Fabrication of high-quality colloidal crystals and its applications

Abstract

In this thesis, high-quality colloidal crystals with sub-micrometer sized colloidal particles as a building block were fabricated via new routes and the applications using the prepared colloidal crystals were demonstrated. In chapter 2, we discussed a self-assembly method, referred to as confined convective assembly, for fabricating well-ordered two-dimensional (2D) and three-dimensional (3D) colloidal crystal films. With a minute amount of a polystyrene colloidal suspension $(50\mu L at on time)$ and without any special equipment, the proposed method can be used to rapidly deposit high-quality colloidal crystal films over a large surface area $(1 cm \times 1 cm)$. By controlling the lift-up rate of the substrate, we modulate the meniscus thinning rate, which determined whether the colloidal particles are assembled into two or three dimensions. The proposed method can be used to fabricate not only monolayered colloidal crystals with colloidal particles of various sizes, but also multilayered colloidal crystals. In addition, the method enables us to fabricate binary colloidal crystals by consecutively deposing large and small particles. In chapter 3.1., we demonstrated that two-dimensional polystyrene colloidal crystals of much higher quality can be fabricated in a single-step confined convective assembly process by introducing water-soluble (viscoelastic material) polymer into the colloidal suspension. The presence of the water-soluble polymer in the aqueous phase enables the colloidal particles to arrange into more hexagonally close-packed single crystalline domains, and thus reduces the defect density. In addition, the physical stability of the final two-dimensional colloidal crystals is improved because each particle is bonded to neighboring particles. In chapter 3.2., we have fabricated robust, high-quality 3-D colloidal crystals using the vertical deposition by introducing a water-soluble polymer into the colloidal suspension. Compared to three...