Monolithic graphene oxide sheets with controllable composition

Abstract

Graphene oxide potentially has multiple applications and is typically prepared by solutionbased chemical means. To date, the synthesis of a monolithic form of graphene oxide that is crucial to the precision assembly of graphene-based devices has not been achieved. Here we report the physical approach to produce monolithic graphene oxide sheets on copper foil using solid carbon, with tunable oxygen-to-carbon composition. Experimental and theoretical studies show that the copper foil provides an effective pathway for carbon diffusion, trapping the oxygen species dissolved in copper and enabling the formation of monolithic graphene oxide sheets. Unlike chemically derived graphene oxide, the as-synthesized graphene oxide sheets are electrically active, and the oxygen-to-carbon composition can be tuned during the synthesis process. As a result, the resulting graphene oxide sheets exhibit tunable bandgap energy and electronic properties. Our solution-free, physical approach may provide a path to a new class of monolithic, two-dimensional chemically modified carbon sheets.

Ultraviolet photoconductive devices with an n-GaN nanorod-graphene hybrid structure synthesized by metal-organic chemical vapor deposition

“…4b ) were observed at peak positions of approximately 1584 cm −1 and 2673 cm −1 , respectively, in the spectrum of the graphene layer ( Fig. 4d ) 29 . This finding provided clear evidence that, even after the growth of n-GaN NRs on the monolayer graphene, the physical existence and material properties of the graphene layer were not affected and the graphene layer was not damaged or impaired.…”

“…In this study, Raman spectroscopy revealed further improvement in the quality and uniformity of the monolayer graphene (with a peak intensity ratio I G /I 2D ≈ 0.38) grown using the CVD process and then transferred to a Si (111) substrate. To our knowledge, this study represents the finest graphene layer transferred directly to a Si substrate reported thus far 29 30 . The electrical properties of the graphene films that were transferred onto Si substrates were evaluated using the circular transfer length method (CTLM) structure, as illustrated in Fig.…”

“…Figure 2b presents a representative Raman spectrum of graphene samples that were obtained at a temperature of approximately 1050 °C and then transferred onto a Si substrate. The spectrum exhibits two primary features: a G-band at approximately 1584 cm −1 and a 2D-band at approximately 2673 cm −1 , which are typical peak positions for defect-free graphene 28 29 . The associated G/2D band and the full-width at half-maximum (FWHM) of the 2D-band maps in Fig.…”

“…2c illustrate the uniformity of the graphene films over large areas (approximately 490 μm 2 ) that predominantly exhibit typical monolayer properties, as identified by the I G /I 2D ≤ 0.38 and the FWHM of the 2D band of ≤38 cm −1 . Chu et al 29 have reported the formation of a graphene layer over SiO 2 /Si (100) with a G-band/2D-band peak intensity ratio ≤0.4, whereas Kwak et al 30 have reported a ratio of approximately 0.5. In this study, Raman spectroscopy revealed further improvement in the quality and uniformity of the monolayer graphene (with a peak intensity ratio I G /I 2D ≈ 0.38) grown using the CVD process and then transferred to a Si (111) substrate.…”

Use of CuO/MgAl2O4 and La0.8Sr0.2FeO3/γ‐Al2O3 in chemical looping reforming system for tar removal from gasification gas

“…Cu is well known to be a potent catalyst for the formation of graphene . Due to the presence of steam in the gas and therefore a rather high oxygen potential of the gas, the formation of graphene oxide may even be plausible . In any case, such a layer may then block the copper surface for the adsorption of C 2 H 4 and thus inhibit the formation of coke from C 2 H 4 .…”