Doctor of Philosophy, The Ohio State University, 2018, Biochemistry Program, Ohio State

The energy crisis of the last decade has led to new and innovative approaches to combat this pressing issue. One leading candidate as an alternative fuel is hydrogen due to its derivability from water, its high energy density, and its status as a clean fuel. However, the current methods for hydrogen production are not economically feasible to replace fossil fuels because of a reliance on precious metal catalysts. A promising alternative for hydrogen catalysis is through the use of the enzymes hydrogenases, which utilize earth-abundant metals such as nickel and iron. Hydrogenases, however, are limited by their intolerance to oxygen, changes in temperature and pH, and the complexity of their biosynthesis. These factors, among others, leave little potential for industrial application, but hydrogenases can serve as inspiration for structural and functional models. One such model is the metalloprotein rubredoxin. Rubredoxin is a robust, electron-transfer protein with a promiscuous, tetrathiolate active site that binds a variety of metals. When the native iron is replaced with nickel, it mimics the primary coordination of the nickel site in the [NiFe] hydrogenase cofactor. We have demonstrated this construct not only acts as a structural model of hydrogenase, but also a functional mimic as it produces molecular hydrogen through the reduction of protons. The construct's catalytic capabilities were probed with protein film electrochemistry (PFE), confirming the presence of a proton-coupled electron transfer process and inhibition from carbon monoxide, characteristics shared by the native hydrogenase. Through spectroscopic studies coupled to density functional theory calculations, a theoretical model of the Ni(II)Rd resting state was constructed and validated by resonance Raman spectroscopy. As typical PFE experiments were insufficient to investigate NiRd by standard enzymatic studies, a new quantitative PFE (qPFE) method that utilizes an internal protein film standard was c (open full item for complete abstract)

Committee: Hannah Shafaat (Advisor); James Cowan (Committee Member); Anne Co (Committee Member); Claudia Turro (Committee Member) Subjects: Biochemistry; Chemistry

Master of Science, The Ohio State University, 2017, Mechanical Engineering

Our current understanding of electrophysiological phenomena is limited by our ability to measure particular processes. There are a number of electrophysiological intracellular and extracellular measuring techniques which currently exist; however, they are not without limitations. These techniques, such as patch-clamping, involve the careful isolation of a singular cell (which removes the cell from its native environment) and subsequent puncturing or suctioning of the cell membrane (which can damage the cellular structure). This research focuses on the development of conducting polymer sensors for in vivo measurements of electrophysiological phenomena. The goal of this work is to create a system by which ion concentration dynamics can be directly measured and analyzed to quantify metrics of biological processes without harming tissues of the organism. Quasi-potentiostatic amperometric sensors were developed using polypyrrole doped with dodecylbenzenesulfonate (DBS) to form PPy(DBS). By applying a cyclic pulse voltage input to the conducting polymer measurement system, and measuring the resulting current response, system parameters can be correlated to deviations from an equilibrium concentration as a function of time. This research will lay the foundation for more complex measurement techniques, both in electrophysiology, as well as in energy storage technology.

Committee: Vishnu Baba Sundaresan (Committee Member); Daniel Gallego-Perez (Committee Member) Subjects: Biomedical Engineering; Cellular Biology; Engineering; Mechanical Engineering; Neurobiology; Neurology; Neurosciences

Doctor of Philosophy, Case Western Reserve University, 2024, Chemical Engineering

