Formation mechanism of hollow microspheres consisting of ZnO nanosheetsElectronic supplementary information (ESI) available. See DOI: 10.1039/c2ce26354h

• Main Authors: Fang, Yanjun, Xia, Zhenbo, Yu, Fengjiao, Sha, Jian, Wang, Yewu, Zhou, Wuzong
• Format: Article
• Language: English
• ISSN: 1466-8033
• DOI: 10.1039/c2ce26354h

Hydrangea-like hollow microspherical ZnO has been synthesized via a transformation from layered basic zinc acetate (LBZA) and characterized using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Investigation of the early stages of the crystal growth revealed a non-classic growth mechanism. With increasing reaction time, (1) amorphous spherical aggregates formed initially, followed by (2) surface multiple nucleation, (3) crystallization into LBZA nanosheets which are vertical to the microspheres' surface, (4) surface condensation leading to the formation of hollow microspheres, (5) extension of the crystallization both inwards and outwards, and (6) transformation to zinc oxide during annealing in air. The detailed formation mechanism of the hydrangea-like microspheres, consisting of thin (∼5.4 nm) LBZA nanosheets, is proposed. The hydrangea-like ZnO exhibited superior photocatalytic performance in dye degradation due to its unique construction and high specific surface area. This work may shed light on crystal engineering of porous microspheres, hollow crystals and thin nanosheets of other materials. We investigated the early-stage crystal growth of hydrangea-like ZnO microspheres, which revealed a non-classic "reversed" growth mechanism.