Master of Science (M.S.), University of Dayton, 2024, Materials Engineering

Rare earth elements (REEs) are essential to many modern-day technological applications. Due to their difficult and environmentally harmful refining methods, many of these REEs are imported to the U.S. from various other countries. With countries like China dominating the market, the U.S. supply chain is at risk. A potential solution to this issue would involve the use of proteins to extract these REEs in an environmentally sustainable manner. Custom proteins would be designed to extract specific REEs from their mixed metal ores through computer simulations, namely molecular dynamics. Currently the design process is stymied by the lack of working force fields for REEs within many molecular dynamics programs. This work seeks to address this issue by creating custom force fields designed around replicating basic experimental properties the REE ions have with water, counterions, and REE binding proteins. This is done utilizing a Bayesian optimization algorithm which can efficiently and accurately choose new parameters to test and verify for a wide variety of systems.

Doctor of Philosophy, The Ohio State University, 2024, Biophysics

Fragment-based quantum chemistry methods provide a way to circumvent the steep nonlinear scaling of electronic structure calculations, enabling the investigation of large molecular systems using high-level methods. First, we present calculations on enzyme models containing 500-600 atoms using the many-body expansion (MBE) and compare them to benchmarks where the entire enzyme-substrate complex is described at the same level of density functional theory (DFT). When amino acid fragments contain ionic side chains, the MBE exhibits oscillatory behavior under vacuum boundary conditions, but rapid convergence is restored using low-dielectric boundary conditions. This suggests that full-system gas-phase calculations are unsuitable as benchmarks for assessing errors in fragment-based approximations. A three-body protocol maintains sub-kcal/mol accuracy compared to supersystem calculations, as does a two-body approach combined with a low-cost full-system correction. In the next section, we use fragmentation to compute protein–ligand interaction energies in systems with several thousand atoms. Convergence tests using a minimal-basis semi-empirical method (HF-3c) indicate that two-body calculations, with single-residue fragments and simple hydrogen caps, are sufficient to reproduce interaction energies obtained using conventional supramolecular electronic structure calculations, to with 1 kcal/mol at about 1% of the cost. Additionally, we show that semi-empirical methods can be used as an alternative to DFT, to assess convergence of sequences of quantum mechanics (QM) models (of increasing size) generated by different automated protocols. Two-body calculations afford a low-cost way to construct a “QM-informed” enzyme model. This streamlined, user-friendly approach to building ligand binding-site models requires no prior information or manual adjustments, making it accessible and practical for a wide range of applications. For the latter parts of this work, we will be focusi (open full item for complete abstract)

Doctor of Philosophy, Case Western Reserve University, 2024, Chemistry

Free radical-induced oxidation of lipids generates a vast array of molecules. One of these is a phospholipid ester of 8-oxo-4-hydroxyoct-2-enoic acid. A chemical mechanistic hypothesis suggested that conjugation of this a,b-unsaturated aldehyde with glutathione could lead to the formation of a molecule, which we named pseudo leukotriene (øLT)C, that bears structural and functional resemblance to leukotriene LTC4. Catabolism of LTC4 to a glycyl cysteine derivative LTD4 and of LTD4 to a cysteine derivative LTE4, suggested that øLTC would be catabolized to produce a glycyl cysteine derivative øLTD and then a cysteine derivative øLTE. Because LTE4 is acetylated in the kidneys and excreted in urine, the production of N-acetyl-øLTE in vivo was also postulated. To test these hypotheses, total syntheses of øLTs and N-acetyl-øLTE were performed. In ten steps, a divergent strategy generated each øLT from a single precursor, ethyl glutaryl chloride. Because two diastereomers were expected to be generated in the Michael addition of a thiol and the reduction of a ketone, each synthesis is expected to produce four enantiomers. Pure samples are especially important for testing the biological activities of øLTs. Therefore, HPLC methodology was developed that provided pure samples, as diastereomeric mixtures, of all synthetic øLTs. The ethyl ester intermediates øLTE-OEt could be separated into two pure diastereomers and a mixture of two other diastereomers, confirming that the syntheses are non-diastereoselective. Heavy isotope derivatives were also prepared and used to develop LC-MS/MS analyses to facilitate the detection, structural characterization, and quantitation of øLTs in vitro and in vivo. The Salomon group exploited these HPLC pure samples of øLTs to determine their production and biological activities in vitro and in vivo. In a pilot model study of Alzheimer's disease, I demonstrated that exposure of differentiated human neuronal SH-SY-5Y cells to the Ab1-42 peptid (open full item for complete abstract)

