Chemistry Commons^™

Application Of Functionalized Organosilicas In Adsorption Of Nitrates, Stephen Amoako

Electronic Theses and Dissertations

This study addresses the critical environmental issue of elevated nitrate levels in water bodies, primarily due to excessive use of nitrogenous fertilizers and improper waste disposal. It focuses on reducing nitrate concentrations in polluted water to permissible levels through the effectiveness of hybrid materials in nitrate adsorption. We synthesized nine amino-functionalized adsorbents using grafting and sol-gel techniques. Batch adsorption tests confirmed the high nitrate adsorption capacities of these adsorbents, with sol-gel materials showing the highest efficiency due to their abundant amino group contents. Among these, the surfactant-free, sol-gel adsorbent was the most effective, combining ease of synthesis with cost-efficiency. Our …

Synthesis And Characterization Of Indole-Based Zinc Dipyrrin Photosensitizers, Jean-Pierre Sanza

Electronic Theses and Dissertations

Metal complexes of dipyrromethene (dipyrrins) used as sensitizers in photocatalysis offer a way to harness solar energy in chemical bonds to create new fuels. This offers the dual role of reducing fossil fuel dependence and atmospheric CO₂ levels. Traditionally, metal dipyrrin complexes are synthesized using substituted pyrroles, aldehydes, and transition metals. Indoles have a more expanded pi-electron system and their dipyrrin-type complex may exhibit visible light absorption, suggesting that they can act as photosensitizers for CO₂ reduction processes. A novel indoledipyrromethene was synthesized using unsubstituted indole and mesitaldehyde. The complex exhibits visible light absorption at 422 nm. Its …

Computational Quantum Chemistry Studies Of The Stabilities Of Radical Adducts Formed During The Oxidation Of Melatonin Derivatives, James Horne

Electronic Theses and Dissertations

Melatonin is a natural antioxidant that has been investigated for properties as a potential spin trap to identify short-lived free radicals. Computational quantum chemistry studies have been performed for the oxidation of melatonin to N¹-acetyl-N²-formyl-5-methoxykynuramine. This research focused on modification of melatonin into derivatives and analyzing the change in total molecular energy from melatonin to its oxidation product, as well as the corresponding derivatives. Each of the molecular geometries were optimized at the DFT/B3LYP/6-31G(d), DFT/B3LYP/cc-pVXZ (X = D, T), HF/6-31G(d), HF/cc-PVXZ (X = D, T), MP2/6-31G(d), and MP2/cc-PVXZ (X = D, T) levels of theory. …

Synthesis Of Bacterial Glycerophospholipids For Biomembrane Model Studies: A Means To Advanced Biofuels, Felix Adulley

Electronic Theses and Dissertations

To reduce reliance on fossil fuels, sustainable biofuels are being pursued, especially advanced biofuels like 1-butanol that have higher energy content and greater compatibility with existing infrastructure than ethanol. A persistent challenge is the yield-limiting toxicity of biofuels and process solvents, such as tetrahydrofuran, to the microbes that ferment biomass into biofuel. The cell membrane is a focal point of toxicity, and understanding how it interacts with fuels and solvents is key to improving yield. Phospholipid bilayers are the core of biomembranes, and model biomembranes of defined composition provide the ideal platform for biophysical studies. To this end, glycerophospholipids characteristic …

Nitrogen-Doped And Phosphorus-Doped Epoxy-Sealed Carbon Fiber Ultramicroelectrodes As Electrochemical Sensors For Detection Of Hydrogen Peroxide, Emmanuel Peprah-Yamoah

Electronic Theses and Dissertations

Ultramicroelectrodes (UMEs) are useful as probes for evaluating electroactive species in confined spaces (e.g., inside living cells) and for measuring fast electrochemical reactions. However, UME applications often require modification of the electrode surface to improve selectivity and sensitivity towards target analytes. Previous research in our group demonstrated that a simple soft nitriding method introduces surface nitrogen (N)-containing groups on carbon fiber (CF), leading to improved electroreduction of hydrogen peroxide (H₂O₂) on CF-UMEs. However, sensitivity for H₂O₂ detection using N-CF-UMEs was low compared to that for other modified UMEs. As an alternative to N-CF-UMEs, …

