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The introduction of amphiphilicity into hyp-polydendrons has been achieved for the first time through the use of tertiary amine functional dendritic chain-ends and branched hydrophobic polymer chains. Explorations into the chemistry and architectural components within the hyp-polydendron structure has been carried out, offering the opportunity to control both structural and chemical behaviour. These have included: variation of the chemical composition of the primary polymer chain; utilisation of different monomers within the polymerisation; variation of dendron surface and linker chemistry; variation of primary chain architecture to produce statistical and block copolymers; variation of the degree of polymerisation; and initiation by multiple initiators (dendron and non-dendron) to result in mixed surface groups on the hyp-polydendron. The synthesis and aqueous nanoprecipitation of these branched materials is compared with their linear–dendritic polymer analogues, showing that the chemical and structural variables are all capable of influencing the ability to generate nanoparticles, the resulting nanoparticle diameter and dispersity, and subsequent response to changes in pH. The incorporation of the monomer, 2-(diethylamino)ethyl methacrylate, and a new acid-cleavable brancher has resulted in the preparation of pH-responsive nanoparticles that undergo solubilisation upon the addition of acid. Additionally, the hydrolysis of aggregated nanoprecipitates into linear-dendritic polymer chains has been confirmed by gel permeation chromatography, and encouraging encapsulation and release studies demonstrate a promising platform for pH-responsive drug delivery vehicles. The co-nanoprecipitation of linear-dendritic hybrids with branched copolymers has produced stable nanoparticle dispersions. Comparative nanoparticle behavioural studies, and consequent response to changes in pH have been conducted between co-nanoprecipitated nanoprecipitates in aqueous media to similarly composed hyp-polydendron nanoprecipitates containing covalently-bound dendron chain-ends. The dye molecule fluoresceinamine has been selected as a model guest molecule for encapsulation (9 wt%) within certain nanoparticles which were stable under physiologically-relevant conditions. Cytotoxicity and transcellular permeability studies were carried out using Caco-2 cells, showing low cytotoxicity at the concentrations studied, enhanced permeation though the Caco-2 cell monolayer, and high accumulation in Caco-2 and ATHP-1 cells. Finally, the ring opening co-polymerisation of ε-caprolactone and 4,4’-bioxepanyl-7,7’-dione using dendron initiators was explored. This resulted in stable ε-caprolactone nanoprecipitates formed in aqueous media, from biodegradable polyester hyp-polydendrons. To the best of our knowledge, this is the first example of stabilised p(CL) nanoparticles in aqueous solution, without the need for additional stabilisers.

The work reported in this thesis systematically investigates the structural, electronic and/or magnetic properties of fcc AxCs3-xC60 fullerides (A = K and Rb) and of sesquioxide Cs4O6 under ambient and non-ambient temperature and pressure conditions, employing X-ray and neutron powder diffraction, muon spin relaxation, and SQUID magnetometry. In the AxCs3-xC60 alkali fullerides, unconventional superconductivity can emerge through tuning of intermolecular distances. While conventional BCS-like response is found in the underexpanded regime of the electronic phase diagram, significant deviations appear in the overexpanded region adjacent to the Mott boundary where strong electron correlations are prominent. In this work, the solid-state synthesis of fcc KxCs3−xC60 (0.12 ≤ x ≤ 2) superconducting materials, with intermolecular distances controlled via adjusting the K+/Cs+ dopant ratio, is reported. Whilst the structural, electronic and magnetic properties of fcc KxCs3−xC60 are reminiscent of those previously reported for fcc RbxCs3−xC60, i.e. the Mott boundary can be shifted to ambient pressure and the metal-insulator crossover temperature can be tuned by such chemical pressurisation of Cs3C60, cation-specific effects are of importance on the electronic properties of fcc AxCs3−xC60. This work also provides strong evidence for correlated behaviour in the overexpanded regime through examining the presence or not of the Hebel-Slichter coherence peak and extracting the superconducting gap magnitude. Crystallographically, the alkali sesquioxides A4O6 (A = Rb, Cs), at high and low temperature, had been reported to adopt a cubic structure which generates a single crystallographic position for dioxygen, implying charge disorder: A4(O2(4/3)-)3. Conversely, spectroscopy studies at 5 K found evidence for two localized valence states of dioxygen, indicating charge ordering: (A+)4(O2−)2(O22−). This issue is addressed with the first systematic investigation of the temperature- and cooling-protocol-dependent structural evolution of Cs4O6, revealing the existence of a valence-ordered state at low temperature and also that valence disorder-order transitions can be induced by temperature, pressure and X-ray illumination.

