The work presented in this thesis involved a study of the photocatalytic oxidation of atmospheric pollutants NOx and S02. Anatase titanium dioxide powder was used as a photocatalyst, and compared with nanostructured titanium dioxide. Two novel coating procedures, screen printed ceramics and spray coated aluminium, were investigated for photocatalytic application. In addition anatase samples containing CeO2 and Zr02 were characterised and investigated for photocatalytic potential. All the samples in this thesis were characterised using X-ray photoelectron spectroscopy (XPS) and time of flight mass spectrometry (TOF-SIMS), with Raman analysis used for crystal phase analysis. Specifically for the Ce02 and Zr02 coated powders, scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX) and X-ray diffraction (XRD) were performed. Electrolysis in a fluorine electrolyte produced anodically grown amorphous titania nanotubes. Annealing of the amorphous nanotubes was conducted at 600°C to produce a reactive anatase layer. In addition an anatase nanotube powder was created by a hydrothermal process in NaOH. These samples were imaged and analysed using scanning electron microscopy (SEM), focused ion beam (FIB) and transmission electron microscopy (TEM). Laboratory tests were performed to study the effect of moisture and ultraviolet (UV) light on the oxidation of the pollutant gases when exposed to photo catalytic samples. The structured testing involved exposure to NOx, S02 and a combination thereof with controlled environmental parameters tor 72 hour periods. XPS, Raman spectroscopy and TOF-SIMS were used for surface analysis of the samples after exposure to the reactive gas compounds. An increase in surface oxidation of reactive gases was observed in the presence of UV light and moisture. The synergistic relationship between SO2 and NOx initially proposed by Alien et al was supported by these observations. The nano-patterned anatase samples, with increased surface area, adsorbed larger quantities of pollutant gas and showed the highest recorded levels of nitrate and sulphate formation. The novel coated substrates also exhibited a photocatalytic activity equal to that of commercial grade anatase powder.

This Thesis describes the synthesis and characterisation of titanium hydrazido(2-) and alkylidene hydrazido(2-) complexes and their reactivity towards unsaturated molecules. Exploration of the bonding in titanium hydrazido(2-) and alkylidene hydrazido(2-) complexes is performed through structural and computational studies. Chapter 1 introduces current Group 4 hydrazido chemistry in comparison to Group 4 imido and mid/late metal hydrazido examples. Current Group 4 alkylidene hydrazido chemistry is also described. Chapter 2 describes the synthesis, bonding and the novel reaction chemistry of titanium hydrazido(2-) half-sandwich complexes. Novel reactivity at the Ti=N, bond is presented with the mechanisms of some of these transformations probed by Density Functional Theory (DFT) calculations. Chapter 3 describes the novel reaction chemistry of Cp*Ti{MeC(Nipr)2} (NNMe2) in comparison to its imido and diphenyl hydrazido analogues. Novel reactivity at both Ti=N, and Na-N~ bonds is presented with the mechanisms of some of these transformations probed by Density Functional Theory (DFT) calculations. Chapter 4 describes the synthesis and characterisation of a new titanium alkylidene hydrazido(2-) complex. The bonding of the alkylidene hydrazido(2-) ligand is explored through structural and computational studies. Novel reactivity at Ti=N, and Na-N~ bonds is presented. Chapter 5 presents full experimental procedures and characterising data for the new complexes reported. CD Appendix contains .cif files for all new crystallographically characterised complexes described.

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Dans ce travail, les propriétés des oxydes de titane mésoporeux organisés ont été étudiées en détail. La synthèse de ces matériaux a été mise au point auparavant au laboratoire à l’aide d’une méthode combinant le mécanisme transcriptif à partir des cristaux liquides du copolymère bloc P123 et la méthode EISA. Tout d’abord, une optimisation des conditions d’élimination du tensioactif a été effectuée en testant des méthodes d’extraction à partir de solvant et des méthodes thermiques. L’élimination du P123 par l’eau suivie d’un rinçage à l’acétone est efficace, simple et rapide et en même temps favorise la formation de la phase anatase du TiO2. Par contre, les propriétés photocatalytiques de ces TiO2 extraits à l’eau sont médiocres et ne sont améliorées qu’après calcination. En combinant une extraction du P123 à l’eau avec une calcination les oxydes de titane mésoporeux possédent une meilleure activité photocatalytique que celle de l’anatase commercial. Dans un second temps l’incorporation du zinc et du tungstène dans les TiO2 mésoporeux organisés a été investie dans le but d’améliorer leur activité photocatalytique. L’introduction de faibles quantités de zinc (<10% mol) augmente la surface spécifique ; au-delà la mésostructuration est perdue. L’incorporation du tungstène dans le TiO2 mésoporeux n’a pas d’influence sur l’organisation des mésopores, mais des agrégats de WO3 orthorhombique coexistent avec le réseau mésoporeux de TiO2 anatase. Même si la présence d’oxyde de zinc ou de tungstène dans la matrice TiO2 mésoporeux diminue bien l’énergie bandgap, l’activité photocatalytique ne s’en trouve pas améliorée. D’autre part, la synthèse de matériaux à porosité bimodale, en utilisant deux systèmes mixtes de tensioactifs hydrogéné/fluoré, CTABr/RF8(EO)9 et P123/ RF8(EO)9, a été explorée. Sur la base des diagrammes de phase de ces deux systèmes dans l’eau, les solutions micellaires et les cristaux liquides ont été investis pour préparer des silices mésoporeuses en utilisant les deux mécanismes CTM et LCT. Quand le CTABr est présent une seule taille de pores dans le domaine mésoporeux est observée, toutefois il est possible qu’une bimodalité de type micro-mésopores existe. Par contre, l’utilisation de la phase hexagonale du système P123/RF8(EO)9 permet d’obtenir des matériaux à deux tailles de pores distincts dans le domaine mésoporeux. / In this work we will study in detail the properties of the mesoporous TiO2 materials, for which the preparation was developed previously via a method combining Liquid Crystal Templating (LCT) and EISA mechanisms, using P123 as template. We have tested, in the first time, extraction and thermal methods efficiency to eliminate surfactant in order to optimize the P123 elimination step. Removal of P123 using water followed by washing with acetone is effective, easy and promotes the formation of the anatase phase of TiO2. Otherwise, the photocatalytic properties of the obtained TiO2 are not important and can be improved after calcination. Combining extraction using water and calcination give rise to mesoporous TiO2 with better photocatalytic activity than that of commercial anatase. The incorporation of zinc and tungsten in the mesoporous well-ordered TiO2 has been investigated in the third time, in order to improve their photocatalytic activity. The introduction of small amounts of zinc (<10 mol%) increases the surface area; beyond this amount the mesostructure is lost. The incorporation of tungsten in the mesoporous TiO2 does not affect the mesopores organization, and orthorhombic WO3 aggregates are formed beside the mesoporous network of anatase TiO2. Although, the presence of zinc or tungsten oxides in the matrix decreases the bandgap of mesoporous TiO2, the photocatalytic activity is not improved. In the third time, the synthesis of bimodal porosity materials, using a mixed surfactant systems hydrogenated/fluorinated, CTABr/RF8(EO)9 and P123/RF8(EO)9, was explored. Based on the phase diagrams of these two systems in water, micellar solutions and liquid crystals have been investigated to prepare mesoporous silicas using two mechanisms CTM and LCT. When CTABr is present, pores of one size in the mesoporous range are observed, however, it is possible that bimodal type micro-mesopores exist. The use of the hexagonal liquid crystal phase of P123/RF8(EO)9 provides two separate pore sizes materials in the mesoporous range.