution and leaving behind a metal-depleted melt and serves to identify the potential contribution of melt inclusion studies to constrain the origin of ore metals in porphyry copper deposits. / Ph. D.

Interfaces are ubiquitous in our daily life. A good understanding of the interfacial properties between different materials, or a single material in different physical states is of critical importance for us to explore the current world and bring benefits to mankind. In this work, interfacial behavior was investigated with the help of surface analysis techniques, such as quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and atomic force microscopy (AFM), in order to gain better understanding on biofuel conversion, gene/drug delivery, and chemical fixation of CO2. Biomimetic chelator-mediated Fenton (CMF) non-enzymatic degradations on cellulose and chitin thin films was studied by liquid-phase QCM-D and AFM. QCM-D is a powerful tool to monitor the kinetics of hydrolysis of regenerated cellulose and chitin model surfaces. Results from QCM-D and AFM showed that the majority of the biomass of the two model surfaces can be hydrolyzed by the CMF system. The initial degradation rates for both model surfaces by the CMF system are faster than that of the corresponding enzyme systems. The CMF system, which is a good non-enzymatic pretreatment agent for cellulose and chitin, may work on a wide variety of polysaccharide systems. Adsorption of cationic cellulose derivatives onto self-assembled monolayer (SAM) surfaces was investigated using liquid-phase SPR. Results from SPR showed that depending upon the cellulose derivative structure, irreversible adsorption ranging from a monolayer to ~1.6 layers of cellulose derivative were formed on the SAM-COOH surface based upon a charge neutralization mechanism. At low salt concentrations, the long-range electrostatic attraction between the cationic cellulose derivatives (6-PyrCA and 6-MeIMCA) and the SAM surfaces facilitates the formation of a 2-dimensional monolayer. While, for TMACE, the energy gained through the hydrophobic interaction between adjacent long polyelectrolyte branches may afford the electrostatic repulsion and chain entropy penalties, resulting in the formation of 3-dimensional adsorbed polyelectrolyte layers. Adsorption of 1,2-epoxybutane gas molecules onto/into VPI-100 metal–organic frameworks (MOFs) was studied by gas-phase QCM-D experiments. Results from QCM-D demonstrated that VPI-100 (Ni) MOFs have higher irreversible adsorption per unit cell (θ) and faster diffusion coefficients (D) than VPI-100 (Cu) MOFs. The presence of bound counter-balancing ions on the metallo-cyclam core was attributed as the cause of the higher θ and faster D through the Ni analogue, which suggests the MOF-epoxide interaction occurs at the metallo-cyclam. This study shed light upon tuning MOF structures for better CO2 sorption and epoxide activation to gain higher catalytic efficiency. Finally, in operando high energy X-ray diffraction (HEXRD) was used to monitor the phase transition of the NaxNi1/3Co1/3Mn1/3O2 cathode material during the sintering process. The first charge/discharge cycle of the NaxNi1/3Co1/3Mn1/3O2 cathode materials in different phases were also studied by in operando HEXRD. It was found that the intergrowth P2/O1/O3 cathode (NCM-Q cathode) can inhibit the irreversible P2–O2 phase transition and simultaneously improve the structural stability of the O3 and O1 phases during cycling. The NCM-Q cathode with triple-phase integration demonstrates highly reversible phase evolution during high voltage cycling, possibly leading to a highly reversible capacity and good cycle stability. / Doctor of Philosophy / Interfaces and surfaces are everywhere. Many critical processes, such as molecular recognition, catalysis, and charge transfer, take place at interfaces. The surfaces of plants and animals provide barriers from pathogens, prevent damage from mechanical impacts, detect external stimuli, etc. Inside the human body, nutrition and oxygen are adsorbed through interactions between substances and cell surfaces. Investigations of interfacial behaviors may help us understand our current world better and bring benefits to mankind. In this dissertation, the interface between bio-renewable natural polymers and biomimetic chelators, the interface between a self-assembled monolayer and cationic cellulose derivatives, and the interface between metal–organic frameworks (MOF) and 1,2-epoxybutane gas molecules, were studied with a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and atomic force microscopy (AFM), to gain insights into biofuel conversion, gene/drug delivery and chemical fixation of CO2, respectively. Additionally, thermally and electrochemically induced phase transitions in sodium-ion battery (SIB) cathode materials were probed via in operando high