Folic Acid – Carbon Dots – Doxorubicin Nanoparticles As Cancer Theranostic, Michael Tetteh

Electronic Theses and Dissertations

This work focused on engineering bi-functionalized nanoparticles (NPs) based on carbon dots (CDs) to improve early cancer detection and treatment. Therefore, using folic acid (FA) as a targeting agent, the CDs were prepared to deliver high concentrations (HC) of doxorubicin (DOX) and gemcitabine (GEM) covalently and non-covalently to cancer cells. The prepared FA-CDs-DOX/GEM-HC NPs were characterized using ultraviolet-visible spectroscopy, fluorescence spectroscopy, and Fourier transform infrared spectroscopy. Assessment of the drug loading capacity (DLC) and drug loading efficiency (DLE) indicated that the non-covalent NPs have low DLC but high DLE compared to the relatively low DLE and high DLC of covalent …

Synthesis Of Phosphatidylethanolamine Lipids For Model Studies Of The Cell Membrane, John Hayford G. Teye-Kau

Electronic Theses and Dissertations

Concerns about global warming have resulted in a surge of research into alternatives to fossil fuels. In recent years, biofuels have gained traction due to their low environmental impact. Biofuel production most commonly employs microorganisms to convert biomass to fuel for industrial and transportation applications. Compounds made in biofuel production, however, are toxic to cell membranes and disrupt their integrity, harming the microorganisms and limiting biofuel yield. A key to overcoming this challenge is understanding how fuels interact with microorganisms’ cell membranes, which perform a host of functions, including transport, cell recognition, transduction, and movement. Phospholipids are the cell membrane’s …

Synthesis Of Phytosulfokine Analogs As Probes For Studying Plant Signaling And Molecular Trafficking, Thomas Ntim

Electronic Theses and Dissertations

Plants are exposed to a wide range of biotic and abiotic stresses that hinder their growth and reduce crop productivity. In their adaptive response, plants use signaling molecules that are trafficked throughout the plant. This research focuses on the chemical synthesis and assessment of analogs of the plant signal phytosulfokine (PSK, a sulfated pentapeptide), its delivery to plants and its observation using a fiber-optic fluorescence microscope. PSK regulates growth, cell expansion, heat tolerance, and tissue longevity. Analogs of PSK were synthesized using solid-phase peptide synthesis. Pure PSK and TAMRA-labeled PSK were delivered into the wild-type Arabidopsis thaliana Col-0 and a …

Study Of The Cell Membrane And The Synthesis Of Chimeric Human Bacterial Phospholipids, Opeyemi O. Tade

Electronic Theses and Dissertations

Phospholipid bilayers are the principal component of the cell membrane. Membranes ensure the maintenance of processes required for cells’ survival by regulating the inflow and outflow of nutrients and other molecules using membrane proteins. However, studying the cell membrane is challenging because of its complexity and small size. In-vitro membrane models made of phospholipids are important tools for studying membranes. In this work, we aim to study the fluidity of phospholipid bilayers of different lipids using general polarization (GP) of the fluorescent probe Laurdan as a measure. We will focus on the relative importance of head groups and fatty acids …

Preparation And Study Of Bacterial Membrane Models, Enoch Asimbisa

Electronic Theses and Dissertations

Fuel molecules are organic solvents that have disruptive effects on the bacterial membrane. This is a significant barrier in biofuel production, as it limits the fuel concentration that can be achieved through fermentation. One potential way of overcoming this barrier is to identify lipid compositions that can better withstand solvent stress, for which it is important to understand how organic solvents disrupt the membrane. Use of biophysical characterization techniques to quantify physical properties like fluidity and thickness will enable us to understand the mechanism by which solvents disrupt membranes. Native membranes are very complex, and we sought to develop in-vitro …

Computational Analysis Of The Spin Trapping Properties Of Lipoic Acid And Dihydrolipoic Acid, Matthew Bonfield

