Organic additive-free synthesis of mesocrystalline hematite nanoplates via two-dimensional oriented attachment

Uniform mesocrystalline hematite nanoplates were readily synthesized through controlled hydrolysis of ferric acetylacetonate (Fe(acac)₃) in ethanol without organic additives. The obtained disc-like hematite mesocrystals consisted of primary nanoparticles and exhibited a single-crystal-like structure with top faces of the (001) plane. It was revealed that the (001)-oriented mesocrystalline nanoplates were formed by two-dimensional (2D) oriented attachment of tiny hematite nanocrystals stabilized by acetate converted from acetylacetonate, which was accompanied by crystallographic fusion. The presence of an appropriate amount of water was essential to the formation of the mesocrystalline hematite nanoplates. The produced disc-like hematite mesocrystals showed considerable magnetism owing to the mesocrystalline structure. Moreover, the mesocrystalline hematite nanoplates exhibited good visible-light photocatalytic activity toward degradation of rhodamine B because of the high surface area.