Ultra-low-damage radical treatment for the highly controllable oxidation of large-scale graphene sheets

We have used low-damage oxygen radical treatment (O-LDRT) - with chemically reactive radicals generated in a plasma system equipped with a complementary filter - to prepare large-scale graphene oxide sheets with highly controllable levels of oxidation. Raman spectroscopy and X-ray photoelectron spectroscopy revealed that oxidative functionalities were formed on the graphene surfaces in a highly controllable manner and with a wide process window. Contact angle measurements revealed the high hydrophilicity of the large-scale graphene after O-LDRT. We measured the current-voltage characteristics of oxidized double-layer graphene (DLG) sheets to confirm the low degree of damage after using O-LDRT for the oxidation process. For treatment times of up to 5 min, the current passing through the DLG sheets remained almost identical to that passing through the corresponding sample that had not been subjected to O-LDRT, indicating that the bottom layer of the graphene sheet remained almost unmodified, whereas a massive number of oxidative functionalities had been formed on the top layer of the graphene sheet; in addition, the adhesion energy increased to approximately twice that of the untreated graphene sheet.