Three-Dimensional Confinement of Water: H 2 O Exhibits Long-Range (>50 nm) Structure while D 2 O Does Not.

Water is the liquid of life thanks to its three-dimensional adaptive hydrogen (H)-bond network. Confinement of this network may lead to dramatic structural changes influencing chemical and physical transformations. Although confinement effects occur on a <1 nm length scale, the upper length scale limit is unknown. Here, we investigate 3D-confinement over lengths scales ranging from 58-140 nm. By confining water in zwitterionic liposomes of different sizes and measuring the change in H-bond network conformation using second harmonic scattering (SHS), we determined long-range confinement effects in light and heavy water. D 2 O displays no detectable 3D-confinement effects <58 nm (<3 × 10 6 D 2 O molecules). H 2 O is distinctly different. The vesicle enclosed inner H-bond network has a different conformation compared to the outside network and the SHS response scales with the volume of the confining space. H 2 O displays confinement effects over distances >100 nm (>2 × 10 7 H 2 O molecules).