Template-free facile solution synthesis and optical properties of ZnO mesocrystals

There have been many examples in preparing complex inorganic materials through biomimetic mineralization, however, it remains a challenge for materials scientists to synthesize highly ordered superstructures with controlled shape and size in the absence of templates. Here, novel ZnO mesocrystal microspheres have been prepared on a large scale by a facile solution-based method without the addition of templates. The mesocrystal forms via a nonclassical crystallization pathway involving an oriented aggregation of nanoplatelet building blocks. The intrinsic dipole interactions between the individual hexagonal nanoplatelets act as the driving force. Because there are not any template additives in the reaction system, the organic solvent of butanol may play an important role in the growth of the crystals and result in the final spherical mesocrystal morphology. Interestingly, the as-synthesized ZnO mesocrystals exhibit strong yellow emission centred at 560 nm and the yellow emission can be clearly visualized under a portable UV light.