Large-Scale Fabrication of Novel Hierarchical 3D CaMoO₄ and SrMoO₄ Mesocrystals via a Microemulsion-Mediated Route

Molybdates such as CaMoO 4 and SrMoO 4 have received much attention recently because of their interesting luminescence and structural properties. Herein, we report a microemulsion-mediated method as a novel technique to synthesize CaMoO 4 and SrMoO 4 mesocrystals with high hierarchy and with hollow structure. The “arms” of the flowerlike 3D mesocrystals are radial and are about 2−3 μm in length. They are constructed from nanoparticles with regular morphology and a size of about 150−300 nm. Study on the formation mechanism of the superstructures reveals that the oriented aggregation mechanism is responsible for the self-assembly. The mesocrystals of CaMoO 4 and SrMoO 4 are shown to be in a thermodynamically metastable state, which can be destroyed by further reaction time or temperature change.