National Physical Laboratory

Thickness-dependent hydrophobicity of graphene

The common (unproved!) believe is that graphene, as many other carbonaceous materials, is hydrophobic a priori. We demonstrate that the question is much more complicated and answer to it would depend on the thickness of graphene layers and type of substrate.

By employing chemical force microscopy with a hydrophobic functionalised probe (OTS molecules), the adhesion force between the probe and epitaxial graphene on SiC has been measured. Owing to the hydrophobic attraction, a larger adhesion force was measured on 2LG Bernal-stacked domains of graphene surfaces, thus showing that 2LG is more hydrophobic than 1LG.

Approximate values of the adhesion force per OTS molecule have been calculated through contact area analysis, being 300 pN for 1LG and 320 pN for 2LG. These results are further confirmed by nanoscale mapping of friction forces on domain of different thickness, and the origin of the effect is discussed in terms of water depletion over hydrophobic domains (2-3LG). Knowledge of the water affinity of graphene and its spatial variations is critically important as it affects both the graphene properties and performance of graphene devices exposed to humidity.

Is graphene hydrophobic or hydrophilic?

Read the full paper online at ACS Nano

Read the news story: Is graphene hydrophobic or hydrophilic?

More on NPL's work on Graphene

For further details, please contact Olga Kazakova

Last Updated: 14 Oct 2015
Created: 13 Oct 2015

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