Chemistry Commons^™

Assessing Dissolved Organic Matter Sources And Dynamics In Urban Stormwater: Implications For Greenhouse Gases, Harper W. Schmalz

Theses and Dissertations (Comprehensive)

Stormwater management ponds (SWMPs) are important aspects of land-use planning and increasingly recognized as active sites of biogeochemical processing that influence carbon cycling; however, little research has investigated the controls on dissolved organic and dissolved inorganic carbon (DOC and DIC) within these systems. This thesis examined the processing and transformations of dissolved carbon between three compartments to support the development of a greenhouse gas (GHG) box-model for urban stormwater ponds, including SWMP sediment, surface water, and vegetation. The objective of this thesis was to assess the biogeochemical processes that govern the rate and transformation of DOC and DIC between these …

Functional Design Of Dissymmetric Ligands For Coordination Systems, Kaitlyn R. Brown

Theses and Dissertations (Comprehensive)

Herein, the functional design of dissymmetric ligands for coordination systems is explored with a focus on their synthesis and structural characterization. The design strategy of these ligands incorporates the ability to coordinate both metal cations and anions along with a ligand site for other functionalization. Their synthesis, structural and other characterization, Hirshfeld surface analysis, and some metal-coordinated complexes are discussed. Chapter 1 introduces supramolecular and coordination chemistry, along with relevant literature that supports this research and outlines the thesis objective. Chapter 2 investigates the hydrogen bonding of a dissymmetric pyrimidine thioether ligand in its neutral form, water solvate, protonated nitrate …

Investigating The Thermal Stratification Patterns Of A Shallow Polymictic Boreal Shield Lake And The Effectiveness Of Models In Predicting Shallow Lake Thermal Profiles, Matthew Roberts

Theses and Dissertations (Comprehensive)

Thermal stratification is a core process of lakes which plays a critical role in shaping the ecological dynamics of lakes, influencing major processes like nutrient cycling and oxygen availability. For shallow polymictic lakes, thermal stratification patterns present some unique differences due to the complex and variable nature of these lakes. In this thesis, I examined thermal stratification in a shallow polymictic lake in northwestern Ontario during the ice-free season of 2019 to investigate the frequency, duration, and driving factors of thermal stratification. The lake underwent 146 separate stratification events, with a median duration of 2 hours per event, with a …

Geochemistry Of Rare Earth Elements In Simulated Natural Waters: Experiments And Modelling Of Precipitation, Complexation, And Bioavailability., Samantha Zulian

Theses and Dissertations (Comprehensive)

Rare earth elements (REEs) are an important part of modern technology and used for many applications. Mining, agriculture, improper recycling and medical applications can increase the concentration of these elements in surface waters. Metals in the environment including REEs can be found naturally but understanding the implications increase concentrations from anthropogenic inputs is important. REE mobility, persistence and toxicity is imperative to risk assessment as Canada begins to mine REE. Ultimately, as with other metals, the impacts of REEs in the environment should be dependent on the specific physical and chemical forms of the elements. Fractionation provides a practical method …

Unexpected Ring Opening Reactions, Solid-State Structures, And A Chemiluminescent Reaction, L Hiscock

Theses and Dissertations (Comprehensive)

Functional π-materials involve the use of an aromatic π-system to carry out a function such as electron transport (organic electronics), absorbing and emitting photons (dyes, fluorescent materials), self-assembly (discotic liquid crystals), or sensors for various analytes. Our lab has recently published the syntheses of heteroaromatic derivatives of tetrafluoroterephthalonitrile (TFTP, 2.24) synthesised via nucleophilic aromatic substitution chemistry. The prepared derivatives have displayed fluorescent (e.g. 2.2)1 and liquid crystalline (1.0)2 properties, as well as displaying close π-π interactions in the solid state (2.8).3 As the materials we are synthesising all belong to the class of aromatic compounds, an introduction to aromaticity and …

