Hierarchic Nanostructure for Auto-Modulation of Material Release: Mesoporous Nanocompartment Films

The preparation of mesoporous nanocompartment films composed of both hollow silica capsules and silica particles by using layer-by-layer (LbL) adsorption is described. The resultant nanocompartment films exhibit stepwise release, of encapsulated water molecules without application of external stimuli. The hollow hierarchic pore structure of the silica capsules, including their internal void and mesoporous walls, is a key factor for the regulation and stepwise release of water, and is probably caused by the non- equilibrated concurrent evaporation of material from the mesopore and capillary penetration into the mesopores. The number of release steps and rate of release can be tuned by variation of several parameters including water content, ambient temperature, layer multiplicity, and co-adduct particle size. Application of the mesoporous nanocompartment films for the release of substances, including therapeutic agents and fragrances, indicates that the stepwise material release can be applied for a wide range of liquid substances. The films should lead to a novel-material release system useful even for biomedical applications capable of controlled and sustained delivery of drug molecules.