Electronic Theses and Dissertations

While the spin trapping properties of thiols have been investigated through EPR analysis and kinetics studies, few groups have studied these properties using strictly computational methods. In particular, α-lipoic acid (ALA) and its reduced form, dihydrolipoic acid (DHLA), one of the strongest endogenously produced antioxidants, show potential for being effective, naturally occurring spin traps for the trapping of reactive oxygen species. This research covers electronic structure calculations of ALA, DHLA, and their corresponding hydroxyl radical spin adducts, performed at the cc-pVDZ/B3LYP/DFT level of theory. The effects on DHLA introduced by other radicals such as ·OOH, ·OCH₃, …

Facile Nitrogen-Doping Of Screen-Printed Carbon Electrodes For Detection Of Hydrogen Peroxide, Emmanuel Nkyaagye

Electronic Theses and Dissertations

Screen-printed carbon electrodes (SPCEs) have garnered much attention as sensors due to their simplicity and relatively low cost. However, to impart necessary selectivity and sensitivity for specific applications, modification of the SPCE surface, which can involve time-consuming procedures or costly equipment/materials, is typically required. Here, a simple nitrogen-doping process based on NH₄OH was used to modify SPCEs prepared from commercially available ink for electrochemical detection of H₂O₂, a common target for biosensing strategies and indicator of cell stress. XPS studies showed that NH₄OH treatment of SPCEs led to a nearly 5-fold increase …

An Electrochemical Immunoassay System For Measuring Circulating Protein Biomarkers Of Pediatric Soft Tissue Sarcoma, Ivy Antwi

Electronic Theses and Dissertations

Measurement of circulating protein biomarkers associated with disease can facilitate early detection, help guide treatment strategies and improve patient outcomes beyond current standards of care. The combination of inexpensive 3D-printed flow cells and electrochemical biosensors has recently emerged as a viable platform for low-cost, reliable biomarker measurements. Here, we report an electrochemical immunoassay system based on simple graphite electrode arrays, 3D-printed flow cells, and signal-generating magnetic bead bioconjugates for simultaneous detection of three biomarker proteins (cancer antigen 125 (CA-125), midkine (MK) and osteopontin (OPN)) associated with pediatric soft tissue sarcomas (PSTS). Magnetic bead bioconjugates are functionalized with large amounts of …

Synthesis Of The Diazonium Zwitterionic Polymer/Monomer For Use As The Electrolyte In Polymer Electrolyte Membrane (Pem) Fuel Cells, Josiah Marshall

Electronic Theses and Dissertations

My research goals are to synthesize new zwitterionic perfluorosulfonimide (PFSI) monomer/polymers. They are expected to replace traditionally used perfluorosulfonic acid (PFSA) polymers as the electrolyte in PEM fuel cells. For the PFSI monomer preparation, we designed a nine-step synthesis route. Thus far, I have successfully completed the synthesis of 4- (2-bromotetrafluoroethoxy)-benzenesulfonyl amide, 4-acetoxybenzenesulfonic acid sodium salt, and 4-chlorosulfonyl phenyl acetate. The coupling reaction of 4-(2-bromotetrafluoroethoxy)- benzenesulfonyl amide with 4-chlorosulfonyl phenyl acetate, was troublesome due to slow reaction kinetics and byproducts. Additionally, I did a methodology study for the homopolymerziation of the perfluoro 3(oxapent-4-ene) sulfonyl fluoride monomer. We compared the weight …

Synthesis Of Flagellin 22 As A Probe For Plant Signaling And Molecular Trafficking Towards Improved Crops, Edward Offei

Electronic Theses and Dissertations

Plant signaling involves the transport of information within and between plant cells from receptors to effectors. Plants are affected by biotic and abiotic stress conditions like insect attack and extreme temperatures, respectively, which cause disease, the induction of senescence and the reduction of crop yield. To improve plant traits for feed, fiber, and energy applications, it is critical to understand the short- and long-range signaling mechanisms plants use to control growth, biomass composition, senescence and responses to environmental stresses. It is known that many plant signaling molecules have profound effects on plants, through mechanisms that remain largely obscure. A key …

