Single-step synthesis of core-shell ZnO microspheres

ZnO core-shell microspheres were successfully synthesised on a large scale through a template-free solvothermal reaction of methanol and zinc acetylacetonate hydrate. Morphologies, microstructures and compositions of the products were investigated by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. The obtained results indicate that the ZnO microspheres are core-shell structures with an average diameter of 1 mm and an average shell thickness of 200 nm. The experimental parameters such as reaction time and solvents played important roles in the formation of the core-shell structures. A possible growth mechanism was proposed. Room temperature photoluminescence spectrum showed an UV emission at similar to 385 nm and a broad green emission at the centre of 550 nm.