Synthesis of porous aluminate microbeads from emulsion droplets: interphase alcohol extraction-driven assembly of sub-10 nm nanoparticles

Abstract

Porous microbeads containing inorganic nanoparticles have attracted considerable attention because they can be endowed with functionalities derived from the metal elements. One representative method for synthesizing porous microbeads containing inorganic nanoparticles is the emulsion method. Here, we develop a novel synthesis concept for the synthesis of pure inorganic porous microbeads using an aluminate system as a model system. The obtained microbeads showed microporosity with a high specific surface area as well as a spherical shape. Porous aluminate microbeads are synthesized by preparing water in oil emulsion droplets using a concentrated dispersion of aluminum hydroxide nanoparticles surface-modified with acetylacetone, followed by destabilizing the nanoparticles by extraction of alcohol from the aqueous droplets to the oil phase. We found that amphiphilic ethanol spontaneously extracted to the oil phase from the aqueous phase, destabilizing the nanoparticles and resulting in porous microbeads.