Lowering energy-related CO2 emissions of the U.S. requires the implementation of renewable energy sources to generate electricity. These sources, e.g. solar and wind power, are intermittent in their output, necessitating some form of grid-scale energy storage. Redox flow batteries, particularly hybrid flow batteries based on zinc (Zn), are a highly attractive solution due to their high energy density, scalability, earth-abundance of Zn, and usage of safer aqueous electrolytes as opposed to flammable organics. However, Zn has notable problems such as forming dendrites during high-rate deposition and spontaneous corrosion in acidic and alkaline electrolytes leading to substantial self-discharge of a battery over time. To address these issues, significant research has been conducted on electrolyte additives that can suppress dendrite formation and prevent corrosion, but many of these conventional additives also polarize the electrode and harm battery energy-efficiency. In the present work, a novel additive, benzyldimethylhexadecylammonium chloride (BDAC), is shown to markedly suppress Zn corrosion (battery self-discharge) rate in a pH = 3 ZnSO4 medium without harming (i.e., by minimizing overpotential losses) the high-rate deposition or stripping performance of Zn. Cyclic voltammetry (CV) measurements show BDAC induces hysteresis, where the electrode can either exhibit passivity or electrochemical activity at a given electrode potential depending on the scan direction. The hysteresis is a result of complex surface adsorption and deactivation behavior of BDAC on Zn. An additive adsorption-deactivation model is proposed which captures above behavior and shows that, at low current densities (i.e. low BDAC deactivation rates), the electrode surface tends towards full additive coverage while, at higher deposition or stripping rates (i.e. rapid BDAC deactivation), the electrode surface tends towards a coverage depending on the additive's adsorption and deactivatio (open full item for complete abstract)

Committee: Rohan Akolkar (Committee Chair); Robert Warburton (Committee Member); Jesse Wainright (Committee Member); Alp Sehirlioglu (Committee Member) Subjects: Chemical Engineering

Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1970, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Arts, The Ohio State University, 1922, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, Miami University, 2024, Chemistry and Biochemistry

The objective of this research is focused on the electrochemical detection of hydrogen peroxide (H2O2) using modified boron doped diamond (BDD) electrodes. BDD is a carbon-based electrode material that is known for its low capacitance, wide potential window, inertness, and resistance to fouling. It is not, however, sensitive to H2O2. Due to this, platinum (Pt) and palladium (Pd) nanoparticles (NPs) were deposited onto the BDD surface using a two-step modification method to enhance the sensitivity of the BDD for H2O2 detection. Deposition charges of 1.00 mC, 3.23 mC, and 5.00 mC were tested along with NP concentrations of 0.25 mM, 0.50 mM, 1.0 mM, and 5.0 mM. Cyclic voltammetry (CV), chronoamperometry (CA), and chronocoulometry (CC) were used to characterize the different modified electrodes and bovine serum albumin (BSA) was used to test these electrodes for biofouling. After modification, the BDD-NP electrodes exhibited enhanced sensitivity to H2O2 with limits of detection in the µM range. Overall, this thesis focused on the development of a modified BDD electrode for the electrochemical detection of H2O2.

Committee: Cory Rusinek (Advisor); Neil Danielson (Committee Chair); Kevin Yehl (Committee Member); Shirmir Branch (Committee Member) Subjects: Chemistry

Doctor of Philosophy, University of Akron, 0, Polymer Science

Lithium-ion batteries (LIBs) are crucial energy sources across diverse sectors, from medical devices in nanotechnology to grid energy storage. However, their liquid electrolytes pose significant safety risks, particularly during overheating, leading to battery explosions. This hazard is especially pronounced in electric vehicles, where breaches can trigger catastrophic cell explosions. Solid-state batteries (SSBs) have emerged as a promising alternative, offering enhanced safety by replacing liquid electrolytes with solid-state electrolytes (SSEs). Despite this, scaling up LIB production and improving energy and power density remain significant challenges. Chapter I presents a novel approach using 3D printing technology to fabricate solid polymer electrolyte membranes for SSBs. This method replaces conventional polymer separators and liquid electrolytes with a thin, ionically conductive composite based on poly(ethylene glycol) diacrylate (PEGDA) reinforced with polyamide for mechanical strength. Using a digital light processing (DLP) 3D printer, we created thin SSE films. Lithium plating/stripping tests showed that the printed PEGDA/polyamide electrolyte maintained stable cycling performance over 1,400 hours at a current density of 0.05 mA/cm². Additionally, LIBs with the 30 μm polyamide-reinforced electrolyte exhibited excellent cyclability at a 0.2 C rate under ambient conditions (30°C). Chapter II addresses issues with traditional cathode electrode processes, such as the insulating polyvinylidene fluoride (PVDF) binder and toxic organic N-methyl-2-pyrrolidone (NMP) solvent. We introduced a solvent-free electrode processing technique using a thermal cross-linkable polymer electrolyte as a binder substitute. This method allows the creation of higher mass loading electrodes without volatile organic compounds (VOCs). Cathode electrodes were prepared on the current collector using hydraulic thermal pressing, with adjustments to the pressing force. Structural parameter (open full item for complete abstract)

