Novel cone-like ZnO mesocrystals with co-exposed (10
1) and (000
) facets and enhanced photocatalytic activity†
Abstract
Unusual designated-tailoring on the preferential growth of ZnO meso-/nanocrystals with different shapes and sizes was successfully achieved through a very facile precursor-hydrolysis process in a water/organic solvent system. The shape-evolution of ZnO from mesocrystal to nanocrystal was achieved by increasing the amount of water in the reaction system under otherwise the same conditions, which can be attributed to selective-capping and preferential growth mechanisms based on DFT calculations. Typically, nanoparticle-aggregated cone-like ZnO mesocrystals enclosed by curved (101) and flat (000
) surfaces were prepared in a lower amount of water, while various ZnO crystals without curved (10
1) surfaces were synthesized in a higher amount of water. In particular, “surface heterojunctions” were constructed in cone-like ZnO mesocrystals with co-exposed curved (10
1) and flat (000
) surfaces, and these displayed greater photocatalytic degradation of methyl orange dye compared to the ZnO nanocrystals. This investigation is of great significance to the synthesis of additive-free ZnO mesocrystals, and offers a good opportunity to understand the formation mechanism and fundamental significance of the preferential growth of ZnO mesocrystals. Importantly, it is believed that the water-induced synthetic strategy reported here could provide a promising way to design more and more metal oxide architectures with controllable morphologies.