Access to clean water is essential for human health and dignity. The increasingly rapid population growth, combined with the emergence of resistant chemical compounds and more concentrated toxic residues in the effluent streams of treatment plants, point towards a decline in freshwater resources resulting in a global water crisis in the next decades. Current wastewater treatment plants rely on Advanced Oxidation Processes (AOPs) for the tertiary (or advanced) step of the treatment. Photocatalysis is one of such processes, by which semiconductors are exposed to radiation of specific wavelengths (traditionally UV) to generate Reactive Oxygen Species (ROS) that can degrade organic molecules through a chain of radical oxidation reactions. Anatase titania (TiO2) has been used for many decades as a photocatalyst. Its electronic band structure has a band gap of 3.2 eV, requiring radiation in the UV range to trigger its photocatalytic properties. One way to reduce the band gap energy and shift the absorption peak wavelength to the visible part of the spectrum (thus reducing operation costs) is by doping the photocatalyst particles with transition metal atoms. Iron (III) is a great candidate due to the placement of its conduction/valence bands within titania’s band gap, its atomic radius similar to titanium (IV) and its variety of oxidation states. However, iron-doped anatase titania synthesized by ordinary sol-gel methods shows a photodegradation efficiency that is much lower than undoped anatase. Previous studies have shown that this is caused by an inconspicuous iron oxide layer on the surface of the catalyst particle, forming a physical barrier to the mobility of charge carriers that trigger the formation of ROS radicals. Small changes to the synthesis protocol, namely slowing down the hydrolysis of the Ti precursor by lowering the solution’s pH and acid-washing the final product, have been shown to result in particles that are photoactive under visible radiation and boast an unobstructed reactive surface. In this work, the novel Fe-TiO2 photocatalyst is studied and characterized in terms of its particle size distribution, inner structure and composition using electron microscopy techniques. It is important to know the particle size profile arising from this novel synthetic method, as the presence of nanoparticles could pose a health risk whereas an abundance of oversized particles is undesirable from the perspective of chemical reaction engineering (low surface-to-volume ratio). Inner structure/composition analyses could reveal whether the iron content inside the photocatalyst segregates into iron oxides, which would hinder reaction rates by behaving as a recombination center for charge carriers. As well, gathering more information about the inner structure of the catalyst (such as degree of crystallinity) is desirable as that could help fine-tune the synthesis protocol in order to obtain optimal photocatalytic activity. The particle size distribution studies using scanning electron microscopy revealed that the catalyst samples contain a significant fraction of nanoparticles (31.55% smaller than 100 nm), even though those particles represent a very small fraction of total sample volume (0.00015%) and reactive area (0.03%). Moreover, oversized particles (bigger than 5 m) account for the biggest fraction of sample volume and reactive surface. It was suggested that the size distribution of the catalyst be shifted to intermediate particle sizes by introducing additional grinding and separation steps into the synthesis protocol. The inner structure studies were carried using a combination of scanning, transmission and scanning-transmission electron microscopy, as well as spectroscopy methods such as EDX and EELS to map composition. It was found that the original anatase lattice structure remained unchanged in terms of interplanar spacings and crystallographic orientations, indicating that the addition of iron impurities at the small concentrations used here (0.5at%) did not result in discernible changes to the lattice. The monocrystalline units of Fe-TiO2 (termed crystallites) often appear to be bound together by amorphous material. No segregation of Fe was observed inside the particles at this concentration, as shown by the apparent homogenous composition of the catalyst across crystalline and amorphous regions. The external iron oxide contamination layer observed in previous studies was theorized to form during the later steps of the sol-gel process due to the precipitation of the iron content in solution that failed to be incorporated into the TiO2 gel network. More in-depth studies must be carried to assess whether preferential segregation of iron within the catalyst could occur at higher dopant concentrations. / Graduate

