Fabrication of graphene nanosheet (GNS)–Fe3O4 hybrids and GNS–Fe3O4/syndiotactic polystyrene composites with high dielectric permittivity

Graphene nanosheet–Fe3O4 (GNS–Fe3O4) hybrids were obtained by a one-step solvothermal reduction of iron (III) acetylacetonate [Fe(acac)3] and graphene oxide (GO) simultaneously, which had several advantages: (1) the Fe3O4 nanoparticles were firmly anchored on GNS surface even after mild ultrasonication; (2) the loading amount of Fe3O4 nanoparticles could be effectively controlled by changing the initial feeding weight ratio of Fe(acac)3 to GO; (3) the Fe3O4 nanoparticles were homogeneously distributed on the GNS surface without much aggregation. Composites based on syndiotactic polystyrene (sPS) and GNS–Fe3O4 were prepared by a solution-blending method and the electric and dielectric properties of the resultant GNS–Fe3O4/sPS composites were investigated. The percolation threshold of GNS–Fe3O4 in the sPS matrix was determined to be 9.41 vol.%. Slightly above the percolation threshold with 9.59 vol.% of GNS–Fe3O4, the GNS–Fe3O4/sPS composite showed a high dielectric permittivity of 123 at 1000 Hz, which was 42 times higher than that of pure sPS. The AC electrical conductivity at 1000 Hz increased from 3.6 × 10−10 S/m for pure sPS to 2.82 × 10−4 S/m for GNS–Fe3O4/sPS composite containing 10.69 vol.% of GNS–Fe3O4, showing an obvious insulator-semiconductor transition.