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Abstract: Nanoplastics (NPls) have been recognized as emerging persistent toxic particulates in aquatic environments and their interactions with biota pose growing ecological concerns. Yet, the mechanisms governing their cellular association and resulting toxicity remain poorly resolved because population-level assays obscure the inherent variability among individual cells. Here, we integrate single-cell inductively coupled plasma mass spectrometry (SC-ICP-MS) with Gaussian mixture modelling (GMM) to quantify the dynamic heterogeneous association of Eu-doped polystyrene nanoplastics (Eu-doped NPls) with the model microalga Chlorella vulgaris. The GMM analysis identified distinct subpopulations exhibiting variable particle association that shift dynamically with exposure time and concentration. Across exposures of 5–20 mg L−1, GMM analysis revealed that the majority of microalgal cells (35–65%) belonged to low-association clusters, whereas only a small fraction (0–10%) exhibited high NPls association, with pronounced temporal and concentration-dependent shifts in subpopulation structure. A generalized linear model (GLM) further demonstrated that these high-burden subpopulations disproportionately account for observed growth inhibition, increasing from 12.75% at 5 mg L−1 to 39.34% and 43.05% at 10 and 20 mg L−1, respectively. Synchrotron-based nano X-ray fluorescence (nano-XRF) provided spatial evidence consistent with particle localization within or closely associated with algal cell, while physiological endpoints (chlorophyll-a content, CO2 fixation, ROS, and MDA levels) validated the toxicity trends. This integrative single-cell and unsupervised machine-learning modelling framework provides quantitative evidence that stochastic, heterogeneous interactions underpin NPls toxicity in microalgae. The approach offers a transferable analytical paradigm for elucidating the fate and effects of persistent plastic pollutants in aquatic ecosystems.

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Abstract: This thesis explores the design and reactivity of novel flavin-metal conjugates, hypothesizing that covalently tethering a redox-active isoalloxazine core to a transition metal overcomes diffusion-controlled kinetic limitations through proximal positioning. To validate the approach, three distinct metallic platforms—Pt(IV), Ru(IV), and Ir(I)—were conjugated to functionalized riboflavin derivatives and systematically investigated. First, linking flavins to Pt(IV) anticancer prodrugs enabled their rapid, reduction to bioactive Pt(II) species using endogenous electron donors, demonstrating superior efficacy compared to controls. Second, a cyclopentadienyl Ru(IV) quinoline scaffold was employed to create a bioorthogonal catalyst that successfully oxidized glutathione with enhanced redox reversibility, simultaneously mediating the activation of Pt(IV) substrates. Third, the strategy was expanded into classical homogeneous catalysis via a Ir(I)-flavin complex, providing a proof-of-concept for the synergistic activation of molecular hydrogen and subsequent intramolecular electron transfer. Across all systems, the covalent linkage proved essential. Ultimately, this work establishes a robust foundation for the rational design of dual-function bio-organometallic agents, paving the way for advanced redox-mediated chemotherapy and sustainable chemical synthesis.

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Abstract: Coal fly ash (CFA), a metal-rich byproduct of coal combustion is produced in vast quantities and poses significant ecological risks. CFA also contains abundant technologically relevant metal oxides and trace metals, including rare earth elements (REE), often at higher concentrations than in primary ores. This makes sustainable recovery strategies a major industrial opportunity. Here, green solvent systems were applied to leach metals from CFA, and the resulting leachates were added to cultures of Magnetospirillum gryphiswaldense (MSR1), a model magnetotactic bacterium that biomineralizes iron into membrane-bound magnetic nanoparticles (magnetosomes) and is capable of interacting with non-iron metals through adsorption and biomineralization. Eleven green solvents, including deep eutectic solvents (DES), were tested for extraction efficiency, with six showing performance comparable to a mineral acid control. Copper (Cu) emerged as the primary toxicant to MSR1, prompting selective precipitation with potassium ferrocyanide trihydrate (PFCT) to reduce its concentration. Cu-depleted lactic acid-based leachates supported MSR1 growth and magnetosome formation even without supplemented iron. Nano-XRF and ICP-MS analysis revealed MSR1 interacts with CFA-derived metals, most significantly showing that produced CFA magnetosomes contained a 5.3–6.1-fold increase in Cu compared to controls. As Cu is both a growth inhibitor and a target pollutant, these findings suggest MSR1 may bioaccumulate Cu within magnetosomes as a detoxification strategy. Overall, this study demonstrates a combined chemical–biological route for CFA valorisation, enabling recovery of diverse metals from waste while producing magnetosomes with distinct compositions.

