Microspheres and layered assemblies constructed with ZnO nanosheets have been directly synthesized on a large-area on the surface of zinc substrates by a solvothermal reaction of Zn slices with H2O in ethylene glycol and ethylenediamine, respectively. The products were characterized with X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and photoluminescence spectra. The results showed that the microspheres with the diameters in the range of 0.3～2 µm are constructed from 2-dimensional ZnO nanosheets with the hexagonal structure and the diameters of 30～50 nm via the hydrogen bond; The layered conglomerates are constructed from the self-assembled nanosheets with the size of 450×900 nm of 20～30 nm nanosheets by the hydrogen bond through the Vander Waals band. The role of the ethylene glycol and ethylenediamine in the growth and self-assembly of ZnO nanosheets into Microspheres and layered conglomerates was investigated, and possible mechanisms were also proposed. A strong UV emission with peak at 397 nm and two very weak green emissions with peaks at 485 and 525 nm are observed from the ZnO microspheres and layered conglomerates under excitation at 300 nm. The 397, 485 and 525 emissions are assigned to the free exciton emission from the wide band gap of ZnO, transition between the oxygen vacancy and interstitial oxygen, and recombination of electrons in singly occupied oxygen vacancies with photoexcited holes in the valence band, respectively.

Key words: ZnO, Microspheres, Layered assemblies, Ethylene glycol, Ethylenediamine, Photoluminescence