Effect of Curvature on the Behaviors of Confined Water Layers

The phase of confined water is ubiquitous in biology, materials science and nanotechnology. Recent studies showed that the spatial confinement influences the arrangement of water molecules and their dynamics. But the effect of confinement in a curved space has not been explored. In this study, we examine the effect of the curvature on the behaviors of confined water. We show that curved water monolayer, bilayer and triple layers can form within the inter-wall space of double-walled carbon nanotubes. We find that while the inter-wall distance affects the diffusion of water molecules along the axial direction of double-walled carbon nanotube, the curvature dominates the diffusion along the circumferential direction. We also find that the electric field helps to trap water molecules in the curved space. These results uncover the effect of curvature on the behaviors of confined water, and shed light on regulating the structure and dynamics of water at nanoscale.