Nitrogen-Doped Carbon Fiber Ultramicroelectrodes As Electrochemical Sensors For Detection Of Hydrogen Peroxide, Eric Wornyo

Electronic Theses and Dissertations

Carbon fiber ultramicroelectrodes (CF-UMEs) are commonly used as electrochemical probes and sensors due to their small size, fast response, and high signal-to-noise ratio. Surface modification strategies are often employed on CF-UMEs to improve their selectivity and sensitivity for desired applications. However, many modification methods are cumbersome and require expensive equipment. In this study, a simple approach known as soft nitriding is used to prepare nitrogen-doped CF-UMEs (N-CF-UMEs). Nitrogen groups introduced via soft nitriding act as electrocatalytic sites for the breakage of O-O bonds during the reduction of peroxides like H₂O₂, a common target of biosensing strategies. …

Investigating The Role Of Charge Separation In Triplet State Formation In Zinc Dipyrrin Photosensitizers, Irene Y. Dzaye

Electronic Theses and Dissertations

About 85% of the world’s energy is derived from non-renewable sources—coal, petroleum, and natural gas. Solar photocatalysis is one way to potentially generate cheap renewable fuels by harnessing energy from the sun using a photosensitizer and converting it into chemical energy. The efficiency of a photosensitizer depends on its capacity to form a prolonged triplet excited state. Zinc dipyrrin complexes have the potential to be efficient sensitizers for reductive photochemistry, but their ability to form long-lived triplet excited states still needs extensive research. The overall aim of this research is to probe the role charge separation plays in the formation …

Electrodeposition Of Hydrogen Molybdenum Tungsten Bronze Films And Electrochemical Reduction Of Carbon Dioxide., Mohammad Bajunaid

Electronic Theses and Dissertations

The foremost aim for performing this study was to focus on the electrodeposition of mixed hydrogen molybdenum tungsten bronze films, which have the potential for e^– transfer interactions carrying out the reduction of carbon dioxide. A yellow peroxymolybdic tungstate solution was prepared and used for the electrodeposition of hydrogen molybdenum tungsten bronze films on conductive carbon paper. Electrodeposition was carried out at -2.0 V from 20 - 120 minutes to determine the effect of deposition time on film thickness and CO₂ reduction. These films were characterized by X-ray photoelectron spectroscopy. The deposited films served as a working electrode …

Theranostic Nanoparticles Folic Acid-Carbon Dots-Drug(S) For Cancer, Godwin Kweku Babanyinah

Electronic Theses and Dissertations

This study aims to prepare theranostic nanoparticles (NPs) that are expected to increase cancer diagnostics and therapeutic efficacy. We prepared the NPs constituting carbon dots (CDs) as an imaging agent, folic acid as a targeting agent, doxorubicin (DOX), or gemcitabine (GEM) as chemotherapy agents. The NPs include noncovalent FA-CDs-DOX, covalent CDs-FA-DOX, and covalent FA-CDs-GEM. Through ultraviolet-visible spectroscopy, fluorescence spectroscopy, and Fourier transform-infrared spectroscopy, the fabrication of these NPs was confirmed. It was discovered that the high drug loading efficiency is the noncovalent series while the high drug loading capacity is the covalent series The in-vitro pH-dependent drug release data indicate …

Alkylation Of Benzene On Immobilized Phosphotungstic Acid, Kofi Kankam

Electronic Theses and Dissertations

Linear alkylbenzenes (LAB) are key intermediates in the synthesis of linear alkylbenzene sulfonate surfactants that are used in the manufacture of detergents. Production of LAB with traditional Lewis acids as catalysts, such as hydrofluoric acid, results in the formation of large amounts of toxic wastes and corrosion of industrial equipment. Phosphotungstic acid (PTA) has gained much attention in recent years as a solid catalyst for various alkylation reactions. This research work aims to develop a novel material based on PTA-containing silica gel, which can effectively catalyze LAB synthesis. Sol-gel synthesis of silica gel in the presence of PTA and tetraethyl …

Photocatalytic Carbon Dioxide Reduction With Zinc(Ii) Dipyrrin Photosensitizers And Iron Catalyst, Senan Rasheed

Electronic Theses and Dissertations

Much of the energy used in the United States and around the globe is obtained from petroleum, natural gas, and coal. Photocatalytic CO₂ reduction can be used to transform CO₂ to useful fuels and making fossil fuels more renewable. Input of energy is required, and the sun can provide the required energy for this transformation. Photosensitizer, catalyst, and electron donor are required for photocatalytic CO₂ reduction.

