Electrophoretic deposition to control artificial opal growth

In this work we propose and demonstrate a solution to the problems which ar ise when SiO2 monodisperse nanospheres of diameters under 300 nm or over 55 0 nm are used to obtain opal-based photonic crystals. If the nanospheres ar e too small, the sedimentation rate is very slow or even may not occur; if they are large enough, no significant order can be achieved because the vel ocity is too high. This method, based on the electrophoretic phenomenon, al lows us to control the sedimentation velocity. Furthermore, other species o f importance in this field, such as SiO2 spheres covered with a thick layer of TiO2, do profit from this method.