Chemistry - Masters by Research Theses

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    Primary and secondary emissions from upland fires in Ireland
    (University College Cork, 2023-04-26) Felberbauer, Clara; Hellebust, Stig; Venables, Dean; Environmental Protection Agency; Horizon 2020
    Emissions from wildfires have detrimental effects on air quality, climate change and human health. Despite frequent occurrence of wildfires and prescribed agricultural burns in upland areas, data on wildfire emissions in Ireland is scarce. This work was conducted as part of FLARES (Fire, Land and Atmospheric Remote Sensing of EmissionS), a project funded by the Irish Environmental Protection Agency (EPA) to improve the understanding of Irish upland fire emissions. Emission factors (EF) of typical Irish wildfire fuels (heather, gorse, purple moor grass) were measured for the first time. Emission factors were measured for a set of gases (carbon monoxide CO, carbon dioxide CO2, methane CH4, sulphur dioxide SO2 and nitric oxides NOx as NO), particulates and particulate fractions (fine particulate matter PM2.5, total particulate matter TPM, black carbon BC, organic carbon OC, elemental carbon EC and total carbon TC) and molecular biomarkers (levoglucosan, mannosan, galactosan, 4-Nitrocatechol 4-NC, 4-Nitrophenol 4-NP and 4-Nitroguaiacol 4-NG). Emission factors of measured gases were as follows: CO: 42 g/kg (heather), 27 g/kg (moor grass) and 80 g/kg (gorse); CO2 1167 g/kg (heather), 1558 g/kg (moor grass) and 1442 g/kg (gorse); SO2: 1.38 g/kg (heather), 1.08 g/kg (moor grass) and 1.68 g/kg g/kg (gorse); NOx as NO: 4.46 g/kg (heather), 5.51 g/kg (moor grass), and 6.85 g/kg (moor grass); CH4: 0.21 g/kg (moor grass) and 0.38 g/kg (gorse). Particulate EFs resulted in EF of 4.71 g/kg (heather), 2.42 g/kg (moor grass) and 10.46 g/kg (gorse) for PM2.5; 3.95 g/kg (heather), 4.26 g/kg (moor grass) and 14.33 g/kg (gorse) for TPM; 0.26 g/kg (heather), 0.21 g/kg (moor grass) and 0.50 g/kg (gorse) for BC; 1.28 g/kg (heather), 1.26 g/kg (moor grass) and 5.43 g/kg (gorse) for OC; 0.80 g/kg (heather), 0.81 g/kg (moor grass) and 2.23 g/kg (gorse) for EC; 2.09 g/kg (heather), 2.07 g/kg (moor grass) and 7.65 g/kg g/kg (gorse) for TC. EFs for biomarkers were 0.09 g/kg (heather), 0.18 g/kg (moor grass) and 0.19 g/kg (gorse) for levoglucosan; 0.01 g/kg (heather), 0.01 g/kg (moor grass) and 0.01 g/kg (gorse) for mannosan and 0.01 g/kg (heather), 0.01 g/kg (moor grass) and 0.02 g/kg (gorse) for galactosan; 0.78 mg/kg (heather), 0.42 mg/kg (moor grass) and 1.36 mg/kg (gorse) for 4-NC; 0.05 mg/kg (heather), 0.04 mg/kg (moor grass) and 0.07 mg/kg (gorse) for 4-NP and 0.25 mg/kg (heather), 0.15 mg/kg (moor grass) and 0.34 mg/kg (gorse) for 4-NG. Combustion took place under flaming combustion conditions, reflected in high modified combustion efficiencies (MCE) of 0.95 to 0.98. Emissions for species like CO, PM2.5 and volatile organic compounds (VOCs) would be expected to be higher under real-world conditions where MCE is lower. Secondary organic aerosol (SOA) formation from combustion emissions of the three fuels was studied under simulated day-time (UV lights and UV+OH precursor addition) and night-time conditions (dark + O3 addition) in an atmospheric simulation chamber. SOA mass increased by 2-11% and was dependent on fuel type and oxidising conditions. Field and laboratory samples were analysed at the Leibniz Institute for Tropospheric Research (TROPOS) in Leipzig, Germany. Filter samples were analysed for the biomarkers levoglucosan, mannosan, galactosan, 4-nitrocatechol, 4-nitrophenol, and 