Doctor of Philosophy in Clinical-Bioanalytical Chemistry, Cleveland State University, 2024, College of Arts and Sciences

Hypoxia Inducible Factor 1 (HIF-1) is a heterodimeric transcriptional factor that plays a physiological role in low oxygen concentration or hypoxia. HIF-1 consists of two dimers: HIF-1alpha (HIF-1α) and HIF-1beta (HIF-1β). HIF-1α is the active oxygen-sensing domain in the cytoplasm that leads to stabilizing and overexpression of HIF-1 in the cells during hypoxia. On the other hand, HIF-1β is a stable domain in the nucleus that is required to form a dimer with HIF-1α in the DNA to express the HIF-1 gene. Upregulation of HIF-1α by either hypoxia or drug molecules has been elucidated to overexpress more than 100 tumor genes. These genes are involved in developing angiogenesis (vascularization), metastasizing, cellular proliferation, switching to anaerobic metabolism, and cellular survival. Hepatocellular carcinoma (HCC) is one of the solid tumors that have a hypoxic intratumor environment and relies on overexpression of HIF-1α to overcome hypoxia and allow cancer cells to survive, proliferate, and metastasize in these harsh conditions. Targeting or downregulating the HIF-1α gene in HCC with chemical compounds may provide a treatment for this cancer. However, inducing and overexpression of HIF-1α has many of benefits, such as accelerating wound healing in diabetic patients. Diabetic patients suffer from hyperglycemia and thick blood that delay wound healing and may cause infections. Upregulation of HIF-1α expression in diabetic wounds will increase the speed of the repair process of wound healing. HIF-1α plays a vi crucial role in all phases of wound healing by facilitating cell division, growth factor secretion, cell migration, survival in hypoxic environments, and matrix synthesis. We screened the LOPAC drug library to discover several chemical compounds that either inhibit or stimulate HIF-1α expression. These drug candidates have been further investigated to confirm their activity against HIF-1α expression. These findings suggest that up or downregulation of HIF-1 (open full item for complete abstract)

Doctor of Philosophy, University of Akron, 2024, Polymer Science

Polymer-based coacervates can be prepared from a large variety of compositions. This provides versatility to coacervates as a material platform, but can also make them difficult to characterize, especially when other molecules or biologics are used in the same solution. The Joy lab has previously developed a platform to make thermoresponsive coacervating polyesters in a modular fashion. This allows us to make incremental changes to the coacervate structure and thus better observe how the structure affects the properties in various applications. In this work, we look at coacervates for hemostatic materials for non-compressible torso hemorrhage, and as sustained release drug delivery vehicles for colchicine release. Through a variety of experimental methods, our goal is to link structural changes in the coacervating polyester to the performance of the coacervate. The performance of our hemostatic coacervate was evaluated using clotting time tests, hemolysis tests, and rheology to determine how our materials interact with blood components. The trend in this data was further confirmed with in vivo mouse model studies which showed that the coacervates can perform well as hemostatic materials, and that the in vitro studies can effectively screen materials. We have also shown that amines in our coacervates are not effective and contrary to expectations and literature may increase bleeding times. To better predict coacervate properties on drug release, we employ NMR techniques such as STD and DOSY to better understand the strength of interactions between the coacervate and drug. The final drug release study confirms our NMR findings, and while the NMR techniques are not easily quantifiable, they do show an excellent relative predictability which can also be used to screen materials for an application. Ultimately, the tools employed for understanding coacervate performance enhance our understanding of their behavior in applications such as hemostasis and sustained (open full item for complete abstract)

Doctor of Philosophy (PhD), Ohio University, 2024, Chemical Engineering (Engineering and Technology)

