Synthesis of complex nanomaterials via Ostwald ripening

In recent years, nanostructured materials with interior cavities and surface porosity have received extensive interest in the materials research community, owing to their many important applications in emerging technologies. Among many synthetic strategies, Ostwald ripening has become a direct matter-relocation approach to create interior spaces for this class of new functional materials. In this short article, we review the general processes of Ostwald ripening in various types of crystalline and noncrystalline materials, as well as stoichiometric and nonstoichiometric solid precursors. Because Ostwald ripening can be operated in a solution environment, this approach provides a simple hollowing means to prepare complex nanostructured materials, such as core-shell, yolk-shell, and multi-shelled solids, when coupled with additional chemical reactions in synthesis. Furthermore, it is possible to perform multiple rounds of Ostwald ripening when fresh solid precursors are deposited into the internal void space or onto the external surface of pre-existing intermediate hollow structures. In addition to the structural and geometrical architectures, compositional tailoring can also be achieved by preparing the solid precursors into multicomponent composites and/or by post-ripening modification and functionalisation. Future research directions and possible improvements of this approach are also addressed.