An air–water interface polymerization method is developed to fabricate polypyrrole inverse opals without overlayers. Colloidal crystals are transferred to the surface of a pyrrole solution, and addition of oxidizer leads to the polymerization of pyrrole on the surface of the colloidal crystals. Since the part of the colloidal crystal protruding from the solution surface are not coated during the polymerization, inverse opals with microbowl arrays at the top could be obtained after removal of the template. The synthesis of an inverse opal multilayer with this approach is also demonstrated. Additionally, polypyrrole inverse opals doped with various acids are used as counter electrodes for dye‐sensitized solar cells, the photoelectric conversion efficiencies of which could approach those achieved with a Pt electrode.

Fabrication of anisotropic particles simply by assembly of swollen spheres on a water surface and evaporation of the swelling agent.