High concentration graphene nanoplatelet dispersions in water stabilized by graphene oxide

The preparation of aqueous graphene nanoplatelet (GNP) dispersions is a challenging task due to their tendency to agglomerate. In contrast, graphene oxide (GO), an oxidized form of GNP, has amphiphilic characteristics which allow it to disperse in an aqueous milieu without the addition of a surfactant. Therefore, we utilize GO as a dispersing agent to prepare highly-concentrated aqueous GNP dispersions, which can be used for various applications. The nature of the dispersed phase is investigated by various material characterization methods. Furthermore, we measure the zeta potentials of the dispersed phased as well as the contact angles of dispersions on different substrates. The latter data are used in the extended DerjaguineLandaueVerweyeOverbeek theory to gain insight into the interactions that determine dispersion stability. We find that the stability of such dispersions mainly depends on the pH value as well as the ratio of GO and GNP concentrations. The rheology of the dispersions is investigated and different nematic phases are identified. Finally, highly-concentrated dispersions are used for printing of graphene films on a flexible substrate. After reduction of the minor GO fraction, the films have a high conductivity of more than 4500 S m(-1). (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

In this study, graphene oxide (GO) was utilized as a dispersing agent to prepare highly-concentrated aqueous graphene nanoplatelet (GNP) dispersions, which were then used for printing graphene films on a flexible substrate with high conductivity. The stability of such dispersions mainly depends on pH value and the ratio of GO and GNP concentrations, and different nematic phases were identified through rheological investigation.