Coordination Chemistry Using Strategic Design Of Ligands For Switchable Properties, Delara Joekar

Theses and Dissertations (Comprehensive)

Coordination-driven self-assemblies are multifunctional molecular systems that provide an efficient method for miniaturization towards functional devices with diverse applications. Herein, the synthesis of novel pyrazole-based ligands suitable for construction of coordination assemblies is reported. These were designed using a strategy that incorporates the presence of both cationic and anionic coordination sites, and a third site for further functionalization. This design strategy has been used because there is still a knowledge gap for controlling the directionality of weak molecular forces in the presence of stronger competing forces. The structural characterization of these ligands, their Hirshfeld surface analysis, and select coordination complexes …

Contrasting Seasonal Cycling Of Arsenic In A Series Of Subarctic Shield Lakes With Different Morphometric Properties, Jeremy Harbinson

Theses and Dissertations (Comprehensive)

The subarctic shield near Yellowknife, Northwest Territories (NWT), is populated with thousands of small lakes (<1.5 km²) and several large lakes. Historic mining activities in the region have left a legacy of environmental impacts and widespread arsenic (As) contamination in both aquatic and terrestrial environments. In particular, several small subarctic lakes near Yellowknife have been previously documented to be contaminated with high levels of As. Subarctic lakes are characterized by seasonal ice-cover that can persist for more than half of the year, yet little is known about the under-ice spatial and seasonal dynamics of As cycling. The objective of …

Mechanistic Studies Of Co2 Electrochemical Reduction (Co2er) On Cu And Cuo Nanoparticles With In-Situ Atr-Ftir Spectroscopy, Jason Hsu

Theses and Dissertations (Comprehensive)

Global climate change is a major challenge facing the world in the 21st century. This environmental crisis originated from excess amounts of atmospheric carbon dioxide (CO2) released from burning fossil fuels. One promising remediation method to decrease atmospheric CO2 levels is called carbon dioxide electrochemical reduction (CO2ER). In CO2ER, the CO2 gas undergoes chemical reduction to other hydrocarbon fuels. For CO2ER to take place, an energy source and a catalyst are needed. In this thesis, three aspects of CO2ER were investigated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy coupled with other surface sensitive characterization tools. First, we studied …

The Design And Characterization Of Gold Nanoclusters As Elementary Building Blocks, Heather Gaebler

Theses and Dissertations (Comprehensive)

Gold nanoclusters with diameters in the quantum size regime (< ~2 nm) are promising building blocks for the design of novel nanomaterials as they exhibit unique size-dependent properties that can be altered and fine-tuned. The research outlined in this PhD thesis employs density functional theory to construct and analyze small ligand-protected cage and rod-shaped nanoclusters. Chapter 2 reports stable halide-protected gold nanocages that were engineered to have a closed-shell valence electron count of 18. This study finds that nanocages comprised of 19 and 20 gold atoms can be converted into stable magic number species containing 18 valence electrons by modifying their charged states via adsorption of halide ligands to the cage’s surface. Chapter 3 reports stable ligand-protected gold nanoclusters with a tetrahedral Au₄ core that were engineered to have a closed-shell valence electron count of 2. This study investigates the structural and electronic effects of halide and alkoxy ligands on the tetrahedral nanocluster and concludes that the results support the broader conclusion that it’s possible to fine-tune the stability and electronic properties of small gold nanoclusters using appropriate ligands. Chapter 4 reports stable gold nanorods that have diameters in the quantum regime that were constructed from elementary building blocks that contain “halide-staples”. This study presents different orientations of the “halide-staple” motifs on …

Phosphorus Release And Recovery From Simulated Ferric Wastewater Sludge, Aseel Alnimer

Theses and Dissertations (Comprehensive)

Phosphorus (P) is a fundamental element necessary for all life forms and a key component in the fertilizer industry. Meanwhile, the excessive load of P to water bodies due to human activities has the potential to promote eutrophication. Wastewater treatment plants remove P either biologically or chemically and produce P rich sludge which could be a potential renewable source for P. At present, commercial technologies exist for P recovery from biological wastewater sludge. However, P recovery from chemical sludge particularly iron(III)-phosphate (Fe-P) sludge generated in chemical P removal plants that use iron(III) salts remains a challenge.

