Chemistry Commons^™

Hydrolysis-Directed Vapor-Phase Synthesis And Solution Processing Of Nanostructured Conducting Polymers, Haoru Yang

Arts & Sciences Graduate Student Theses and Dissertations

Conducting polymers are a class of organic material that possesses semiconducting properties. Their unique molecular structure facilitates charge transport via delocalized π-electron network in the polymer backbone. Creating nanostructures in a conducting polymer increases its surface area to volume ratio and promotes molecular interaction at the surface of the polymer, resulting in enhanced physical and chemical properties, such as ion transfer, adsorption/desorption efficiency, and electrical conductivity. This dissertation focuses on synthesizing nanostructured conducting polymers and their composites from the vapor phase. The mechanisms in a novel synthetic strategy that utilizes iron corrosion products to initiate polymerization and template nanostructure formation …

Non-Adjacent Anti Cyclobutane Pyrimidine Dimers As Intrinsic Probes Of Non-B Form Secondary Structures Of Dna, Natalia Eugenia Gutierrez Bayona

Arts & Sciences Graduate Student Theses and Dissertations

G-quadruplexes are four-stranded structures of DNA composed of G-quartets that have been proposed to play an extremely important role in replication, transcription, and translation. It has, however, been extremely difficult to unequivocally demonstrate that G-quadruplexes form in living cells due to the lack of probes that would allow for their unambiguous detection and location without disrupting the DNA or the cellular environment. To circumvent these problems, it was proposed that DNA itself could be used as an intrinsic photoprobe for certain classes of G-quadruplex structures and other non-B DNA conformations in vivo. Recently, we discovered that UVB irradiation of human …

New Methods Of Selectivity Using Electrochemistry, Qiwei Jing

Arts & Sciences Graduate Student Theses and Dissertations

This project has been working on introducing new type of method to induce chemoselectivity into electrochemical reactions by modifying the surface of an electrode and then confining chemical reactions to the region of the reaction close to that surface. The goal is to translate the extremely high levels of site-selectivity seen in chemical reactions on a microelectrode array into a tool for preparative synthetic reactions.As a proof-of-principle experiment, Pt-anode was coated with a diblock copolymer that is known to have an affinity for pyrene groups. The electrode is then used in the oxidation of two alcohol substrates: one having the …

Photophysical And Photochemical Processes In Small Molecules And Materials For Solar Energy Conversion, Ethan Lambert

Honors Theses

The work covered in this thesis all falls under the theme of photophysical processes after light and matter interact. Those of primary interest are Raman scattering induced vibrations and excited state dynamics probed by transient absorption spectroscopy. Small molecules are studied with Raman spectroscopy and computational chemistry. These studies unearth the shifts in vibrational frequency as a function of charge transfer or receipt and how a quantitative assay of natural orbital populations and delocalization can offer both the nature and magnitude of this charge transfer. Further, a method is presented that builds upon previous work within the academic family tree; …

Microhydration Of Hexachlorophosphate Anion, Anna Robertson

Honors Theses

The microhydration of the hexafluorophosphate anion has been the focus of many previous experimental and computational studies, due to its use in room temperature ionic liquids.This preliminary study examines the analogous hexachlorophosphate anion and its interactions with one to two water molecules (PCl₆⁻(H₂O)_n, n = 1-2), identifying the structural and energetic differences in the microhydration of PCl₆⁻ versus PF₆⁻. A systematic investigation of the possible orientations of one to two water molecules around PCl₆⁻ was done. Full geometry optimizations were performed using the ab initio method …

Diffusion Of Ionic Liquid-Modified Polymer Nanoparticles Through Nasal Mucus, Mary Vanlandingham

Honors Theses

Mucosal barriers are a natural defense system for preventing the entry of foreign objects into the body; however, they pose as obstacles for effective drug delivery. Coated polymer nanoparticles have been proven to possess improved rates of diffusion across mucus compared to their uncoated, or bare, counterparts. When choline-based ionic liquids (ILs) are introduced to an aqueous system, their dissociation leads to an increase in solution conductivity which ultimately reduces the viscosity of mucus without significantly affecting its structure. Additionally, ILs are highly tunable, so they work well in a range of pHs and conductivities, making ILs an ideal choice …

