▎ 摘　　要

Although the dispersion of graphene oxide in solution has been well studied, there still exists mysteries. Here the graphene oxide was synthesized by the modified Hummers method. By the circle acid-base titration, we reported a bistable and pH hysteretic behavior of the graphene oxide in aqueous solution. To interpret the phenomena, a varying pK(a) mechanism based on the self-assembly of graphene oxide sheets in the circle titration is proposed.