Graphene oxide and Fumed silica graphene oxide nanocomposites modification by thermal treatments

In the present study we investigate post synthesis thermal treatments up to 400 °C of graphene oxide (GrO) prepared from commercial graphite and of GrO-silica nanocomposites prepared by a solution of commercial Fumed silica nanoparticles (average diameter 7 nm or 40 nm) and the GrO. The thermal treatments were carried out in air, vacuum or He atmosphere to highlight tunable changes. Two GrO batches with small differences in the D (∼1350 cm^-1) and G (∼1580 cm^-1) Raman bands have been employed to evaluate effects depending on preparation. Thermal effects have been monitored through the Raman spectroscopy focusing on D, G and 2D (2500-3500 cm^-1) bands spectral ranges. The experiments evidenced that the I(D)/I(G) amplitude ratio and the 2D region profile change during thermal treatments in the range below 180 °C with maximum rate at ∼120 °C. At higher temperature, with maximum efficiency at about 200 °C, only the D and G bands show modifications with a tendency to decrease I(D)/I(G) and reduce the G band width. The comparison among GrO batches and nanocomposite evidences that the thermal history during preparation and defective structures of GrO are key factors for the final material.