The structure and synthesis of N,N'-disubstituted thiourea-S,S-dioxides were investigated experimentally and computationally. Hydrogen peroxide oxidation of acyclic and cyclic N,N'-dialkylthioureas furnished S,S-dioxides in agreement with computational predictions. Some s,S,S-trioxides were also isolated. An X-ray crystallographic study of N,N'-diisopropylthiourea dioxide, fIrst synthesised in this work, verilled computational models. The prediction of a stable N,N'-diarylthiourea dioxide derivative was supported by successful isolation of the dioxide. The application of N,N'-diisopropylthiourea dioxide as a reducing agent was investigated. Removal of tosyl groups from N-tosylaziridines, deprotection of CBz-amines and reduction of nitriles could not be realised. However, aldehydes and ketones were successfully reduced to the respective alcohols in yields comparable with that of thiourea dioxide. Disulfides and N-tosylsulfIIDides were reduced to a higher degree with N,N'· diisopropylthiourea dioxide than thiourea dioxide under simple, mild conditions. The mechanism of decomposition of N,N'-diisopropylthiourea dioxide to give radical anions was investigated with N-tosylsulfIIDides and a cyclopropylketone. The study revealed that at high pH, heterolysis of the C-S bond in N,N'-diisopropylthiourea dioxide led to the formation of a sulfmate dianion sol. The dianion was thought to rapidly oxidise to a powerful reducing species, the radical anion SO;- and subsequently effect reduction via a single-electron transfer pathway. A full mechanism of decomposition and reduction is proposed. An investigation into the role of thiourea dioxides as N-heterocyclic carbene (NHC) synthons was carried out. It was thought that decomposition of ethylenethiourea dioxides, via the elimination of sulfur dioxide, would provide an alternative approach to metal NHC complex synthesis. Oxaziridine oxidation of acyclic thioureas, successfully established in this work, was applied to the preparation of ethylenethiourea dioxides. A short study revealed considerable potential for thiourea dioxides as NRC precursors.

Electrocatalysts and their support materials used for fuel cell (FC) technology remain at the forefront of research in this field. Typically FC electrocatalysts are comprised of Pt nanoparticles (NPs) supported by carbon. Improvement of both the efficiency and the durability of the materials is required to increase the overall FC performance. To achieve these goals requires a fundamental understanding of electrocatalysis at composite materials and the exploration of alternative materials. These aspects are explored in this thesis. Highly oriented pyrolytic graphite (HOPG) and poly-(3,4-ethylenedioxythiophene) PEDOT-coated HOPG were used as support materials for the electrodeposition of Pt NPs. The NPs were characterised using atomic force microscopy (AFM) which showed that by applying an ultra-thin (ca. 2 nm) of PEDOT, a conducting polymer (CP), onto HOPG, there was less tendency for NP aggregation, with no preferential deposition, i.e. at step edges, and also smaller particles were formed. PEDOT-coated HOPG as the support material for Pt NPs showed a significant enhancement of electroactivity for methanol oxidation, by an order of magnitude, compared with similarly prepared NPs on native HOPG. An alternative support material; explored in this thesis, was polycrystalline boron doped diamond (pBDD), owing to its stability in harsh environments, analogous to FCs. During growth, boron uptake varies across the exposed surface of pBDD, leading to a heterogeneous substrate with typical grain sizes of 5-40 μm. Two new scanned probed techniques; intermittent contact - scanning electrochemical microscopy (IC-SECM) and scanning electrochemical cell microscopy (SECCM) were employed to investigate the impact of this heterogeneity on the local electrochemical properties. Maps using IC-SECM revelaed that the entire surface was active, but that areas with higher boron concentration were more electroactive. Grain boundaries showed no enhanced activity. The maps were sucessfully correlated to the boron dopant density using micro-Raman mapping and field emission scanning electron microscopy (FE-SEM). Similarly, SECCM maps also proved that the entire surface is electrochemically active with the heterogeneities relating to boron content. For data obtained by both techniques finite element simulations (FEM) were employed to extract values for the standard rate constant, k0. With knowledge of the fundamental properties of pBDD, the successful fabrication of a pBDD rotating disk electrode (RDE) is reported which is fully characterised. By functionalisation of pBDD with Pt NPs, the oxygen reduction reaction (ORR) has been studied and compared with a bulk Pt RDE. These preliminary studies show potential for gaining insight into the kinetics of the ORR.

