Hydrophobic graphene nanosheets decorated by monodispersed superparamagnetic Fe3O4 nanocrystals as synergistic electromagnetic wave absorbers

The comprehension of the interactions between the building blocks in hybrids can give us an insight into the design and application of highly efficient electromagnetic wave absorption materials. Herein, we report a facile in situ thermal decomposition route for the fabrication of superparamagnetic Fe3O4 nanocrystals anchored on hydrophobic graphene nanosheets as synergistic electromagnetic wave absorbers. The microstructures and interactions of the Fe3O4-graphene hybrids are systematically investigated, and the results suggest that the Fe3O4 nanocrystals are uniformly decorated and chemically bonded on the surface of graphene nanosheets without obvious conglomeration or large vacancies. The Fe3O4-graphene hybrids show hydrophobic and superparamagnetic characteristics. Combing the benefits of superparamagnetic Fe3O4 nanocrystals and electrically conducting graphene, the Fe3O4-graphene hybrids show a maximum reflection loss (RL) of -40 dB at 6.8 GHz with a matching thickness of 4.5 mm, and the effective absorption bandwidth (RL < -10 dB) is 4.6-18 GHz with an absorber thickness of only 2-5 mm. However, due to the lack of dielectric loss, only a weak RL of -5 dB is obtained in bare Fe3O4 nanocrystals. The remarkably enhanced electromagnetic wave absorption properties of the Fe3O4-graphene hybrids are owing to effective impedance matching and synergistic interaction. Moreover, compared with other reported graphene-based electromagnetic wave absorption materials, the hydrophobic Fe3O4-graphene hybrids prepared in this work are considered to be more stable and suitable to be applied in some particular environmental conditions, such as rain.