Reversible Oxidation of Graphene Through Ultraviolet/Ozone Treatment and Its Nonthermal Reduction through Ultraviolet Irradiation

Abstract

We present alternative methods to oxidize a graphene layer through ultraviolet (UV)/ozone (O3)-treatment, resulting in chemically homogeneous graphene oxide (GO), and then to reduce GO through UV-irradiation. Both UV/O3-treatment and UV-irradiation were performed at room temperature in atmospheric pressure for only several minutes and did not involve any wet chemical treatments. The quantity of doped oxygen, determined using X-ray photoelectron spectroscopy, increased after oxidation and decreased after reduction. The quantity of doped oxygen reached its maximum, which was around 20% (approximately one oxygen atom in every five or six carbon atoms) after performing UV/O3-treatment for 6 to 10 min. Conducting UV/O3-treatment for around 6 or 10 min resulted in a chemically homogeneous GO surface with only oxygen epoxide groups on the graphene surface. Performing UV/O3-treatment beyond 15 min as well as multiple turns of UV/O3-treatment could lead to the formation of defects and carbonyl groups on graphene lattice. The oxygen quantity gradually decreased after conducting 6 min UV-irradiation several times, indicating that the resulting GO was successfully reduced. How the doped oxygen atoms distributed on graphene surface was directly investigated using scanning tunneling microscopy. Moreover, changes in electrical properties of three identical single-layer graphene field-effect transistors (G-FETs) after being oxidized through UV/O3-treatment were investigated. The electron mobility of G-FETs decreased after oxidation; however, it recovered after irradiating the oxidized G-FETs with UV-lights, indicating that GO was successfully reduced nonthermally through UV-irradiation. The reversibility in electron mobility was confirmed even after conducting redox processes twice. Furthermore, the reversibility of oxidation was also verified from the graphene lattice disorder point of view using Raman spectroscopy. We concluded that UV/O3-treatment produced chemically homogeneous GO that is nonthermally reversible through UV-irradiation, and changes in the electron mobility were nonthermally reversible also.

Pure Pyridinic Nitrogen‐Doped Single‐Layer Graphene Catalyzes Two‐Electron Transfer Process of Oxygen Reduction Reaction

“…In our approach, the amount of oxygen atoms generated in graphene can be tuned by controlling the UV/O 3 treatment time in air . It is worth noting that the low oxygen concentration existing in atmosphere is essential for preventing graphene from being over‐oxidized.…”

Efficient Catalytic Ozonation over Reduced Graphene Oxide for p-Hydroxylbenzoic Acid (PHBA) Destruction: Active Site and Mechanism

“…Literatures revealed that ozonation also resulted in changes in surface chemistry of nanocarbons, which would affect their adsorption capabilities. [32][33][34] In order to investigate the changes in adsorption capacity arising from ozonation, rGO-300 was treated in solution by ozone for different time intervals and its adsorption abilities in PHBA were evaluated and compared (Fig. S6).…”

Magnetism in graphene oxide induced by epoxy groups

“…In detail, by introducing CVD growth methods for largescale graphene sheet, instead of the graphite powder we used here, the amount and distribution of the epoxy groups are precisely manipulated. 42,43 Accordingly, it is possible to engineer the magnetism of the GO sheet and consequently employ GO for spintronic device applications. …”