This study explored, in …

Influence Of Dissolved Organic Matter On Phosphate Interactions With Hydrous Ferric Oxides, Alaa Hasan Alsherbi

Theses and Dissertations (Comprehensive)

Phosphorus, iron oxides, and dissolved organic matter (DOM) are components present in all aquatic systems. Excess amounts of phosphorus in aquatic systems have the potential for toxic effects, in particular, contributing to eutrophication. Most of the previous studies performed looked at the surface complexation of inorganic phosphate anions (P) to mineral surfaces such as hydrous ferric oxide (HFO). However, the role of DOM on the interactions between HFO and P is unknown. This study investigates the influence of DOM on the surface complexation of P onto HFO surfaces. Moreover, this study looks at the possibility of cation bridging formation (Ca …

Utilization Of The Yamamoto Cyclotrimerization Reaction Towards The Synthesis Of Polycyclic Aromatic Compounds, Josh Ledrew

Theses and Dissertations (Comprehensive)

The overall theme of this research was to synthesize and study the structure-property relationships of novel polycyclic aromatic compounds capable of self-assembling to form liquid crystalline, and microporous structures, as well as molecules capable of molecular recognition. The unifying theme that connects this research is the utilization of the Yamamoto coupling reaction to access the desired polycyclic aromatic hydrocarbon targets. More specifically, the scope of the Yamamoto coupling reaction was explored for the synthesis of electron-deficient triphenylene derivatives that are otherwise difficult to prepare. The molecules prepared via the Yamamoto coupling reaction are expected to be further utilized as intermediates …

The Potential For Remote Sensing Measurement Of Dissolved Organic Carbon As A Tool For Metal Risk Assessments, Mickey Nielsen

Theses and Dissertations (Comprehensive)

The biotic ligand model (BLM) is a tool used to quantitatively evaluate how receiving water chemistry affects the bioavailability of metals. Sensitivity testing can be used to understand how the model outputs vary in response to systematic changes in water chemistry inputs. This will allow users of such models to understand how accurate their input parameters must be for a specified level of confidence in the output. Our focus was on dissolved organic carbon (DOC), which is often the most limiting data for application of BLM approaches to metals risk management. To potentially address DOC data limitations remote sensing can …

Determination Of Samarium And Dysprosium Solubility, Seana Brennan

Theses and Dissertations (Comprehensive)

In recent years, the use of Rare Earth Elements (REE) has rapidly increased, resulting in numerous potential anthropogenic inputs to the environment. As a result, these metals are emerging as microcontaminants and pose a potential threat to aquatic life. However, the toxicity of REE are largely unknown due, in part, to the limited information on their chemical speciation. The purpose of this project was to gain an understanding of REE precipitate formation and solubility as the foundation for the development of the chemical equilibrium component of toxicity prediction models. Solubility experiments were conducted with Samarium, (Sm), a light REE, and …

Reconstructing Hydrologic Conditions And Metals Supplied By The Peace River To The Peace-Athabasca Delta, Jelle André Faber

Theses and Dissertations (Comprehensive)

The Peace-Athabasca Delta (PAD) in northern Alberta, Canada, is recognized internationally for its ecological, historical, and cultural significance. The delta is mostly within Wood Buffalo National Park, a UNESCO World Heritage Site, and is a Ramsar Wetland of International Importance. The construction of the WAC Bennett Dam (1967) and the Site C Dam (ongoing, 2024) on the Peace River, and expansion of the Alberta Oil Sands industry along the Athabasca River have raised concerns over water quantity and quality in the delta. When industry operations began, effective monitoring had not been implemented. Consequently, pre-industrial reference conditions are unknown and can …

