Fe3+-doped SnO2 inverse opal with high structural color saturation

The structural color of inverse opal derived from the interaction between visible light and nanostructure is widely known for the extensive selection of materials, excellent light resistance stability, and environmental friendliness. In contrast to the opal structure, the light scattering in inverse opal is higher and results in milky appearance or even lack of color. In this work, we introduced Fe3+ into the structure of SnO2 inverse opal and successfully obtained an Fe3+-doped SnO2 inverse opal with high color saturation. The direct template method was applied, and the fcc arrangement of template spheres was well kept. Because of the charge transfer transition of Fe3+-O2-, Fe3+ absorbed most of the unwanted scattered light, thereby highlighting the band gap color. Meanwhile, the refractive index of inverse opal increased with the increase in Fe3+ content. It enabled the full spectral coverage in the visible region of the highly saturated structural color only by three particle size templates.