Oil refineries must adapt to unfamiliar crude oil chemistries originating from modern unconventional oil resources. Additionally, they face statutory requirements to co-process acidic bio-oils with ordinary crude oils. This results in exotic crude chemistries which can aggravate concerns for naphthenic acid and sulfidation corrosion related failures, amongst other processing challenges. Therefore, a reliable corrosion prediction tool becomes indispensable for oil refineries to ensure the safety and integrity of processing/distillation units while refining these unconventional oils. For the construction of such a corrosion prediction model, the reaction mechanisms of both naphthenic acid and sulfidation corrosion are further deciphered in this dissertation research. Associated kinetic equations are modeled to calculate the rates of the proposed elementary steps. These elementary rate equations are combined using mass conservation principles to obtain equations for overall corrosion rates. The derived corrosion rate equations capture the trends of experimental corrosion rates with respect to time, temperature, and concentrations of corrosive species. The phenomenological coefficients of the kinetic equations are derived from experimental and literature data. A computer program consisting of the derived kinetic equations has been built for the prediction of refinery corrosion. Simulations of the corrosion rates with respect to system parameters have been demonstrated.

Master of Science, University of Akron, 2024, Polymer Engineering

Highly branched low-density polyethylene (HB-LDPE) synthesized from solely ethylene monomer through Brookhart-type α-diimine nickel or palladium catalysts have unique microstructure, low melting temperature and thermal plastic elastomer (TPE) properties. With the increasing demand for recyclable material, synthesis of HB-LDPE has been extensively studied. However, details of its microstructure and the impact of the microstructure on solid structure as well as mechanical/thermal properties have not been fully understood. In this study, various characterizations and mechanical testing are conducted on HB-LDPE entries synthesized by original Brookhart catalyst, 8-p-tolylnaphthylimino substituted sandwich catalyst, and a multinuclear heterogeneous crosslinked catalyst. First, 13C solution-state NMR spectroscopy was employed to obtain detailed insights into their branch structure, including branch density, identity and localization. Using chemical superposition methods, detailed localization structure of the branches were revealed. Formation mechanisms of several localization structures are proposed in supplementary for existing chain walking mechanisms. Second, the solid structure of HB-LDPEs was investigated by using differential Scanning calorimetry (DSC), X-ray diffraction (XRD) and solid-state NMR spectroscopy. The formers are no longer capable of quantitative characterization due to the low crystallinity. Through solid-state 13C NMR analysis, it was found that some entries are entirely amorphous, while the others are semi-crystalline entries which range between 1 and 5 %. The molecular dynamics in the crystalline phase is characterized through 13C spin-lattice relaxation time (T1C), which ranges from 4s to 80s, implying a variable crystalline size. By examining the combination of microstructure and crystalline structure, it is revealed that only those entries with both low levels of long chain branching (LCB) below 10 b/1kC and short chain branching (SCB) below (open full item for complete abstract)

Master of Science (M.S.), University of Dayton, 2023, Chemistry

Rare earth elements are found in relative ubiquity within the earth's crust and have a multitude of application to both everyday life and military defense. On the periodic table, rare earth elements consist of all 15 lanthanides, along with scandium and yttrium. These elements have a wide variety of application, spanning from private and public sector applications, all the way to military defense, thus making them highly desirable metals for eventual utilization. Current methods of rare earth element extraction and purification involve environmentally harmful processes, leading to North America's decision to not mine for rare earth elements within its territories. This decision has created a distinct lack of self-sufficiency in rare earth element production, currently resulting in a complete reliance of rare earth element imports from other countries, namely China. Due to the current processes of rare earth element extraction and purification posing large detriment to environmental stability along with a decrease in U.S. autonomy, determination of new, safer routes of rare earth element processing is of utmost priority. Specific proteins are known to bind metal ions, which has provided the scientific foundation for a protein-based extraction and purification method targeting rare earth elements. Previous research has identified a protein which is known to bind lanthanides, providing a high potential prospect for the solution to this problem. The protein of interest, named lanmodulin (LanM), contains four regions, denoted as EF hands, with three of which being involved in lanthanide binding. Building upon the previously mentioned solution is a thioredoxin protein found in the extremophile Pyrococcus furiosus. P. furiosus thioredoxin has shown the ability to stably accept newly introduced peptide sequences within its native amino acid sequence. The area of insertion possesses closely located cysteine residues which show p (open full item for complete abstract)

