23 Matching Results

Results open in a new window/tab.

Ultrafast Charge Transfer in Donor-Acceptor Push-Pull Constructs (open access)

Ultrafast Charge Transfer in Donor-Acceptor Push-Pull Constructs

Ultrafast charge and electron transfer, primary events in artificial photosynthesis, are key in solar energy harvesting. This dissertation provides insight into photo-induced charge and electron transfer in the donor and acceptor constructs built using a range of donor and acceptor entities, including transition metal dichalcogenides (TMDs, molybdenum disulfide (MoS2), and tungsten disulfide (WS2)), N-doped graphene, diketopyrrolopyrrol (DPP), boron-dipyrromethene (BODIPY), benzothiadiazole (BTD), free base and metal porphyrins, zinc phthalocyanine (ZnPc), phenothiazine (PTZ), triphenylamine (TPA), ferrocene (Fc), fullerene (C60), tetracyanobutadiene (TCBD), and dicyanoquinodimethane (DCNQ). The carefully built geometries and configurations of the donor and (D), acceptor (A), with a spacer in these constructs promote intramolecular charge transfer, and intervalence charge transfer to enhance charge and electron transfer efficiencies. Steady-state UV-visible absorption spectroscopy, fluorescence and phosphorescence spectroscopies, electrochemistry (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)), spectroelectrochemistry (absorption spectroscopy under controlled potential electrolysis), transient absorption spectroscopy, and quantum mechanical calculations (density functional theory, DFT) are used to probe ground and the excited state events as well as excited state charge separation resulting in cation and anion species. The current findings are useful for the increased reliance on renewable energy resources, especially solar energy.
Date: August 2022
Creator: Jang, Young Woo
System: The UNT Digital Library

Computational Modeling of Cancer-Related Mutations in DNA Repair Enzymes Using Molecular Dynamics and Quantum Mechanics/Molecular Mechanics

This dissertation details the use of computational methods to understand the effect that cancer-related mutations have on proteins that complex with nucleic acids. Firstly, we perform molecular dynamics (MD) simulations of various mutations in DNA polymerase κ (pol κ). Through an experimental collaboration, we classify the mutations as more or less active than the wild type complex, depending upon the incoming nucleotide triphosphate. From these classifications we use quantum mechanics/molecular mechanics (QM/MM) to explore the reaction mechanism. Preliminary analysis points to a novel method for nucleotide addition in pol κ. Secondly, we study the ten-eleven translocation 2 (TET2) enzyme in various contexts. We find that the identities of both the substrate and complementary strands (or lack thereof) are crucial for maintaining the complex structure. Separately, we find that point mutations within the protein can affect structural features throughout the complex, only at distal sites, or only within the active site. The mutation's position within the complex alone is not indicative of its impact. Thirdly, we share a new method that combines direct coupling analysis and MD to predict potential rescue mutations using poly(ADP-ribose) polymerase 1 as a model enzyme. Fourthly, we perform MD simulations of mutations in the protection of …
Date: May 2022
Creator: Leddin, Emmett Michael
System: The UNT Digital Library

Parameterization of Ionic Liquids and Applications in Various Chemical Systems

In this work, the development of parameters for a series of imidazolium-based ionic liquids molecules, now included in the AMOEBA force field, is discussed. The quality of obtained parameters is tested in a variety of calculations to reproduce structural, thermodynamic, and transport properties. First, it is proposed a novel method to parameterize in a faster, and more efficient way parameters for the AMOEBA force field that can be applied to any imidazolim-based cation. Second, AMOEBA-IL polarizable force field is applied to study the N-tert-butyloxycarbonylation of aniline reaction mechanism in water/[EMIM][BF4] solvent via QM/MM approach and compared with the reaction carried out in gas-phase and implicit solvent media. Third, AMOEBA-IL force field is applied in alchemical calculations. Free energies of solvation for selected solutes solvated in [EMIm][OTf] are calculated via BAR method implemented in TINKER considering the effect of polarization as well as the methodology to perform the sampling of the alchemical process. Finally, QM/MM calculations using AMOEBA to get more insights into the catalytic reaction mechanism of horseradish peroxidase enzyme, particularly the structures involved in the transition from Cp I to Cp II.
Date: December 2022
Creator: Vazquez Cervantes, Jose Enrique
System: The UNT Digital Library