energy X-ray diffraction (HEXRD). Biomimetic chelator-mediated Fenton (CMF) non-enzymatic degradations of cellulose and chitin thin films were studied by liquid-phase QCM-D and AFM. It was found that the majority of the biomass of the two model surfaces can be degraded by the CMF system. Adsorption of cationic cellulose derivatives onto self-assembled monolayer (SAM) surfaces was investigated using liquid-phase SPR. It was found that both the absorbed layer conformation and the absorbed amount depend upon the interplay between long-range electrostatic interactions and short-range interactions. Adsorption of 1,2-epoxybutane gas molecules onto/into VPI-100 MOFs was studied by gas-phase QCM-D experiments. Data from QCM-D revealed the irreversible gas molecule absorption onto/into MOFs and shed light upon tuning MOF structures for better CO2 sorption and epoxide activation to gain higher catalytic efficiency. Finally, the in operando high energy X-ray diffraction (HEXRD) was used to probe thermally and electrochemically induced phase transitions in sodium-ion battery (SIB) cathode materials. It was found that the NCM-Q cathode with triple-phase integration demonstrates highly reversible phase evolution during high voltage cycling, possibly leading to a highly reversible capacity and good cycle stability.

The advancements of chemists, engineers, and material scientists has yielded an enormous and diverse library of high-performance materials with varying chemical and physical properties that can be used in a wide array of applications. A molecular-level understanding of the nature of gas–surface interactions is critical to the development of next generation materials for applications such as gas storage and separation, chemical sensing, catalysis, energy conversion, and protective coatings. Quartz crystal microbalance (QCM) and in situ infrared (IR) spectroscopic techniques were employed to probe how topological features of a material as well as structural differences of the analytes affect gas sorption. Detailed studies of the interactions of three categories of molecules: aromatic hydrocarbons, triatomic ambient gases, and chemical warfare agents, with metal-organic frameworks (MOFs) and polyurethane coatings were conducted to build structure–property relationships for the nature and energetics of gas sorption within each material. Differences in the molecular structure of the guest compounds were found to greatly influence how, and to what extent each molecule interacts with the MOF or polyurethane film. Specifically, IR studies revealed that transport of aromatic compounds within the zirconium-based MOF, UiO-66 was limited by steric restrictions as molecules passed through small triangular apertures within the pore environment of the MOF. In contrast, the smaller triatomic molecules, CO2, SO2, and NO2, were able to pass freely through the MOF apertures and instead reversibly adsorbed inside the MOF cavities. Specifically, SO2 and NO2 were observed to preferentially bind to undercoordinated zirconium sites located on the MOF nodes. In addition, uptake of CO2, SO2, and NO2 was also aided by dispersion forces within the confined pore environments and by hydrogen bond formation with μ3 OH groups of the MOFs. Dimethyl chlorophosphate (DMCP), a nerve agent simulant that contains several electronegative moieties, was also found to strongly adsorb to undercoordinated zirconium; however, unlike in the aromatic and triatomic molecule systems, DMCP remained permanently bound to the MOFs, even at high temperatures. Finally, QCM studies of mustard gas simulant uptake into polyurethane films of varying hard:soft segment compositions revealed that dipole-dipole and dipole-induced dipole interactions were responsible for favorable absorption conditions. Furthermore, the ratio of hard and soft segment components of the polyurethane had a minor impact on simulant adsorption. Higher hard-segment content resulted in a more crystalline film that reduced simulant uptake, whereas the rubbery, high soft segment polyurethane allowed for greater vapor absorption. Ultimately, molecular-level insight into how the chemical identity of a guest molecule impacts the mechanism and energetics of vapor sorption into both MOFs and polymeric films can be extended to other relevant systems and may help identify how specific characteristics of each material, such as size, shape, and chemical functionality impact their potential use in targeted applications. / Doctor of Philosophy / The nature in which specific gases interact with materials will largely dictate how the material can be utilized. By understanding where and how strongly gas molecules interact with a material, scientists and engineers can rationally design new and improved systems for targeted applications. In the research described in this thesis, we examined how the