This thesis is concerned with the synthesis and characterisation of TiO2 based photocatalyst thin films and the assessment of their antimicrobial properties. When exposed to light of wavelength less than 380 nm TiO2 films can demonstrate self-cleaning and self-disinfecting properties. This is due to photocatalytic processes occurring on the film surface resulting in film superhydrophilicity and reactive oxygen species (ROS) production. These ROS and radicals readily oxidise organic pollutants and microbes adherent to the material surface. Consequently, TiO2 thin films are of great research interest as self-cleaning, antimicrobial coatings. TiO2 and doped TiO2 materials were prepared by a simple sol-gel route from titanium n-butoxide as the principle precursor material. Film deposition was carried out using a dip-coating technique, with substrates withdrawn from the precursor sol at a fixed speed. Deposited films were calcined to produce crystalline thin films, with excellent adherence to the substrate (glass slides). Films were characterised using a number of analytical techniques including UV-visible spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and EXAFS/XANES. Photocatalysis and film hydrophilicity were investigated using established methods. Stearic acid photodegradation, monitored by FT-IR was used to assess film photocatalysis, by monitoring the peak areas of the C-H stretching region. Relative film hydrophilicities were determined by measuring the contact angle of a sessile droplet of water. Antimicrobial properties of the films were assessed with typical examples of Gram- positive and Gram-negative organisms. Staphylococcus aureus (NCTC 6571) and Escherichia coli (NCTC 10418) were selected. Films demonstrated microbicidal activity against both organisms under 365nm UV illumination, and under illumination by a typical hospital lamp (28W 2-D fluorescent). Microbial adhesion to various substrates was also examined, using a dip-blot method. Films produced in this study demonstrate excellent potential as durable surface coatings with significant antimicrobial activity against microbes of clinical importance.

The main focuses of this project have been investigations of a variety of hydrogen bonding systems for unusual behaviour such as disordered or migrating hydrogens/protons with both single crystal X-ray and neutron diffraction, crystallisation of a large number of molecular complexes of the chloranilic acid molecule, and examining the bifurcated hydrogen bond motif found in many of the chloranilic acid co-crystals discovered. The neutron single crystal diffraction instruments SXD and VIVALDI have been used to provide conclusive results in cases of suspected unusual hydrogen bond behaviour in molecular materials. 2,4-dihydroxybenzoic acid and its isomer 2,5-dihydroxybenzoic acid have been examined using X-ray and neutron diffraction to investigate possible disordered cooperative hydrogen bond systems. The energy difference of the three possible tautomers of 2,4-dihydroxybenzoic acid in different environments have been calculated in theoretical computations which concur with the neutron results. Single crystal neutron diffraction experiments were also carried out on isonicotinamidium formate, 2-iodoaniliium picrate, chloranilic acid 2,4-lutidine and malonic acid, where unusual behaviour in the hydrogen systems was also suspected. The molecular complexes of chloranilic acid with various pyridine-based molecules have been the main focus of the X-ray diffraction work of this thesis. Multiple crystallisations over a range of different conditions were set up for chloranilic acid with various series of molecules including lutidines (dimethylpyridines) and picolines (methylpyridines). This resulted in a large number of new crystal structures, determined by X-ray diffraction and all found to contain a bifurcated hydrogen bond motif producing two robust hydrogen-bonded supramolecular synthons. The investigation examines the bifurcated hydrogen bond interactions and the suitability of chloranilic acid complexes for crystal engineering. The two related supramolecular synthon units are discussed and difference Fourier maps and Hirshfeld surfaces used to examine the hydrogen bond architecture. Bromanilic acid co-crystals are also studied to examine the effect of the halogen in the crystal structures.

