Abstract
Role of water and ammonium hydroxide is investigated in evolution of shape of silica structures in the polyvinylpyrrolidone-pentanol emulsion droplet system. Shape control of silica structures is demonstrated by localization of the reagents. A uniform dispersion of reagents provided straight silica rods, while localization of the reagents at the emulsion droplet periphery provided a new type of structures––half sphere-half funnel. The absence of water in the initial stages prompted a different nucleation process for the structure growth compared to when water was present in the intial stages. Effect of effective water concentration appeared to be related to the ease of diffusion of silica percursor inside the emulsion droplet,i.e., the higher the water concentration, the lower the silica precursor diffusion. Additionally, mixing the reagents in different combinations before adding to the reaction mixture also affected the silica structure thickness, length, and shape.