Investigating Reactivity Of Artificial Copper Peptides With Small Molecules, Allyson Bryant

Honors Theses

The design of artificial enzymes has been a topic of significant interest in the field of biochemistry, as they can provide new opportunities for catalytic processes and drug development. De novo protein design has emerged as a promising approach to create such enzymes, and the study of metalloproteins, particularly copper-binding peptides, has become a focus of this research. This thesis investigates the reactivity of a mutated copper-binding peptide, I5A-3SCC, with oxygen and its implications in the development of artificial enzymes.

The parent peptide, 3SCC, was mutated by replacing Isoleucine residues with smaller Alanine side chains, which was hypothesized to enhance …

Photocatalyzed Hydrogen Evolution Using Nickel-Bound Metallothionein Protein, Windfield Swetman

Honors Theses

The continued burning of fossil fuels is not only a cause of increasing deterioration of the environment but also a financially unsustainable source of energy. Advances in energy production must be investigated to avoid the long-term effects of this current main source of energy. One of the avenues being explored is the use of metalloenzymes to catalyze hydrogen evolution via water splitting that occurs during the reductive half of artificial photosynthesis. Metalloenzyme catalysts with a single Ni(Cys)₄ active site have been previously studied, and this study explores the possibility of increasing hydrogen production by using metalloenzyme catalysts with multiple …

Structural Integrity And Stability Of Dna In Ionic Liquid And Near-Infrared Indolizine Squaraine Dye, Ember Yeji Suh

Honors Theses

Luminol, the most common presumptive test for blood at a crime scene, has multiple issues, such as false positive results with chemical agents, no luminescence due to “active oxygen” cleaning agents on bloodstains, and inability to penetrate textile materials. A combination of indolizine squaraine dye and ionic liquid (IL), or Dye Enhanced Textile Emission for Crime Tracking (DETECT), have shown potential to address these issues. The purpose of this study was to assess the binding mechanism of CG (1:1) and SO₃SQ dye to HSA and how the mechanism can explain the W214 fluorescence quenching effect and to determine …

A Synthetic Approach To The Optimization Of Silicon-Rosindolizine Swir Fluorophores, Timothy Lewis

Honors Theses

Fluorophores emitting within the near-infrared (700 – 1000 nm) or shortwave-infrared (1000 – 1700 nm) regions of the electromagnetic spectrum are of particular interest for their potential to supplement or even outright replace commonly used biological imaging techniques, such as magnetic resonance imaging and computed tomography scanning. Various characteristics make these molecules particularly appealing to researchers, such as their ease of synthetic tunability, generally low toxicity, and high solubility in biological media in comparison to other NIR- and SWIR-emissive fluorophores. Different molecular skeletons have been examined for use as the core of these imaging agents, such as squaraine, cyanine, and …

Synthesis And Characterization Of Sodium Cathode Materials, He Zhou

McKelvey School of Engineering Graduate Student Theses & Dissertations

As sodium batteries hold great promise as a next-generation energy storage device to replace lithium batteries, the development of sodium battery materials has become increasingly urgent. The current study aims to investigate two potential sodium-ion battery cathode materials, Sodium Vanadium Phosphate, and Sodium Manganese Hexacyanoferrate, optimize the experimental procedures, conduct a systematic analysis of material properties and characterization, and ultimately determine the ideal synthesis conditions for these materials.

