. Synthesis of GO membranes on PDA-modified α-Al2O3 disks
The GO slurry with different amount (0.02–2.0 g) was dissolved
in 50 ml deionized water to prepare GO suspension with different
concentrations (0.01–1.0 mg/mL). The resulting GO suspension
was treated ultrasonically several hours to exfoliate all GO to form
GO nanosheets. Afterwards, 2 mL as-prepared GO suspension was
added on the top surface of the PDA-modified α-Al2O3 disks which
were mounted in a home-made model (Fig. S4). After 30 min
vacuum filtration, GO membranes with different thicknesses were
obtained, and then the GO membranes were dried in an oven at
100 °C over night.