A smooth TiO2 hollow-spheres array, a kind of inverse opals, was prepared in a wide area (>1 × 5 cm) in a short time (less than 1 min excluding sintering) using a spin-coating technique. A two-dimensional colloidal crystal was used as a template. The TiO2 sintering process, especially the rate of the temperature increase, was important to copy the periodicity of the colloidal crystal structure. The electron diffraction image taken by the transmission electron microscopy observation showed that the hollow-spheres arrays have anatase-type crystal structure.
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