Master of Science in Chemistry, Youngstown State University, 2023, Department of Biological Sciences and Chemistry

Herein, density functional theory (DFT) was used for optimizing the geometry of proposed intermediates, built using Spartan Student, in the synthesis of the indium infinite-chain secondary building unit. Dimeric indium species with similar backbones were proposed for each system as a representative of the indium infinite-chain secondary building unit. By calculating the enthalpies of formation for intermediates created from InCl3(H2O) and In(NO3)3(H2O), similar and contrasting enthalpic trends between systems and individually proposed mechanisms were found and compared. All systems consist of motifs 1, 2, 3a, and 3b, which attempt to describe similar mechanistic routes from starting material to proposed dimer. The deprotonation of water before and after becoming a µ2 bridge with respect to two indium atoms was compared among systems, and the most enthalpically favorable bridge to form first (hydroxyl or carboxylate) in the synthesis of the indium infinite-chain secondary building unit was examined. After analyzing the results, they support the possibility that there may be multiple enthalpically reasonable methods of self-assembly and repair.

Doctor of Philosophy, University of Akron, 2023, Polymer Science

Polymer mechanochemistry explores the selective response of designed chemical structures (mechanophores) on polymer chains to force. Among the many applications, included but not limited to, biasing reaction pathways, self-strengthening materials, and conductivity/color switching, one field that is of particular interest is the mechanochemically controlled degradation due to the recent focus on polymer recycling. Here in the first two studies, two unique force-responsive degradable polymers and their potential applications in sustainable materials are investigated. First, the concept of “locked degradability” is demonstrated by a cyclobutane-fused lactone polymer. With the lactone gated by cyclobutane mechanophore, the polymer backbone remains intact under common environmental stimuli (locked state). When degradation is needed, the cyclobutane mechanophore can undergo force-induced cycloreversion, and unlock the degradability by formation of a degradable linear polyester (unlocked state), which can degrade into esters and alcohols small molecules. Second, this strategy is envisioned to be useful in addressing the stability issue of low-Tc polymers. A high-Tc unsaturated polyether that contains cyclobutane-fused THF in each repeat unit is designed and mechanochemically converted into a depolymerizable low-Tc poly(2,5-dihydrofuran) (PDHF). The following depolymerization of PDHF shows a quantitative generation of 2,5-dihydrofuran in the presence of a ruthenium catalyst. In these two research projects, the fundamentals and applications of the above-mentioned research reveal the potential of applying polymer mechanochemistry to address challenges in plastics sustainability. In the third study, we investigate the coordinating atom effect on the reactivity of oxanorbornene monomers during ring opening metathesis polymerization initiated by Grubbs third-generation catalyst (G3). Single monomer addition to G3 catalyst and monomer homoaddition were observed for (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2023, Neuroscience Graduate Studies Program

Single nucleotide variants (SNVs) in the gene encoding Kinesin Family Member 5A (KIF5A), a neuronal motor protein subunit involved in transport along microtubules, have been associated with amyotrophic lateral sclerosis (ALS). ALS is a rapidly progressive and fatal neurodegenerative disease that primarily affects motor neurons. Numerous ALS-associated KIF5A SNVs are clustered near splice site junctions of the penultimate exon 27 and are predicted to alter the carboxy-terminal (C-term) cargo-binding domain of KIF5A. Mis-splicing of exon 27, resulting in exon exclusion, is proposed to be the mechanism by which these SNVs cause ALS. Whether all KIF5A SNVs proximal to exon 27 result in exon exclusion is unclear. To address this question, we designed an in vitro minigene splicing assay in HEK293 cells which revealed heterogeneous site-specific effects on splicing: only 5´ splice site (5´ss) SNVs resulted in exon skipping. We also quantified splicing in select CRISPR-edited human stem cells differentiated to motor neurons and in neuronal tissues from a 5´ss SNV knock-in mouse (Mouse: c.3005+1G>A; Human homolog: c.3020+1G>A), which showed the same result. Moreover, survival of representative 3´ splice site (3´ss), 5´ss, and truncated C-term (ΔC) variant KIF5A (v-KIF5A) motor neurons was significantly reduced compared to wildtype (WT) motor neurons, and overt morphological changes were apparent. While total KIF5A mRNA levels were comparable across cell lines, total KIF5A protein levels were decreased for v-KIF5A lines, suggesting an impairment of protein synthesis or stability. Thus, despite the heterogeneous effect on RNA splicing, KIF5A SNVs near exon 27 similarly reduce the availability of the KIF5A protein, leading to axonal transport defects and motor neuron pathology.

