Abstract
A new approach using X-ray photoelectron spectroscopy (XPS) was employed to give insight into the reduction of graphene oxide (GO) using a green approach with polydopamine (PDA). In this approach, the number of carbon atoms bonded to OH and to nitrogen in PDA is considered and compared to the total intensity of the signal resulting from OH groups in polydopamine-reduced graphene oxide (PDA-GO) to show the reduction. For this purpose, GO and PDA-GO with different times of reduction were prepared and characterized by Raman Spectroscopy and XPS. The PDA layer was removed to prepare reduced graphene oxide (RGO) and the effect of all chemical treatments on the thermal and electrical properties of the materials was studied. The results show that the complete reduction of the OH groups in GO occurred after 180 min of reaction. It was also concluded that Raman spectroscopy is not well suited to determine if the reduction and restoration of the sp2 structure occurred. Moreover, a significant change in the thermal stability was not observed with the chemical treatments. Finally, the electrical powder conductivity decreased after reduction with PDA, increasing again after its removal.
Highlights
Graphene, a 2D monolayer of sp2-hybridized carbon atoms arranged in a hexagonal lattice with a carbon–carbon bond length of 0.142 nm, has been extensively studied since it was first isolated in 2004 by Novoselov et al [1,2]
The main drawbacks are the high cost of silicon carbide (SiC) wafers and the high temperatures involved in the process [4,8]
Considering the limited knowledge on this topic, in this work, we propose a new approach using X-Ray photoelectron spectroscopy (XPS) to supply evidence for the molecular reduction of graphene oxide (GO) by PDA
Summary
A 2D monolayer of sp2-hybridized carbon atoms arranged in a hexagonal lattice with a carbon–carbon bond length of 0.142 nm, has been extensively studied since it was first isolated in 2004 by Novoselov et al [1,2]. The reduction of GO can be performed, for instance, through a chemical approach to remove the oxygen-containing functional groups and restore the conjugated graphene structure [11] Compared to others, this process allows the production of large quantities of graphene at a low cost since no special equipment or high temperatures are needed and the starting materials, graphite and chemical reductants, such as hydrazine and sodium borohydride, are usually cost-effective [12]. Considering the limited knowledge on this topic, in this work, we propose a new approach using X-Ray photoelectron spectroscopy (XPS) to supply evidence for the molecular reduction of GO by PDA This reduction process is a good example of the use of green chemistry to replace traditional methods since no toxic solvents are used and PDA is a natural and renewable raw material, and only a little amount of waste is generated. The effect of the chemical treatments in the thermal and electrical properties of GO and PDA-GO was studied and a better understanding of the chemistry behind the green reduction of GO with PDA is presented
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