4-nitroguiacol. Laboratory experiments were complemented by field studies. Ambient levels of PM2.5 and BC were measured during an 8-week field study in Glencree, rural Co. Wicklow, Ireland. Source appointment of BC and analysis of biomarkers found no unambiguous signals that could be associated with wildfires. However, this dataset represents a valuable glance at air quality in a rural setting in Ireland. Despite the remote location and low population density in Glencree Valley, anthropogenic influences on air quality were significant, most notably from residential solid fuel burning. Monthly PM2.5 concentrations in Glencree (4.6 μg m–3) were lower than in nearby urban Tallaght (7.0 μg m–3), but less than expected based on the difference in population and local pollution sources. Other field observations included opportunistic sampling of the plume of a major wildfire at Killarney National Park, Co. Kerry, in April 2022. Findings presented in this thesis contribute to the understanding of wildfire emissions in Ireland and highlight the influence of anthropogenic air pollution from solid fuel burning on rural locations.
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    Computational analysis and partialsynthesis of resolvin analogues
    (University College Cork, 2022-06-02) Daly, Kevin; O'Sullivan, Tim; Irish Research Council
    An introduction to the role of resolvins in inflammation is outlined in Chapter 1. In addition, a literature survey of the structure-activity relationships of resolvins, protectins and maresins is also included. Chapter 2 briefly outlines the aims and objectives of this project. Chapter 3 focuses on the computational analysis of the outlined virtual library of Resolvin D2 analogues. The key physicochemical properties of each candidate are calculated and unsuitable candidates are eliminated using standard screening protocols. Chapter 4 describes the attempted synthesis of a key intermediate for the preparation of an aromatic resolvin analogue. This attempted synthesis encompasses a monosilylation of a diol, a selective oxidation of an alcohol to an aldehyde, a Wittig olefination and, finally, a comprehensive trial of acetal deprotection methods for a 1,2 dioxane acetal in the presence of a silyl ether. Chapter 5 summarises the overall findings of this project and outlines possible future avenues for exploration. The full computational data set and experimental procedures, including spectroscopic data, are detailed in Chapter 6.
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    Scalable solid state synthesis of core-chell Pt@Cu2O nanocubes with controlled size and shape
    (University College Cork, 2021-09) Neill, Hazel; Collins, Gillian; Long, Brenda
    This works reports a novel solid state synthesis approach for the formation of shape controlled Pt@Cu2O nanoparticles immobilized onto Cu substrates. High nanoparticle loading was achieved by the use of a self-assembled monolayer consisting of a long chain diamine. The SAM enabled immobilization of citrate stabilized Pt nanoparticles onto the Cu substrate. Annealing under a reducing atmosphere led to the formation of core-shell nanostructures with a cubic morphology. Characterisation showed the nanocubes to consist of a Pt core and crystalline oxide shell. A key question that is addressed in this work was determining the composition of the shell material. A combination of detailed materials characterisation including XPS, XRD and high resolution TEM analysis confirmed the composition to be Cu2O. Preliminary measurements have demonstrated the use of the substrates in glucose sensing applications.