Aromaticity, Supramolecular Stacks, and Luminescence Properties of Cyclic Trinuclear Complexes

The dissertation covers three major topics: metal-assisted aromaticity, synthetic approaches to tailor donor-acceptor supramolecular stacks, and photoluminescence properties of cyclic trinuclear complexes (CTCs) of d10 metals. First, multiple theoretical approaches are adapted to discuss in detail the origin of aromaticity of CTCs, putting forward a metal-assisted aromaticity model. Next are the discoveries of donor-acceptor stacked CTC–CTC' complexes from both experimental and computational perspectives, reporting multiple novel crystallography-determined structures and revealing their pertinent intermolecular ground-state charge transfer. The spontaneous binding behavior is also determined by UV-vis and NMR titrations and rationalized as the cooperation of multiple supramolecular interactions, including metallophilicity, electrostatic attraction, and dispersion. The last part includes systematic investigations of photoluminescence properties of halogen-metal-bonded CTCs and sandwich-like cation–π-bonded heptanuclear clusters based on CTCs. The cooperative effects of metal-centered conformation, the heavy-atom and relativistic effects from both the halogen and metal atoms play complementary roles in the phosphorescence process to promote the inter-system crossing and radiative transitions.
Date: December 2022
Creator: Lu, Zhou
System: The UNT Digital Library

Investigation of Ionic Liquid Phases for Chromatographic Separation of Fentanyl Analogues

Opioid abuse and in particular fentanyl, a synthetic opioid, has been of concern in the last decade. Fentanyl is an illicit drug of concern to due to its prevalence and potency. Research to date has focused on supporting law enforcement by developing methods suitable for chemical profiling and identifying fentanyl from various matrices. However, methods geared towards analysis of fentanyl isomeric analogues are rare. Analysis of isomers is challenging due to similar mass spectral fragmentation patterns and exhibiting co-elution using common gas chromatographic columns. Developing methods to use in forensic labs utilizing already available equipment will advance current capabilities in the detection of fentanyl compounds. Thus, investigation into alternative stationary phases and development of special gas-liquid chromatographic (GLC) based methods for isomeric fentanyl analogues has been done. Several studies were done to investigate the use of ionic liquid chromatographic phases in analyzing fentanyl analogues. The first study focused on investigating the thermal stability of ionic liquids to identify those suitable to withstand the high oven temperatures that was needed to elute fentanyl analogues in gas chromatography. Total synchronous fluorescence spectroscopy and differential scanning calorimetry were demonstrated to be sensitive enough to detect the decomposition products of ionic liquids. In the …
Date: December 2022
Creator: Smart, Katherine Rose
System: The UNT Digital Library

Sulfur-Based Organic Compounds as Novel Corrosion Inhibitors for Brass and Aluminum Alloy Protection in Acid Cleaning Solutions

In this study, thiol and two disulfide compounds have been tested as new corrosion inhibitors for brass and aluminum alloys. Pyridine-2-thiol and 2,2'-dipyridyl disulfide were tested for brass alloys in 0.5 M H2SO4 solution and both inhibitors showed excellent corrosion protection against the aggressive corrosive ion attack. Both inhibitors adsorbed to brass surface forming a protective film via a chemisorption process. XPS studies showed formation of Cu-S bond which allows these molecules to chemisorb on to brass surfaces. Pyridine-2-thiol, 2,2'-dipyridyl disulfide and 4'4-diaminodiphenyl disulfide were tested as corrosion inhibitors for AA6061-T6 alloy in 1 M HCl solution and all inhibitors showed excellent corrosion protection over wide range of temperatures. To evaluate the corrosion inhibition efficiencies many different instruments and electrochemical techniques were used. Overall results from this study showed sulfur-based corrosion inhibitors can be used effectively to mitigate the corrosion process of brass and aluminum alloys in acidic solutions.
Date: December 2022
Creator: Karunarathne, Darshan Jayasinghe
System: The UNT Digital Library