Characterization Of The Microbial Phosphonate-Activating Pntc Enzymes, Kyle Rice

Theses and Dissertations (Comprehensive)

New strategies are urgently needed to combat infectious diseases in an era of rising antibiotic resistance. Furthermore, an emerging appreciation for the human microbiome’s role in maintaining health motivates discovery of species-specific antibiotics that minimally disrupt our native bacterial communities. Small molecule modifications to bacterial cell surfaces represent a potentially rich source of new targets for next generation antibiotics, as these molecules mediate virulence and evasion of the host immune response. Phosphocholine (PCho) is a rare cell surface modification that contributes to virulence, and modifications with phosphonates like 2-aminoethylphosphonate (AEP) are even more unusual and therefore provide opportunities for species- …

Nanoscale Building Blocks: Bridging The Gap Between Potential And Realized Applications, Nicole Ritter

Theses and Dissertations (Comprehensive)

The vast potential of nanoparticles and nanotechnology remains largely untapped; the crucial bottleneck being the knowledge gap between making and using nanoparticles (NPs). This PhD work bridges this gap by focusing on synthesizing nanoparticles with applications at the forefront. Four peer-reviewed publications are presented in Chapters 3-6, a safety and toxicological perspective is given in Chapter 7, and current work and future progress are summarized in Appendix 1. Bimorphic silver nanoparticles were prepared, presenting an innovative method to synthesize diverse nanostructures using polymeric surface blocking to break symmetry in seeded regrowth (Chapter 3).¹ Silver stars with D_5h symmetry …

Temperature-Dependent Kinetic Studies Of Arsenicals Adsorption From Solution To Hematite Nanoparticles, Sara Soldoozy

Theses and Dissertations (Comprehensive)

Surface chemistry is the study of the chemical and physical phenomena that transpire at interfaces such as liquid-solid, solid-gas, liquid-gas, and liquid-liquid. To study the reactions occurred at the surfaces, surface sensitive techniques come to play. Adsorption of arsenical compounds (liquid adsorbate), particularly arsenate (iAs) and dimethylarsinic acid (DMA), to the surface of iron bearing materials (solid adsorbent) that frequently are found in geosorbents such as hematite (Fe₂O₃) has been studied in this thesis. Arsenical compounds can pollute the environment through natural sources and anthropogenic activities, and ultimately contaminate water. Absorbing these pollutants to a material …

The Effect Of Oxidation, Thionation, And Dimerization On The Self-Assembly And Photophysical Properties Of Novel Discotic Materials, Katie M. Psutka

Theses and Dissertations (Comprehensive)

This thesis aims to increase understanding of the relationship between molecular structure and liquid crystalline temperature range by exploring the effects of oxidation, thionation, and dimerization on the self-assembly and properties of novel discotic materials. First, two alkoxy-substituted dibenzanthracenequinones were prepared by oxidation of the corresponding dibenzanthracenes. The quinone induced a liquid crystalline phase in the hexaalkoxy dibenzanthracene derivative, but not in the tetralkoxy derivative. However, both of the resulting materials were un-reactive to any further synthetic modifications that could be used to improve their properties. In comparison, two heteroaromatic dithienoanthracenedicarboximides were successfully prepared, although the addition of the thiophene …

Synthesis, Properties, And Solid-State Structures Of A Series Of 6,13-Dicyanoheteropentacene Analogues: Towards New Liquid Crystalline Materials, L Hiscock, Kenneth E. Maly, Louise N. Dawe

Theses and Dissertations (Comprehensive)

The focus of this thesis is the synthesis of novel heterocyclic pentacene analogs and the investigation of their self-organization for the development of new materials for organic electronics. The thesis consists of two interrelated projects: the first being development of an improved synthesis of a series of liquid crystalline dicyanotetraoxapentacenes (DCTOPs) while the second entails the exploratory synthesis of several novel dicyanoheteropentacene analogues and a preliminary investigation of their photophysical properties and solid-state structures. Both of these projects centre around the use of nucleophilic aromatic substitution reactions on tetrafluoroterephthalonitrile.

