Available on-demand - S.NM06.10.08
Restoration of Lattice Defects in Graphene Oxide by Organic Solvent-Assisted Thermal Annealing
Kanishka De Silva1,Masamichi Yoshimura1
Toyota Technological Institute1
From last decade, the interest of graphene is rising spanning almost all research areas due to its outstanding electrical, optical, mechanical, etc. properties inherited by its 2D structure . Due to this remarkable discovery, the material graphene oxide (GO) became famous as a precursor for graphene synthesis, even though it was discovered about 150 years ago . The GO is oxygenated form of graphene with many oxygen-containing groups (O-groups) and lattice defects. Hence, to fabricate graphene from GO, removal of these O-groups and repairing of the lattice defects is vital. This process is known as reduction . However, to obtain pristine graphene from GO is the most challenging task due to the difficulty in complete removal of O-groups and repairing of lattice defects by conventional reduction method.
It has been reported that, reduction of GO by high temperature annealing (>1500 oC) is an effective reduction method, particularly in producing conducting RGO films . However, high temperature annealing transforms into high-energy consumption. Further, high temperatures cannot be used on all types of substrates in making graphene films. Therefore, the road to make pristine graphene like material by reducing GO still poses obstacles. As an alternative strategy, thermal annealing of GO in the presence of a carbon source (C-source) such as, ethanol, methane, ethylene, and acetylene via chemical vapour deposition (CVD) has been reported (<1000 oC) [5,6]. In our previously published work, fabrication of conducting RGO films by the restoration of graphitic structure via ethanol-CVD was reported . As a continuation of this work, here we report, with the objective to understand the restoration behaviour of lattice defects, thermal annealing of GO in the presence of various organic solvents such as ethanol, methanol, isopropanol, tert-butanol, ethylene glycol, and toluene.
To mention the methodology in brief, first a dispersion of GO was spin-coated on SiO2/Si substrates and thermal annealing was done in the presence of the above solvents using a CVD device. Characterization of the synthesized samples was done by Raman spectroscopy, atomic force microscopy (AFM) along with Kelvin probe force microscopy (KPFM), and X-ray photoelectron spectroscopy (XPS). Preliminary results showed that there is a significant effect on restoration of lattice defects depending on the organic solvent used. Particularly, the Raman spectroscopic results show the evolution of the G’-peak, which is an indication of restoration of lattice defects, and depending on the C-source the spectral properties change (intensity of G’-peak increases with more carbon atoms). The AFM results showed that the thickness of a single GO sheet has reduced from 1 nm to 0.4 nm due to removal of O-groups upon thermal treatment. Further, conductivity measurements of the synthesized RGO films will be carried out to clarify the solvent dependence on the restoration of lattice defects.
 Novoselove, K.S., et al., Nature, 2012, 490, 192-200
 Brodie, B.C., Phil. Trans. R. Soc. Lond., 1859, 149, 249-259
 Pei, S., Cheng, H., Carbon, 2012, 50, 3210-3228
 Rozada, R., et al., Nano Res., 2013, 6, 216-233
 Su, C., et al., ACS Nano, 2010, 4, 5285-5292
 Lopez, V., et al., Adv. Mater., 2009, 21, 4683-4686
 De Silva, K.K.H., et al., Jap. J. Appl. Phys., 2019, 58, SIIB07