The Development of the Attitudes Towards Organic Chemistry Instrument

In this study, undergraduate student attitudes towards organic chemistry and the influences that shape those attitudes were explored using the Attitudes Towards Organic Chemistry Instrument (ATOC) to collect both qualitative and quantitative data. The findings from the qualitative ATOC items provide evidence that students displayed a wide range of attitudes towards organic chemistry, including positive, negative, neutral, and blended attitudes. Five major influences were shown to have shaped these attitudes including the reputation of the course, students' educators, experiences with organic chemistry, experiences with introductory chemistry, and individual experiences. Students responses longitudinally provide evidence that their influences and attitudes change over time in the course. The findings from the quantitative ATOC items provided evidence that the data generated was valid and reliable, and a relationship was found to exist between what students think and what they had heard about the course. Limitations of this investigation, as well as implications for research and practitioners, are discussed.
Date: August 2022
Creator: Collini, Melissa Anne
System: The UNT Digital Library
Synthesis and Characterization of Vanadium and Cobalt Oxynitride Surface Chemical and Electronic Structure for Electrochemical Reduction of N2 to NH3 (open access)

Synthesis and Characterization of Vanadium and Cobalt Oxynitride Surface Chemical and Electronic Structure for Electrochemical Reduction of N2 to NH3

Cobalt oxynitride films formed by magnetron sputter deposition of a Co target in N2 or NH3 plasma or, alternatively, by NH3 plasma nitridation of a Co film deposited on Si(100), show a divergence of properties arising from (a) N and O interactions for N and O atoms bonded to each other or through a common metal center and (b) the oxophilicity of the metal center itself. Core and valence band X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and plane wave density functional theory (DFT) calculations have been used to probe chemical and electronic interactions of nitrogen-rich cobalt oxynitride CoO1-xNx (x > 0.7) films. DFT-based calculations supervised by the Cundari group show the zinc blende (ZB) structure is found to be energetically favored over the rocksalt (RS) structure for x > ~ 0.2, with an energy minimum observed in the ZB structure for x ~ 0.8 - 0.9. There is also agreement with experiment for core level binding energies obtained for DFT calculations based on the ZB structure and this forms the basis of a predictive model for understanding how N and O interactions impact the electronic and catalytic properties of these materials. Vanadium oxynitride films were deposited in a mixture …
Date: May 2022
Creator: Osonkie, Adaeze
System: The UNT Digital Library

In vitro Biomedical Application and Photothermal Therapy Evaluation of Gold Complexes and Gold Nanoparticles

Plasmonic photothermal therapy (PPTT) has a rising promise for treating different cancer cells such as lymphoma or stomach cancer. Technique development of PPTT using metallic nanoparticles is developed upon a modification of the irradiation therapy using two major changes: using a less harmful visible amber light (excluding blue light) and using gold-loaded biocompatible nanoparticles. Acrylate nanoparticles were loaded with desired types of gold nanoparticles at different sizes. The gold-loaded gold nanoparticles were conjugated to cancer cells. By selectively delivering the gold nanoparticles into cancer cells, irradiating a harmless amber visible light will achieve thermal ablation of the cancer cells. Based on imaging spectroscopy, flow cytometry, and cell viability assays, results showed reduction of gold-loaded viable cancer cells upon irradiating with amber visible light, no change in the number of cancer cells with irradiating with light only. On the other hand, DNA intercalation of a trinuclear gold(I), [Au(3-CH3,5-COOH)Pz]3 (Au3) is contrasted with the standard organic intercalators ethidium and ellipticine, as investigated computationally. Frontier molecular orbital energies of intercalators and DNA base pairs were determined and found that all intercalators are good electron acceptors with Au3 being the best electron acceptor having the lowest LUMO. DNA base pairs are better electron donors …
Date: May 2022
Creator: Shennara, Khaled A
System: The UNT Digital Library

Porous Materials as Drug Delivery Systems

The porous materials discussed in this dissertation are metal-organic frameworks (MOFs) and porous liquids. Due to their high surface areas, tunable structures, and controllable porosities, MOFs have been explored for a wide variety of drug delivery applications. In chapter 2, MOFs have been used as magnetothermal-triggered release carriers through spatially distributed iron oxide nanoparticles within MOF matrix as a magnetic heating mediator and surface-grafted thermal-responsive nanocap as an alternating magnetic field (AMF)-responsive gatekeepers, achieving monitoring of drug release via external AMF by a conformational change of nanocap. In chapter 3, MOF, as a non-toxic loading carrier, encapsulate naringin, a natural product to serve as a multifunctional bio-platform capable of treating Gram-positive bacteria and certain cancers by slowly and progressively releasing the encapsulated naringin as well as improving and modulating immune system functions through the synergies between naringin and MOF. In chapter 4, porous liquid with unique solvent-free fluidity properties as a drug delivery platform for the first time. The interaction between hollow silica nanoparticle and polymerized ionic liquid, followed by ionic grafting brush of poly (ethylene glycol) telomer, makes this designed porous liquid responsible for high drug-loading and pH-responsive drug-releasing abilities along with slow degradation behavior. In addition to their …
Date: December 2022
Creator: Ge, Xueying
System: The UNT Digital Library

