Aerosol-assisted self-assembly of mesostructured spherical nanoparticles

Particles possessing nanometre-scale pores of well-defined size and connectivity are of interest for catalysis, chromatography and controlled release of drugs, and as fillers with low dielectric constant, pigments and hosts for optically active compounds(1,2). Silica containing ordered mesopores (of nanometre-scale width) can be prepared by templating of surfactant(3,4) and block copolymer(5) liquid-crystalline mesophases, and interfacial phenomena have been used to control the macroscopic form of these materials, providing mesoporous particles(1,6), fibres(7,8) and films(9,10) A variety of spherical or nearly spherical particles has been reported(1,6,7,11-13), but the degree of ordering and the range of the porous mesostructures have been limited. Here we report a rapid, aerosol-based(14-16) process for synthesizing solid, well-ordered spherical particles with stable pore mesostructures of hexagonal and cubic topology, as well as layered (vesicular) structures. Our method relies on evaporation-induced interfacial self-assembly(17) confined to spherical aerosol droplets. This simple, generalizable process can be modified for the formation of ordered meso-structured thin films.