Large-scale fabrication of novel hierarchical 3D CaMoO4 and SrMoO4 mesocrystals via a microemulsion-mediated route

Molybdates such as CaMoO4 and SrMoO4 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 CaMoO4 and SrMoO4 mesocrystals with high hierarchy and with hollow structure. The "arms" of the flowerlike 3D mesocrystals are radial and are about 2-3 mu m 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 CaMoO4 and SrMoO4 are shown to be in a thermodynamically metastable state, which can be destroyed by further reaction time or temperature change.