The thesis describes the development of various novel emitters for the production of gaseous ions from solutions of non-volatile, thermally labile samples for the purposes of mass spectrometry. Nano-electrospray emitters each containing two separated channels running throughout the length of the emitter were fabricated and evaluated. These emitters were made from “theta-shaped” borosilicate capillaries, employing a number of different coating procedures. Loading of different solutions into the channels demonstrated the possibility of studying solute interactions on ultrashort timescales. It is proposed that interactions took place in a shared Taylor cone. The formation of specific adducts from vancomycin and diacetyl-l-lysyld- alanyl-d-alanine was observed by mass spectrometry. From consideration of the extent of H/D exchange between vancomycin and deuterated vancomycin, it was concluded that the interaction times were of the order of 10-5 s. Underlying theoretical considerations, design and fabrication from carbon nanotubes (CNTs) of emitters for field desorption and field ionization ion sources are described and discussed. The emitters fabricated made use of arrays of vertically aligned multi-walled CNTs with in most cases an average length and radius of 15 μm and 35 nm respectively. Emitters using dense coverings of nanotubes and emitters with nanotubes selectively grown so that the height of each nanotube was twice its separation from its nearest neighbour were investigated. Characterisation of the CNTs by field electron-emission confirmed their effectiveness as field emitters. Fowler-Nordhein plots indicated fields of 6.14x109 +/- 0.72x109 V/m at a potential of 700 V. Field ionization of He, Ar, Xe, methane and acetone was achieved with these same CNTs; neither the inert gases nor methane have been field ionised with conventional activated-wire emitters. The fields generally accepted to be required for field ionisation of He and Ar are of the order of several 1010 V/m. To create emitters which would not need to be removed from vacuum between experiments, a means of injecting both liquids and gaseous samples directly to the bottom of the CNTs was devised. This involved drilling 20 μm diameter holes through the silicon substrate between intended sites of nanotube growth, but before actually growing the CNTs. It was discovered that the presence of the holes led to surface migration of the nickel catalysts initiating CNT growth. Experiments undertaken to achieve mass spectrometric measurements with the arrays of CNTs as emitters are described and discussed.

Miniaturisation of devices and components is becoming increasingly important in the field of molecular devices. The design of multicomponent supramolecular systems that undergo photoinduced energy or electron transfer processes has been well recognised in view of its potential for development of nanosized molecular devices for solar energy conversion and components in photonic devices. Consequently research has expanded to the properties of monolayers formed from rather simple organic molecules to biological systems and metal complexes. In the present approach, surface active Ru(II) and Os(II) complexes have been designed. Their attachment to surfaces and their photophysical properties in solution, as powders and as self-assembled monolayers have been investigated. The complexes present relatively high quantum yields and long lifetimes in solution, as powders and in monolayers. The complexes have been developed further to carry \(\beta\)-cyclodextrin recognition sites in their structure. This new group of molecules opens a window into guest-host chemistry on surfaces, with the view to examining photophysical properties of supramolecular functional surface-active systems. The surface active Ru(II) and Os(II) complexes bearing \(\beta\)-cyclodextrin exhibit formation of emissive monolayers. Later Ir(III) and Ru(II) metalloguests with a specific design to bind to \(\beta\)-cyclodextrin cavity have been synthesised and the photo-induced communication between metals were investigated both in solution and on gold surface. Finally, we propose a new and efficient method of sensitising Nd(III) NIR emission by non-covalent attachment of a BODIPY dye attached to \(\beta\)-cyclodextrin (BODIPY-CD). The BODIPY-CD has been proved to be a good sensitizer for neodymium complexes. This is the first time that NIR lanthanides have been sensitised through non-covalent host-guest approach using cyclodextrin. The inclusion of the hydrophobic biphenyl and phenyl tails in the cyclodextrin has been proved by the NMR studies.

A series of lanthanide complexes based on tetraphenyl imidodiphosphate ligand have been prepared in order to investigate the ligand ability to act as a sensitiser for f-f based luminescence for the visible and NIR emitting ions. Furthermore, novel bimetallic luminescent lanthanide complexes based on two imidodiphosphate binding sites have been prepared for the examination of dinuclear lanthanide complexes formation. The sensitising properties of the bistpOp have been investigated by luminescence spectroscopy. A new ligand based on biphenyl sensitisers has been developed utilising an imidodiphosphate binding site. The lanthanide complexes have been prepared and their photophysical properties analysed.

