| Summary: | This thesis focuses on the synthesis, characterisation and testing of semiconductor nanomaterials and heterojunctions, for photocatalytic and UV attenuation applications. Titanium dioxide (TiO2) and zinc oxide (ZnO) nanomaterials were synthesised via a continuous hydrothermal flow synthesis (CHFS) process, where solutions of chemical precursors were mixed with hot, pressurised water. Samples were collected as slurries and processed to obtain dry powders. Synthesis of TiO2 investigated the addition of boric acid as a dopant species to determine (i) its potential to dope TiO2 in the continuous hydrothermal process, and (ii) any effects on reaction conditions and subsequently nanoparticle properties. The powders were prepared as ceramic wafers, and tested for their ability to photocatalytically evolve hydrogen from water, in a sacrificial system. ZnO synthesis was investigated from a scale-up perspective, comparing a mini-pilot scale CHFS reactor to a larger pilot-scale reactor already reported in literature. The observed variation in particle sizes were explained in terms of the nucleation and growth mechanisms of zinc oxide. Additionally, an investigation was carried out to explore the effects of additives in the CHFS reactor to (i) reduce ZnO particle sizes and (ii) obtain dispersions of ZnO nanoparticles. Selected materials from these experiments were investigated as UV attenuators in polymer coatings. Heterojunction ceramic wafers of TiO2 and WO3 were prepared by a simple technique, reported here for the first time. The wafers displayed interesting charge transfer characteristics, and they were investigated for photocatalytic applications in the destruction of organic pollutants and disinfection of water. In these applications, the heterojunction wafers were found to have photocatalytic rates that were greater, or more beneficial than, their corresponding individual semiconductor materials.
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