In the first part of the study, we focused on optimizing the synthesis of Sodium Vanadium Phosphate. By investigating various synthesis conditions, such as annealing temperature, pressure, ascorbic acid content, and material …

Mechanisim Of Plasmon-Driven Photochemical Reactions, Hamed Kookhaee

Chemistry and Chemical Biology ETDs

Understanding a photocatalytic reaction condition that selectively leads to a desired product on metal surfaces is a longstanding research problem in heterogeneous catalysis. Here, using plasmon enhanced N-demethylation of methylene blue (MB) as model reaction, we show that high degree of product selectivity can be achieved by switching the mechanism from charge transfer to adsorbate electronic excitation and vice versa using surface ligands. In the presence of cetyl trimethyl ammonium bromide (CTAB) surface ligand on gold nanoparticles, MB is selectively transformed to thionine at 633 nm excitation wavelength that overlaps with the electronic transition of the adsorbate. At resonant excitation …

New Methods For Core-Hole Spectroscopy Based On Coupled Cluster Theory, Megan Simons

Chemistry Theses and Dissertations

X-ray absorption spectra (XAS) is a method used to investigate atomic local structure and electronic states. Coupled cluster method is a numerical method used for describing many-body systems and electron correlation in a wavefunction. When equation-of-motion coupled cluster is used in XAS calculations, the ground state is applied to the excitation operator, which excites or ionizes the electron. This causes a large orbital relaxation error, normally ~5 eV, which leads to the need for triple excitations in order to obtain accurate results.

This dissertation introduces a coupled cluster method that uses "transition potential" reference orbitals to reduce the orbital relaxation …

Sunflower Oil-Based Wood Adhesive With High Mechanical Strength And Enhanced Bonding By Introducing Fillers, Arjun Chaudhari

Electronic Theses & Dissertations

Petroleum-based compounds are generally utilized in industries for getting higher mechanical strength for wood application, where the process of synthesis releases toxins into the environment and causes health issues.

Because of this, scientists are trying to make biobased compounds and products. In this research, sunflower polyol was used to make polyurethane (PU) resin. For the formation of polyol, an epoxidation reaction followed by a ring-opening reaction was performed. The presence of hydroxyl groups was confirmed using Fourier transform infrared spectroscopy (FT-IR) and hydroxyl value determination test to confirm the polyol formation. After that, hydroxyl groups of polyol were reacted with …

Effect Of Graphene-Based Fillers On The Properties Of Sunflower-Based Polyurethane, Vishwa Suthar

Electronic Theses & Dissertations

Polyurethane market majorly depends on synthetic materials which are noxious. This stimulated an idea to replace petrochemical resources with renewable resources for polyurethane production. Keeping this in mind, this research focused on the use of sunflower oil for the preparation of polyol and its use in polyurethane composition. The reaction mechanism of epoxidation and ring-opening was approached for the conversion of sunflower oil to polyol. During the conversion of sunflower oil, unsaturated groups of sunflower oil were converted into hydroxyl groups of polyol.

Sunflower oil-based polyol was successfully blended with methylene diphenyl diisocyanate (MDI) to form urethane bonds. Confirmative tests …

Evaluation Of Promising Eco-Friendly Flame Retardants For Bio-Based Rigid Polyurethane Foams Based On Modified Castor Oil, Prasadi Abeysinghe Arachchilage

Electronic Theses & Dissertations

Fossil fuel derivatives in the polyurethane industry are gradually being replaced with environmentally friendly alternative bio-based resources. Vegetable-oil-based polyols are emerging bio-based resources that can decrease cost competitiveness in polyurethane markets, reduce environmental impacts, and meet the urgent need for green and sustainable development strategies. Among this, interest is the use of castor oil to make polyurethane because of its inedibility and the fact that it contains many functionalizable chemical groups. However, the poor thermal stability and low load-bearing capacity of castor-oil-based rigid polyurethane foam limits its application. Two methods were used to address these limitations: (i) more hydroxyl groups …

Electrochemical Properties Of Mof-Derived Nickel Compounds For High-Performance Supercapacitors And Electrocatalysts, Shiva Bhardwaj

