Formation of Organic Nanoparticles by Freeze-Drying and Their Controlled Release

The utilization of water-insoluble active species in aqueous systems is of very broad relevance in areas such as pharmaceuticals, agrochemicals, coatings, and pigments. The preparation of organic nanoparticles from such actives provides a potential strategy via the easy dispersion of the nanoparticles in water to produce water-based formulations. Here, oil-in-water emulsions with the organic compound dissolved in the oil droplet phase and hydrophilic polymer dissolved in the continuous aqueous phase are employed to produce organic nanoparticles directly in the porous materials via a freeze-drying process. The size of the organic nanoparticles is around 80 nm measured by dynamic laser scattering. The organic nanoparticles can be released into water to form stable aqueous nanoparticle dispersion simply by dissolving in water. The release of the nanoparticles into an organic solvent is also investigated. By changing the volume ratio of oil to water phase in an emulsion, pore volume and interconnectivity of the porous materials can be adjusted. The effect of porous structure on the release of nanoparticles is also investigated.