Organic photovoltaics (OPV) and hybrid organic-inorganic photovoltaics (HOPV) have the potential to provide alternative and economical energy sources; with the long-term goal of delivering renewable resources with longevity. Recent improvements in cell design and material combinations have revealed the true potential of this field. For this to be reached, continuous advancements in materials, concept development, encapsulation and scientific understanding are necessary. This thesis focuses on the use of zinc oxide (ZnO) in the field of both HOPVs and OPVs. ZnO had been successfully implemented for decades in a range of applications, including light emitting diodes and biological sensors due to its diverse chemical and physical properties along with the ease of fabrication. Initially ZnO is investigated as a direct replacement for a fullerene acceptor offering the potential of improved energetic matching to the donor material used. The latter stages of this thesis looks at the use of ZnO as an electron extracting layer for a polymeric active layer. Chapter 1 provides a brief introduction to the field of photovoltaics and the materials used in this thesis. In Chapter 2 an overview of the experimental techniques used is given. In Chapter 3, inverted HOPV devices are fabricated. The potential of ZnO as a promising electron acceptor is shown, utilizing the donor material boron subphthalocyanine chloride (SubPc), a typical small molecule (SM) organic semiconductor. X-ray photoelectron spectroscopy (XPS) shows subtle differences in the electronic structure of ZnO films in terms of Zn:O ratio when the processing temperature is varied, and Kelvin Probe (KP) revealed a significant difference in the surface work function. Variation in annealing temperature is shown to improve the open circuit voltage (from 0.82 V to 1.23 V) of the device and therefore enhance the performance. Chapter 4 compares two methods used to probe energy levels. The chapter compares the differences between the data obtained for identical ZnO samples using ultra-violet photoelectron spectroscopy (UPS) and KP. The surface composition is also monitored throughout by XPS. The chapter reveals that ZnO is susceptible to UV irradiation and the impact on the measurements is discussed. One of the main limitations of the planar HOPV is photocurrent. Chapter 5 looks to improve this through the implementation of a molybdenum oxide (MoOx) optical spacer layer. Optical modelling is initially used to predict the impact of varying the layer thickness of SubPc and MoOx. The model is developed further by including the diffusion length (LD) of the SubPc donor material. The improved estimates are compared to an experimental data set of 40 different thickness combinations. Optical optimisation resulted in a 62 % improvement in device performance, compared to the layer thicknesses used in Chapter 3. The use of ZnO as an electron extracting layer with a polymeric active layer is investigated in Chapter 6. Two methods for ZnO layer formation, electrodeposition (ED) and sol-gel (SG) are compared using two different transparent electrodes, indium tin oxide (ITO) and transparent gold (tAu). ED ZnO layers have issues with transparency and reproducibility lowering the overall averaged performance. This thesis highlights the important role ZnO can play in the development of OPV and HOPV devices. The research provides an important step for understanding the fundamental principles governing the operation of hybrid solar cells and helps to close the gap between TMO/polymer and TMO/SM devices. The performances of these TMO/SM devices reach efficiencies exceeding 0.70 %, compared to previous published devices only reaching 0.017 %.

In this thesis the one-pot subcritical hydrothermal synthesis of several novel complex oxides with potential applications in catalysis is reported. The hydrothermal synthesis of nanocrystalline pentavalent ion-substituted cerium dioxide is reported. The materials were all characterised by powder diffraction and a range of spectroscopic techniques in order to elucidate their structures. Up to approximately 30% pentavalent ion-substitution the mixed metal oxides continue to adopt the fluorite unit cell, and the lattice parameter decreases as substitution increases. The choice of mineraliser in the hydrothermal reaction was found to affect the composition and structure of the oxide: when prepared in NaOH, Na is incorporated into the structure as well as the pentavalent ion, and the combination of these allows charge balance to be achieved without the need for Ce reduction or the incorporation of interstitial oxygen. The inclusion of Na greatly improves both the measured oxygen storage capacity and the stability of the fluorite phases, as measured by in situ powder X-ray diffraction. Precious metals Pt and Pd have also been successfully incorporated into the fluorite ceria structure by hydrothermal synthesis, with up to 20 – 25% precious metal substitution. A study of both the average structure and local environment of the precious metals leads to the conclusion that neither precious metal sits on the same crystallographic site as the Ce. Pd adopts a square-planar geometry by shifting ¼ of a unit cell in one direction, to sit in an oxide plane, and thereby expanding the unit cell. The Pt exists a distorted octahedral environment. These oxides were found to be inherently unstable, with precious metal extruded from the fluorite under even mildly reducing conditions. The hydrothermal reaction of KRuO4 with AO2 (A = Ca, Sr, Ba) peroxides at 200 °C yields a range of previously unreported ruthenium oxides. Ca1.5Ru2O7, an A-site deficient pyrochlore containing a mixed Ru(V/VI) B-site. SrRu2O6 adopts the PbSb2O6 structure and contains antiferromagnetically ordered Ru(V) moments. In situ powder neutron diffraction shows that this ordering persists up to 563 K, an extraordinarily high temperature. Ba2Ru3O9(OH) is an example of a new structure type, which is made up of puckered layers of quasi-trimeric edge-sharing Ru(V)O6 octahedra which are corner-linked together with layers of Ba atoms separating them. Ba4Ru3O12 is an 8H hexagonal perovskite with a previously unreported stacking order, containing Ru with an average oxidation state of +5.33. Structural refinements and magnetometry of all new materials are presented.