chemical structure of three different groups of compounds, which have relevance in many industrial, environmental, and defense-related applications, affected the type and strength of interaction between the gas and material of interest. From these studies, we have identified how key properties and features within the examined materials such as size, shape, and chemical composition, lead to significant differences in how vapor molecules interacted with the materials. For example, benzene, toluene, and xylene, which are incredibly important chemicals in industry, were found to be restricted by narrow passageways as they moved through materials with small pores. In contrast, small gases present in the environment from combustion exhaust such as CO₂, SO₂, and NO₂ were able to freely traverse through the passageways, and instead weakly interacted with specific chemical groups inside the cavities of the material. On the same material however, a third class of compounds, organophosphorus-containing chemical warfare agent mimics, irreversibly reacted with chemical groups of the surface, and remained bound even after exposure to high temperatures. Ultimately, the work presented in this thesis is aimed at providing key fundamental insights about specific classes of materials on how, and how strongly they interact with targeted hazardous vapors, which can be utilized by synthetic chemists to design next generation materials.

A one-dimensional, physical model describing two-phase fluid flow is used to simulate the effect of boiling on silica precipitation in geothermal and epithermal precious metal systems. The extent to which decreasing temperature and fluid vaporization are responsible for quartz precipitation is dependent on three related factors - the temperature of the fluid entering the two-phase system, the change in fluid temperature with respect to distance of fluid travel, and the extent of fluid vaporization in regions of gradual temperature decline. Boiling contributes to significant quartz precipitation in systems with high-temperature basal fluids, and in deeper portions of systems in which extensive vaporization occurs. Temperature reduction is a dominant precipitation mechanism in near- surface regions where temperature reduction is rapid, and in systems with lower temperature fluids. Owing to the small difference in quartz solubility between the liquid and vapor phases at low temperatures, boiling does not contribute to significant quartz precipitation in low temperature, near-surface regions. Quartz precipitation is most intense in systems with high mass flux/permeability ratios and low initial fluid temperatures. Geothermal systems with high mass flux/permeability and moderately low initial fluid temperatures are most effective in producing epithermal systems with abundant gold. Numerical modeling indicates that sufficient copper can be partitioned from a "typical" calc-alkaline melt into an exsolving fluid to produce an economic porphyry copper deposit. Neither non-magmatic sources nor an additional hidden magma source are necessary to provide copper to the system and an elevated initial copper concentration in the melt is not necessary. Melts in shallow systems with initial water concentrations of at least 2.5 wt.% water and Cl/H₂O as low as 0.03 can produce economic deposits with volumes of 50 km³ or less, regardless of copper compatibility. In deeper systems deposits may be produced from melts of less than 30 km³ if copper behaves incompatibly prior to water saturation or if the initial melt is water-rich and requires only minor crystallization to achieve water saturation. If copper behaves compatibly prior to water saturation very large volumes of melt may be required. High salinity fluids may be produced directly from a crystallizing melt and immiscibility is not necessary to produce the high salinities observed in some systems. Depending on the temperature, pressure, initial water content, and the extent of crystallization of the melt, the bulk salinity of the aqueous fluids exsolved from a melt may vary from < 2.0 wt.% NaCl to saturation levels (84 wt.% NaCl at 700°C). Fluid evolution during the magmatic-hydrothermal transition and coincident molybdenite precipitation at Questa, New Mexico, has been traced using fluid inclusion microthermometry. The lack of cogenetic liquid- and vapor-rich inclusions, plus final homogenization of most saline, liquid-rich inclusions by halite dissolution indicate that high-salinity fluids were generated by a mechanism other than fluid immiscibility. Pressure fluctuations, responsible for the formation of a magmatic-hydrothermal breccia, are capable of producing the observed fluids and inclusion behavior. Solubility data indicate that the crystallizing aplite porphyry generated fluids with salinities as high as 57 wt.% NaCl equivalent. / Ph. D.