Committee: Yu Zhu (Advisor); Steven S.C. Chuang (Committee Chair); Chunming Liu (Committee Member); Weinan Xu (Committee Member); Tianbo Liu (Committee Member) Subjects: Chemistry; Energy; Materials Science

PhD, University of Cincinnati, 2024, Arts and Sciences: Chemistry

Mechanochemistry has witnessed remarkable growth as an effective method for performing chemical transformations in minimal or solvent-free conditions, this aligns with the global shift towards environmentally friendly, green protocols in chemical processes. Unique reaction selectivity and reactivity exhibited by mechanochemical processes offer the potential for discovering novel products and processes not achievable through conventional solution-based approaches. Additionally, mechanochemistry facilitates reactions involving reactants with low solubility, a challenging task in solution-based setups, and allows for shorter reaction times and more convenient setups for synthetic transformations. Despite these advantages, further investigation is needed to fully comprehend the potential of mechanochemistry for various synthetic purposes and applications. This dissertation explores mechanochemistry, emphasizing its interplay with electrochemistry, solvent-free reductions, its scalability using a twin-screw extruder, and diverse applications. Initially, water and metal combination mediated carbonyl group reduction under mechanochemical conditions was explored. The aim was to comprehend the precise temperature control required for mechanochemical reactions and unravel the reaction mechanisms in greater detail. The study also explored the galvanic cell's similarity to the mechanochemical vial with metal combinations in the presence of water. However, tuning the metal combination to selectively reduce the carbonyl group proved difficult in the presence of water. Water promoted hydrogen gas evolution and hydrogenation of the organic substrates, which rendered it challenging to isolate the effect of metal combinations on selective reduction, Furthermore, the development of a mechanoelectrochemical cell allows for the integration of mechanochemistry and electrochemistry, examining various metal combinations for electrochemical reduction. The designed cell which was connected t (open full item for complete abstract)

Committee: James Mack Ph.D. (Committee Chair); Ashley Ross Ph.D. (Committee Member); Hairong Guan Ph.D. (Committee Member) Subjects: Chemistry

PhD, University of Cincinnati, 2024, Arts and Sciences: Chemistry

Real-time monitoring of neurotransmitters is of great importance because of the roles these neurochemicals play in vital bodily functions. Fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes (CFMEs) has advanced our understanding of neurotransmitter dynamics as a prominent electroanalytical technique. Innate biocompatibility, functionalization, etc. make carbon an attractive electrode substrate; unfortunately, decades of research have rarely branched away from dopamine due to poor CFME morphology tunability and reliance on adsorption interactions. Here, we developed tunable carbon-based microelectrode surfaces through geometry manipulation and surface chemical doping for enhanced neurochemical interfacial interactions. Chapter 1 provides a critical perspective on the future of carbon-based neurochemical detection with a summary of novel FSCV electrode materials used to date; we identified three challenges FSCV detection faces and routes to address these challenges through novel carbon electrodes. Challenge one involves unobserved events caused by diminished temporal resolution. Chapters 2-5 addressed this issue by introducing porous structures to CFMEs or surface roughness to graphene oxide microelectrodes (GFMEs) for improved electrochemical reversibility. Chapter 2 uses nanoporous carbon nanofibers electrodeposited onto CFME frameworks. These microelectrodes improve dopamine sensitivity and electron transfer kinetics, but low pore dimensions fail to trap dopamine generating negligible changes in temporal resolution. Chapter 3 uses biomass syntheses of macroporous carbon demonstrating the first instance of the use of biomass-derived porous carbons for implantable electrode applications. Macroporous framework-modified CFMEs provide increased surface defects and pores large enough to momentarily trap dopamine for improved electrochemical reversibility, sensitivity, and frequency independence. Chapter 4 uses copolymer wetspinning to synthesize u (open full item for complete abstract)