This thesis aims to develop an understanding of the fundamentals and applications of electrochermistry at pristine single-walled carbon nanotubes (SWNTs), synthesised by the chemical vapour deposition (CVD) method. The SWNTs grown by CVD on the insulating SiO2 substrates were chosen for the reason being clean, free of amorphous carbon and readiness of nanotube morphology control. 2D random SWNT networks and individual ultra-long flow-aligned SWNTs were employed in the electrochemical studies throughout. SWNT networks were studied either by the microcapillary electrochemical method (MCEM) or in the format of disk-shaped ultramicroelectrodes (UMEs). By challenging the SWNT UMEs with enhanced mass-transport rates in a thin-layer cell (TLC) reversible quasi-steady state cyclic voltammogramms (CVs) were acquired, which allowed the numerical simulations of the voltammetric response and derivation limits for the standard electron transfer (ET) rate constants. Individual SWNTs also generate very high intrinsic mass-transport rates and were studied by the MCEM method, coupled with finite element modelling, highlighting that SWNT sidewalls are active towards outer-sphere redox reactions. By using a sparse surface coverage (typically less than 1%) of pristine SWNTs on an insulating substrate, it has also been demonstrated that electrodeposition of nanoparticles (NPs) is highly directional. By varying electrodeposition driving force (potential) and time one can control the NP density and size. The findings suggest that nucleation of Au on SWNTs is essentially 'instantaneous', and that the nucleation density increases with increase of the deposition potential. This knowledge has enabled the synthesis of a range of different nanostructures, from isolated Au NPs to Au nanowires (NWs), which were used as expedient platforms for analytical and electrocatalytical purposes. While some common inner-sphere redox processes do not readily undergo electrochemical reactions on the carbon nanotubes, which was established in experiments employed SWNT UMEs and individual ultra-long SWNTs, the outer-sphere redox processes were shown to be reversible on the same nanotube electrodes. Novel scanning electrochemical cell microscopy (SECCM) studies allowed individual Pt NPs, electrically connected by the sub-centimeter long SWNT, to be electrochemically assessed. Significantly, this work highlights that individual NPs have their intrinsic electrochemical characteristics.

We have shown new applications and synthetic routes for polymer colloids in the field of home and personal care products by controlling polymer and/or colloidal architectures. Our initial aim was to develop functional particles that imparted beneficial properties to fibrous substrates and as such our first goal was to develop a method for depositing particles onto such surfaces. Chapter 2 describes the method by which we achieved this goal, namely adding a small amount of a low glass transition polymer to an otherwise non-adhesive polymer to enhance colloidal deposition. Following on from this work we looked into ways in which to impart desirable characteristics from the particles onto fibres. In Chapter 3 we describe how the use of a hydrazide functional monomer in polymer gels can provide a continuing slow release of fragrance molecules that reacts to the environment it is held in such that if the local fragrance concentration is low then more is released. In Chapter 4 we describe the synthesis of highly porous particles with controlled pore sizes and the use of such particles in oil absorption for applications in water-free cleaning systems. The particles are capable of carrying many times their own weight in oil and are shown to be reusable. In Chapter 5 we describe a computational model that predicts the ability of a particle to stabilize emulsions. The model is highly adaptable and can be used to predict the surface activity of almost any particle morphology. Chapter 6 builds on this work and described the synthesis of highly anisotropic polymer particles by templating preexisting structures and explains their surface activity, or lack thereof.

Interest and utilisation of polycrystalline boron-doped diamond (pBDD) as an electrode material has rapidly grown over the last decade, due to its unique properties and advantages over other available electrode materials. The possibility of lower detection limits and an increased range of detectable analytes has seen pBDD flourish in electroanalysis. Due to its stability at high temperatures, pressures and acidity, pBDD also has the potential to perform electrochemistry in extreme conditions. These unique properties, however, make the material difficult to manipulate in order to produce well defined and reproducible electrodes. Deviations in electrical and electrochemical responses can also arise from sample to sample, due to differing synthesis conditions and experimental set-ups. This thesis aims to characterise pBDD available from a commercial source and through fabrication of electrodes of various designs, best utilise the material in the electroanalysis of several species. Characterisation is performed using high resolution microscopic and spectroscopic techniques which show a heterogeneous material with negligible levels of non-diamond like carbon and boron concentrations of at least 1 x 1020 atoms cm-3 throughout. Disc electrodes, fabricated using laser machining, are electrochemically characterised showing low background currents, wide solvent windows and close to reversible behaviour for Ru(NH3)6 3+/2+, IrCl6 2-/3- and Fe(CN)6 3-/4. Functionalisation of these pBDD disc electrodes with nanoparticles enables the detection of dissolved oxygen and glucose to detection limits of ~ ppb. Furthermore, the fabricated electrodes are used in the study of Pb deposition and stripping behaviour at a pBDD surface, as well as Pb2+ detection. The last chapter in this thesis details the next step in diamond electrode development; the fabrication of all-diamond electrodes, where the pBDD is insulated with intrinsic diamond. Two electrode geometries are described, the first being a tubular flow ring electrode which has well-defined hydrodynamics and is used in the detection of dopamine. The second all-diamond geometry is a dual band electrode which it utilised as a solution conductivity sensor.