Nanofluidic Membrane Based on Covalent Organic Framework: Design Strategies and Applications

Nanofluidic is an emerging field of applying fluid properties in nanochannels or nanostructures. The nanoporous channel with a pore size of less than 100 nm will strongly affect the motion of the fluid. Meanwhile, the pore environment, such as hydrophilic and hydrophobic properties, charge density, and host-guest recognition would be crucial for the transportation of molecules and ions in the pore. This thesis is focused on the synthesis, characterization of nanofluidic membranes and their applications to reverse electrodialysis. Chapter 1 focuses on the importance and objective of this work. Chapter 2 gives an overview of nanofluidic and classical nanofluidic structure–covalent organic frameworks (COFs). In Chapter 3, a series of COFs membranes with different surface charge densities were designed by employing a multivariate (MTV) strategy. A volcano-like relationship between the surface charge density and output power density was observed when the membranes were applied for osmotic energy harvesting. Chapter 4 integrates the temperature gradient to the covalent organic frameworks nanofluidic system to further explain the thermophoretic mobility of ions. The recorded osmotic energy production density was obtained while ion concentration polarization was alleviated with increasing hydrodynamic convection effects. In Chapter 5, a coupled photon-electron-ion transport behavior across ionic covalent organic framework …
Date: December 2022
Creator: Zhu, Changjia
System: The UNT Digital Library

An Investigation into the Micromechanical and Corrosion Properties of Additively Manufactured Stainless Steel 316L

In this thesis, micro-mechanical properties and corrosion resistance of laser powder bed fusion (L-PBF) processed additive manufactured (AM) 316L stainless steel parts were investigated for different combinations of processing parameters. Various laser powers were employed for the fabrication of all AM 316L stainless steel parts. Nanoindentation, areal roughness, and electron backscattered diffraction (EBSD) characterization were used to characterize the surface of the AM samples prior to corrosion testing. Open circuit potential (OCP), linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization tests were done to compare AM L-PBF 316L stainless steels with different processing parameters. Overall, it was observed that the AM part having a 56.67 J/mm3 volumetric energy density (VED) exhibits the best micro-mechanical characteristics. This sample also had the lowest areal surface roughness and smallest grain size. Consequently, this parameter combination had better corrosion resistance compared to the other AM processed 316L parts. The results are useful in process calibration when fabricating for corrosion resistance applications and provide insights into the relationship among nano-mechanical, crystallography, and long-term corrosion performance.
Date: December 2022
Creator: England, Jennifer
System: The UNT Digital Library
Novel LC-MS Method for the Analysis of Beta-Hydroxybutyric Acid (BHB) in Health Formulations (open access)

Novel LC-MS Method for the Analysis of Beta-Hydroxybutyric Acid (BHB) in Health Formulations

The rise of nutraceutical health formulations has increased the need for more stringent analytical testing methods. Complex matrices present a new problem when determining concentration of compounds of interest. The presented method uses LC-MS analysis with a novel sample preparation method in the determination of Beta-hydroxybutyric acid in health formulations. The use of an aqueous analytical column allows for separations of polar compounds after non-polar compounds are removed through C18 packed column filtration. The samples were analyzed through time-of-flight mass spectrometry and results show that this is an effective method for the presented samples with a range of expected concentrations of total BHB was from 11.80% to 38.92%. It was seen that all samples exhibited a less than 10% percent deviation from the expected concentrations of the nutraceutical health samples with the highest being 9.74 % for sample 9 and the lowest being sample 3 with a deviation of 0.08 % from expected values.
Date: May 2022
Creator: Smith, Garret Mackenzie
System: The UNT Digital Library
Ranaspumin Protein Characterization and Applications for Both Environmental and Medical Purposes (open access)