The field of implantology is centred around interfacial interactions with the surrounding bone tissue. Assessing the suitability of novel engineering materials as implants for clinical application follows a preliminary workflow that can be simplified into three main stages: (i) implant design, (ii) in vitro compatibility, and (iii) in vivo compatibility. This thesis is subdivided to mirror each of these three themes, with a specific focus on the multiscale features of the implant itself as well as appositional bone tissue. In Chapter 3, a biomimetic approach to generate porous metallic implants is presented, using preferential seeding in a 3D Voronoi tessellation to create struts within a porous scaffold that mirror the trabecular orientation in human bone tissue. In Chapter 4, cytocompatible succinate-alginate films are generated to promote the in vitro activity of osteoblast-like cells and endothelial cells using a methodology that could be replicated to coat the interior and exterior of porous metals. In Chapter 5, two types of porous implants with graded and uniform pore size are implanted into rabbit tibiae to characterize the biological process of osseointegration into porous scaffolds. In Chapter 6, these same scaffolds are probed with high-resolution 2D and 3D methods using scanning transmission electron microscopy (STEM) and the first-ever application of plasma focused ion beam (PFIB) serial sectioning to observe structural motifs in biomineralization at the implant interface in 3D. This thesis provides new knowledge, synthesis techniques, and development of characterization tools for bone-interfacing implants, specifically including a means to: (i) provide novel biomaterial design strategies for additive manufacturing; (ii) synthesize coatings that are compatible with additively manufactured surfaces; (iii) improve our understanding of mineralization process in newly formed bone, with the ultimate goal of improving the osseointegration of implants. / Thesis / Doctor of Philosophy (PhD) / Metallic implants are widely used in dental and orthopedic applications but can be prone to failure or incomplete integration with bone tissue due to a breakdown at the bone-implant interface as defined by clinical standards. In order to improve the ability of the implant to anchor itself into the surrounding bone tissue, it is possible to use novel three-dimensional (3D) printing approaches to produce porous metals with an increased area for direct bone-implant contact. This thesis examines strategies to design porous implants that better mimic the structure of human bone, possible coating materials to accelerate early bone growth at the implant interface, and the microscale-to-nanoscale origins of bone formation within the interior of porous materials.

Methanation of CO2, a greenhouse gas component, using bimetallic catalysts is considered. Rh, Pd and Ru were combined separately with Co on silica support to form bimetallic catalysts with 5 % metal loading and atomic ratio to Co equal to 1. Pore volume of the silica was measured using physisorption analysis. The unreduced catalyst samples were characterized using XPS, TPR and SEM-EDS. XPS results showed low Rh, Pd, Ru and Co concentrations at the surface for the three bimetallic catalysts. The oxidation states of metals detected by XPS supported the likely presence of metals in their oxide form. Detection of alloys and/or bimetallic particles on the surface of the catalysts was difficult through the XPS results, but presence of bimetallic particles was confirmed in Ru-Co and Pd-Co catalysts through the TPR results. Surface segregation of cobalt was observed. This was supported and extended to other metals through the SEM-EDS results.

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The relationships between molecular parameters and microdomain formation of a variety of block- and graft-copolymers were studied by Transmission Electron Microscopy (TEM). Molecular variables included chemical composition: dimethyl-, fluoropropyl and diphenyl-siloxane , sulfone styrene, paramethylstyrene, t-butylstyrene, arylester and methyl methacrylate, as well as molecular weight and distribution. Effects of the kinetics of phase-separation were also determined . Thick (approximately lmm) films cast from solvent showed more complete phase separation than either thin (about 10nm) cast films or compression-molded specimens. Spherical domains formed in alternating poly(ester/siloxanes), and phase mixing seemed to correlate with the solubility parameters of the three siloxane types. Shear-stresses during molding changed domain shapes and eliminated short-range ordering. In the PMMA-graft-dimethyl siloxane system, SK, 10K and 20K <M_n> siloxanes were incorporated at 16% and 45% by weight. At 16%, spherical siloxane domains formed in both thick- and thin-cast films. The domain sizes and interdomain distances scaled with siloxane molecular weight and total block molecular weight respectively to a 2/3 power law in excellent agreement with theoretical predictions for di- and triblock copolymers. Thin films cast from the 45% siloxane graft copolymers also showed spherical domains with sizes dependent on molecular weight. However, the thick films showed phase transitions from disordered bicontinuous (M_n = 5K) to lamellar (M_n = 10K) to cylindrical <M_n = 20K). Qualitative TEM/EDX analysis of other systems was used to identify oligomers, homopolymers, and contaminants, thus monitoring the effects of novel reaction conditions and work-up procedures. / Master of Science

