Building Hematite Nanostructures by Oriented Attachment

摘要

Oriented attachment (OA) is one of the important mechanisms that govern the crystal growth in the nanoscale regime. Unlike the classic kinetics of Ostwald ripening, which is widely used to explain the formation of complex nanostructure such as hollow nanomaterials, the essence of OA is that small nanocrystals with common crystallographic orientation aggregate and form larger ones. The attachment of these primary nanoparticles are irreversible and occurs in a highly oriented manner, leading to the elimination of the interfaces of the joint crystals and the formation of chemical bonds after the removal of the solvent and/or adsorbed molecules at these interfaces. Thus, the reduction of the surface energy and the increase in entropy serve as the driving force for the OA growth process.