Committee: Ashley Ross Ph.D. (Committee Chair); Ryan White Ph.D. (Committee Member); Noe Alvarez Ph.D. (Committee Member) Subjects: Chemistry

PhD, University of Cincinnati, 2024, Arts and Sciences: Chemistry

This dissertation represents an in-depth investigation into the rapidly evolving field of electrocatalytic conversion, which holds significant promise for advancing renewable energy applications. The primary objective of this research is to harness electrocatalysis for the efficient transformation of small molecules into valuable feedstocks. A key focus is on the synthesis and application of electrocatalysts, particularly metalated porphyrins, to expedite reaction kinetics and improve product selectivity. In this dissertation, we present several novel molecular catalysts tailored for distinct electrochemical transformations. Central to this dissertation is the development of novel electrocatalysts, exemplified by the synthesis of an innovative iron porphyrin complex (FePEGP) featuring a strategically placed poly(ethylene glycol) unit. Controlled-potential electrolysis using FePEGP exhibited an impressive Faradaic efficiency of 98% and a current density of –7.8 mA/cm2 at –2.2 V vs. Fc/Fc+ in acetonitrile with water as the proton source. Our mechanistic investigations revealed that the PEG unit's presence enhances catalytic kinetics, leading to improved CO2 reduction efficiency. This catalyst demonstrates exceptional selectivity and activity in the electrochemical reduction of carbon dioxide to carbon monoxide, offering a promising avenue for sustainable energy generation. Collaborative research endeavors with the University of Tennessee have further expanded the scope of this work, particularly in exploring tin porphyrin complexes (SnPEGP) for hydrogen evolution. SnPEGP displayed high activity (–4.6 mA/cm2 at –1.7 V vs. Fc/Fc+) and selectivity (H2 Faradaic efficiency of 94%) in acetonitrile with trifluoroacetic acid (TFA) as the proton source. Spectroelectrochemical analysis and quantum chemical calculations suggested an Electron-Chemical-Electron-Chemical (ECEC) pathway for proton reduction mediated by the tin porphyrin catalyst. Through synergistic e (open full item for complete abstract)

Committee: Jianbing Jiang Ph.D. (Committee Chair); Peng Zhang Ph.D. (Committee Member); Hairong Guan Ph.D. (Committee Member) Subjects: Chemistry

Doctor of Philosophy, University of Akron, 2024, Chemistry

Electrochemical methods, which collect data on potential and/or current, are useful techniques that have been utilized in various fields, including energy storage, medicine, and biology. My PhD research employs electrochemical methods in three areas: investigating redox flow batteries (RFBs), understanding heterogeneous electron transfer (ET) theories, and establishing a connection with machine learning (ML). This dissertation is organized into three parts accordingly. The first part of this dissertation (Chapters II through V) is the investigation of ferrocene-based aqueous redox flow batteries (ARFBs). The development of RFBs has gained significant attention in recent years due to the growing demand for efficient and reliable energy storage systems. ARFBs, which use water-soluble compounds, have become increasingly popular because of their lower electrolyte resistance, reduced cost, enhanced safety, and lower environmental impact. Ferrocene (Fc), which can be modified to be soluble in water, possesses a high reversibility and electron transfer rate, making it an ideal candidate for ARFBs. During my Ph.D. period, several new water-soluble sulfonated Fc based ARFBs were characterized, including 1,1′-bis(sulfonate)ferrocene dianion disodium (1,1'-FcDS), ferrocene-1,1'-bis(sulfonate)ferrocene dianionic salts with varying imidazolium cations, pyridinium salts of the ferrocene bis(sulfonate) dianion (FcPyr), 3-((ferrocenyl)methyldimethylammonio)-1-propanesulfonate (Fc3), and 4-((ferrocen-yl)methyldimethylammonio)-1-butanesulfonate (Fc4). The suitable structures of Fc for ARFB applications have been revealed. The second part of this dissertation focuses on understanding heterogeneous electron transfer. Various electroanalytical techniques, including steady-state current, cyclic voltammetry (CV), and differential pulse voltammetry (DPV), were simulated in COMSOL Multiphysics, and the results are presented in Chapter VI. Chapter VII describes the ET processes in a non- (open full item for complete abstract)

