Fig. 13. The schematic illustration of four different steps for bulk nanobubbles creation through microvortices and graphene oxide sheets. In the first step (nucleation step), gas supersaturation nucleation caused by two miscible solvents with different gas solubility forms nanobubbles on a graphene sheet (growth step). Warm water and cold nitrogen saturated NaCl are the mentioned solvents. In the growth step, nanobubbles on the surface of the graphene sheet grow until reaching their critical size and detach from the surface (detachment step) and form bulk nanobubbles inside the solution (bulk and surface nanobubbles step).¹²⁹.