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Abstract: Nickel-based single crystal superalloys exploit a γ/γʹ microstructure, providing exceptional high- temperature strength and environmental stability, outperforming other known alloy systems. These properties make them useful for gas turbine applications. However, enhancing gas turbine efficiency requires higher operating temperatures, which place greater temperature and stress demands on these materials. One critical factor influencing their mechanical properties is the lattice misfit between the γ and γʹ phases. Consequently, extensive research has been dedicated to optimising lattice misfit values to achieve the desired mechanical performance. Accurate determination of lattice misfit is challenging due to the similar cubic crystal structures of the two phases. Conventional diffraction analyses are complicated by peak overlap of these phases, making precise peak position measurements difficult. To address this, a series of synchrotron X-ray, and neutron diffraction studies were conducted to explore the possibility of more reliable lattice misfit determination and how it varies across the microstructure as well as during deformation. Firstly, a monochromatic synchrotron X-ray source was used to investigate a high misfit Ni-based single crystal superalloy, which involved rocking the sample to ensure the Bragg condition was maintained during in situ loading at elevated temperature. Whilst this technique highlighted difficulties in fitting diffraction peaks where the Ewald sphere was not perfectly intersecting the reciprocal lattice point, it also revealed substantial differences in the lattice parameter when sampling regions across the γ/γʹ interfacial region and the bulk material. This suggested that further exploration of the interfacial region and the effect it has on the overall mechanical properties of the material is required. For this reason, a novel X-ray diffraction (XRD) approach utilising a synchrotron X-ray nanoprobe was developed to analyse local lattice parameters in the γʹ and γ phases. As a result of current technological constraints, and challenges in aligning single crystal superalloys to satisfy the Bragg condition, there were complications in accessing the diffraction signal. However, the method yielded reasonable results and demonstrated capabilities beyond those of conventional techniques that only probe larger volumes of material. Local misorientations and significant lattice parameter variations were observed, demonstrating the heterogeneity of the microstructure at smaller length scales. As such, future in situ studies using this technique appear promising. Whilst in situ heating experiments were unsuccessful in yielding diffraction data, the X-ray fluorescence (XRF) collected in conjunction demonstrated the potential for compositional analysis at elevated temperatures, particularly for polycrystalline or thermally unstable alloys. Additionally, pulsed source neutron diffraction was used to track lattice rotations during tensile deformation, employing a multi-peak 2D Gaussian fitting approach. While the measurements from this experiment do not directly indicate how slip progressed the extent of misorientation occurring during slip was successfully quantified. Furthermore, conventional fitting techniques were used to assess the evolution of lattice misfit during tensile deformation, corroborating the measurements obtained in previous studies. This research demonstrates both the challenges and potential of diffraction techniques for enhanced characterisation. While the deconvolution of γʹ and γ phase peak positions remains a significant challenge, valuable insights have been gained into stress gradients at interfacial regions and local misorientations within the microstructure. Furthermore, a foundation for methods to probe local microstructural changes and track lattice rotation during deformation have been established.

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Abstract: Understanding the role of metal ions in normal and abnormal cell function continues to emerge as a critical research area in the biological and biochemical sciences. This is especially true in the context of brain health and neurodegenerative diseases, as the brain is especially enriched in metal ions. A range of microscopy and bioanalytical techniques are available to assist in characterizing and observing changes to the brain metallome. As is the case in many other scientific fields, the integration of multiple analytical methods often yields a more complete chemical picture and deeper biological understanding. Herein, we present a case study applying 4 different analytical methods to provide spatially resolved characterization of chemical and biochemical parameters relating to the iron (Fe) metallome within a specific brain region, cornu ammonis sector 1 (CA1) of the hippocampus. The CA1 hippocampal sector was chosen for investigation due to its known endogenous enrichment in Fe and its selective vulnerability to neurodegeneration. The 4 analytical techniques applied were X-ray fluorescence microscopy (to quantify Fe distribution); X-ray absorption near-edge structure (XANES) spectroscopy to reveal information on Fe oxidation state and coordination environment; immuno-fluorescence to reveal relative abundance of Fe storage proteins (heavy chain ferritin and mitochondrial ferritin); and spatial transcriptomics to reveal gene expression pathways relevant to Fe homeostasis. Collectively, the results highlight that although pyramidal neurons in lateral and medial regions of the hippocampal CA1 sector are morphologically similar, key differences in the Fe metallome are evident. The observed differences within the hippocampal CA1 sector potentially indicate a higher oxidative environment and higher metabolic turnover in medial CA1 neurons relative to lateral CA1 neurons, which may account for the heightened vulnerability to neurodegeneration that is observed in the medial CA1 sector.