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In this thesis, optical and electrochemical techniques are used to study the factors controlling catalytic function in solar-to-fuel conversion systems. Chapter 3, the first results chapter, considers a system for CO2 reduction based on a Re photocatalyst anchored to TiO2. This chapter reports evidence that the immobilisation of the photocatalyst via covalent bonds improves the stability of one of the key reaction intermediates resulting in higher catalytic yields. This chapter also provides insight into the nature and timescale of the steps in the mechanism of CO2 reduction. Chapter 4 considers a proton reduction system based on a Ru absorber, a Ni electrocatalyst and a sacrificial electron donor. This chapter discusses the mechanism behind the strong pH dependence in this system. The results show that whereas the electron transfer between the dye anions and the electrocatalyst is pH independent, the generation of dye anions and the catalytic function of the electrocatalyts have opposite pH-dependencies. Chapter 5 considers a photocathode for proton reduction based on a Cu2O/Al:ZnO buried p-n junction with protection and catalyst layers. The results presented show that the buried junction controls charge separation and the photocurrent onset. Furthermore, the catalyst layer is found to slow down charge recombination and help achieve high reduction yields. This chapter also discuses the mechanism of proton reduction and how the nature of the rate-limiting step has an impact in the recombination kinetics. Chapter 6 discusses the use of transient absorption spectroscopy to study high refractive index materials with high quality interfaces. This chapter investigates light interference effects in TiO2, Cu2O and a CH3NH3PbI3 perovskite device. The results show that interference effects in these materials can dominate their transient spectra, hindering its interpretation. However, it is found that this spectroscopy can also be used to extract information about the changes of the refractive index.

This thesis investigates self-assembled monolayers (SAMs) of molecules of various complexity with a special focus on fabrication of surfaces that could exhibit an intrinsic active function, more precisely a capability to switch between two stable states upon external stimuli (spin crossover phenomenon) or to expose functional groups upon irradiation with light, i.e. photocleavage of a SAM. SAM formation of a complex novel molecule, lipoic acid ester of α-hydroxy-1-acetyl-pyrene (reagent 1), was studied in chapter 3. It contains i) a dithiolane headgroup capable of binding to gold surfaces via two sulfur atoms, and ii) a chromophore that makes it light sensitive (photocleavable) and leads to a deprotection of lipoic acid molecule upon exposure to soft UV (365nm). Reagent 1 successfully forms SAM1, but it interacts with the gold surface weaker than conventional thiol based SAMs, due to cross-linking of dithiolane headgroups. Nevertheless, SAM1 is a relatively stable monolayer and exerts a higher barrier against diffusion of copper ions towards gold surface in electrochemical deposition than SAMs of similarly complex molecules but with thiol headgroups or shorter alkanethiol SAMs terminated with carboxylic acid groups (COOH). SAM1 undergoes photolysis upon soft UV (365nm) irradiation, but only in the acidic catalyst 100mM HCl in isopropanol (IPA). Unexpectedly, this also leads to a removal of the resulting lipoic acid monolayer, thus ultimately leading to SAM1 with lower surface coverage, and changes packing and ordering. SAMs of alkanethiols terminated with COOH and of varying chain length were investigated in order to better understand the cause for the instability of lipoic acid monolayer. Loss of molecules from the surfaces was found to be a common issue in the COOH SAMs, however, the severity of the loss is strongly related to the initial SAM thickness. Thin SAMs like DTBA SAM yield huge (∼50%) loss, while thick SAMs like MUA SAM show no detectable loss. On the other hand, photo-patterned SAM1 produces especially high selectivity of Cu deposition between UV treated and non-treated regions, which is associated to this loss of surface coverage, packing and ordering. Surprisingly, reagent 1 also interacts with glass and silicon oxide surfaces to form hydrophobic films that exhibit green fluorescence under soft UV light. Such surfaces are photo-sensitive and can be photo-patterned in the air or in the acidic catalyst to produce non-fluorescent hydrophilic regions due to photo-bleaching of pyrene groups and photo-deprotection of lipoic acid molecules, respectively. The films and patterns stored under ambient conditions are detectable for at least 35 days. Formation of those films is associated with an interaction of pyrene group with adsorbates on the surfaces, while film growth is attributed to the cross-linking of dithiolane headgroups. SAM fabrication of metal complexes was explored in chapter 4. Two novel ligands L1 and L2, and their corresponding Fe(II) complexes C1 and C2, which can exhibit spin crossover (SCO) behaviour in bulk, were investigated. Both ligands successfully form SAMs. However, SAM L1 does not coordinate Fe(II), while its preformed complex C1 is not stable on Au surface and forms SAM L1 instead of SAM C1. In contrast, SAM L2 coordinates Fe(II) at nearly 100% yield, which leads to almost the same chemical composition as in a SAM of its preformed Fe(II) complex C2 (SAM C2). Although complex C2 with MeCN as the sixth exogenous ligand (SEL) exhibits low spin (LS) state in bulk at room temperature, only high spin (HS) state was detected in SAM C2. Complex C2 exhibits a unique property of changing its spins state in certain solvents, because a solvent molecule can easily displace the sixth exogenous ligand (SEL). However, rinsing SAM C2 with such solvents did not lead to a spin transition, and LS state was never observed for the SAM. This implies that the strength of the ligand field may need to be increased or SEL with a higher affinity coordinated to complex C2, in order to change the spin state by rinsing or to detect SCO in SAM C2. A long-chain alkanethiololigoethyleneglycol (LCAT-OEG) type molecule terminated with the azide group (reagent 2) was investigated for the facilitation of click chemistry on gold surfaces (chapter 5). Reagent 2 forms a good quality SAM (SAM2), and the concentration of reagent 2 in the SAM can be reduced in a controlled and predictable manner by the addition of LCAT-OEG-1 or LCAT-OEG-4 to the growth solution. QCMD measurements indicate that the whole surface of SAM2 successfully undergoes click reaction with cycloalkyne in aqueous solution without any catalyst. Finally, simple alkanethiol and aromatic type SAMs were investigated for use in surface-enhanced Raman spectroscopy (SERS) with nanoparticle-on-mirror configuration and for studying plasmonic systems, due to their ability to yield optimum precision over the control of thickness and dielectric function (chapter 5).

