Highly Concentrated and Conductive Reduced Graphene Oxide Nanosheets by Monovalent Cation–π Interaction: Toward Printed Electronics

A novel route to preparing highly concentrated and conductive reduced graphene oxide (RGO) in various solvents by monovalent cation– π interaction. Previously, the hydrophobic properties of high‐quality RGO containing few defects and oxygen moieties have precluded the formation of stable dispersion in various solvents. Cation– π interaction between monovalent cations, such as Na + or K + , and six‐membered sp 2 carbons on graphene were achieved by simple aging process of graphene oxide (GO) nanosheets dispersed in alkali solvent. The noncovalent binding forces introduced by the cation– π interactions were evident from the chemical shift of the sp 2 peak in the solid 13 C NMR spectra. Raman spectra and the I ‐ V characteristics demonstrated the interactions in terms of the presence of n ‐type doping effect due to the adsorption of cations with high electron mobility (39 cm 2 /Vs). The RGO film prepared without a post‐annealing process displayed superior electrical conductivity of 97,500 S/m at a thickness of 1.7 μm. Moreover, mass production of GO paste with a concentration as high as 20 g/L was achieved by accelerating the cation– π interactions with densification process. This strategy can facilitate the development of large scalable production methods for preparing printed electronics made from high‐quality RGO nanosheets.