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

Abstract

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 5min, 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.