The research presented in this thesis aims to uncover the intricate manner in which BRCA1 interacts with RNAP II during mRNA production utilizing a unique microchip system developed in our lab. We were first able to prove the effectiveness of our tunable system using a breast cancer model of patient derived triple negative breast cancer (TNBC) cells. Here we switched out different mammalian antibodies and collected images of the same structure from different angles. This served many purposes: (1) it proved the system could be tuned for specific uses; (2) it demonstrated that all subunits were present in the complex; (3) it eliminated the need for the tilt function allowing for a less intensive computational procedure. In the BRCA1 wild type cell line we were able to incorporate into our 3D reconstruction, atomic models of the BRCA1-BARD1 heterodimer and the RNAP II core in regions of major unoccupied density. Other areas of minor missing density were overlaid with a short strand of DNA and ubiquitin moieties, which proved agreement with Co-IPs. Next we sought to compare the wild type structure with a BRCA1 mutant variety. Using these techniques, we determined the 3D structure of the mutated complex. After further analysis slight differences were detected between the two complexes, especially in the placement of the atomic models. Overall we were able to determine structural abnormalities that occur when a mutation is present in BRCA1 that may have future applications for targetable therapy in TNBC patients. Moreover, by using TNBC as the disease model, we have created a platform that can be used to evaluate other human diseases due to the tunable nature of our microchip system. / Master of Science

This project concerns the non-classical crystal growth of various porous and non-porous materials. In order to determine their crystal growth mechanism, the reaction was stopped at several different reaction times with the size, morphology, crystal structure and orientation of the particles analysed using scanning electron microscopy and high resolution transmission electron microscopy as the principal characterisation techniques. Other techniques used include X-ray diffraction, energy dispersive X-ray spectroscopy, selected area electron diffraction and thermal gravimetric analysis. Selected biomimetic systems include the early stage crystal growth of ZnO/gelatin composite twin-crystals and the time dependent microstructural evolution of CaCO₃/gelatin composite particles from spherulites into rods. Further investigations of the role of gelatin molecules were carried out by replacing gelatin by gum arabic. Using knowledge gained from synthetic systems, several travertine crust specimens collected from hot springs were investigated to gain an insight into the possible formation mechanisms of naturally occurring biominerals. Another form of ZnO investigated was the formation of core-shell ZnO hexagonal microdisks and selective dissolution of their core to form microstadiums followed by the selective growth of nanorods and nanocones onto the columnar surfaces of the microstadiums to generate branched-microstadiums. The formation mechanism of ultrasonically prepared BiOBr displaying a flower-like architecture was investigated. These BiOBr assemblies are found to exhibit excellent photocatalytic activity and stability during the photodegradation of Rh.B under visible-light irradiation. Finally mesoporous silicate plates displaying a single crystal-like property were re-investigated to clarify whether the previously reported mesoporous silicate plates exhibiting a single crystalline property were one-phase materials or a composite of non-crystalline mesoporous silicate and crystalline zeolite.

This thesis concerns the experimental application of the technique of optical sectioning in the aberration-corrected scanning transmission electron microscope (STEM). Another aim was to perform optical sectioning experiments on the still relatively new scanning confocal electron microscope (SCEM). To test the feasibility of this technique, experiments were performed on a variety of samples to measure the achievable depth response. Deconvolution methods were explored in an attempt to further improve the depth response. Finally, some of the first optical sectioning experiments were performed in the SCEM using both elastic and inelastically scattered electrons. The results showed a clear need to investigate confocal electron microscopy due to the missing cone problem for incoherent imaging in the STEM. This is particularly evident when imaging objects of greater width than the STEM probe. Confocal electron microscopy using inelastic electrons appeared to be a promising imaging mode for the future with this thesis consisting of early work in the field.