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 x 10(-1) S/m for pure sPS to 2.82 x 10(-4) S/m for GNS-Fe3O4/sPS composite containing 10.69 vol.% of GNS-Fe3O4, showing an obvious insulator-semiconductor transition. (C) 2013 Elsevier Ltd. All rights reserved.