Fabrication of microstructured colloidal titania and their optical characteristics

Abstract

This thesis concerns the fabrication and optical characterizations of titania colloidal microstructures. Titania particles are commonly used as ultra-white pigments because of their high refractive index and no absorption at visible. As well, they have taken lots of attractions due to good light scattering within their microstructure, which is potentially useful for photonic glass or random scatterer. Therefore, it is a great challenge to synthesize titania particles for controlling their optical properties more precisely. However, it is difficult to deal with titanium precursors due to fast reaction rate. Here, the synthesis of a variety of titania microstructures by using hybridization between titanium precursor and polyol will be demonstrated. Firstly, monodisperse titania spheres with fine tunability of the sizes have been successfully synthesized by surfactant-assisted controlled hydrolysis of glycolated titanium alkoxide. Then, the self-assemblies of spherical particles inside emulsion have been studied for the potential as photonic molecules. Secondly, the fabrication of 2-D titania structures from room-temperature polyol process is described. Unlike unidentified structures produced from high temperature polyol process, this process produces well-defined or plate-like structures with polygonal cross section. It will be expected that these structures can be used as optical or photonic structures such as random laser, strong light scatterers, and whispering gallery mode sensors. Finally, the fabrication of optically activated colloidal particles was demonstrated. Here, phosphor or dye doped particles and clusters are prepared on high refractive index titanium glycolate matrix. The luminescence characterization of as-prepared particles shows that uniform particles sensitive to specific wavelength of light can be conveniently prepared.