Ranaspumin Protein Characterization and Applications for Both Environmental and Medical Purposes

The Túngara frog (Engystomops pustulosus) from Central America creates a bio-foam that protects their young from dehydration, microbial degradation, and even predators during early development. The foam is composed of unique proteins known as Ranaspumin 1-6 (RSN 1-6). These RSN proteins have been synthetically synthesized and verified with Circular Dichroism (CD) to determine their critical micelle concentration, antimicrobial properties, and stability at varying temperatures and pH ranges. Throughout these characterizations, RSN 2 was determined to establish/produce antimicrobial properties, express stability at temperatures between 20 – 60oC, and express stability at a pH range of 5-8. Therefore, RSN 2 was isolated and utilized for medical and environmental applications. With the addition of RSN 2, the separation of aromatics was achieved in tar-sands with the assistance of a Tangential Flow Filtration (TFF) system. With only three passes through the TFF system, the RSN 2 solution isolated approximately 35% of the aliphatic region, and approximately 70% of the aromatic region. Finally, RSN 2 was implemented into an organ preservation solution for organ transplant surgery. By observing two different biomarkers, including Cardiolipin (CL) and alkali metals/alkaline earth metals for a change in concentration to verify organ viability. Resulting in the RSN 2 solution as …
Date: December 2022
Creator: Koerber, Rachel
System: The UNT Digital Library

Computational Investigations of Catalytic Activity by Metal-Containing Complexes

This dissertation delves into the catalytic activity of multiple metal-containing complexes with an emphasis on the activation of C–H bonds in small molecules and olefin oligomerization. The research contained in these works employs computational methodologies to better understand the thermodynamics and kinetics of the reactions. Computations can be used to quickly identify novel models and find ideal substitutions for improved catalyst design. Within this dissertation, multiple molecules of divalent and trivalent main group element-containing complexes as well as Group 13 dimetallene complexes were investigated with density functional theory (DFT) to identify their ability to activate C–H of hydrocarbons, including methane, by quantifying their thermodynamics and kinetics of reaction. With several substitutions to the base complex, improved catalysts were designed to decrease the energy barriers of the activations. Multiconfiguration self-consistent field methods were also employed to characterize the biradical character of these Group 13 compounds. Olefin oligomerization by zirconium boratabenzenes with various ancillary pendant groups was also investigated via DFT to identify the most ideal variations as well as the most likely reaction pathway.
Date: August 2022
Creator: Carter, Carly Catherine
System: The UNT Digital Library

Bifunctional Enamine‐Metal Lewis Acid Catalysis and α-Enaminones for Cyclization Reactions

The use of enamines continues to be an important tool in organic syntheses as both a catalyst and reactant. The addition of metal catalysts coupled with enamine catalysis has generated many reactions that normally would not occur separately. However, catalysts' incompatibility is an issue that we wish to solve allowing new chemistry to occur without hindrance. The use of enamines has continued to be a well-studied area of organic chemistry, but the field is ripe for different types of enamines to gain the spotlight. Enaminones are enamines with both nucleophilic and electrophilic properties. They allow reactions that are normally not possible with enamines to become obtainable. Chapter 1 is a brief introduction on enamines and the reason they gained so much attention. Then ends with enaminones and what makes them interesting reactants. Chapter 2 described a new synthesis for the tricyclic synthesis of chromanes using a novel bifunctional catalyst system of enamine-metal Lewis acid giving great yields (up to 87 %yield) and excellent stereoselectivity (up to 99 % ee). Chapter 3 covered new reactions for ring-open cyclopropane (up to 94% yield), tetrahydroquinolinones (up to 84% yield) and enantiospecific tetrahydroquinolinones (up to 84% yield and 97% ee) using α-enaminone and donor-acceptor …
Date: August 2022
Creator: Davis, Jacqkis
System: The UNT Digital Library
Deposition and Characterization of Thin Metal Oxide Heterostructures for Electronic and Magnetic Device Applications (open access)

Deposition and Characterization of Thin Metal Oxide Heterostructures for Electronic and Magnetic Device Applications