Committee: Aliaksei Boika (Advisor); Christopher Ziegler (Committee Member); Chrys Wesdemiotis (Committee Member); Chunming Liu (Committee Member); Zhong-Hui Duan (Committee Member) Subjects: Chemistry; Computer Science; Education; Energy

Master of Science, The Ohio State University, 2024, Chemistry

Both C(sp3)-H fluorination and C(sp3)-H methylation methods have increasingly gathered interest over the last decade. Most current fluorination methods use electrophilic fluorine reagents such as NFSI or Selectfluor to achieve C(sp3)-F bond formation. However, there are limited reports that harness nucleophilic fluorine sources to form such bonds. On the other hand, while there exist “state-of-the-art” methods for C(sp3)-H methylation, there are no reported examples of high-valent copper complexes that can achieve such a transformation. The Zhang lab has synthesized several high-valent copper complexes, most notably a novel LCuIIIF complex (L = PDA) that exhibits dual reactivity of hydrogen atom abstraction (HAA) and fluorine radical capture. Furthermore, in collaboration with the Sevov lab, this complex was employed using electrochemistry to achieve catalytic reactivity in situ to achieve C(sp3)-F bond formation. Despite this, limitations arise, most notably low catalyst turnover due to a sluggish HAA step. Herein, electrochemically generated oxidants were explored to accelerate the HAA step. It was found that LCuIIIOH generated in situ from [LCuIIOH][TBA] helped to lower substrate loading and achieve C(sp3)-H fluorination in high yields, albeit stoichiometrically. In addition, the syntheses of LCuIIICH3 and LCuIIICF2H complexes were explored to use as mechanistic probes for C(sp3)-H functionalization. An efficient route towards obtaining these compounds proceeds through transmetalation of [LCuIIF][TBA] with zinc-based organometallics, followed by oxidation of the isolated [LCuIIR][TBA] (R = CH3, CF2H) salts. It was found that these salts exhibit negative redox couples. Furthermore, LCuIIICF2H exhibits unique reactivity that targets aryl C(sp2)-H bonds.

Committee: Shiyu Zhang (Advisor); Christine Thomas (Committee Member) Subjects: Chemistry

PhD, University of Cincinnati, 2023, Arts and Sciences: Chemistry

Lead contamination can cause serious health effects in humans, especially in young children. While there are various sources of lead contamination, the two major sources are drinking water and paint. The lead in drinking water comes from the lead service lines (LSLs) or lead soldering, while lead was added to paints originally as either pigments or additives. Traditionally, the gold standard for detecting lead in drinking water and paint is inductively coupled plasma-mass spectroscopy (ICP-MS) or atomic absorption spectroscopy (AAS) since these techniques can detect lead ions and insoluble lead compounds. However, these methods are expensive and require trained personnel, so samples must be collected and sent off for analysis. Therefore, homeowners concerned about their water or paint must wait for results. There has been an effort to develop electrochemical sensors that can detect low concentrations of lead in water and paint; however, they require a sample preparation step, typically acidification with nitric acid, to dissolve the insoluble lead compounds before analysis. Again, this makes these methods less user-friendly. This dissertation focuses on using electrochemical methods for acidifying water samples containing drinking water and detecting the lead, either a lead corrosion scale from LSLs or lead paint. The first part of this work focuses on membrane electrolysis, a technique that allows for the in situ generation of nitric acid so that no reagent has to be handled. This technique was used to dissolve the lead corrosion scale and lead paint samples so they could be detected by square wave anodic stripping voltammetry (SWASV). Standard addition is used to estimate the lead concentration from the electrochemical method for either sample, and the results are then compared to ICP-MS. The results show good agreement between the comparisons of the concentrations determined through the electrochemical method and ICP-MS for both the lead corrosion scale a (open full item for complete abstract)

