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Ordering-Induced Fast Diffusion of Nanoscale Water Film on Graphene Jae Hyun Park and N. R. Aluru*

Summary: Ordering-Induced Fast Diffusion of Nanoscale Water Film on Graphene
Jae Hyun Park and N. R. Aluru*
Beckman Institute for AdVanced Science and Technology, Department of Mechanical Science and Engineering,
UniVersity of Illinois at Urbana-Champaign, Urbana, Illinois 61801
ReceiVed: August 4, 2009; ReVised Manuscript ReceiVed: December 16, 2009
We show that ordering in nanoscale water film on a hydrophobic surface gives rise to fast diffusion of water.
Specifically, as the surface coverage of water increases, the diffusion coefficient of water increases until a
critical surface coverage and a further increase in surface coverage results in a decrease of water diffusion
coefficient. For thin nanoscale films that form two layers of waters on a hydrophobic surface, the first layer
of water forms a hexagonal structure, very similar to the ice Ih structure, that is independent of the surface
coverage. As the surface coverage increases, the ordering of water molecules in the second layer increases
and for a critical surface coverage the ordering in the second layer is maximized and the hydrogen bonding
between first and second layers is minimal giving rise to fast diffusion. As the surface coverage further increases,
the hydrogen bonding between the first and second layers increases and the diffusion coefficient of water is
reduced. This "ordering-induced diffusion enhancement" on hydrophobic surfaces is contrary to the ordering-
induced slow mobility in hydrophobic nanotubes (e.g., in a carbon nanotube).
Rapid advances in surface nanotechnology have enabled the
manufacturing of various nanoscale architectures on surfaces
(e.g., nanolithography,1


Source: Aluru, Narayana R. - Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign


Collections: Engineering; Materials Science