α-Calcium Sulfate Hemihydrate Nanorods Synthesis: A Method for Nanoparticle Preparation by Mesocrystallization.

The past decades have witnessed great advances in nanotechnology since tremendous efforts have been devoted for the design, synthesis, and application of nanoparticles. However, for most mineral materials such as calcium sulfate, it is still a challenge to prepare their nanoparticles, especially with uniform size and high monodispersity. In this work, we report a route to regulate the morphology and structure of α-calcium sulfate hemihydrate (α-HH) and successfully synthesize and stabilize its mesocrystals for the first time. The ellipsoidal mesocrystals in length of 300-500 nm are composed by α-HH nanoparticles arranged in the same crystallographic fashion and interspaced with EDTA. The time-dependent experiments indicate the α-HH aggregates evolve from irregular structure to mesocrystal structure with the subsequent growth of subunits and then partially fuse into single crystals. Disorganizing the mesocrystal structure before the emergence of fusion reaps α-HH nanorods in a length of 30-80 nm and a width of 10-20 nm with high monodispersion. This ingenious concept paves an alternative way for nanoparticle preparation and is readily extended to other inorganic systems.