The purpose of this work was to assess the potential of the Ru(II)(bipy)₃ complexes as photogalvanic systems, using the criteria obtained from the theory for an ideal photogalvanic solar cell developed by Albery and Archer. To this end two techniques were developed to measure the rate of the thermal back reaction between the high energy photoproducts Ru(III) and Fe(II) The thermal back reaction is a serious loss process in such a cell. The first technique, the Optical Rotating Disc Electrode, was improved by the design and construction of new apparatus. It allowed measurement of most of the important parameters of a photogalvanic cell and confirmed much of the theory for such a cell. The second technique, Flash Electrolysis, first used by Perone, was developed for use with a transparent disc electrode. Further investigations of the thermal back reaction were made using the Stopped Flow technique. The results of these experiments on Ru(IIl)(bipy)₃ and its derivatives show that the reaction obeys the Marcus theory of electron transfer. However the activation parameters are dominated by "compensation effects" which, at the elevated temperatures of a practical photogalvanic cell (> 60°C) , reduce the differences between different derivatives. The very similar rates of reaction so produced are much too high for the development of an efficient photogalvanic cell. Ru(II) (bipy)₃ systems thus provide a useful model for other possible photogalvanic systems buc cannot be of any practical use themselves.

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No description available.

Photoisomerization of the membrane-bound light receptor protein rhodopsin leads to a highly energetic species called bathorhodopsin, which is stable at temperatures below 125 K. Bathorhodopsin stores about 2/3 of the absorbed photon energy but the mechanisms with which this energy is stored is not completely understood. A new insight into these mechanisms by means of low-temperature solid-state NMR is both subject and aim of this Ph.D. thesis. The issue of the energy storage has been investigated by a solid state magic angle spinning technique which combines modern symmetry-based recoupling techniques with in situ cooling of the sample. Production of bathorhodopsin is also done in situ in a customized NMR probe. Three kind of experiments are discussed: chemical shift, distance and torsional angle measurements. The first kind of experiments led to carbon chemical shifts values for almost all the carbons along the retinylidene chain of the retinal chromophore of bathorhodopsin. Our measurements show a significant perturbations of the 13C chemical shifts in bathorhodopsin which is interpreted in terms of charge delocalization along the chain and therefore indicates a participation of an electrostatic mechanism to the energy storage. This is at variance with an earlier solid state NMR study where only minor perturbations of the electronic structure in the isomerized retinylidene chain were observed. We believe that these data incorrectly refer to bathorhodopsin because of the incorrect conditions of temperature and illumination applied. To sample for other local mechanisms that may contribute to the energy storage, the C-C distance of the last two carbons of the retinylidene chain, at the link with the protein opsin, was also measured but no significant differences with rhodopsin have been found. Finally, the H-C=C-H torsional angle at the double bound where the isomerization takes place was measured in a double-quantum heteronuclear local field spectroscopy (2Q-HLF) experiment. Results indicate a deviation from planarity of at least 40˚ about this double bond in bathorhodopsin suggesting an unquantified amount of torsional strain acting as a further energy storage mechanism. In addition to these very interesting results, this thesis reports methods, equipment and procedures ready to be used for the study of other similar light-triggered processes.

Y2WO6: RE, Y2O2S: RE, Gd2O2S: RE phosphors have been prepared using the urea homogeneous precipitation method and firing. Stokes luminescence properties of Y2WO6: RE excited with a FRED (frequency doubled argon ion) UV laser (257 nm) have been studied. The emissions have been assigned to their corresponding energy levels. Differences in the emission spectra of Y2WO6: RE, Y2O2S: RE, Gd2O2S: RE and Y2O3: RE have been attributed to the different site symmetries of the rare earth ions and to the different phonon energies of the lattices. Fine nanostructures present within butterfly wing scales have been faithfully replicated using a precursor Y2O3: Eu phosphor solution. Monodisperse polystyrene spheres and SiO2 spheres were synthesised and they were used to synthesise well ordered bare opal templates. Photonic phosphor crystals of Y2O3: Eu, Tb, Gd and Y2O3: Tm were synthesised using these templates to study the photonic band gap properties. Nano-sized Y2O3: Eu phosphors have been successfully incorporated into mono-dispersed silica spheres which have been assembled into photonic crystals. It has been observed that when light-emitting phosphors (e.g. Y2O3: Eu) and dyes (e.g. acid red dye) are incorporated into the opal structures, their emission spectra are modified when the stopbands of the opals overlap the emission bands of the light-emitting materials.