Committee: Noe Alvarez Ph.D. (Committee Chair); Ryan White Ph.D. (Committee Member); Neil Ayres Ph.D. (Committee Member) Subjects: Analytical Chemistry

Master of Science (MS), Wright State University, 2023, Chemistry

PART A: GREEN SYNTHESIS OF COPPER NANOPARTICLES AND THEIR UTILIZATION IN THE DETECTION OF NEUROTRANSMITTERS Neurotransmitters, such as dopamine and epinephrine, are chemicals frequently found in the brain and are responsible for a number of human moods, needs, and emotions.1, 2 Detection of such neurotransmitters allows for a better judgement of a person's physical and mental state, a utility that is vital in determining the presence of disease and mental illnesses.2 Electrochemical detectors used for such detections are often modified by materials such as metal nanoparticles.3 However, synthesizing nanoparticles can involve or produce chemicals, ammonium hydroxide among them, that are not safe for the environment.4 The goal of this research was to synthesize copper oxide nanoparticles utilizing environmentally-friendly techniques involving lemon juice and to detect dopamine and epinephrine in the presence of an interferant, ascorbic acid, using those nanoparticles. Creation of the nanoparticles, confirmed by a UV-Vis, indicated a successful synthesis. Voltametric analyses utilizing these nanoparticles display an improvement to detection of the neurotransmitters and indicate the possibility of further improvements to the methods of synthesis to better produce nanoparticles for this particular purpose. iii Part B: GREEN SYNTHESIS OF SILVER NANOPARTICLES AND THEIR UTLIZATION IN THE DETECTION OF PHENOLS A second unrelated research study included in this thesis is the development of a silver nanoparticles attached to a carbon electrode to detect phenol, a carcinogen and pollutant, electrochemically. The silver nanoparticles (AgNPs) were synthesized in an environmentally-friendly method utilizing honey. The successful synthesis of the AgNPs was confirmed by UV-Vis spectroscopy before being utilized to detect phenol. Phenols are extremely harmful to humans and aquatic organisms, thus making development of a sensor that is compact, easy to transport and capable of qu (open full item for complete abstract)

Committee: Suzanne K. Lunsford Ph.D. (Advisor); Christopher C. Barton Ph.D. (Committee Member); Travis B. Clark Ph.D. (Committee Member) Subjects: Chemistry

Doctor of Philosophy, Case Western Reserve University, 2023, Chemical Engineering

The work of my Ph.D. thesis focuses on understanding the physical and electrochemical properties of deep eutectic solvents (DESs) and concentrated hydrogen bonded electrolytes (CoHBEs) through experiments concerning their use as electrolytes for redox flow batteries. My work aims to provide a fundamental understanding of how DES components govern bulk properties and double-layer structure with the ultimate goal of leveraging the gained knowledge to design new electrolytes for flow battery applications. Thesis Goals ● Bulk liquid properties: To determine how molecular structure and composition of DES components affect bulk macroscopic properties such as density, viscosity, and conductivity. ● Electrode-electrolyte interface: To develop a physical model of the voltage-dependent ion accumulation in DESs and CoHBES near the electrode and to identify surface species during the course of a redox reaction. ● Redox active organics: To study redox active organics as potential candidates for redox material in a CoHBE-based flow batteries. Chapter 3: In Chapter 3, we investigate the differential capacitance of choline chloride (ChCl) and ethylene glycol (EG) as a function of potential and composition using electrochemical impedance spectroscopy (EIS) on glassy carbon, Au, and Pt electrodes. We compared these results to glyceline (ChCl:glycerol, 1:2). The capacitance-potential curves on glassy carbon were best explained by the modified Gouy-Chapman model. We observe a dampened U-shape similar to dilute electrolytes. However, the presence of significant ionic and hydrogen bonding interactions in these electrolytes introduced ambiguity regarding the point of zero charge, where the capacitance weakly depended on potential. When using Au electrodes, we observe an increase in capacitance due to desolvation and specific adsorption of Cl ions. Conversely, with Pt electrodes, we observe increased capacitance with decreasing Cl concentrations. These results indicate that deep e (open full item for complete abstract)