No description available.

No description available.

This thesis describes the development of a fragment library in order to identify the value of shape-diverse molecules in their ability to target novel areas of shape-space. Chapter 1 introduces known approaches to ligand discovery as well as the concept of chemical space and molecular shape diversity. Chapter 2 describes the computational tools and protocols used to identify fragments of interest from both commercial and Leeds libraries, that fulfil the criteria of maximum coverage of reference shapes as well as high shape-diversity. The synthesis of fragments based on Leeds chemistry is described in Chapter 3, focusing on four key chemistries established within the Nelson group, as well as the reselection of molecules to overcome synthetic challenges. Chapter 4 describes the screen of the library of fragments using high-throughput X-ray crystallography, as well as the development of a novel fragment hit against Aurora A kinase. Overall my fragment library was successful in its ability to investigate unexplored shape-space and presented valuable hits against a useful target.

Three separate topics are presented covering the temperature dependence of isotropic hyperfine coupling constants, an anharmonic analysis of molecular hydrogen in interstellar ice and the microscopic structure of doped crystalline silicon lattices. The temperature dependence and vibrational effects of isotropic hyperfine coupling constants are studied using the ab-initio density functional methods BLYP and B3LYP with the common double and triple zeta basis sets 6-31G(d,p) and 6-311(d,p). Harmonic oscillator wavefunction averages for all normal modes of a molecule are accounted for and the temperature dependence is developed from the Boltzmann distribution. An ab-initio study of the atomic displacements and microscopic structure of phosphorus and arsenic in doped silicon is carried out. The structures and relative displacements are estimated using SCF, DFT and MP2 methods with STO-3G, 3-21G, 3-21G(d,p) and 6-31G(d,p) basis sets with a 13 atom silicon molecular cluster. The calculations are carried out on clusters using empirical parameters for Si-Si and Si-H bond lengths in addition in fully optimised clusters. Following the discovery of a species thought to be molecular hydrogen in interstellar clouds by IR spectroscopy, ab-initio density functional B3LYP calculations are performed to back up experimental and semi-empirical studies of molecular hydrogen in amorphous ice. Anharmonic calculations are carried out on hydrogen molecules adsorbed onto ice and trapped in a cage. The issue of species other than molecular hydrogen and surface transport of hydrogen is addressed.