Abstract
This research focuses mainly on the preparation and applications of colloidal spheres for photonic crystals, photo-catalysis, and dye-sensitized solar cells. The diameter of the polystyrene colloidal spheres can be fine-tuned by controlling the addition amounts of co-monomer in an emulsifier-free polymerization process. The diameter of the resulted polystyrene colloidal spheres can be adjusted to range from 100 nm to 595 nm with uniform size distributions. With an evaporation assisted self-assembly process, the obtained polystyrene colloidal spheres form large scale and good quality synthetic opal structures which possess periodic structures in the close-pack arrangement under controlled temperature and colloidal sphere concentrations. Inverse opal structures of a wide variety of materials such as gold, silver, nickel, zinc oxide, titanium dioxide and polypyrrole were successfully prepared by using the polystyrene opal as the starting template and infiltrating the void with electrochemical deposition. Photonic band gaps were clearly identified in both opal and inverse opal structures. The feasibility of applications for building practical devices such as waveguides and sensors was demonstrated via the procedures developed in this research. As compared to the dielectric materials commonly used to construct three-dimensional photonic crystals, metallic opaline photonic crystals were successfully built via a double templated electrochemical deposition process and were demonstrated to possess absolute photonic band gaps in the visible range. In addition, the photo-catalytic efficiency of titanium dioxide coated sub-micron silica colloidal spheres was also investigated and showed a comparable efficiency as compared to commercial photocatalysts. Titanium dioxide inverse opals post-treated with titanium tetrachloride were also employed to serve as the anode in dye-sensitized solar cells and the resulted cells showed an overall conversion efficiency of 4%.