Preparation, Microstructure And Photonic Bandgap Properties Of Complex Colloidal Crystals

This dissertation focuses on complex colloidal crystals. The formation mechanism, microstructure and photonic bandgap properties of complex colloidal crystals were investigated systematically based on three different preparation ways, i.e. layer-by-layer method, co-assembly method, and crystalline colloidal arrays.Template-assisted electric field-induced assembly (TAEFIA) on the basis of layer-by-layer method was developed. It was revealed that the mismatch of relative permittivity between the colloidal particles and water in template layer was the driving force in the formation of binary colloidal crystals, and the steric constraint of the interstitial sites in template layer was the dynamic factor responsible for the structure of binary colloidal crystals. The influence of particle size ratio, volume fraction and electric field parameters on the structure of binary colloidal crystals was systematically studied. By TAEFIA, we were able to overcome the limit on size ratio in current layer-by-layer methods, and fabricated ternary colloidal crystal for the first time.Binary colloidal crystals were prepared by accelerated evaporation deposition, and the influence of particle size ratio and relative content on crystal structure was discussed. It was revealed that the critical size ratio of binary colloidal crystals fabricated in capillary force-induced co-assembly method is 0.33 from the viewpoint of space-filling. It was found that with a size ratio higher than the critical value the particles with larger diameter cannot form ordered close-packed basic lattice, and as a result the corresponding binary colloidal crystal had a low degree of order, which was in accordance with previous literatures. Moreover, with binary colloidal crystals as templates, complex ordered porous silica films were fabricated by sol-gel technology. The as-prepared films replicated the structure of colloidal crystal templates, and its pore size shrunk compared with those of the particles in templates.Crystalline colloidal arrays (CCAs) were prepared via ion-exchange technology. It was found that the relation between the photonic bandgap wavelength of CCA and its volume fraction conformed to Bragg equation. The effect of different solvent on the photonic bandgap of CCA was investigated, and the suppression on dye fluorescence by photonic bandgap in CCA was confirmed. Moreover, polymerized crystalline colloidal arrays (PCCAs) were fabricated by ultraviolet-initiated polymerization. It was revealed that the photonic bandgap wavelength of PCCA film was reversibly proportional to extrinsic pressure in certain load range.Binary CCA was prepared for the first time, and the influence of effective particle size difference on its particle arrangement and photonic bandgap properties was studied. It was found that the photonic bandgap wavelength of binary CCA and the effective lattice parameter of particle lattice were proportional to the particle number percentage in binary CCA with a small size difference. But the particle arrangement exhibited a mixed structure of order and disorder with a large size difference, whereas degradation of photonic bandgap properties was also resulted. The resemblance between binary CCA and solid solution on microstructure and phase transition was revealed via comparison. We suggested that binary CCA can be used as a research model in condense matter physics and metal physics, and may find potential applications in many fields, such as photonic crystals.