Master of Science, Miami University, 2023, Chemistry and Biochemistry

Grp94 is the ER-resident molecular chaperone of the heat shock protein 90 (hsp90) family that aids in folding and activation of misfolded proteins, called clients. Client remodeling by Grp94 requires ATP-driven conformational changes resulting from nucleotide hydrolysis. The long pre-N domain of Grp94, a conserved region preceding the NTD, is a regulator of Grp94 function. Truncation of the pre-N domain (Δ73) produces faster ATPase rates, but the effect on conformational sampling has not been determined. In this study, we used DEER spectroscopy to monitor Grp94 ∆73 intraprotomer distances and continuous-wave EPR to monitor ATP lid mobility. Distances between labels in the NTD and MD were measured with ATP, ADP, AMP-PNP, and the ER-resident BiP, a closure-accelerating hsp70 chaperone. We demonstrate that nucleotide-induced closure of Grp94 is conserved in the hsp90 family, but unique aspects exist in its response to nucleotide and BiP in conformational sampling and ATP lid mobility. Ongoing studies in the lab are investigating conformational sampling of the full-length construct. The data from both studies will be compared to determine the effect of the pre-N domain on Grp94 conformational sampling. Understanding Grp94 function will support research in novel cancer therapeutics.

Doctor of Philosophy, Case Western Reserve University, 2023, Systems Biology and Bioinformatics

Recently, novel and unrecognized endogenous metabolites have been found to impact the risk of CVD not related to established risk factors (residual risk), including metabolites produced by gut microbes. Discovery platforms including metabolomics and metagenomics have identified new biomarkers associated with residual risk, but these platforms' usefulness is limited by the available methods of data analysis. This thesis aims to develop models of gut microbial metabolism using metagenomic data and new methods to identify unseparated structural isomers in metabolomics data. The gut microbial metabolism of trimethylamine-N-oxide, a metabolite associated with residual CVD risk, is used as a model system to develop predictive models of metabolism based on metagenomic information. An integrated analysis of metabolomics, metagenomics, and several other data types to predict circulating trimethylamine-N-oxide levels shows that while gut microbes play an essential role in trimethylamine-N-oxide synthesis, community composition does not quantitatively predict metabolism well enough to predict clinical risk. Analytical methods are developed to detect and identify structural isomers in metabolomics data. Two structural isomers, the terminal metabolites of niacin metabolism, are detected in human serum and characterized. Multiple clinical studies show these niacin metabolites are associated with residual CVD risk, and animal models show N1-methyl-4-pyridone-3-carboxamide (4PY) enhances vascular inflammation and thrombosis potential. Thus, new microbial and endogenous targets for therapy have been proposed, and new analytical methods have been introduced that may enable further study of residual CVD risk.

Doctor of Philosophy, University of Akron, 2022, Polymer Science

Novel modifications of styrene-butadiene rubber were studied using conventional curatives, sulfur curing packages or peroxides, to efficiently utilize supramolecular reinforcement strategies that improve the mechanical properties of rubber. Thiol-ene coupling proved to be an effective method for modifying styrene-butadiene rubber during peroxide curing, but it was inadequate when attempted during sulfur vulcanization. Supramolecular reinforcement was achieved by grafting mercapto-functionalized sodium phosphate esters to styrene-butadiene rubber during peroxide curing which electrostatically associate. The association strength between these ionic grafts played a critical role in determining the degree of reinforcement. Possible mechanisms by which reinforcement occurs were discussed and, at low grafting densities, at least one mechanism was determined not to play a major role. It was shown that substantial modification of cis-1,4-polyisoprene does not occur by thiol-ene coupling and that another chemical means must be used to modify this substrate. Reagents consisting of thioaldehydes derived from thiosulfinates were used in Alder-ene reactions to modify cis-1,4-polyisoprene. Based on this chemistry, new grafting and crosslinking agents were developed that react quickly and at relatively low temperatures. Important elements in the molecular design of these curatives were discussed and it was demonstrated that good mechanical properties are attainable.

