(397be) Hierarchical FeOx@SiO2-ZnO Koosh Ball Nanostructure With Tunable Magnetic Core, Fluorescent Nanowire Shell and Enhanced Photocatalytic Property

A mild, wet chemical strategy has been developed to synthesize three-dimensional (3D) multicomponent koosh ball nanoarchitectures comprised of tunable magnetic iron oxide core and 3D fluorescent ZnO nanowire shell, which demonstrates enhanced photocatalytic property towards dye degradation under UV irradiation. The synthesis involves a hydrothermal preparation of magnetite particles followed by the coating of an amorphous silica layer using Stober sol-gel process. ZnO nanowires are successfully assembled on the seed mediated surface by low temperature solution synthesis. The phase transition of magnetic iron oxide core and the native defects induced fluorescence of the nanowire shell can be simultaneously manipulated by post-hydrogen annealing to produce various koosh balls with retained morphology in Figure 3 but with different magnetic and photocatalytic properties. Specifically, ambient annealing at 350 °C will lead to the formation of nano koosh balls with maghemite cores, while 600 °C ambient annealing will produce koosh balls with hematite cores. The 5% hydrogen treatment at 400 C transforms maghemite cores into bcc-iron and the 1% hydrogen treatment at the same temperature can make hematite into magnetite. During the hydrogen annealing, the surface defect of ZnO nanowires can be tuned. The photoluminescence in the visible light region is quenched . The reduced population of surface defects contributes to the worse photocatalytic performance of Rhodamine B degradation. This unique koosh ball architecture initiates the three-dimensional nanowire growth on micro-scale spherical substrate and enables the rational combination of multiple desired functionalities originated from dissimilar constituents. The obtained nano koosh ball will open up new opportunities towards environmental application of nanomaterials such as photocatalytic water treatment.

Reference

[1] Z. Ren, Y. Guo, G. Wrobel, D. A. Knecht, Z. Zhang, H. Gao and P. X. Gao,  J. Mater. Chem., 2012, 22, 6862-6868.