GO solution is purchased from NiSiNa Materials Japan Co. The concentration of the obtained original GO suspension was 15 mg/mL, and then the original suspension was further diluted to 1 mg/mL stock concentration with de-ionized (DI) water. The fabrication of GOM was carried out with vacuum filtration. In a typical process, 2 mL of GO stock suspension (1 mg/mL) was added into a beaker and added DI water to 50 mL, then the diluted suspension was ultrasonicated for 10 min under ambient conditions. The obtained suspension was added into the vacuum filtration setup with a PVDF substrate (0.2 μm pore size, 47 mm diameter) and a pressure of about 0.9 bar.