The artificial colloidal crystal with the three-dimensional periodic structure was prepared through the self-assembly of silica microspheres in the cell. Silver is assembled into the voids of the colloidal crystal by an electrochemical reduction of Ag<sup>+</sup> in aqueous solution. The position of the stop band could be tuned by controlling the ratio of Ag/silica.
The colorful artificial 3D silica colloidal crystals (opal) were prepared through self-assembly of silica spheres in the visible frequency range. We directly synthesized nano silver particles in the void of the silica artificial opal film using the photolysis of silver nitrate under UV light, nano silver particles were self-deposited around the surface of silica sphere. The shifts of the stop band of the artificial crystals after exposing different time under UV light were studied. Synthetic silica opal with three-dimensional (3D) structure is potentially useful for the development of diffractive optical devices, micro mechanical systems, and sensory elements because photonic band gaps obtained from self-assembled closely packed periodic structures.