Synthetic SiO2 Opals

SiO2 opals of higher quality can be achieved by a procedure involving the stricter selection of SiO2 spheres. Monodispersity of the spheres is one of the major factors for obtaining opals with interesting optical properties and large size. In addition, the infiltration process of TiO2 into SiO2 opal in order to form inverse opal structures (see Figure) is discussed.