Synthesis of hollow ZnO microspheres by an integrated autoclave and pyrolysis process

Hollow zinc oxide microspheres have been synthesized from a micro ZnBr(2)(.)2H(2)O precursor obtained by an autoclave process in bromoform steam at 220 degrees C/2.5 MPa. Field-emission scanning electron microscropy (FE-SEM) and transmission electron microscopy (TEM) show that the products are about 1.0 mu m single crystal spherical particles with hollow interiors, partly open surfaces and walls self-assembled by ZnO nanoparticles. X-ray diffraction (XRD) analysis shows that the as-prepared ZnO hollow spheres are of a hexagonal phase structure. A possible formation mechanism is suggested on the basis of the shape evolution of ZnO nanostructures observed by SEM and TEM. The room-temperature photoluminescence (PL) spectrum shows UV emission around 386 nm and weak green emission peaks indicating that there are few defects in the single crystal grains of the ZnO microspheres.