ZnO纳米片组装的微球和层状集聚体的控制合成及其发光性质

通过锌片与水分别在乙二醇和乙二胺中120 ℃反应12 h，直接在锌片上原位合成出ZnO纳米片组装的微球和层状集聚体。利用X射线粉末衍射、扫描电子显微镜、透射电子显微镜和红外光谱对产物进行了表征和分析。结果表明，在乙二醇中得到的直径为0.3～2 µmZnO微球是由直径为30～50 nm纤锌矿结构的ZnO纳米片通过氢键组装而成；在乙二胺中得到的层状集聚体是由20～30 nm的纤锌矿结构的ZnO纳米片通过氢键组装成尺寸约为450×900 nm纳米片，这些较大尺寸纳米片再通过范德华力组装而成。研究了乙二醇和乙二胺在ZnO微球和层状集聚体形成过程中的作用并提出了可能的生长机理。在波长为300 nm光的激发下，发现ZnO微球和层状集聚体具有发光峰位于397 nm强的紫外光发光、485和520 nm弱的蓝绿光发光，它们分别起源于ZnO宽带隙的激子发射，氧空位与间隙氧之间的跃迁以及表面上离子化氧空位中的电子与价带中光激发的空穴之间的复合。

Controlled Synthesis and Photoluminescence of ZnO Nanosheet-based Microspheres and Layered assemblies

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.