This thesis is concerned with the use of electrochemical microscopy, in particular the development and application of the scanning electrochemical microscope (SECM). The concept of intermittent contact (IC), i.e. detecting the oscillation amplitude damping of an SECM imaging probe as it makes physical contact with a surface, is presented as a non-electrochemical means to provide tip-substrate distance feedback, in IC-SECM. This is briefly demonstrated for localised etch pit formation on a calcite crystal. A new imaging mode that incorporates a hopping imaging mode with the principles of intermittent contact is demonstrated for a range of samples, in hopping (H)IC-SECM. HIC-SECM uses an oscillating probe, so alternating current data are also obtained, and this type of scanning mode allows three-dimensional visualisation of the flux around an interface, which greatly enhances the information content compared to other types of electrochemical imaging. The resolution achievable by constant-distance imaging using IC-SECM is greater than constant-height imaging, although the dimensions of the electrode used in imaging will limit the resolution. Pt disk nanoelectrodes were also prepared, that were milled using focussed ion beam-scanning electron microscopy (FIB-SEM). These probes were used to image a model substrate, a gold band on glass, using IC-SECM in a low-force soft-tapping setup. The extension of this work to electrochemical systems focuses on studies of electrodeposition of silver nanoparticles on basal plane highly oriented pyrolytic graphite (HOPG). A nucleation-aggregative growth-detachment mechanism is proposed as an important feature of the process, through both macroscopic and microscopic scanning electrochemical cell microscopy (SECCM). The active sites for electron transfer on HOPG, a topic of recent debate, were also probed in macroscopic and microscopic experiments for silver electrodeposition. The difficulties of working on the electrochemistry of quinones in non-aqueous media are highlighted, with particular focus on methods to overcome the issue of electrode fouling. Different degrees of surface fouling were observed depending both on the electrode material, the compound studied and its concentration. IC-SECM was introduced as a means of establishing a close tip-substrate gap without needing to do electrochemistry for positioning and thus minimising fouling effects, from which high rate constants could be measured and the effect of electrode material on electron transfer kinetics investigated.

Within this thesis we explore the synthesis and modification of hierarchical composite particles and responsive microgels. Initially in Chapter 2 we describe the encapsulation of calcium carbonate particles within a polymeric shell, wherein the inorganic core is kinetically trapped within a cross-linked polymer network. Once primed in this shell we illustrate control of polymer shell thickness through a secondary polymerization. We also begin to investigate the possibility of preparing nano-rattles, using the calcium carbonate core as a sacrificial template. In Chapter 3 we expand on the work presented in Chapter 2, by incorporating pendant vinyl groups into the polymer shell of the composite particles from which we use thiol-ene Michael addition to modify their surface. In Chapter 4 perform the encapsulating polymerization from Chapter 2 and 3, but in the absence of the calcium carbonate core. The stable particles formed were found to be pH responsive microgel particles. We illustrate the gelling behaviour of these particles and use as Pickering stabilizers for oil-in-water emulsions which show reversible flocculation on adjustment of the pH. In investigating these microgel particles we also begin to elucidate unanswered questions from Chapters 2 and 3. Finally in Chapter 5 we go back to encapsulation, this time to synthesize multi-layered particles by encapsulation of Laponite armoured soft latexes. We infer how alterations to particle morphology affect the bulk properties of polymer films by mechanical and thermal analysis.

Polycrystalline boron-doped diamond (pBDD) has acquired great interest as a electrode material exhibiting low background currents, wide potential windows and a host of extreme physical properties such as mechanical hardness, chemical inertness and a high resistance to harsh environments. pBDD’s exceptional electrochemical characteristics have made its application as a material for high performance electrochemical sensors the basis of a hugh amount of research over the last decade. Work in this thesis describes the fabrication and application of pBDD sensors in both stationary and fluid flow environments where conventional electrode materials would be unsuitable or problematic. pBDD electrodes functionalised with catalytic metal nano-particles are demonstrated as a means of detecting hydrazine, a genotoxic impurity of interest in pharmaceutical analysis, even in the presence of potentially interfering pharmaceutical matrix. This same sensor is then employed as a means of detecting the presence of non-polar oils on an electrode surface in dual-phase, aqueous/oil systems. An investigation of electrochemical techniques for detecting and characterising phase changes in the form of microdroplets moving under flow in microfluidic systems is detailed. Limitations to the use of conventional materials used to fabricate such microfluidic devices are discussed. In an effort to address these issues as well as those expected in extreme environments, with aggressive media, a fabrication route for realising all-diamond microfluidic devices with integrated, high-quality pBDD electrodes is outlined.