Committee: Burcu Gurkan (Advisor); Clemens Burda (Committee Member); Robert Warburton (Committee Member); Robert Savinell (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy (PhD), Ohio University, 2023, Chemistry and Biochemistry (Arts and Sciences)

The purpose of this study was to examine the redox behavior of the fac-[Re(bpy)] Lewis base catalysts in CO2 reduction processes using the Lewis acid co-catalyst [Zn(cyclam)]2+. Experimental and computational data indicate that [Zn(cyclam)]2+ facilitates Cl ion dissociation, thus shifting the ReI(bpy) first reduction to a less negative potential, allowing the catalyst to be activated with a lower energy requirement. Further, the addition of [Zn(cyclam)]2+ usually reduced the amount of energy needed for CO2 reduction, except for catalysts with electron-withdrawing groups (EWGs). In another study, with the help of a new ligand and Europium ions, we have designed and synthesized a lantern-shaped coordination cage. It is capable of selectively trapping charged molecules and exhibits changes in its photophysical properties when compared to individual molecules. We measured the strength of the interaction and the binding constant of guest molecules. The luminescence properties of the cage were affected by the presence of the guest molecules.

Committee: Michael Jensen Dr. (Committee Member); Eric Masson Dr. (Advisor); Katherine Fornash Dr. (Committee Member); Jixin Chen Dr. (Committee Member) Subjects: Chemistry

PhD, University of Cincinnati, 2023, Arts and Sciences: Chemistry

Detection of zinc (Zn(II)) electrochemically has been explored over the last several years specifically for environmental applications; however, electrochemical detection in a biological environment is severely underdeveloped. This is due to the rapid change in concentration that can occur on a millisecond time scale, or faster, which makes using traditional voltammetry difficult for biological processes. Fast-scan cyclic voltammetry (FSCV) has been used in the mechanistic study of neurochemicals, like dopamine, in the brain and lymph node. This dissertation aims to develop electrochemical methods for Zn(II) detection with FSCV and under biological conditions with emphasis on stability, sensitivity, and selectivity. Chapter 2 discusses the detection of Zn(II) with FSCV at carbon-fiber microelectrodes (CFME) and the need for novel waveform development. Chapter 3 investigates the extent to which Zn(II) interacts at graphene-based microfibers and demonstrates co-detection of Zn(II) with purines to improve the possibilities of neurochemical measurements in the brain. Chapter 4 and 5 expand beyond carbon-based materials and explore the use of functionalized gold fibers to improve sensitivity and selectivity of Zn(II) versus interfering analytes. Chapter 4 will investigate the impact of various plasma treatments on the surface characteristics of gold-fiber microelectrodes (AuMe) and correlates those changes in electrochemical detection of Zn(II). In Chapter 5, I develop a novel ionophore-modified AuMe to significantly improve Zn(II) selectivity. A summary of the work shown, and a future outlook will be presented in Chapter 6. This dissertation establishes a complete electrochemical characterization of Zn(II) for FSCV, as well as an in-depth study of how different substrates can affect the detection of Zn(II). Further understanding of Zn(II)'s interaction with different microelectrodes provides mechanistic insight into the Zn-electrode interface leading to im (open full item for complete abstract)

