Fabrication of single crystal molybdate: A new protocol of coupling metal ion interaction and oriented-attachment with assistance of supercritical CO2

The fabrication of single crystals has always been the fundamental to the development of semiconductor, microelectronics, and the related solid-state science. However, synthesis of large-sized single crystals with anisotropic structures for functional materials remains challenging. In this work, we design a novel method to obtain single crystal molybdate nanostructures, in which it combines the metal ions intercalation into α-MoO₃ crystal structure to form molybdate nanocrystals, and subsequently the efficient oriented attachment (OA) of nanocrystals to form single crystalline molybdate nanostructures. Three typical large-size single crystals as CoMoO₄, Fe₂(MoO₄)₃ and ZnMoO₄ have been successfully fabricated. Our study indicates supercritical CO₂ plays a crucial role in the formation process of single crystal molybdate nanostructures no matter for intercalation process or oriented attachment. Further the crystal growth mechanism behind the experiment is explored carefully and stated in detail in this work.