Carbon materials, such as graphite and conducting diamond, are highly popular for analytical and electrochemical applications, and fundamental knowledge of heterogeneous electron transfer is required to understand and optimise applications. In this thesis, the relationship between the structure of HOPG (Highly Oriented Pyrolytic Graphite) and its electrochemical behaviour has been thoroughly studied from the macroscale to the nanoscale. With the use of data collected from a wide range of techniques, spanning voltammetry, electrochemical imaging and high resolution microscopy, on 5 different grades of basal plane HOPG whose surfaces vary in defect density, the contribution of edge plane vs. basal plane on the electrochemical activity of HOPG has been re-examined. The significant body of work presented herein shows, without doubt, that the basal plane of HOPG is a very active electrode for Ru(NH)6 3+/2+; Fe(CN)6 4-/3-; the oxidation of the neurotransmitter, dopamine (DA), and quinones in aqueous solution. This overturns a well-established (textbook) model that the basal surface is inert, which researchers have assumed for two decades, with implications that carry over to related sp2 carbon materials, such as graphene and carbon nanotubes. A second aspect has considered polycrystalline boron-doped diamond (pBDD) to study neurotransmitters, such as DA and serotonin (5-HT). The electrode surface was found to be resistive towards permanent surface blocking during the electrochemical oxidation of these neurotransmitters. The properties of the film formed by 5-HT oxidative products, was thoroughly investigated using voltammetry and high resolution microscopy. It is shown, for the first time, that electro-oxidation of 5-HT results in an electrically insulating, but charged and porous film, but procedures are demonstrated that allow the pBDD to be renewed in-situ for precise electroanalysis.

Control of molecular motion is an important step towards the envisaged development of molecular scale devices and machines. A large amount of research has been documented regarding the control of molecular rotation and shuttling processes, but relatively few examples of control over nitrogen pyramidal inversion exist and so far no examples that require solely physical inputs such as light and heat have been reported. The first part of this thesis describes attempts to control nitrogen pyramidal inversion in aziridines and azetidines, using only light and heat to switch between two states with differing rates of inversion. Three avenues of research utilising anthracene photochemistry are discussed. The strategies employed include modifying ring strain by fused macrocycle formation; introduction of ring strain via small ring formation; and disruption of transition state stabilising hydrogen bonds through macrocycle formation. Finally, and more successfully, azobenzene photochemistry was used to modify a π-system adjacent to an aziridine nitrogen centre resulting in different inversion rates in the cis and trans azobenzene isomers. The experimentally derived inversion rates were supported by ab initio calculations. The second part of this thesis outlines attempts to develop photoactivated β-lactam antimicrobial agents. Two families of compounds were synthesised, based on amine linked bis-anthracene, and 2-pyridone isomerisations. Their antimicrobial activity was evaluated against B. Subtilis and E. Coli using the Kirby-Bauer disk diffusion method. One β-lactam produced by anthracene photodimerisation displayed modest activity against B. Subtilis. However, control experiments suggested the acyclic precursor possessed higher levels of antimicrobial activity.

Chapter 1 is an introduction to the solution self assembly of amphiphilic polymers. Initially focusing on the complexity involved in the formation of these structures, followed by a review of the common analysis techniques used to characterise them. Chapter 2 reports the synthesis of a Pd containing amphiphilic poly(acrylic acid) homopolymer. Its self-assembly in water is studied by SANS and cryo-TEM and its catalytic activity is compared to a small molecule analogue for a literature Suzuki- Mayura coupling reaction. Chapter 3 uses a similar synthetic strategy to Chapter 2 in order to produce three amphiphilic poly(N-isopropyl acrylamide) homopolymers of different molecular weights. Their self-assembly in water is studied by laser light scattering, small angle neutron scattering and cryo-TEM. The results from each technique are compared in detail and used to asses the effect of polymer molecular weight on the assemblies. Chapter 4 investigates the use of graphene oxide as a substrate for multiple microscopy techniques in relation to the analysis of polymer aggregates. The images are compared to those by more standard techniques and the benefits of using graphene oxide are demonstrated through the use of advanced imaging techniques. Chapter 5 shows that graphene oxide supports can be used in conjunction with cryo-transmission electron microscopy. The benefit of having a stable nearly electron transparent support is shown by comparing images to those taken by standard cryo-transmission electron microscopy.

