A new insight for the self-assembly of graphene oxide by hydrothermal method

3D self-assembly or gelation of graphene oxide (GO) by hydrothermal method was interpreted as π-π stacking or hydrophobic interaction between reduced graphene oxide (rGO) sheets, however, it ignored the colloidal metastability of GO, and cannot interpret the gelation of GO at low concentrations and pH. Herein, except for π-π stacking or hydrophobic interaction, colloidal metastability of GO was considered for GO gelation. Based on the results of GO gelation at different concentrations and pH (or other positive ions), a hydrothermal sol-gel transition phase diagram of GO was proposed, which was divided into three parts including gel, sol-gel and sol regions, assisted by the diagram, the different gelation concentrations of GO from different labs can be interpreted. Furthermore, the hydrothermal gelation of GO was described as a percolation process and consisted with the site-bond percolation model, which ascribed for the psite and pbond respectively, psite was attributed to the GO concentration and pbond was to the pH or other counter ions. Our works provide a more comprehensive understanding on the gelation behavior of GO colloids. [Display omitted] •Colloidal metastability of GO was considered for GO gelation.•A hydrothermal sol-gel transition phase diagram of GO was proposed.•Gel, sol-gel and sol regions were proposed in the phase diagram.•A site-bond percolation model was proposed for the sol-gel transition of GO.