Surface Decoration and Dispersibility of Graphene Nanoplatelets in Aqueous Surfactant Solution

Preparing highly homogeneous and stable aqueous graphene nanoplatelets (GNPs) suspension plays a significant role in practical applications. To achieve good dispersion for the GNPs, a method utilizing ultrasonic processing and dispersants was employed. In this study, four dispersants, including gum arabic (GA), polyvinylpyrrolidone (PVP), polyoxyethylene (40) nonylphenylether (Igepal, CO890) and cetyltrimethyl ammonium bromide (CTAB), were used individually and in combination at given concentrations for dispersing the GNPs in aqueous solution. The dispersing performance for GNPs suspension was characterized by standing test and UV-vis absorbance. The maximum achievable dispersing status for GNPs in aqueous solution was demonstrated by optical microscope and transmission electron microscopy (TEM) from both macro and micro aspects. Some experimental results demonstrated that the best dispersion was achieved with CTAB addition of 0.3 g/L, meaning that the optimum concentration ratio of GNPs to CTAB was 1:3. In addition, the dispersing mechanism was also assessed using Fourier transform Infrared (FTIR) spectroscopy. The CTAB molecules were adsorbed on the surface of GNPs, which prevented aggregation of GNPs by electrostatic repulsion.