Due to lack of earth-abundant sensitizers, zinc dipyrrin complexes were synthesized by previous group members and have been used as photosensitizers in this research. The ground and excited state electrochemical properties …

Mesoporous Adsorbents For Perfluorinated Compounds, Bertha Lotsi

Electronic Theses and Dissertations

Effective adsorbents for polyfluorinated compounds (PFCs) were successfully prepared. And they were tested in the adsorption of perfluorooctanoic and perfluorooctanesulfonic acids. Bridged silsesquioxanes containing secondary and tertiary amino groups were synthesized by sol-gel condensation of bis[3-(trimethoxysilyl)propyl]amine and bis[3-(methylamino)propyl]-trimethoxysilane in acidic media with surfactants. Obtained materials are mesoporous with a high BET surface area. They combine high structural stability with a high concentration of surface amino groups serving as adsorption sites. Batch adsorption tests demonstrated their extremely high adsorption capacity on PFCs: in some experiments, it reached up to 88% of the adsorbent weight. Adsorption of PFCs changed the surfaces of …

Immobilization Of Phosphotungstic Acid On Silica Surface For Catalytic Alkylation Of Aromatic Compounds, Anastasia Kuvayskaya

Electronic Theses and Dissertations

Superacidic mesoporous materials containing covalently embedded PTA were synthesized by sol-gel method. Tetraethyl orthosilicate (TEOS) and phosphotungstic acid (PTA) were used as precursors in the synthesis, ionic and nonionic surfactants were used as pore-forming agents, the reaction proceeded in acidic media. TEM images revealed mesoporous structure with embedded PTA clusters. FT-IR spectra of obtained materials contained characteristic bands of PTA at 957 cm-1. Synthesized catalysts had high BET surface area and high concentration of acidic sites. Alkylation of 1,3,5-trimethylbenzene by 1-decene demonstrated high catalytic activity. The catalyst obtained with Pluronic P123 as a template was the most effective and resulted …

Computational Quantum Study Of Intermediates Formed During The Partial Oxidation Of Melatonin, Oladun Oladiran

Electronic Theses and Dissertations

Melatonin is a neurohormone produced by the pineal gland in the brain. It functions as an antioxidant to scavenge free radicals. Free radicals are reactive species; they often oxidize the cells leading to oxidative stress which may lead to severe health complications. Reaction of melatonin with free radicals is known to be stepwise, as such the stability of the intermediates can be examined. Thus, the possibility of using melatonin as an in vivo spin trap can be determined. Spin traps allow characterization of unstable radical species using electron spin resonance spectroscopy. In this research, ab initio quantum chemistry techniques were …

Synthesis And Study Of Hydroxytyrosol Derivatives, Ebenezer Ametsetor

Electronic Theses and Dissertations

Hydroxytyrosol is one of the most powerful known antioxidants. It is a naturally occurring polyphenol, most commonly produced in olive trees, (Olea europaea). The remarkable antioxidant and pharmacological properties of hydroxytyrosol has made it an outstanding compound in the polyphenol family and of great interest to many researchers. Hydroxytyrosol can scavenge free radicals produced during cellular oxidative stress and helps to protect the integrity of cells in living systems. Despite its numerous biological and pharmacological uses, it is found in very low concentration in olive oil, this limits its availability for biomedical applications. This work reports a novel and effective …

Structure Elucidation Of A Pyrrolobenzodiazepine Alkaloid And A Biologically Active Polyketide Produced By Rhodococcus Sp. Mtm3w5.2 Via Two-Dimensional Nmr Spectroscopy, Garrett Johnson