Soluble, tetrakis(bis(alkoxy)phenyl)-substituted DCTOPs were originally synthesised via a short synthesis complicated …

Size And Shape Control In Metal Nanoparticles And Nanocomposites, Tomendro Subedi

Theses and Dissertations (Comprehensive)

This thesis describes major findings on the shape transformation of the precursor silver decahedral nanoparticles (AgDeNPs) with pentagonal symmetry and twin defects into silver pentagonal prism nanoparticles (AgPPNPs) using Br¯ as a shape selective reagent. Silica-encapsulation of the gold-plated AgDeNPs was also carried out forming ordered arrays of silica encapsulated gold-plated AgDeNPs (SiO₂@Au@AgDeNPs) of different sizes. At first, synthetic procedures for AgDeNPs (pentagonal bipyramids), silver pentagonal rod nanoparticles (AgPRNPs) and gold-plating of AgDeNPs (Au@AgDeNPs) were optimized. Gold plating enhances the chemical stability of AgDeNPs and preserves the superior plasmonic properties of silver. This thesis deals with the transformation …

Natural Organic Matter Characterization And Lead Speciation As Indicators Of Potential Lead Bioavailability In Aquatic Environments, Giselle Cimprich

Theses and Dissertations (Comprehensive)

Trace metals and natural organic matter (NOM) are ubiquitous in aquatic environments. Some trace metals are essential for aquatic life, while other non-essential metals (like lead) can be toxic if present in great enough concentrations. Natural waters contain a combination of inorganic, and organic ligands capable of binding metals. While the chemistry of inorganic Pb species is well understood, and National Institute of Standards and Technology (NIST) certified K values are readily available, the interactions between metals and organic matter is not so clearly defined. It is important to understand how NOM interacts with metals in the environment, as the …

Quantifying The Interactions Of Nickel With Marine Dissolved Organic Matter Using Fluorescence, Elissa Dow

Theses and Dissertations (Comprehensive)

Nickel (Ni) is a versatile metal with an abundance of applications, namely its role in stainless steel, electronics, and batteries, making it a popular choice in industry. Unfortunately, with increasing demand and production comes higher amounts of Ni pollution. Nickel enters ocean waters - either directly or indirectly - and can have profound effects on marine life. Nickel has been established as a toxicant to a variety of aquatic biota, with the divalent cation (Ni²⁺) thought to be the most bioavailable fraction and thus the most toxic. Having a reliable means of quantifying free Ni ion is pertinent …

The Synthesis Of Symmetric Polycyclic Aromatic Hydrocarbons And The Mesomorphic Properties Of Their Brominated Derivatives, Vanessa Bellemore

Theses and Dissertations (Comprehensive)

In this thesis, the synthesis of a series of brominated alkoxy-substituted trinaphthylenes was developed using a nickel-mediated Yamamoto coupling as the main step. Characterization of these compounds led to the discovery of a new set of broad range liquid crystals. They were found to undergo higher order transitions (i.e. glass phases/soft crystals/liquid crystal) via DSC, and also to decompose before reaching an isotropic liquid, as verified via thermogravimetric analysis. Polarized optical microscopy showed a texture characteristic of a columnar hexagonal mesophase. In addition, the aggregation in solution was studied using concentration dependent NMR studies, and the brominated-derivatives were determined to …

A Computational Study Of Silver Doped Cdse Quantum Dots, Heather Gaebler

Theses and Dissertations (Comprehensive)

Due to quantum dot’s ability to emit photons when subjected to light of sufficient energy, they have become optimal candidates for biomedical research and for optoelectronic applications. Fascination towards quantum dots arises from the fact that their properties are easily fine-tuned through a variety of different techniques. Electronic doping is a popular technique used to control the properties of quantum dots through the addition of different elements.

