Formation Mechanism of Porous Single-Crystal Cr₂O₃ and Co₃O₄ Templated by Mesoporous Silica

Porous single crystals of Cr2O3 and Co3O4 templated by mesoporous silicas, SBA-15 and KIT-6, have been fabricated. Specimens at different stages of crystal growth were characterized by using XRD and high-resolution transmission electron microscopy. The final products of oxide porous single crystals were also characterized by nitrogen adsorption/desorption experiments. A multiseed formation mechanism can eventually be established. The present investigation revealed that the original mesostructures in SBA-15 and KIT-6 were negatively replicated by the crystals of oxides, and therefore, the dimension of the building blocks (nanorods or nanowires) in the porous crystals of oxides depends on the pore diameter of the silica. It was also found that a mesopore system, regarded as a nanoreactor, had a significant influence on the size and morphology of produced oxide particles and on the route and temperature of the crystallization.