Abstract:
It has long been an aspirational goal to create artificial structures that allow fast
permeation of water but reject even the smallest hydrated ions, replicating the feat
achieved by nature in protein channels (e.g., aquaporins). Despite recent progress in
creating nanoscale pores and capillaries, these structures still remain distinctly larger
than protein channels. We report capillaries made by effectively extracting one atomic
plane from bulk crystals, which leaves a two-dimensional slit of a few angstroms in
height. Water moves through these capillaries with little resistance, whereas no permeation
could be detected even for such small ions as Na+ and Cl−
. Only protons (H+
) can
diffuse through monolayer water inside the capillaries. These observations improve our
understanding of molecular transport at the atomic scale.