Electronic Theses and Dissertations

As the battle against ever-increasing drug resistence bacteria rages on, novel and sometimes more complex natural products can be used to combat this. In this study, two-dimensional NMR techniques were utilized to collect a complete spectral data set for two natural products. The first structure, a synthesized Pyrrolobenzodiazepine alkaloid natural product was confirmed through these methods. The second, a strain of Rhodococcus, MTM3W5.2, produces a novel antibacterial molecule in broth cultures and the active compound was fractionated using a Sephedex LH-20 column. Chromatographic purification yielded a pure sample at 58.90 minutes, RT.58. HRMS data deduced an exact mass of …

Preparation Of Folic Acid-Carbon Dots-Doxorubicin Nanoparticles As Targeting Tumor Theranostics, Samson Dada

Electronic Theses and Dissertations

Carbon dots (CDs) have attracted much attention as an excellent gene/drug delivery and biological imaging agent for early cancer theranostics. In this study, we prepared two series of nanoparticles (NPs), which are composed of (CDs) with a targeting agent, folic acid (FA), and a chemotherapeutic agent Doxorubicin (Dox). All the NPs and their intermediates were characterized using ultraviolet-visible spectroscopy (UV-vis), fluorescence spectroscopy, and Fourier transform-infrared spectroscopy (FT-IR). The drug loading capacity (DLC) and drug loading efficiency (DLE) of two series of FA-CDs-Dox were assessed using UV-vis absorption spectroscopy at the wavelength of 485 nm. Both showed good DLE and DLC …

Electrodeposition Of Hydrogen Molybdenum Bronze Films And Electrochemical Reduction Of Carbon Dioxide At Low Over Potentials, Sami Alharbi

Electronic Theses and Dissertations

Hydrogen molybdenum oxide, known has molybdenum bronze, is a material of interest due to catalyzing electron transfer reactions. Specifically, molybdenum bronze is an electrocatalyst toward carbon dioxide reduction. Electrochemical deposition from a peroxymolybdic acid solution is a method for preparing molybdenum bronze films. This work demonstrates reproducible electrodeposition on indium tin oxide substrates and conductive carbon paper. Film thickness depends on concentration, time and pH. After characterization by film thickness, resistance, XRD and XPS, the as deposited films served as the working electrode for electrochemical reduction of carbon dioxide in 0.1 M NaHCO₃. Ion chromatography determined formate resulting …

Modification Of Chemical Vapor-Deposited Carbon Electrodes With Electrocatalytic Metal Nanoparticles Through A Soft Nitriding Technique, Enoch Amoah

Electronic Theses and Dissertations

Metal nanoparticles have been widely used for many catalytic and electrocatalytic applications due to their larger surface area-to-volume ratios and higher densities of active sites compared to bulk materials. This has resulted in much interest in understanding the electrocatalytic behavior of metal nanoparticles with respect to their structure. However, most research on this topic has employed collections of nanoparticles. Due to difficulties in controlling and characterizing particle loading and interparticle distance in nanoparticle ensembles, single nanoparticles studies have recently become a topic of great interest. In this study, a soft nitriding technique was applied to chemical vapor-deposited carbon ultramicroelectrodes (UMEs) …

Synthesis, Characterization And Biological Evaluation Of Novel (S,E)-11-[2-(Arylmethylene) Hydrazono] Pyrrolo [2,1-C] [1,4] Benzodiazepine Derivatives, David Mingle

Electronic Theses and Dissertations

Pyrrolo [2,1-c] [1,4] benzodiazepine (PBD) is a class of natural products obtained from various actinomycetes which have both anti-tumor and antibiotic activities and can bind to specific sequences of DNA. PBD-dilactam was initially produced using isatoic anhydride and (L)-proline which was then converted to the PBD-thiolactam using Lawesson's reagent. Reaction of thiolactam with hydrazine in ethanol afforded PBD-11-hydrazinyl. Condensation of 11-hydrazinyl PBD with aldehydes possessing various substitutions was performed to obtain (S,E)-11-[2-(arylmethylene) hydrazono] pyrrolo [2,1-c] [1,4] benzodiazepine derivatives. ¹HNMR, ¹³C-NMR, DEPT, IR, GC-MS and X-ray crystallography were used for the characterization. Inhibition activity of the products …