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Graphene oxide dispersions and liquid crystals

How graphene oxide flakes behave and assemble in water, from liquid-crystal phases and flow instabilities to droplets that self-assemble into shaped hydrogel and aerogel particles.

Left: high-speed photographs of graphene oxide droplets entering a surfactant bath and forming donut, spherical and jellyfish shapes within 30 seconds. Right: thickness of the aligned graphene oxide shell growing with time, with a histogram of shell layer spacing.
High-speed imaging of graphene oxide droplets forming donut (D), spherical (S) and jellyfish (J) particles in a cationic surfactant bath (left), and the growth of their aligned graphene oxide shell (right). Reproduced from Y. Shao, K. Nie, M. Iliut, F. Box, D. Luan, Y. Shen, W. Wang, W. W. Sampson, I. Dierking and A. Vijayaraghavan, Journal of Molecular Liquids (2023), Fig. 4(a) and Fig. 5(f), doi:10.1016/j.molliq.2023.121341, under CC BY 4.0; panels rearranged.

At modest concentrations, graphene oxide flakes in water line up into a liquid-crystal phase. The group studies how these phases respond to flow, confinement and added molecules: large flakes, for example, show elastic flow instabilities that appear as helical bands under shear.

When a drop of graphene oxide dispersion falls into a solution of oppositely charged surfactant, the vortex-ring effect and electrostatic attraction together shape it into a hydrogel particle with a shell of aligned flakes. High-speed imaging shows spheres, donuts and jellyfish forming in real time, and the conditions that select each shape. Freeze-dried, these particles become the aerogels used in the group’s water purification work.

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Publications 7