Via density functional theory calculations, this work investigated how the structural energies and HOMO-LUMO gaps were altered by the addition of impurity atoms. First, interstitial and substitutional doping styles were investigated at 0 …

A Density Functional Theory Study Of Intrinsically Chiral Semiconductor Nanocrystals, Richard Edwards

Theses and Dissertations (Comprehensive)

A plethora of work has been done in the area of nanoparticles of late due to the fact that chemists (and physicists) have discovered that the properties of nanoparticles differ from both those of the bulk material and the atoms themselves. Nanoparticles have become of high interest for the use as catalysts while materials like graphene, being only one atom thick, have been shown to be great electrical conductors in comparison with the 3D structure of diamond. Among these peculiar nanoscale properties is the phenomenon of nanochirality, where a nanoparticle can exhibit chirality that does not extend to the macroscale …

Seasonal Evolution Of Active Layer Formation In Subarctic Peat Plateaux And Implications For Dissolved Organic Matter Composition And Transfer, Jennifer L. Hickman

Theses and Dissertations (Comprehensive)

Peat-accumulating wetlands are ecosystems whose rate of photosynthetic production of organic matter is greater than that of its decomposition, resulting in a build up of soil organic matter that may take centuries to fully decompose. Carbon (C) stocks within these ecosystems are a function of inputs from photosynthesis, and losses from heterotrophic decomposition. Due to the short growing season and overall cold climate of boreal and tundra regions, C has been accumulating within these landscapes, mostly in soil organic matter, since the last glaciation. Climate change, predicted to result in rising temperatures and increased precipitation, has begun to degrade the …

Sm And Dy Interaction With Dissolved Organic Matter (Dom) In Freshwater Measured By Ion-Selective Electrode And Fluorescence Quenching Analytical Techniques, Alexandra Carvajal

Theses and Dissertations (Comprehensive)

With the increased demand for lanthanide metals in various industries, companies are looking into mining of these metals in Northern Canada. The release of these metals into the environment may have adverse effect on aquatic ecosystems; thus, it is important to understand potential toxicological effects of lanthanides on aquatic organisms. One way to predict these effects is by using a Biotic Ligand Model (BLM). Although incorporation of lanthanides into the model will require a substantial amount of future research, initial studies into speciation and toxicity can provide a useful basis for future reference. There are two main objectives to this …

The Role Of Organic Matter In The Surface Chemistry Of Arsenic Compounds On Iron−(Oxyhydr)Oxides Studied By Atr-Ftir, Arthur Situm

Theses and Dissertations (Comprehensive)

The interaction of organic matter with the interfaces of active soil components such as iron oxides is ubiquitous within soil environments. The presence of organics at these interfaces may have implications for other soil constituents whose mobility is controlled by their ability to bind to active soil components. Most of the studies performed to date which look at these interactions are bulk/batch studies performed ex-situ. Attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was utilized within this work to study interactions between select model organics (citrate, oxalate and pyrocatechol) and iron−(oxyhydr)oxides, as well as their effect on the surface …

Phosphorus Removal Using Titanium Dioxide Nanoparticles In Wastewater Treatment, Suyoung Choi Mr.

Theses and Dissertations (Comprehensive)

Due to eutrophication caused by nutrients such as phosphorus (P), local surface water near military garrisons and camps has been deteriorated for several years in the Republic of Korea. Thus, in order to remove excessive P in local fresh water, various size of titanium dioxide (TiO₂) were used.

In the first investigation, TiO₂ mixed bulk powder (particle size > 5µm) showed maximum P removal with pH dependence (higher pH shows lower P removal), that was approximately 27%. To determine adsorption isotherms, Langmuir and Freudlich models were used. The experimental data was better fit by a Langmuir model compared …