Control of self-organized colloidal photonic structures

Abstract

Close packings of colloidal particles has been studied due to its unusual optical properties or highly efficient mass transfer when it is used as catalytic support. In particular, controlling the light with these materials always require the precision in their periodic positions and size uniformity of building blocks at nanometer scale. Therefore, any additional process in photonic crystals or molecules should be nano-fabrication, of which uncertainty would be one billionth meter. In this thesis, fabrication and application of colloidal crystals and molecules by self-assembly of monodisperse building blocks were studied. In particular, we have controlled shapes of polymeric microspheres in their close-packed structures by hyperthermal neutral beam etching, keeping the lattice constants, which have caused change of their optical property precisely. Monodisperse microspheres of silica were packed into colloidal micro-clusters by aerosol-assisted method and general method for small aggregates of water-borne colloids inside waterin-oil emulsions was also developed. Moreover, simple and facile method for small colloidal clusters of microspheres was proposed which is evaporation-induced assembly of water-borne colloids in water-in-oil (W/O) emulsions by microwave heating. New types of binary colloidal clusters were fabricated from water-in-oil emulsions using various combinations of two different colloids with several size ratios: monodisperse silica or polystyrene microspheres for larger particles and silica or titania nanoparticles for smaller particles. Interestingly, the configurations of the large microspheres were not changed by the presence of the small particles. However, the arrangement of the smaller particles was strongly dependent on the nature of the interparticle interactions. The experimentally observed structural evolutions were consistent with the numerical simulations calculated using Surface Evolver. Moreover, micro-clusters of polystyrene microsph...