The work presented in this thesis represents the chemical modification of waste and renewable vegetable oils to yield monomers for polyurethane, azide-alkyne click and nitrile-oxide click polymerisations. Chapter 1 provides a brief introduction to use of waste materials for new products, following on to a more detailed overview of triglyceride chemistry, finishing with an introduction to ‘Click’ chemistry. Chapter 2 discusses the optimisation studies of acid catalysed ring-opening of epoxidised cocoa butter followed by polyurethane synthesis. Percentage of ring-opening was found to be influenced by the amount of phase-transfer catalyst, concentration of reaction and equivalents of acid. Mechanical properties (Young’s Modulus (YM), Tensile strength (TS) and Elongation at break (EoB)) were determined and thermal analysis (TGA, DSC) measured on cocoa butter based polyurethanes both with and without food-safe dyes as an alternative more environmentally friendly renewable oil source for polyurethane synthesis. Chapter 3 focuses on the use of azide-alkyne click chemistry to produce renewable polymers from dimeric fatty amides (capable of H bonding) with increasing linker length and azide functionality. Samples were synthesised from purified oleic acid and linoleic acid and cheaper, more commercially available rapeseed oil and soybean oil. Thermal properties (TGA, DSC) of copper mediated and thermally produced polymers were analysed and mechanical properties (YM, TS and EoB) of thermally produced polymers were also investigated showing increasing linker length increased elongation and decreased tensile strength and also showed the importance of H bonding between polymer chains drawn. Chapter 4 expands on azide-alkyne click polymerisation by synthesis of a range of monomers containing both azide and alkyne units therefore capable of homopolymerisation. Increasing chain length, azide functionality and hydrogen bonding possibilities were again tested using the same four starting materials as Chapter 3 as well as increasing cross-linking possibilities and results were found to compare with those established in Chapter 3. Chapter 5 concentrates on using nitrile oxide-alkyne click polymerisations as an alternative and safe method of producing renewable polymers derived from vegetable oils. Two approaches were used for polymerisations, base mediated and thermal mediated polymerisations with polymers produced subjected to thermal analysis (TGA, DSC). Chapter 6 describes the experimental and chemical analysis of the key reactions and processes described in the thesis.

The research presented in this thesis uses laboratory and synchrotron based structural techniques in combination with electrochemistry to test the durability of selected conservation methods. A new piece of portable spectroelectrochemical equipment (the peCell) is also described: the peCell was designed for the long-term monitoring of conservation treatments. Lead carboxylates were selected as the focal point of this research due to the interest in studying their deposition from ethanolic solution and the effectiveness of this type of coating on lead. Therefore the spectroscopic analysis, electrochemical testing in an electrolyte modelling atmospheric corrosion, short-term and longterm volatile organic compound (VOC) exposure, and museum testing of this inhibitor demonstrates an entire package of tests which might be used as a benchmark for testing conservation treatments prior to use on artefacts. In addition the contrasting effects of lead carboxylates in oil paintings and as conservation coatings are discussed. Alongside laboratory spectroelectrochemical data, the corrosion by oak VOCs of a conserved lead sample was studied, (a) using a state-of-the-art in situ timelapse technique on a synchrotron and (b) within a museum environment. Surface analysis by X-ray diffraction (XRD) was used to compare the growth of crystalline surface corrosion products over time: the extent of corrosion can be related to the effectiveness of the various conservation techniques. The peCell is a portable electrochemical or environmental cell which was invented in order to provide a way of tracking the chemical changes occurring in a conserved sample in situ over a long period of time. The cell is capable of holding three samples which can be monitored continuously using open circuit potential and sporadically (i.e. whenever a synchrotron beam line is accessible) using SR-XRD. Other environmental parameters within the cell can also be monitored, such as temperature. The prototype cell was successfully trialled at the XMaS beamline, ESRF using an alternative copper corrosion system.

