Droplet-guided self-assembly of colloids for photonic nanostructures

Abstract

Self-assembled colloidal aggregation routes to dielectric structure with face-centered cubic symmetry and submicrometer periodicity have been extensively studied in the past decade because of their potential applications including anisotropic building-block, photonic crystals and color pigments. Aggregates of colloidal particles can be classified into several categories including the aggregates of small number of colloidal particles, so-called colloidal cluster, spherical colloidal crystals, so-called photonic balls and amorphous colloidal aggregates, so-called photonic glass. Various approaches have been studied to achieve 3 dimensional structures composed of colloidal particles. In order to fabricate these colloidal suprastructures, confined geometry with mobile interface have been one of the best way. When colloidal particles are dispersed in confined emulsion droplets, the droplets can supply two dimensional (2D) space for colloids confinement as well as 3D space. Colloids which residue on the interface can reduce the surface energy and stabilize the droplets by replacing free interface of excess energy. When decrease of surface energy is much larger than the thermal energy (~kT), the colloids are anchored on the 2D spherical interface and do not escape from the interface to droplet or continuous phase under week external disturbance. Therefore, particle size and surface property determine the type of confining dimension. In the case of 2D confining geometry, colloidal particles are moved with mobile interface whereas, colloidal particles confined in 3D geometry can freely move in emulsion droplets during solvent evaporation. Accordingly, rheological and optical properties of colloidal aggregates can be modulated by varying number of colloidal particles inside droplet, surface moiety of colloidal particles or evaporation time of liquid. Here, I describe various colloidal aggregates prepared by different confined geometry with applications. In chapter 2, I ...