Preparation and Application of Nanoemulsions in the Last Decade (2000-2010)

An emulsion is a system containing two immiscible phases: a dispersed phase and a continuous phase. Components needed to prepare an emulsion are oil, water, surfactant, and energy. The nature of surfactant determines the type of emulsion (oil-in-water (O/W) or water-in-oil (W/O)). A nanoemulsion is an emulsion with 20200 nm droplet size. The required energy to form a nanoemulsion can be obtained from a mechanical device (high-energy emulsification) or from the chemical potential of the components (low-energy emulsification). High-energy emulsification consists of high-pressure homogenization (HPH), ultrasonication, and microfluidization and low-energy emulsification consists of phase inversion temperature (PIT), phase inversion composition (PIC), and solvent diffusion. O/W nanoemulsions have been studied more than W/O nanoemulsions and the preparation of nanoemulsions with high-energy emulsification is more reported than low-energy emulsification. The small droplet size of a nanoemulsion enhances the emulsion stability; therefore, nanoemulsions have various applications in the industrial field, such as personal care and cosmetics as well as health care, food, and agrochemicals. Pharmacy and cosmetics are fields where more direct applications of nanoemulsions are proposed.