The first study investigated the deposition and characterization of the CoO and Co3O4 phases of cobalt oxide. It was determined that both phases can be easily distinguishable by XPS, LEED and EELS and grown by only altering the oxygen partial pressure during MBE deposition. This fundamental knowledge gives a foundation for further experiments involving graphene growth on cobalt oxides. The second study focused on the layer-by-layer growth of graphene on another metal oxide, MgO. Past research gives promise of favorable interfacial interactions at the graphene/MgO interface though the exact growth mechanism is unknown. Layer by layer growth by MBE resulted in the characterization of a complex graphene oxide/buckled graphene/ graphene heterostructure confirmed by XPS, AES, LEED and EELS and supported by DFT calculations performed by the project's collaborators at the California Institute of Technology. This detailed look into graphene growth give valuable information that can be allied to graphene growth on similar oxide surfaces. The last project deviates from graphene-based studies and instead focused on interfacial interactions between two metal oxides, chrome oxide and titanium oxide. A corundum phase TiO2-x film was grown on Al2O3 via MBE and characterized using XPS, AES, LEED, and EELS. Data taken gives evidence of …
Date: May 2022
Creator: Ladewig, Chad Samuel
System: The UNT Digital Library

Machine Learning in Computational Chemistry

Machine learning and artificial intelligence are increasingly becoming mainstream in our daily lives, from smart algorithms that recognize us online to cars that can drive themselves. In this defense, the intersection of machine learning and computational chemistry are applied to the generation of new PFAS molecules that are less toxic than those currently used today without sacrificing the unique properties that make them desirable for industrial use. Additionally, machine learning is used to complete the SAMPL6 logP challenge and to correlate molecules to best DFT functionals for enthalpies of formation.
Date: May 2022
Creator: Kuntz, David Micah
System: The UNT Digital Library

Metal-Macrocyclic Frameworks based on Aza-Macrocycles: Design Strategies and Applications

The present thesis mainly proposes to explore the potential of aza-macrocycles in metal-organic frameworks (MOFs) for applications related to unprecedented open macrocycle cavities. Strategies such as direct arylation of secondary amines as well as multidentate coordination were applied to constrain the intramolecular flexibility of as-obtained macrocyclic compounds. Several desired materials, i.e. MMCF-4, MMCF-5/MMCF-5t/MMCF-5t-aa, MMCF-5, HMMCF-1, were obtained. They are proved superior to traditional materials in the field of "turn-on" lanthanide luminescence, deep desulfurization of flue gas, recovery of Platinum-group metals, etc. Powder/single-crystal X-ray diffraction (PXRD/SCXRD), synchrotron-based X-ray and extended X-ray absorption fine structure (EXAFS), density functional theory (DFT) theoretical calculations, etc., were employed for deep-understanding the mechanisms. These studies shed light on the construction of hierarchically porous materials with two levels of porosity, i.e., one from the frameworks and the other one from the aza-macrocycles. Incorporation of aza-macrocycles into the MOF architectures not only leads to fundamental significance in bridging the chemistry of MOFs with supramolecular chemistry but also elicits unique properties from the hybrid materials obtained. As a paradigm for constructing frameworks with accessible macrocyclic cavities based on "constrained" aza-macrocycle ligands, this thesis paves the way for the further development of this framework family in the future.
Date: May 2022
Creator: Ren, Junyu
System: The UNT Digital Library
Porphyrin and BODIPY Derived Donor-Acceptor Multi-Modular Systems: Synthesis, and Excited State Energy and Electron Transfer Studies (open access)

Porphyrin and BODIPY Derived Donor-Acceptor Multi-Modular Systems: Synthesis, and Excited State Energy and Electron Transfer Studies

This dissertation demonstrates that it is possible to create a donor-acceptor system that can transform sunlight into electrons. By using site-directed synthesis, it was possible to create a novel trans-A2B2 porphyrin. In the pursuit of creating a supramolecular system, both the novel (TPA-BT)2ZnP and C60imidazole combined in solution such that the nitrogenous lone pair of C60 imidazole would coordinate axially to the zinc atom in the porphyrin. The conjugates' characterization utilized spectral, electrochemical, and computational techniques. Computational studies revealed in the optimized structure that the HOMO localized on the porphyrin and LUMO centered over the C60imidazole entity. Rehm-Weller calculations showed feasibility of singlet-electron transfer. Femtosecond transient absorption studies documented an efficient photoinduced charge separation in the conjugate. The subsequent work through steady-state and time-resolved transient absorption techniques that photoinduced electron transfer takes place between the synthesized phenylimidazole functionalized bisstyrylBODIPY (BDP(Im)2) and three selected zinc tetrapyrroles. This dyad consisted of BDP(Im)2 and either zinc tetratolylporphyrin (ZnP), zinc-tetra-t-butyl phthalocyanine (ZnPc), or zinc tetra-t-butyl naphthalocyanine (ZnNc) in a solution solvated by σ-dichlorobenzene (DCB). The three dyads (BDP(Im)2:ZnP, BDP(Im)2:ZnPc, and BDP(Im)2:ZnNc) were investigated by spectroscopic, computational, and electrochemical methods. The 1:1 complex of the dyads in optical absorption studies were approximately ~104 M-1 suggesting …
Date: May 2022
Creator: Benitz, Alejandro Daniel
System: The UNT Digital Library