Developing methods to detect, adsorb, and decompose chemical warfare agents (CWAs) is of critical importance to protecting military and civilian populations alike. The sorption of dimethyl methylphosphonate (DMMP), a CWA simulant, into trisilanolphenyl-POSS (TPP) films has previously been characterized with reflection absorption infrared spectroscopy, x-ray photoelectron spectroscopy, and uptake coefficient determinations [1]. In our study, the quartz crystal microbalance (QCM) is used to study the sorption phenomena of DMMP into highly ordered Langmuir-Blodgett (LB) films of TPP. In a saturated environment, DMMP sorbs into the TPP films, binding to TPP in a 1:1 molar ratio. Although previous work indicated these DMMP-saturated films were stable for several weeks, DMMP is found to slowly desorb from the TPP films at room temperature and pressure. Upon application of vacuum to the DMMP-saturated films, DMMP follows first-order desorption kinetics and readily desorbs from the film, returning the TPP film to its original state. [1] Ferguson-McPherson, M.; Low, E.; Esker, A.; Morris, J. J. Phys. Chem. B. 2005, 109, 18914. / Master of Science

Plant cell wall polysaccharides are abundant natural polymers making them potential sources for sustainable and biodegradable materials. Interfacial behavior, including adsorption and enzymatic degradation, of several plant cell wall polysaccharides and their derivatives were studied with a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and atomic force microscopy (AFM). Xyloglucan adsorption isotherms were obtained to probe how cellulose-hemicellulose interactions were affected by the type of cellulose substrate and molar mass of xyloglucan. Xyloglucan as small as a heptasaccharide still adsorbed irreversibly onto cellulose. Carboxymethyl cellulose (CMC) adsorption onto cellulose and viscoelastic properties and water contents of the adsorbed CMC layers were obtained from a combination of QCM-D and SPR data. The CMC samples formed hydrated and viscoelastic layers compared to the relatively rigid xyloglucan layer. Pectin model surfaces were prepared by pectin adsorption from citric phosphate buffer onto gold substrates. These pectin model surfaces were used for subsequent interaction studies with xyloglucan and enzymatic degradation behavior. There is a strong correlation between the degree of esterification (DE) and film resistance to degradation with the high DE being the most susceptible to degradation. The adsorption of two mixed linkage glucans (MLG), barley and lichen MLG, onto regenerated cellulose (RC) surfaces in the absence and presence of other matrix polysaccharides was studied. Viscoelastic properties of the resulting layer were compared as a function of the proprotion of '-(1''3) linkages with lichen MLG forming softer gel-like layers on RC. The lichen MLG layers were further used for enzymatic degradation studies with respect to enzyme concentration, temperature, pH and ionic strength. These studies show that polymer adsorption is a promising strategy to modify material surfaces and provides fundamental understanding of interactions and biodegradation of cell wall polysaccharides at solid/liquid interfaces. / Ph. D.

