Structuring, diffusion and dynamics of nanoconfined water

Abstract

Exploring fluid transport at the nanoscale has necessitated the development of original experimental devices, which allow flow to be measured through an individual nanochannel. In contrast to this " nano " approach, " macroscopic " approaches, i.e. studies of nano-confined fluid properties across billions of billions of nano-channels, provide complementary information.

The objects of study are imogolite nanotubes, stoichiometrically SiAl2O7H4. These clay nanotubes found in soils can also be synthesized by soft chemistry. The coupling of molecular dynamics simulations with two experimental approaches " macroscopic ", X-ray scattering and quasi-elastic neutron scattering, gives access to the structuring of water in nanotubes, as well as its diffusion coefficient. Two types of water have been identified in nano-channels, one diffusing along the axis of the nanotube and the other, with an original structuring, not diffusing along this axis. A flux measurement on an individual nanotube would have probed only the central mobile water. Other results from " macroscopic " experiments, on the very particular dynamics of water in carbon nanotubes, will finally be discussed.

Pascale Launois

Pascale Launois, Director of Research at the CNRS, carries out fundamental physics research at the Orsay Solid State Physics Laboratory in the fields of nanofluidics and hydrogen storage. She approaches the nano field from a macroscopic angle, with the statistical study of a large number of nano-objects. The experimental methods used are mainly X-ray scattering and quasi-elastic and inelastic neutron scattering. They are coupled with simulations, essential for extracting physical parameters from experiments. These studies are highly complementary to those carried out by other teams at the single nano-object scale.