Electronic Theses & Dissertations

There are various forms in which humans use energy in daily life. From applications that require a high energy density to long-term storage, the requirements for energy usage are diverse. Therefore, with the continuous increase in users worldwide, more practical energy-driven sources are required, allowing manufacturers to look toward emerging functional materials. An emerging class of functional porous materials referred to as metal-organic framework (MOF) has received considerable attention over the past two decades, partially because of their potential use in various applications, including gas storage, molecular separations, electrocatalyst, and energy devices. For example, metal oxide and hydroxide-based MOF materials …

Optimizing Process Conditions And Characterizing Elastomeric Properties Of Immiscible Polymers For 3d Printing Applications, Matthew Long

Electronic Theses & Dissertations

Within recent years, 3D printing within the plastics and polymer industries has becoming increasingly prevalent. Also known as additive manufacturing, 3D printing enables the creation of rapid prototypes for short production runs without the need for complex tooling. This allows for runs that are shorter and lower in cost than conventional processes. Polylactic acid (PLA) is a thermoplastic that is widely used in 3D printing for its mechanical properties and low cost. The qualities of PLA however are lacking in the areas of flexibility and toughness which is required in many prototyping scenarios. The solution to this is to incorporate …

Decoding The Flavor Of Kentucky's Native Pawpaw Fruit, Mackenzie Leanne Roark

Online Theses and Dissertations

The objective of this research was to decode the flavor of Asimina triloba, or the pawpaw fruit, to identify and quantitate the aroma-active compounds that are present. Gas chromatography – olfactometry (GC-O) was applied on capillary GC columns with various means of extraction. The volatile compounds present were extracted using both headspace solid phase micro-extraction (HS-SPME) for 30 minutes at 23°C and 50°C, and solvent extraction using methylene chloride. The sample extracts were analyzed with both gas chromatography – mass spectrometry (GC-MS) and gas chromatography – olfactometry (GC-O). To eliminate potential artifacts that were observed when using HS-SPME at 50°C, …

Synthesis, Characterization And Spectroscopic Studies Of Novel Donor-Acceptor Complexes, Shiyue Gao

Chemistry and Chemical Biology ETDs

Square-planar compounds of the (dichalcogenolene)Pt(diimine) series are possess unique photophysical properties that include long-lived excited state lifetimes, which result in their being potential candidates for numerous applications. These applications include solar energy conversion, photocatalysis, nonlinear optics, and photoluminescent probes of biological systems. The most interesting feature of the (dichalcogenolene)Pt(diimine) series of molecules is the bpydichalcogenolene ligand-to-ligand charge transfer (LL’CT) band. To better understand their photoluminescent decay mechanism, and understand their excited dark state properties, we have synthesized and characterized new compounds that include (Thp-bpy)Pt(CAT), (Thp2-bpy)Pt(CAT), (Thp-bpy)Pt(bdt), and (Thp2-bpy)Pt(bdt). Through interpretation of electronic absorption, resonance Raman, XAS, photoluminesce spectroscopy, in addition …

Design And Synthesis Of Dinucleating Phthalazine-Based Ligands Toward Bimetallic Ruthenium Catalysts For Water Oxidation, Alex Bromley

Honors Theses

Two synthetic pathways were developed to construct dinucleating ligands towards the synthesis of bimetallic ruthenium-based water oxidation catalysts. The motivation for this work stems from earlier observations of related ligands that are susceptible to oxidative decomposition. The design pursued here incorporates a phthalazine core into the dinucleating ligand, which, we hypothesize, will prevent the previously established cleavage of a pyridazine unit at the same position. The ligand precursors involved in the multi-step syntheses are characterized by Nuclear Magnetic Resonance (NMR) spectroscopy. Synthetic protocols were refined to ensure reproducibility. In addition, our hypothesis for which of the two target ligands will …

Celebrating Native Chemists And Encouraging More Native Talent In Stem, Lisa Villa

Staff publications

This editorial was written to accompany cover art submitted to the American Chemical Society's 2023 ACS Diversity & Inclusion Cover Art Series, and selected as the July cover for Environmental Science & Technology Letters. The artwork design features several prominent chemists who are also strong advocates for increasing the number of Native American/First Nation scientists. They recognize how cultural beliefs may often be in conflict with scientific conversations, but have been working to attract and encourage Native American talent in the STEM fields.