Mixed-metal oxides were prepared via hydrothermal synthesis and characterised using various analytical techniques. Three different class of materials were studied, namely perovskites, hexagonal perovskites and doped TiO2. By using hydrothermal synthesis, control on the crystal size, morphology and phase purity was achieved, which are difficult by conventional methods. A new titanate perovskite solid solution with nominal composition, NaCe1-xLaxTi2O6, containing three different metals on the A-site was produced by a single step hydrothermal synthesis. Rietveld analysis of powder X-ray and neutron diffraction data enabled the space group R c to be assigned for the whole series. The particle size and morphology can be changed by varying the solvent and NaOH concentration. 23Na MAS NMR showed that a genuine solid solution was produced, with no A-site ordering present, while 2H MAS NMR of the samples prepared in D2O showed the inclusion of D2O in the lattice in place of Na, greatest for the cerium-containing materials, in which oxidation to Ce4+ can occur. The preparation of B-site substituted perovskites was possible via hydrothermal synthesis. The effect of substituting Zr for Ti was studied for two different perovskites namely NaLaTi2O6 and NaBiTi2O6. For NaLaTi2O6, Zr substitution had a drastic effect on the crystal morphology. Other factors that can affect the morphology such as the solvent, reaction time, temperature and NaOH concentrations were also investigated. In the case of NaBiTi2O6, the effect of Zr substitution on ferroelectric and piezoelectric properties was studied. Pure hexagonal YMnO3 was achieved by a comproportionation hydrothermal reaction between KMnO4 and MnCl2. The possibility of doping YMnO3 with Fe was investigated. Fe doping up to 10% was possible but above this level, impurity phases were observed. Pure orthorhombic YFeO3 can also be prepared and the Fe3+ was replaced by up to 30% Mn3+. The oxidation states of these materials were determined using XANES. Phase pure rutile TiO2 was prepared via two different hydrothermal routes. Attempts at doping W into TiO2 were only achieved at 1% W doping level. With Sn, a rutile Sn-TiO2 complete solid solution is formed. In contrast, Ce-TiO2 with up to 15% Ce is formed as the anatase structure with a mixture of Ce3+ and Ce4+. The photocatalytic properties of the Ce-TiO2 materials show promise for high activity hydrogen production by UV splitting of water.

In this thesis the in vivo cleavage of the phosphorus-carbon bond of 2-aminoethyl phosphoric acid (AEP) is discussed, and attempts to achieve a similar cleavage in vitro investigated. Diazotisation of AEP failed to cause P-C bond rupture but led instead to 2-hydroxyethyl phosphonic acid, which itself was unexpectedly labile, undergoing fragmentation to ethylene and inorganic phosphate. A mechanism involving a 4-membered phosphorus containing ring is proposed to explain this lability. An improved synthetic route to amino-phosphonic acids has been developed and is discussed. The rearrangement of phosphoenol pyruvate to 3-phosphono pyruvate as a step in the biosynthesis of AEP has been studied in the general context of 4-centre rearrangements. The evidence for these rearrangements in phosphorus chemistry, together with analogous observations in carbon chemistry, is reviewed and discussed. Evidence for the rearrangement of enol phosphates to B-keto phosphonates, although in very low yields, is presented and the significance of this observation discussed. The relationship between enol phosphates and B-keto phosphonates in the Perkow reaction has stimulated some work directed towards an understandings of the mechanism of the reaction. Whilst the results of experiments with acyclic phosphates and halocarbonyl compounds can be adequately explained by existing theories of the Perkow reaction mechanism, other studies have necessitated a reappraisal of the route to enol phosphates in certain cases. Chloral was found to react with cyclic phosphates to form relatively stable intermediates. These intermediates were characterised and shown to contain pentacovalent phosphorus. Thermal decomposition has been shown to yield enol phosphates. On the basis of these results, a mechanism has been proposed for the course of the reaction between cyclic phosphites and [?]-halocarbonyl compounds. Scanty evidence has been obtained for similar intermediates in "normal" Perkow reactions. A parallel has been drawn between the Perkow reaction and the reaction of other activated carbonyl compounds with phosphites.