Extended Data Fig. 2: Optical images of the graphene film after in situ sputtering.
From: Cascaded compression of size distribution of nanopores in monolayer graphene
a, Optical image of the as-prepared nanoporous graphene on copper substrate. b, Optical image of the sample after being immersed in 80 °C water for 5 min. The contrast shows the wet-oxidation of different copper domains by water54, suggesting the presence of nanopores in the graphene film. c, Optical image of the sample after being oxidized in 150 °C ambient air for 2 min. The colour change indicates Cu oxidation owing to nanopores in graphene film. The arrow indicates a bilayer island that is not oxygen-permeable. Scale bars, 100 μm. d, Optical image of the whole sample after oxidation, in which only the indicated region was overlapped with the graphite electrode and sputtered.
