Preparation of inorganic nanoparticles in oil-in-water microemulsions: A soft and versatile approach

In this review, the synthesis of inorganic nanoparticles using oil-in-water (O/W) microemulsions as confined reaction media is discussed. Synthesis using (O/W) microemulsions has been demonstrated for a great variety of inorganic nanoparticles: metallic (Pt, Pd, Rh, Ag), single metal oxides (CeO2, ZrO2, TiO2, Fe2O3), mixed and doped metal oxides (Ce0.5Zr0.5O2, Ce0.99Eu0.01O2, Zr0.99Eu0.01O2, and Fe2Mn0.5Zn0.5O4), semiconductors (PbS, CdS, Ag2S, ZnS, CdSe, PbSe, Ag2Se), fluorides (CaF2, YF3, NdF3, PrF3), phosphates (CePO4, HoPO4), and chromates (BaCrO4 and PbCrO4). There are two synthetic strategies: 1) the use of oil-in water (O/W) microemulsions, in which the precursor is an ionic salt which is dissolved in the continuous aqueous phase; and 2) use of O/W microemulsions, in which the precursor is an organometallic salt dissolved in the oil droplets of the microemulsion. The latter approach keeps more resemblance to the typical W/O microemulsion reaction method, as it has the greatest level of precursor confinement.