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    Doping of group IV semiconductor nanowires
    (University College Cork, 2020-03) Game, Alexander; Holmes, Justin; Science Foundation Ireland
    As Moore’s Law predicted in the 1960s, advancements in technology have led to an exponential increase in the numbers of transistors required per square inch of integrated circuits, leading to an ever pressing need for smaller transistors. In turn, there is a need for novel transistor architectures and materials, with the conventional Si FETs soon approaching the limits of modern technology. With the need for channel lengths and widths below 7 nm fast approaching, much research has turned to new materials and devices to fulfil these requirements when they are needed. With NWs being prominently used in studies of alternative device architectures, and a resurgence in research of Ge as a semiconductor for FET channels, Ge NWs show great promise as components for novel FET designs. GeSn also shows great potential over Si and Ge due to its direct bandgap allowing for lower energy devices. While most reported syntheses of Ge NWs use gas-based vapour-liquid-solid growths, some research has been reported on solution-based VLS growth of both Ge and Ge Sn NWs, although no literature to date has reported solution-based doping of VLS grown Ge or GeSn NWs. This thesis reports liquid-phase VLS growth and in-situ doping of Ge and GeSn NWs using a variety of dopant precursors. SEM and TEM were used to analyse the morphology of NWs grown. TEM, XRD and Raman Spectroscopy were used to analyse the crystal structures of the wires, including the presence of defects. Raman spectroscopy and EDX analysis were used to determine the atomic composition of the NWs. Electrical testing was also carried out on the NWs. Chapter 1 of this thesis outlines the advantages of the Ge and GeSn NWs over conventional FET materials and architectures, as well as introducing the mechanisms of the growth and doping of semiconductor NWs and summarising the existing literature of doping of NWs, particularly focusing on in situ doping. Chapter 2 outlines the experimental methodology for the synthesis of the Au NPs used for NW synthesis, as well as the syntheses of Ge and GeSn NWs, as well as detailing the equipment and chemicals used. Chapter 3 details how the dopant molecules impact the morphology of the NWs, with decreases in the diameters and lengths of NWs in most samples. The dopants are also shown to decease the NW yield, with most samples yielding cubic crystalline NWs grown in the (111) direction. Dopant precursors are also shown to have prominent effects on the Sn concentration of GeSn NWs, as well as having more pronounced effects on the crystallinity of the NWs. These results are followed by conclusions and an outline of potential future work in this field.
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    Ultrasoft magnetic materials processing and characterisation
    (University College Cork, 2020-08-31) Dixon, Ehren; Rohan, James; Science Foundation Ireland
    The objective of this research was to develop, characterise and test post-processed magnetic materials used for in-package or on-chip devices such as micro-inductors. The electrochemical post-processing has been shown to improve the magnetic properties of the NiFe alloy. The aim of this research was further to test this process on alloys such as CoNiFe as well as integrating these ‘ultrasoft’ magnetic materials into on-chip micro-inductors for device functionality testing. A material with a hysteresis of Hc = <10 A/m is referred to as an “ultrasoft” material. Magnetic devices such as inductors and transformers are essential devices in power supplies. Power supplies have been decreased in size and increased in speed and efficiency over the past few decades with the creation of on-chip power supply circuitries. One key barrier in the miniaturisation of these circuitries in their power storage and transfer devices, inductors, and transformers, which currently occupy ~30% of the circuit’s volume. Decreasing the volume of these devices requires the improvement of their efficiency and functionality, which relates to the magnetic materials used in these devices. Ferrites have been used extensively over the past decades due to their low cost and low loss performance. Unfortunately, ferrite’s low magnetic flux density and resistivity make them less suitable for miniature devices or devices which work at high frequencies. Current alternative high flux materials are limited by high cost or high-power loss and work at very low frequencies. Therefore, there is a need for more efficient magnetic material for improved power supplies. The newly created post-processed magnetic materials and devices were tested for magnetic and electrical properties such as inductance, inductance density, DC resistance, quality factor, and high-frequency response of the devices. They were compared with devices supporting cores made of the as-deposited version of the materials. Oxi-NiFe, the post-processed version of NiFe, saw a noticeable increase in both its electrical and magnetic properties as a material, as well as showing improved properties as a core in the inductor devices, in comparison to NiFe and the NiFe devices. CoNiFe also showed improvement in both electrical and magnetic properties, as well as device improvements when used as a core, in comparison to the standard NiFe. Oxi-CoNiFe saw diminished properties when compared to CoNiFe.