Three-dimensional SiO2@Fe3O4 core/shell nanorod array/graphene architecture: synthesis and electromagnetic absorption properties

We developed a new strategy, i.e., a seed-assisted method, to fabricate a three-dimensional (3D) SiO₂@Fe₃O₄ core/shell nanorod array/graphene architecture. The fabrication processes involved deposition of β-FeOOH seeds on the graphene surfaces in the ferric nitrate aqueous solution, subsequent growth of β-FeOOH nanorod arrays on the graphene surfaces in the ferric chloride aqueous solution under hydrothermal conditions, deposition of SiO₂ coating on the surfaces of β-FeOOH nanorods, and final formation of the 3D architecture by a thermal treatment process. Scanning electron microscopy and transmission electron microscopy measurements showed that the SiO₂@Fe₃O₄ core/shell nanorods with a length and diameter of about 60 and 25 nm, respectively, were almost grown perpendicularly on both side surfaces of graphene sheets. The measured electromagnetic parameters showed that the 3D architecture exhibited excellent electromagnetic wave absorption properties, i.e., more than 99% of electromagnetic wave energy could be attenuated by the 3D architecture with an addition amount of only 20 wt% in the paraffin matrix. In addition, the growth mechanism of the 3D architecture was proposed, and thus, the strategy presented here could be used as a typical method to synthesize other 3D magnetic graphene nanostructures for extending their application areas.We developed a new strategy, i.e., a seed-assisted method, to fabricate a three-dimensional (3D) SiO₂@Fe₃O₄ core/shell nanorod array/graphene architecture. The fabrication processes involved deposition of β-FeOOH seeds on the graphene surfaces in the ferric nitrate aqueous solution, subsequent growth of β-FeOOH nanorod arrays on the graphene surfaces in the ferric chloride aqueous solution under hydrothermal conditions, deposition of SiO₂ coating on the surfaces of β-FeOOH nanorods, and final formation of the 3D architecture by a thermal treatment process. Scanning electron microscopy and transmission electron microscopy measurements showed that the SiO₂@Fe₃O₄ core/shell nanorods with a length and diameter of about 60 and 25 nm, respectively, were almost grown perpendicularly on both side surfaces of graphene sheets. The measured electromagnetic parameters showed that the 3D architecture exhibited excellent electromagnetic wave absorption properties, i.e., more than 99% of electromagnetic wave energy could be attenuated by the 3D architecture with an addition amount of only 20 wt% in the paraffin matrix. In addition, the growth mechanism of the 3D architecture was proposed, and thus, the strategy presented here could be used as a typical method to synthesize other 3D magnetic graphene nanostructures for extending their application areas.

Electronic supplementary information (ESI) available: The detailed synthesis process, structural characterization, and electromagnetic measurements for the 3D SiO₂@Fe₃O₄ core/shell nanorod array/G architecture. HAAD-STEM and EDX analyses for 3D SiO₂@β-FeOOH core/shell nanorod array/G and SiO₂@Fe₃O₄ core/shell nanorod array/G architectures, XPS and SEM image of XRD patterns of 3D SiO₂@Fe₃O₄ core/shell nanorod array/G architecture, SEM images of the product obtained without SiO₂ coating, the reflection losses of the pure Fe₃O₄ nanorods and the tangent losses of the 3D architecture and the pure Fe₃O₄ nanorods, and the reflection losses of 3D architecture with low loading amounts of Fe₃O₄. See DOI: 10.1039/c3nr04058e