High‐Quality Monolayer Reduced Graphene Oxide Films via Combined Chemical Reduction and Ethanol‐Assisted Defect Restoration

Abstract

at a low cost is another advantage in using GO for such applications. [10] However, the oxygen functional groups and lattice vacancies present in GO are accountable for opening up a large bandgap in the graphene lattice, which makes it electrically insulating. [11] Many deoxygenation or reduction strategies have been established to improve the graphitic structure and the electrical conductivity in GO, yet its quality is inferior to pristine or chemical vapor deposition (CVD) grown graphene. Chemical reduction (CR) of GO using different types of chemicals have been reported ranging from harmful chemicals to green reducing agents. [12][13][14] However, the CR is not sufficient to obtain graphene-like films from GO, because the vacancy type defects cannot be repaired. On the other hand, thermal annealing can effectively remove most of the oxygen functionalities resulting in highly conductive reduced graphene oxide (RGO) films. [15,16] Yet, carbon etching from the graphitic lattice along with the oxygen groups, as CO 2 and CO molecules, and rearrangement of the carbon atoms in the basal plane leading to Stone-Wales type defects are inevitable. [17] All these defects degrade the structural and electrical properties of the RGO films and hence, the overall quality. Research has also been done to obtain high-quality RGO films by lattice defect restoration using additional carbon sources, such as acetylene, ethanol, and methane during thermal annealing. [18][19][20] Although this method proves that the vacancies are being repaired, still the quality is inferior to graphene since carbon etching can occur simultaneously with the restoration. Recently, Yoon et al. have reported in situ deoxygenation and graphitization of GO using Fischer-Tropsch reaction catalyst (CuFeO 2 ) to obtain high-quality few-layered (5-10 layers) RGO with an I D /I G ratio of 0.19 and a crystallite size of 95.57 nm. [21] Yet, the total process time can be longer, as 12 h, involving several steps. Voiry et al. has reported a microwave-assisted reduction of GO into high-quality RGO with a lower I D /I G ratio, a large crystallite size (180 nm), and a large distance between defects (38 nm). [22] However, during microwave treatment, care should be taken because of the large volume expansion accompanied by the release of gases and violent sparking. Even though many efforts have been taken in attaining high-quality RGO films, the Here, a facile two-step reduction method is introduced to fabricate reduced graphene oxide (RGO) films with remarkable structural qualities. Many attempts are made to fabricate RGO with high structural qualities resembling pristine graphene. However, designing a reduction method to obtain highquality RGO more productively is highly desirable. To address this matter, in the present work, monolayer graphene oxide films are, at first, chemically reduced using a mixture of hydroiodic acid and trifluoroacetic acid vapor within a few minutes. Second, the films are reduced thermally at 800 °C for 30 min with ethanol, to repair the latti...

Large-Area Synthesis and Fabrication of Few-Layer hBN/Monolayer RGO Heterostructures for Enhanced Contact Surface Potential

“…In the N 1s spectra (Figures c and S7b), two peaks appear at 398.1 and 399.2 eV, corresponding to N–B and N–H bonds, respectively. − The peak at 284.5 eV is attributed to sp 2 (CC), while the peak at 288.6 eV can be assigned to CO (Figures d and S8c). The C–O peak on GO is higher than that on RGO, which is evident in the heat reduction under N 2 /H 2 (Figure S8). In the O 1s deconvolution spectra (Figures e and S8d), the large peak at 532.5 eV is assigned to C–O and the weak peak at 533.6 eV could be attributed to an O–C–O …”

“…The modified Hummers’ method was used to synthesize graphene oxide (GO), 31 , 32 and the reduced graphene oxide (RGO) film was prepared according to our previous report. 33 In detail, the SiO 2 /Si substrate was cleaned with acetone and distilled water, followed by UV–O 3 plasma treatment (TC-003, Meiwafosis.Co., Ltd.), which was performed to remove all chemical residues and improve the hydrophilicity. GO was dispersed in DMF (1 mg/mL), followed by ultrasonication and centrifugation, which were performed several times to remove bulk GO flakes.…”

Scalable synthesis of high-quality, reduced graphene oxide with a large C/O ratio and its dispersion in a chemically modified polyimide matrix for electromagnetic interference shielding applications

“…On the other hand, Wei et al 15 found that multistep reduction of GO was more effective compared to the single-step process. For instance, De Silva et al 16 employed a mixture of hydroiodic acid and trifluoroacetic acid followed by thermal reduction with ethanol to obtain high-quality RGO of as low as 0.46 kΩ sq −1 sheet resistance. Nevertheless, the second step reduction was carried out at an elevated temperature of 800 °C for 30 minutes, limiting the practicality and scalability of the method.…”