One-step solution synthesis of urchin-like ZnO superstructures from ZnO rods

The urchin-like ZnO superstructures have been directly prepared by the assistance of poly (acrylic acid) (PAA, M_w 5000) under a one-step solution-based process. X-ray diffraction (XRD) patterns indicate that the crystal structure of the special ZnO urchins is hexagonal. The results of Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) tests show that the urchins are composed of rods and the average aspect ratio of them is about 10 with a length of about 1.5 μm. Selected area electron diffraction (SAED) pattern reveals that the rods are single crystal in nature, which preferentially grow up along the 〈0001〉 direction. Furthermore, the sizes and aspect ratios of the rods can be easily controlled by regulating the concentration of ZnSO₄ solution. It is believed that the process of crystallization, including nucleation and crystal growth, happens along PAA chains resulting in the production of rods and assembly of them into superstructures.