Synthesis Route for the Self-Assembly of Submicrometer-Sized Colloidosomes with Tailorable Nanopores

We present a synthesis route to fabricate submicrometer-sized colloidosomes at ambient conditions and mild pH with tailorable nanopore sizes and porosity. The capsules are formed via self-assembly of metal oxide nanoparticles on emulsion droplets in a water-in-oil emulsion. Through the adsorption of oil-soluble surfactants on emulsion droplets, which carry the same sign of charge as the colloidosome-forming particles in aqueous media, colloidosomes with positive and negative zeta potentials were synthesized. The hollow capsules are inherently rigid and necessitated no further stabilization. By varying the sizes and shapes of the nanoparticles, we were able to tailor the pore diameters and pore size distributions on the surface of the capsules. Particles of high spherical uniformity with narrow size range generated colloidosomes with a mainly hexagonal close packed surface structure and narrow pore size, while particles of elliptical and uneven shape created colloidosomes with no surface order and an inconsistent structure. Synthesizing colloidosomes on the submicrometer scale and tailoring the pore shapes and diameters is a crucial step toward their application as a versatile encapsulation and release platform of active agents in the field of life sciences.