Microemulsion is a solution phase synthesis
Microemulsion is a solution phase synthesis, which has been recently used for preparation of metallic and oxide MNPs with defined size and shape. A microemulsion is a dispersion of two immiscible liquids of an aqueous and oily phase. There are two types of microemulsions; water-in-oil and oil-in-water. The second one, which is the most common one, is known as reverse micelles. In a normal microemulsion synthesis, water microdroplets are formed in a mixture of an oily phase and surfactants. The generated micelles act as micro-reactors, with a certain volume, which can be tuned by varying the ratio between water and surfactant. These microdroplets are surrounded by an interfacial layer of surfactants and contains a certain amount of metal salts acting as a precursor. By adjusting the concentrations of the dispersed phase and surfactant, the size of the droplets can be tuned in the range 1 – 100 nm approximately. The metal salt is subjected to a reduction process and eventually particles are formed inside microdroplets. The availability of the precursor inside micelles determines the particle growth rate.71-72 One of the advantages is that the reactions can be done economically at ambient conditions within a few hours in order to obtain particles with narrow size distribution. However, the adjustment of many parameters renders this method complicated to control. The low yield of this method and the proneness for agglomeration when no additional surfactants are used speak against the use of the microemulsion method.