Rapid room-temperature synthesis of nanosheet-assembled ZnO mesocrystals with excellent photocatalytic activityElectronic supplementary information (ESI) available: Extra morphological and structural data. See DOI: 10.1039/c2ce26660a

• Main Authors: Wang, Mingsong, Zhang, Yiping, Zhou, Yajun, Yang, Fengwu, Kim, Eui Jung, Hahn, Sung Hong, Seong, Seung Gie
• Format: Article
• Language: English
• ISSN: 1466-8033
• DOI: 10.1039/c2ce26660a

We have investigated the growth of ZnO in a simple alkaline solution by chemical precipitation. ZnO nano(micro)structures with well-defined morphologies have been realized by tuning the Zn 2+  : OH − ratio and the amount of the complexing agent NH 4 F. Importantly, we have demonstrated a fast spontaneous room-temperature formation of ZnO mesocrystals constructed with nanosheet subunits. The growth of ZnO involves the phase transformation from two intermediate compounds ZnF(OH) and Zn(OH) 2 . The nanosheets are observed to be ZnO (101&cmb.macr;0) facets from the side- and top-view high-resolution TEM measurements. By comparing the arrangement of the (101&cmb.macr;0) nanosheets in the mesocrystal with the organization of the {101&cmb.macr;0} planes in the wurtzite crystal structure of ZnO, we identify for the first time the assembly of 2D nanosheets into 3D architectures by epitaxy. This unique self-assembly by epitaxy effectively separates the nanosheets in an ordered manner, producing a robust, geometrically ideal photocatalyst that is easily separable and recyclable. Being constructed of reactive (101&cmb.macr;0) facets, the microstructured ZnO exhibits much higher photocatalytic efficiency than its nanoparticle counterpart. The defective nature of the (101&cmb.macr;0) facets confirmed by the photoluminescence study explains the visible photocatalysis of the nanosheet assemblies. Simple chemical precipitation produces complex ZnO mesocrystals. Being assembled with {101&cmb.macr;0} facets, the mesocrystals exhibit excellent photocatalytic activity.