The published cover art is included as a supplemental file.

Natural Amino Acid Derived Iron (Iii) Catalysts For Green Oxidation Chemistry Applications, Karie Sanford

Theses and Dissertations

Tetraamido macrocyclic ligand activators are a group of catalysts that have been developed to perform green oxidation chemistries. In this thesis, the traditional synthesis of these catalysts was successfully altered to begin with natural amino acids, rather than the conventionally used synthetic derivatives of amino acids, which has never been shown in previous research. This was confirmed using a variety of characterization techniques including electrospray ionization-mass spectrometry. One of these catalysts was utilized in several dye degradation studies, where it was determined that the catalyst can remove about 98% of methylene blue and indigo carmine pollutants from water within 45 …

Halide Substitution Of Ternary Bismuth Chalcogenides For Photovoltaic Applications, Thomas Boggess

Theses and Dissertations

Semiconductors play an integral part in modern society. From computing to LEDs their use is ubiquitous, and no field is more reliant on them than that of power generation. Current political movements have seen a push to decrease reliance on traditional forms of power generation, which relies on fossil fuels, to renewable sources such as solar power. However, current commercial solar panels, based on silicon, are lacking in efficiency, only reaching between 18% and 22% efficiency.¹ In recent years, materials called perovskites have been garnering significant attention as possible replacements for silicon cells due to their favorable optoelectronic properties. …

Genomic And Phenotypic Characterization Of A Red-Pigmented Strain Of Massilia Frigida Isolated From An Antarctic Microbial Mat, Jacob M.C. Scaffer, Lesley Ann Giddings, Robert M. Samples, Jill A. Mikucki

Chemistry: Faculty Publications

The McMurdo Dry Valleys of Antarctica experience a range of selective pressures, including extreme seasonal variation in temperature, water and nutrient availability, and UV radiation. Microbial mats in this ecosystem harbor dense concentrations of biomass in an otherwise desolate environment. Microbial inhabitants must mitigate these selective pressures via specialized enzymes, changes to the cellular envelope, and the production of secondary metabolites, such as pigments and osmoprotectants. Here, we describe the isolation and characterization of a Gram-negative, rod-shaped, motile, red-pigmented bacterium, strain DJPM01, from a microbial mat within the Don Juan Pond Basin of Wright Valley. Analysis of strain DJMP01’s genome …

Exploring Electrolyte Effects On Metal-Alkyl Bond Stability: Impact And Implications For Electrosynthesis, Dylan G. Boucher, Zachary A. Nguyen, Shelley D. Minteer

Chemistry Faculty Research & Creative Works

Transition metal catalysis hinges on the formation of metal-carbon bonds during catalytic cycles. the stability and reactivity of these bonds are what determine product chemo-, regio-, and enantioselectivity. the advent of electro synthetic methodologies has placed the current understanding of these metal-alkyl bonds into a new environment of charged species and electrochemically induced reactivity. in this paper, we explore the often-neglected impact of supporting electrolyte on homogeneous electrocatalytic mechanisms using the catalytic reduction of benzyl chlorides via Co and Fe tetraphenyl porphyrins as a model reaction. the mechanism of this reaction is confirmed to proceed through the formation of the …

Ramie (Boehmeria Nivea): An Underutilized Plant For A Multipurpose Industrial Application; A Perennial Plant With Protein Identification Using Maldi-Ms, A Biosorbent For Hg (Ii) Removal From Water And As A Bast Fiber Production Via Enzymatic Degumming, Abdul Rashid Issifu

Master's Theses

Identifying plant species that can offer life support to humans and animals without damaging the environment is quite challenging. Ramie, one of the oldest fiber crops was studied due to its nutritional value as fodder and other multipurpose applications in, e.g., medicinal, environmental, and textile industrial fields.

