Fabrication of synthetic opals composed of mesoporous SnO2 spheres with an anodization-assisted double template process

Synthetic opals composed of mesoporous SnO2 spheres were successfully fabricated from anodization of Sn opals, double templated from polystyrene opals. The mesoporous SnO2 spheres were 440 nm in diameter containing mesopores of 20–40 nm. The resultant mesoporous SnO2 opals possessed a high specific surface area of 196 m2/g and a grain size of 12 nm as estimated from XRD patterns. Such a hierarchical structure of SnO2 is a promising candidate for applications in gas sensors, catalysts, and electrode materials since the regularity of the sub-micron opal structure eases transfers of relevant chemical species within the structure while the mesoporosity of the constituent SnO2 spheres offers sufficient functioning surfaces for targeted applications.