Master of Science, Miami University, 0, Chemistry and Biochemistry

The COVID-19 pandemic has highlighted the importance of diagnostics in detecting and containing infectious diseases. Recently, a class of CRISPR-Cas enzymes, known as Cas12, has been discovered and is being utilized as a biosensor for detecting genetic biomarkers. Cas12 is similar to other CRISPR-Cas proteins, in that it forms an RNA-protein complex with crRNA, which then recognizes and cleaves target DNA determined by the crRNA sequence. Cas12 is unique in that upon activation, it non-specifically cleaves any nearby DNA. This non-specific cleavage property can be leveraged to create molecular biosensors by adding in a fluorescent reporter DNA substrate to the reaction. In our system, Cas12 is programmed to recognize a specific sequence of the SARS-CoV-2 genome. This class of biosensor is useful due to a faster response compared to traditional PCR-based assays. However, CRISPR-Cas biosensors suffer from off-target activity, meaning that similar sequences can activate the biosensor, resulting in false positive signal. The goal of this project is to systematically study factors that affect Cas12 activity. Specifically, we investigated how the role of crRNA concentration, crRNA length, and mutation position affect Cas12 activity. Findings from this research will aid in developing next-generation point-of-care diagnostics for detecting and containing disease outbreaks.

Doctor of Philosophy (PhD), Ohio University, 2022, Physics and Astronomy (Arts and Sciences)

In this dissertation, studies on atomic-scale characterization and manipulation of molecular systems and heterostructures for potential applications in the emerging field of molecular nanotechnology are presented. Observing and investigating exotic properties of molecular systems often require novel techniques and state-of-the-art instrumentation; thus, we report the development and commissioning of the world's first synchrotron Xrays beamline, dubbed “XTIP”, dedicated to the synchrotron X-rays scanning tunneling microscopy (SX-STM) technique that was used on all the research projects in this dissertation. For the projects, first, we report on unexpected magnetic interface phenomena in molecular Co adsorbed on oxygenated Fe film as well as in Co/Ni/Cu(111) nanoscale heterostructure probed using the X-ray dichroism technique (XMCD). We observed that the magnetic moment of Ni islands in the heterostructure shows a considerable reduction due to partial filling of the unoccupied Ni 3d orbitals due to charge injection. In addition, using the SX-STM technique, we also report on the first-ever elemental and chemical characterization of individual Fe atoms in a molecular environment. Finally, guided by the X-rays absorption spectroscopy measurements on a rare-earth-based molecule, which shows the existence of net charges in the molecule on Au(111), we have developed a molecular motor with 100% control over its rotation direction mediated by counterions. These results open a new dimension of research where synchrotron X-rays are used to characterize materials one atom at a time.

Doctor of Philosophy, The Ohio State University, 2021, Computer Science and Engineering

Life sciences literature is replete with detailed and not-so-detailed instructions for wet-lab processes, called protocols, that communicate biological experiments to the scientific community. Nevertheless, due to the manual execution of these protocols, over 70% of researchers have failed to reproduce another scientist's experiments, with more than 50% unable to reproduce their research. An estimated $28B/year is spent on research that is not reproducible, with about 11% attributed to execution errors. Hence, there is a significant reproducibility and scalability crisis in scientific research. A researcher can spend weeks or even months setting up, optimizing, and validating new experimental techniques. And thus, he/she can at best realize the experiments in minimal ways (small sample sizes, etc.). With an ever-increasing need for reproducibility and error-free replication of experimental procedures, laboratory automation is becoming increasingly crucial in many sectors of life science research. However, compared with manufacturing and service industries, the life science research industry is lagging in utilizing large-scale industrial automation for productivity, capacity, and quality improvements. Technological advancements (e.g., AI, modern software architectures and best practices, and sensing) can spur the development of intelligent automation systems for experimental procedures at higher precision and throughput that can also provide a significant reduction in human error. However, currently offered solutions have not seen widespread adoption. One of the barriers in the intelligent automation of wet lab protocols is that the vast majority of them are written in natural language that effectively disseminates practical procedures within the research community but is difficult for automation systems to interpret. Through years of experience, life science researchers can naturally interpret wet lab instructions by understanding sentence structure, grounding (open full item for complete abstract)

