| Tin oxide materials are commonly used commercially as electroactive semiconductors for the detection of toxic gases such as carbon monoxide and methane. Surfactant and colloidal templating routes have been used to develop tin oxide materials which have a large range of porous architectures, from microporous/mesoporous solids to macroporous opals and inverse opals. Structure-property relationships between the underlying microstructure of the tin oxide architectures and the sensor response towards carbon monoxide were examined.; Mesostructured tin oxide materials were synthesized using non-aqueous chemistry in ethylene glycol, as well as using anionic dodecylsulfate and dodecylsulfate templates. An unusual two-step surfactant decomposition was observed for latter mesostructures, as the surfactants decomposed to give stable sulfated mesoporous SnO2 materials upon calcination. FT-Raman Spectroscopy, Powder X-ray diffraction, nitrogen gas adsorption and AC-Impedance spectroscopy were used to monitor the evolution of the sulfated mesostructures upon calcination. It was postulated that the sulfate groups stabilized the mesostructure and also inhibited the sensitivity towards carbon monoxide by preventing adsorption of carbon monoxide on the tin oxide surface.; Tin oxide opals and inverse opals were fabricated from silica and polystyrene sacrificial colloidal crystal templates. The tin oxide opals were synthesized by micromolding in inverted polymer opals (MIPO). The sensor response of the resulting structures was examined towards carbon monoxide, toluene and ethanol. The inverted tin oxide opals were found to exhibit near-ideal sensing behaviour, whereas the tin oxide opals showed large deviations from ideality. The structures were studied theoretically by considering them as resistor networks which could be broken down into simple resistor units consisting of agglomerates and junctions.; Further studies were undertaken on the tin oxide opals to vary the neck diameter between adjacent spheres by variable sintering of the parent silica colloids. Relationships between the neck diameter and the sensor behaviour were observed. Future work in these systems includes the development of platinum-tin oxide opalene structures which can operate as room temperature carbon monoxide sensors, opal structures grown directly into the grooves of interdigitated arrays used for sensing, lithium battery anode materials, photocatalysts, and light harvesting materials. |