Committee: Ashley Ross Ph.D. (Committee Chair); Yujie Sun Ph.D. (Committee Member); Michael Baldwin Ph.D. (Committee Member) Subjects: Analytical Chemistry

PhD, University of Cincinnati, 2023, Engineering and Applied Science: Chemical Engineering

The issue of global warming brought on by the buildup of greenhouse gases, particularly CO2, has presented a serious threat to human survival over the past few years. As a result, the recovery and utilization of CO2 have emerged as critical areas of focus in environmental science and catalysis. The electrocatalytic conversion of CO2 into multi-carbon (C2+) products with higher commercial value has drawn the most interest among these initiatives. This dissertation will focus on a fundamental understanding of how to improve the electrochemical CO2-to-C2+ products conversion by modulating the coverage and binding strength of essential intermediates (e.g., *CO, *CH2CHO, and *O), as well as controlling the activation energy for crucial elementary steps (i.e., C–C coupling for C2+ products and *CH2CHO hydrogenolysis for ethylene). The approaches to achieve these goals can be summarized as: CO electroreduction kinetics investigation, tandem catalyst design, high-density planar defect exposure, and oxygen-bound intermediate regulation. Specifically, Chapter 2 would elucidate how CO-dependent kinetics of higher-order products distinguish different mechanistic sequences, kinetically relevant intermediates and *CO adsorption strength. With the aid of a flow electrolyzer integrated with gas diffusion electrode, the *CO dimerization is identified as the rate-determining step for ethylene and ethanol production. Kinetic studies also reveal that product-specific active sites are responsible for activity and selectivity toward specific C2+ products. In Chapter 3, a model tandem catalyst is prepared to verify the local CO concentration and the CO spillover effect in CO2 electroreduction toward C2+ products. More importantly, it is demonstrated as how to combine the modulation of both tandem catalyst compositions and spatial arrangement of two active sites for maximizing *CO utilization efficiency. Besides the *CO coverage, the *CO adsorption strength is anothe (open full item for complete abstract)

Committee: Jingjie Wu Ph.D. (Committee Chair); Vesselin Shanov Ph.D. (Committee Member); Wei Liu Ph.D. (Committee Member); Junhang Dong Ph.D. (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2023, Chemistry

The direct, reductive coupling of two electrophilic carbons has become an attractive alternative to traditional cross-coupling methodologies, which traditionally rely on the presence of a nucleophilic and electrophilic component. A renaissance in electrochemical techniques have helped to facilitate these transformations owing in part to the tunability of reaction potentials to facilitate electron transfer. Although these transformations are robust, there are still many incompatible/unknown combinations of Csp2-Csp3 couplings from various sources. Recently, reports have led to the reevaluation of the established cross-electrophile coupling (XEC) mechanism, invoking NiI as the catalytic intermediate responsible for activating both the alkyl and aryl component. This creates a scenario in which successful couplings are entirely dictated by their ease of activation. Tertiary substrates are easier to activate than primary and as such undergo deleterious side reactions. This also creates a scenario in which more difficult to activate aryl halides remain untouched during these processes. Critical to the success of this methodology was the application of a dual-catalyst system in which each catalyst is responsible for activating a single component. Ligand design and detailed mechanistic studies were crucial to guide the development of a wide scope of traditionally incompatible substrates (Chapter 2). Despite the successes of this work, there still exist several limitations in the ability to activate several classes of coupling partners. Other radical precursors (absent of aryl halides) were not tolerated under these conditions owing to their low reduction potentials. Heteroatom containing arenes were also unable to perform the reactions. Stoichiometric analysis showed that NiII-Ar complexes were capable of capturing radicals generated in situ from several of these challenging precursors. Utilizing a simple redox-non innocent ligand system, were developed a library of NiII (open full item for complete abstract)

Committee: Christo Sevov (Advisor); Dennis Bong (Committee Member); T. V. Rajanbabu (Committee Member) Subjects: Chemistry; Organic Chemistry