Elevated levels of lipids and LDL-cholesterol in the blood are significant risk factors associated with developing cardiovascular diseases (CVDs). A potential strategy to combat these risk factors is decreasing lipid absorption by modulating the digestibility of lipids in the human intestinal tract. Since bile salts (BS) play key roles during this process, lipid digestion could be controlled ultimately by limiting the access of BS to the lipid surface. Cellulose ethers (CEs), surface-active dietary fibers and common food additives, might be promising ingredients to control lipid digestion either by creating surface layers around lipid droplets that hinder adsorption of BS, or by sequestering BS in the aqueous phase. However, the precise mechanisms behind these interactions remain unclear. Surface analysis techniques were used to better understand the mechanisms by which CEs with diverse molecular structure and charge (commercial and novel hydroxypropyl-cellulose (HPC)) interact with BS at the solid surface and in the aqueous phase. The potential of CE-stabilized emulsions to influence lipid digestion was also investigated in vitro. Both CEs show potential in modulating lipid digestion; the potential of the commercial HPC to interfere with lipid digestion may be more related to its ability to sequester BS in solution and form mixed HPC-BS complexes that are not easily removed from the surface, whereas the novel HPC seems more effective at creating strong surface layers that resist displacement by BS. These findings can be exploited in developing strategies to design novel food matrices with improved functional properties to optimize lipid digestion and absorption. / MSLFS / Diseases of the heart and circulation are the number one cause of death in the United States (US) and it is predicted that at least 45% of the US population (131.2 million) will have some form of these diseases by 2035. Consumption of reduced-fat foods is one strategy to combat CVDs, but fats contribute to various sensory and nutritional properties of foods. Another strategy is to develop foods that incorporate dietary fibers which could interfere with the digestion of fat. However, the mechanism behind the ability of dietary fiber to interfere with fat digestion remains unclear and depends on the fiber type. One of our objectives was to look at the main interactions between a type of dietary fiber, cellulose derivatives (which are ingredients used in the food industry), and two types of bile salts, (BSs) which are important intestinal components present during fat digestion, at a surface representing a fat droplet and in the aqueous phase. Another objective was to look at the digestibility of cellulose derivative systems, compared to another food ingredient (Tween 20). We found that the different BSs played different roles at the surface and interacted differently with the cellulose derivatives. We also found that both cellulose derivatives showed potential in interfering with lipid digestion. This allows a better understanding of how cellulose derivative systems are affected by digestion and could allow us to design new foods with natural products from plants to improve wellness in the US.

Dynamically recrystallized quartz microstructure and grainsize evolution along mid-crustal shear zones allows for the estimation of tectonic driving stresses and strain rates acting in the mid-crust. Quartz-rich tectonites from three exhumed mid-crustal shear zones, the Main Central Thrust (MCT; Sutlej valley, NW India), South Tibetan Detachment System (STDS; Rongbuk valley, S Tibet), and Moine thrust (NW Scotland), were analyzed. Deformation temperatures estimated from quartz microstructural and petrofabric thermometers indicate steep apparent thermal gradients (80–420 °C/km) across 0.5–2.3 km thick sample transects across each shear zone. Quartz recrystallization microstructures evolve from transitional bulging/sub-grain rotation to dominant grain boundary migration at ~ 200 m structural distance as traced away from each shear zone. Optically measured quartz grainsizes increase from ~ 30 μm nearest the shear zones to 120+ μm at the largest structural distances. First-order Zener space analysis across the Moine nappe suggests strong phyllosilicate control on recrystallized quartz grainsize. Recrystallized quartz grainsize piezometry indicates that differential stress levels sharply decrease away from the shear zones from ~ 35 MPa to 10 MPa at ~ 200 m structural distance. Strain rates estimated with quartz dislocation creep flow laws are tectonically reasonable, between 10⁻¹² – 10⁻¹⁴ s⁻¹. Traced towards each shear zone strain rate estimates first decrease one order of magnitude before rapidly increasing one to two orders of magnitude at structural distances of ~ 200 m. This kinked strain rate profile is likely due to the steep apparent thermal gradients and relatively constant differential stress levels at large structural distances. / Master of Science

The mechanical behavior of discrete atoms has been studied with molecular dynamics whose computational time is proportional to the square of the number of atoms, O(N²). Recently, a faster algorithm, Atomic-scale Finite Element Method (AFEM) with computational time proportional to the number of atoms, O(N), had been developed. The main idea of AFEM, compared with conventional finite element method is to replace nodes with atoms and elements with electric forces between atoms. When interpreting a non-linear system, it is necessary to use an iteration scheme. A simulation of molecular dynamics based on the Verlet's method was conducted in order to validate AFEM in one dimension. The speed of AFEM was investigated in one and two dimensional atomic systems. The results showed that the computational time of AFEM is approximately proportional to the number of atoms, and the absolute computation time appears to be small. The frameworks of AFEM not only for multi-body potential but also pair potential are presented. Finally, AFEM was applied to analyze and interpret the mechanical behavior of a carbon nanotube and a quartz. The buckling behavior of carbon nanotube showed a good agreement with the results illustrated in the original literature. / Master of Science