With a brief discussion of background in Chapter I, Chapter II focused on using a proteomic method to investigate unknown proteins in the leaves of ramie and to study their benefits to the biological system. PPiase and RuBisCO with molecular weight 15 and 52 KDa were identified as the proteins after peptide mass …

Du Undergraduate Showcase: Research, Scholarship, And Creative Works, Caitlyn Aldersea, Justin Bravo, Sam Allen, Anna Block, Connor Block, Emma Buechler, Maria De Los Angeles Bustillos, Arianna Carlson, William Christensen, Olivia Kachulis, Noah Craver, Kate Dillon, Muskan Fatima, Angel Fernandes, Emma Finch, Colleen Cassidy, Amy Fishman, Andrea Francis, Stacia Fritz, Simran Gill, Emma Gries, Rylie Hansen, Shannon Powers, Jacqueline Martinez, Zachary Harker, Ashley Hasty, Mykaela Tanino-Springsteen, Kathleen Hopps, Adelaide Kerenick, Colin Kleckner, Ci Koehring, Elijah Kruger, Braden Krumholz, Maddie Leake, Lyneé Alves, Seraphina Loukas, Yatzari Lozano Vazquez, Haley Maki, Emily Martinez, Sierra Mckinney, Audrey Mitchell, Kipling Newman, Audrey Ng, Megan Lucyshyn, Andrew Nguyen, Stevie Ostman, Casandra Pearson, Alexandra Penney, Julia Gielczynski, Tyler Ball, Anna Rini, Christina Rorres, Simon Ruland, Helayna Schafer, Emma Sellers, Sarah Schuller, Claire Shaver, Kevin Summers, Isabella Shaw, Madison Sinar, Claudia Pena, Apshara Siwakoti, Carter Sorensen, Madi Sousa, Anna Sparling, Alexandra Revier, Brandon Thierry, Dylan Tyree, Maggie Williams, Lauren Wols

DU Undergraduate Research Journal Archive

DU Undergraduate Showcase: Research, Scholarship, and Creative Works

Peroxisome Biogenesis Initiated By Protein Phase Separation, Zhenghao Zhang, Lydia Kisley

Faculty Scholarship

Peroxisomes are organelles that carry out β-oxidation of fatty acids and amino acids. Both rare and prevalent diseases are caused by their dysfunction. Among disease-causing variant genes are those required for protein transport into peroxisomes. The peroxisomal protein import machinery, which also shares similarities with chloroplasts, is unique in transporting folded and large, up to 10 nm in diameter, protein complexes into peroxisomes. Current models postulate a large pore formed by transmembrane proteins; however, so far, no pore structure has been observed. In the budding yeast Saccharomyces cerevisiae, the minimum transport machinery includes the membrane proteins Pex13 and Pex14 and …

Balancing Functional Tradeoffs Between Protein Stability And Ace2 Binding In The Sars-Cov-2 Omicron Ba.2, Ba.2.75 And Xbb Lineages: Dynamics-Based Network Models Reveal Epistatic Effects Modulating Compensatory Dynamic And Energetic Changes, Gennady M. Verkhivker, Mohammed Alshahrani, Grace Gupta

Mathematics, Physics, and Computer Science Faculty Articles and Research

Evolutionary and functional studies suggested that the emergence of the Omicron variants can be determined by multiple fitness trade-offs including the immune escape, binding affinity for ACE2, conformational plasticity, protein stability and allosteric modulation. In this study, we systematically characterize conformational dynamics, structural stability and binding affinities of the SARS-CoV-2 Spike Omicron complexes with the host receptor ACE2 for BA.2, BA.2.75, XBB.1 and XBB.1.5 variants. We combined multiscale molecular simulations and dynamic analysis of allosteric interactions together with the ensemble-based mutational scanning of the protein residues and network modeling of epistatic interactions. This multifaceted computational study characterized molecular mechanisms and …