"You get what you pay for" vs "You can alchemize": Investigating Discovery Research Experiences in Inorganic Chemistry/Chemistry Education via an Undergraduate Instructional Laboratory

Synthesis of d10 complexes of monovalent coinage metals, copper(I) and gold(I), with dithiophosphinate/diphosphine ligands -- along with their targeted characterization and screening for inorganic or organic light emitting diodes (LEDs or OLEDs, respectively) -- represents the main scope of this dissertation's scientific contribution in inorganic and materials chemistry. Photophysical studies were undertaken to quantify the phosphorescence properties of the materials in the functional forms required for LEDs or OLEDs. Computational studies were done to gain insights into the assignment of the phosphorescent emission peaks observed. The gold(I) dinuclear complexes studied would be candidates of OLED/LED devices due to room temperature phosphorescence, visible absorption/excitation bands, and low single-digit lifetimes -- which would promote higher quantum yield at higher voltages in devices with concomitant lower roll-off efficiency. The copper(I) complexes were not suited to the OLED/LED applications but can be used for thermosensing materials. Crystallographic studies were carried to elucidate coefficients of thermal expansion of the crystal unit cell for additional usage in materials applications besides optoelectronic devices. This has uncovered yet another unplanned potential application for both copper(I) and gold(I) complexes herein, as both types have been found to surpass the literature's threshold for "colossal" thermal expansion coefficients. Two other investigations …
Date: August 2022
Creator: Bodenstedt, Kurt Wallace
System: The UNT Digital Library

Chemically Optimized Cu Etch Bath Systems for High-Density Interconnects and the FTIR Operando Exploration of the Nitrogen Reduction Reaction on a Vanadium Oxynitride Electrocatalyst

Printed circuit board manufacturing involves subtractive copper (Cu) etching where fine features are developed with a specific spatial resolution and etch profile of the Cu interconnects. A UV-Vis ATR metrology, to characterize the chemical transitions, has been developed to monitor the state of the bath by an in-situ measurement. This method provides a direct correlation of the Cu etch bath and was able to predict a 35% lower etch rate that was not predicted by the three current monitoring methods (ORP, specific gravity, and conductivity). Application of this UV-Vis ATR probe confirmed that two industrial etch baths, in identical working conditions, confirmed a difference in Cu2+ concentration by the difference of the near IR 860nm peak. The scope of this probe allowed chemically specific monitoring of the Cu etch bath to achieve a successful regeneration for repeated use. Interlayer dielectrics (ILDs) provide mechanical and electrical stability to the 3D electrical interconnects found in IC devices. It is particularly important that the structural support is created properly in the multilayered architecture to prevent the electrical cross signaling in short range distances. A combined multiple internal reflection and transmission FTIR has been employed for the characterization of silicon oxycarbonitride (SiOCN) films. These …
Date: August 2022
Creator: Caperton, Joshua M
System: The UNT Digital Library
Earth Abundant Transition Metal Catalysts for Activation and Functionalization of Light Hydrocarbons (open access)

Earth Abundant Transition Metal Catalysts for Activation and Functionalization of Light Hydrocarbons

Light hydrocarbons activations, functionalization, and reactions have been a subjects of catalysis research for decades but dominated by the rarer and more expensive noble metals. Switching over to using the more earth abundant third row transition metals could be more economical and less toxic but come with their own challenges. Their use as catalysts with light hydrocarbons could be employed better utilize and more efficiently use our hydrocarbon resources that the world still depends on.
Date: August 2022
Creator: Grumbles, William M
System: The UNT Digital Library