Doctor of Philosophy (PhD), Ohio University, 2021, Chemistry and Biochemistry (Arts and Sciences)

This dissertation is focused on the study of the fragmentation chemistry of carbohydrates by mass spectrometry and computational methods. By investigating the behavior of model systems, we hypothesize that a general model for carbohydrate fragmentation can be found. The model systems studied are sodiated cellobiose and gentiobiose (Chapter 2), deprotonated lactose (Chapter 3), and β-cyclodextrin (Chapter 4), each representing a different aspect of carbohydrate fragmentation. Experimental techniques, including tandem mass spectrometry, stable isotopic labeling, and infrared multiphoton dissociation were employed. Throughout, we also utilize computational modeling to add a dimension of clarity to the experimental results and provide values usable in subsequent predictive efforts.

Doctor of Philosophy, University of Akron, 2021, Polymer Science

Melanin is a ubiquitous natural pigment that has a high refractive index (RI) and broad absorption across ultraviolet and visible wavelengths (200−700 nm). Even though melanin is known for its optical properties and absorption of light, we know very little about the chemistry and optical properties of these materials. Accordingly, we also know very little about how the structure and optical properties of melanin change after exposure to UV light. To address the questions on structure of melanin, we applied in-situ experiment with dynamic light scattering (DLS) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-IR) to monitor the polydopamine synthesis in aqueous solution. Solid-state nuclear magnetic resonance (ssNMR) and FTIR has been used to understand the chemical structure of synthetic melanin (polydopamine and polydopa). Upon exposure to UV, we observe an increase in the aromatic components and some of the indole repeating units convert into furopyrrole structures, which also results in a release of CO2. We also observed the reduction in the aliphatic amine groups by using 15N ssNMR. In addition to the elucidation of the chemical structure of melanin, we have also used ellipsometry to measure changes in the complex RI in the visible and near IR wavelengths (360-1700 nm) after UV irradiation. Interestingly, both the real component of RI and absorption (imaginary component of refractive index) increase after UV absorption, indicating higher absorption efficiency of melanin after UV exposure. To exploit the change in complex RI of melanin after extremely high UV exposure, we have developed structural colors that do not fade upon UV exposure. Melanin is an important component in protecting us from UV radiation and has been an important material that produces structural color in nature. The observation of melanin being more effective after UV radiation may help in developing new materials to block UV radiation.

Doctor of Philosophy, Case Western Reserve University, 2021, Chemistry

The scope of this dissertation is the synthetic design and fundamental characterization of a novel type of platinum based lumophore. The discovery of a new type of cyclometallated Pt(II) phosphor that features a rare tetrahedrally distorted geometry and emits efficiently in solid state or as a 2 % (w/w) PMMA film is detailed. The bis(imidazolyl)carbazolide ligand is utilized as a monoanionic tridentate scaffold from which to design a family of Pt(II) complexes with variable alkynyl ligands. Full synthetic procedures are developed and optimized. Computational modeling with TD-DFT complements experimental data to rationally design complexes with charge-transfer character responsible for their emissive state. Physical characterization of crystal structure, thermal stability, and electrochemical probing are undertaken. The resulting species are found to have no close-contacts between Pt(II) centers due to their unusual and bulky geometries. The species are all strongly emissive in the solid state with up to 93 % quantum yield and all feature long lived millisecond excited state decay lifetimes. Similarly dispersions in PMMA film also experience significant enhancement in emission parameters as compared to when they are in solution. As a result significant thermal non-radiative relaxation is implicated that is attenuated when the species are in a rigidified state or matrix.