Graduate Theses & Dissertations

Effect of Water Surface Simulated Rain Drop Impacts on Water to Air Chemical Transfers of Perfluorinated Carboxylic Acids (PFCAs)
Perfluorinated carboxylic acids (PFCAs) are anthropogenic environmentally ubiquitous surfactants that tend to concentrate on water surfaces. This investigation looked at the effect of simulated rain on the atmospheric concentration of a suite of PFCAs (C2 - C12) above the bulk water system. Increased air concentrations of all PFCAs were detected during simulated rain events. Long chain PFCAs (>C8) were found to be much more concentrated in the air above the bulk water system than their short chain counter parts (
origin and ecological function of an ion inducing anti-predator behaviour in Lithobates tadpoles
Chemical cues are used commonly by prey to identify predation risk in aquatic environments. Previous work has indicated that negatively-charged ions of m/z 501 are possibly a kairomone that induces anti-predator responses in tadpoles. This thesis found that this ion species: (i) is produced by injured tadpoles; (ii) exhibits increased spectral intensity with higher tadpole biomass; and (iii) is not produced by starved predators. These results refute the hypothesis that the ion is a kairomone, and rather support its role as an alarm cue released from tadpoles. High resolution mass spectrometry (HR-MS) revealed a unique elemental composition for [M-H]-, m/z 501.2886, of C26H45O7S-. Collision induced dissociation (CID) of ion m/z 501 formed product ions of m/z 97 and m/z 80, HSO4- and SO3-, respectively, indicating the presence of sulfate. Green frog (Lithobates clamitans) tadpoles exposed to m/z 501, and an industrial analogue, sodium dodecyl sulphate (NaC12H25O4S), exhibited similar anti-predator responses, thereby suggesting the potential role of organic sulfate as a tadpole behavioural alterant. Author Keywords: Alarm cue, Amphibian, Chemical Ecology, Mass spectrometry, Predator-prey interactions
Research and development of synthetic materials for presumptive testing in bloodstain pattern analysis
Chemical presumptive tests are used as the primary detection method for latent bloodstain evidence. This work focuses on developing a forensic blood substitute which mimics whole blood reactivity to a luminol solution commonly used in presumptive testing. Designing safe and accessible materials that mimic relevant properties of blood is a recognized research need in forensic science. Understanding the whole blood dynamics related to reactivity with presumptive testing chemicals is important for developing accurate analogues. Provided in this thesis is a quantitative and qualitative characterization of photoemission from the reaction of a luminol solution to ovine blood. Luminol reactivity of a horseradish peroxidase encapsulated sol-gel polymer was validated against this ovine blood standard. This material, the luminol-reactive forensic blood substitute, is a key deliverable of this research. An optimized protocol for implementing this technology as a reagent control test, and as a secondary school chemistry experiment are presented. This thesis outlines the research and development of a forensic blood substitute as it relates to presumptive testing in bloodstain pattern analysis. Author Keywords: bloodstain pattern analysis, forensic science, luminol, presumptive testing, secondary school education, sol-gel chemistry
Electrochemical Biosensors for Neurodegenerative Disease Biomarkers
The onset of neurodegenerative diseases such as Alzheimer’s disease (AD) and amyotrophic lateral sclerosis (ALS) are typically characterised by the aggregation of protein biomarkers into cytotoxic fibrils. Novel means of analysing these biomarkers are needed to expand the literature toward earlier diagnosis of these conditions. Electrochemical sensors could offer the sensitivity and selectivity needed for specialised analysis, including potential point-of-care applications. The AD biomarker Tau, and ALS biomarker TDP-43 proteins are explored here by using a label-free electrochemical sensors. Tau protein was covalently bound to gold electrode surface to study the in vitro mechanisms of aggregation for this protein. An immunosensor to TDP-43 was developed by covalently binding primary TDP-43 antibodies (Abs) on gold electrode surface. A novel direct ELISA sensor for TDP-43 with visual detection and electrochemical quantification was also developed. The results validated the experimental designs toward specialised and selective analysis of these biomarkers and their aggregation mechanisms. Author Keywords: ALS, Alzheimer's, Biosensors, Electrochemistry, Tau, TDP-43
Electrochemical versus Chemical Oxidation of Bulky Phenols
Phenolic compounds are used in industry, such as agriculture and biotechnology, and inevitably end up in our environment. These compounds may serve as a phenolic precursor to produce raw materials for a wide range of applications. Chemical oxidation has been the common synthetic pathway to oxidize phenols and related compounds. However, traditional chemical approaches suffer from use of harsh chemicals, waste generation, and lack of reaction selectivity. Electrochemical synthesis has emerged as an alternative method to mitigate common challenges associated with organic synthesis. Herein, electrochemical oxidation of 2,6-diphenylphenol (DPP) and 2,2-dihydroxybiphenol (DHBP) was carried out and compared to traditional chemical oxidation. Contrasted with chemical oxidation, cyclic voltammetry of DPP resulted in a range of products based on the specific potential ranges used, whereas chemical oxidation of DHBP yield a dark-coloured polymeric product. The electrooxidation and chemical oxidation of DPP and DHBP resulted in a solution colour change, indicative of the formation of new, but different products monitored by UV-vis, and characterized by nuclear magnetic spectroscopy (NMR), X-ray single crystal diffraction, IR spectroscopy, transmission electron microscopy (TEM), and gas chromatography-mass spectrometry (GC-MS). The data indicate that the synthetic outcomes are dependent on the synthetic methodology employed, and that electrooxidation and chemical oxidation can form products unique to the pathway utilized. Author Keywords: chemoselectivity, electrochemistry, phenols, radical, synthesis
Molecular Architectures for Improved Biomaterials Derived from Vegetable Oils – Application to Energy Storage and Lubricants
The replacement of petroleum with renewable feedstock for energy and materials has become a priority because of concerns over the environment and finite nature of petroleum. The structures of the available natural biomass feedstocks fall short in delivering key functionality required in materials such as lubricants and phase change energy storage materials (PCMs). The approach taken in this thesis was to combine select functional groups with vegetable oil derivatives to create novel PCMs and lubricantswhich deliver desired functionality. One series of diester PCMs were prepared with terephthalic acid and fatty alcohols to address known shortcomings of esters. The second class of PCMs are sulfones prepared from oxidation of fatty sulfides to improve thermal energy storage. Overall, the new PCMs presented narrow phase change temperature ranges, high transition temperature (between 67 to 110℃), high transition enthalpy (210 to 266J/g), minimal supercooling and congruent phase transitions unaffected by cooling rates. They also demonstrated higher thermal degradation stability with onset of degradation from 290 to 310℃. The series of lubricants studied consists of sulfide and sulfonyl functional groups attached to the unsaturation sites of oleyl oleate as pendant groups to improve the thermal and flow properties. The new lubricants present subzero crystallization temperatures, very low crystallization enthalpy and dynamic viscosity as high as 180mPas. Furthermore, they also presented high onset of degradation (up to 322℃) and oxidation (up to 298℃). The PCMs and lubricants of the present thesis demonstrate that select functional groups can be used with common structural elements of vegetable oil such as fatty acids, ester groups and unsaturation sites to make a variety of molecular structures capable of delivering desired properties Author Keywords: Crystal Structure, Lubricant, Phase Change Material, Renewable, Structure-Property Relationships, Vegetable Oil

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