title: Preparation of ZnO colloids by aggregation of the nanocrystal subunits.
abstract: Colloidal ZnO particles with narrow size distribution were prepared via a sol-gel process by base-catalyzed hydrolysis of zinc acetate. The morphology of ordered arrays of the particles was recorded by SEM. SEM also reveals that these uniform particles were composed of tiny ZnO subunits (singlets) sized of several nanometers. The size of the singlets, which is confirmed by X-ray diffraction and UV-vis absorption spectra, increases as the aging time is prolonged. The size-selective formation of colloids by aggregation of nanosized subunits is proposed to consist of two-stage growth by nucleation of nanosized crystalline primary particles and their subsequent aggregation into polycrystalline secondary colloids. The aggregates are all spherical because the internal rearrangement processes are fast enough. The ZnO colloids, i.e., the aggregates, tend to self-assemble into well-ordered hexagonal close-packed structures. Room-temperature photoluminescence was characterized for green and aged ZnO.
authors.affiliation: Key Laboratory of Excited State Processes, Chinese Academy of Sciences, Changchun Institute of Optics, Fine Mechanics and Physics, No. 16 Eastern South-Lake Road, Changchun 130033, People's Republic of China.
authors.forename: L
authors.initials: L
authors.lastname: Dong
authors.forename: Y C
authors.initials: YC
authors.lastname: Liu
authors.forename: Y H
authors.initials: YH
authors.lastname: Tong
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Xiao
authors.forename: J Y
authors.initials: JY
authors.lastname: Zhang
authors.forename: Y M
authors.initials: YM
authors.lastname: Lu
authors.forename: D Z
authors.initials: DZ
authors.lastname: Shen
authors.forename: X W
authors.initials: XW
authors.lastname: Fan