Figure 1.

Schematic drawing of the fabrication of TiO₂–Fe₂O₃ IOs and their shell composition. (a) Different steps in the fabrication process show (i) self-assembly of PS spheres, (ii) an assembled PS sphere opal template, and (iii) a TiO₂ inverse opal after ALD coating and burn-out of the polymer template. The latter scheme presents cuts through the front row of spheres to visualize the hollow inside and gaps connecting neighboring macropores. (b) The TiO₂ IO structure presented in (i) and (ii) is further modified by ALD functionalization to produce (iii) TiO₂–Fe₂O₃ bilayer IOs and (iv) TiO₂–Fe₂O₃–TiO₂ multilayer IOs.