Background This study aims at proposing a facile method to prepare rGO/Fe3O4 composite film with adjusted magnetic properties and electronic conductivity. Methods Colloidal solution of graphene oxide (GO)/Fe3O4 nanoparticles (F-NPs) with a size in the range of 20-80 nm were prepared by a solution-blending method and heated step-by-step from room temperature to 60°C, 120°C and 160°C for 12 hours, respectively, to obtain a reduced graphene oxide (rGO)/F-NP composite film. The structure, morphology, components, magnetic properties and electrical conductivity of the composite films were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, superconducting quantum interference devices and 4-probe instrument. Results The results indicated that the F-NPs were uniformly distributed on the graphene film, and the composite exhibited good ferromagnetic properties and conductivity, which could be adjusted easily via different loadings of F-NPs. A high content of F-NPs (200 mg) led to a strong saturation magnetization of 63.6 emu·g−1, with a coercivity of about 104.9 oersted (Oe). Whereas a high conductivity of 6.5 S·m−1was obtained at low amounts of F-NPs (40 mg). Notably, rGO/Fe3O4 composite film fabricated by this simple method is widely used in various fields including magnetoelectronics, electrochemical energy conversion and storage, and magnetic nanodevices and others. Conclusions A graphene-based film deposited by Fe3O4 nanoparticles with controllable loadings has been fabricated by a step-by-step heating treatment of GO/Fe3O4 colloidal solution.

Abstract.Carbon-based lightweight, thin, and self-standing composite film/paper could be a promising material for electromagnetic shielding applications because of their high flexibility, good electromagnetic properties, and high electrical conductivity. In this paper, a new-type composite of reduced graphene oxide (rGO) and Fe 3 O 4 nanoparticles (F-NPs) has been investigated for potential applications in electromagnetic microwave absorbing film. The results indicated that with increasing the loading of F-NPs in the films, the values of saturation magnetization increased, contributing to an enhanced permeability of rGO/F-NPs composite films, while the dielectric loss decreased corresponding to a low conductivity. A maximum reflection loss of -11.04 dB was obtained at 5.19 GHz for the composite with 100 mg graphene oxide and 200 mg F-NPs with a matching thickness of 3.0 mm, and the effective absorption bandwidth with reflection loss values less than -10 dB covered 2.8-8.6 GHz.