The aim of the work presented in this thesis is to explore computational approaches to the modelling and discovery of spin crossover (SCO) transition metal complexes. Both ‘ab initio’ methods, based mainly on density functional theory, and empirical force fields based on ligand field molecular mechanics (LFMM) have been considered. It is shown that whilst a user can choose a functional and basis set combination through validation to experimental data which will yield accurate results for a series of related systems this combination is not necessarily transferable to other metal-ligand combinations. The ability of density functional approaches to model remote substituent effects is explored. Using the iron(II) R,R’pytacn complexes2 as a case study it is shown that whilst density functional approaches predict the correct trend for these substituted pyridine complexes there are occasional outliers. Traditional quantum approaches to the study of SCO, whilst accurate, are too time-consuming for the discovery of new complexes. Several LFMM parameter sets are optimised within this work. It is shown that this approach can accurately reproduce spin state energetics and geometries of iron(II) and cobalt(II) amines. A mixed donor type iron(II) amine/pyridine force field is also proposed. Through the utilisation of the drug discovery tools of the Molecular Operating Environment high throughput screening of cobalt(II) tetramine complexes is carried out. It is shown that ligands derived from macrocyclic rings display the most promise. These complexes, which are predicted to adopt a sawhorse geometry, show promise as SCO candidates are proposed as potential synthetic targets. This work illustrates the many exciting possibilities LFMM provides in the field transition metal computational chemistry allowing for theory to lead experiment rather than follow.

Organic photovoltaic (OPV) devices are attracting significant attention as an alternative renewable energy source. Recent advancements have led to an increase in device efficiency and stability; however a greater focus on reducing material and processing costs is needed. This thesis sets out to consider these issues. Indium-tin oxide (ITO) is widely believed to be a major contributor towards the material cost of the device. Highly conductive poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was investigated as an alternative and inexpensive transparent conducting electrode (TCE). The intrinsic conductivity of the PEDOT:PSS films was improved by dimethyl sulfoxide (DMSO) treatments. Ultra-violet absorption spectroscopy (UV-Vis), X-ray photoelectron spectroscopy (XPS) and conductive atomic force microscopy (CAFM) were used to gain understanding as to how the different treatments improved the film conductivity and how this influenced OPV device performance. This study highlighted the possibility of using PEDOT:PSS as an alternative electrode and emphasised the importance of optimising and tailoring the electrode to the specific photoactive layer. Careful control over processing conditions has widely contributed to the development of OPV devices. However, although inert atmospheres and casting from halogenated solvents results in high efficiencies, they also further add to the processing costs. A method to process the poly(3-hexylthiophene):phenyl-C61- butyric acid methyl ester (P3HT:PCBM) photoactive layer under ambient conditions was developed, which was found to be applicable on both ITO and PEDOT:PSS electrodes. This methodology was then used to process inverted P3HT:PCBM devices spin cast out of non-halogenated solvents which gave comparable overall device performance to those cast out of dichlorobenzene (DCB). This indicates the potential of producing low-cost OPV devices processed using more environmentally friendly solvents and under an ambient environment which can be more easily incorporated in a roll-to-roll process.

The aim of this thesis was to investigate crystal nucleation, growth and dissolution processes, focussing particularly on the behaviour of the crystal surface. To facilitate this various methods of microscopy were used, as well as electrochemical techniques, with the goal to separate mass transport towards the crystal surface and the processes which occur close to the crystal surface, and measure intrinsic growth/dissolution rates. In order to do this, crystal systems were screened for their relevance to applications in industrial processes, and those chosen were related to pharmaceutical crystallization and scale formation in o↵ shore oil wells. For each system, different methods of electrochemical measurement and microscopy were investigated to chose a technique which works best for the problem in hand. Further to the experimental data produced, these were supported by mass transfer models, with the aim of finding out more quantitative information about the surface behaviour of the crystal systems observed. Firstly, salicylic acid micro-crystals were observed in aqueous solution by optical microscopy to visualise growth/dissolution rates of individual faces. It was found from finite element method (FEM) simulations that the most active (001) face was strongly mass transport controlled, and that the (110) and ( ¯ 110) were closer to the surface controlled regime. Salicylic acid crystals were further analysed by scanning electrochemical microscopy (SECM) using 3 dimensional (3D) scans containing a series of approaches to the surface. By inducing dissolution on the crystal surface, and measuring a change in ultramicroelectrode (UME) current, the dissolution rate constant of the (110) face of salicylic acid was determined for this heterogeneous surface. Barite nucleation and growth was observed by optical microscopy, using a flow cell with hydrodynamic flow. High supersaturations were used and the crystals were deposited onto foreign surfaces with differing surface charge. It was found that the flux of material, once initial nucleation was achieved, matched closely to simulated mass transport fluxes. Finally, nanoprecipitation was induced at the opening of a nanopipette (ca. 100 nm) diameter and an ion current was applied to induce the early stages of barite nucleation. It was possible to observe nucleation and blockage of the nanopipette from the current transient produced. This process was used to test the effectiveness of different phosphonate inhibitors.