3D confinement of water: H2O exhibits long-range (> 50 nm) structure while D2O 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 that influence chemical and physical transformations. Although confinement effects occur on a < 1 nm length scale, the upper length scale limit is not known. 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. D2O displays no detectable 3D-confinement effects < 58 nm (< 3.10^6 D2O molecules). H2O 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. H2O displays confinement effects over distances > 140 nm (> 4.10^7 H2O molecules).