Synthesis of Half-Sphere/Half-Funnel-Shaped Silica Structures by Reagent Localization and the Role of Water in Shape Control

Shape control of silica structures is demonstrated by localization of the reagents. A uniform dispersion of reagents provided straight silica rods, whereas localization of the reagents in the emulsion droplet periphery provided a new type of half-sphere/half-funnel structure. The effect of water concentration appeared to be related to the ease of diffusion of the silica precursor inside the emulsion droplet (i.e., the higher the water concentration, the lower the silica precursor diffusion).