3D confinement of water: H2O exhibits long-range (> 50 nm) structure while D2O does not

TL;DR

This study reveals that light water (H2O) exhibits long-range structural changes under 3D confinement over 140 nm, unlike heavy water (D2O), which shows no such effects below 58 nm, highlighting fundamental differences in their hydrogen-bond networks.

Contribution

The paper demonstrates for the first time that H2O exhibits long-range confinement effects over 140 nm, whereas D2O does not, using second harmonic scattering in liposome systems.

Findings

H2O shows confinement effects over > 140 nm.

D2O shows no effects below 58 nm.

H2O's hydrogen-bond network conformation differs inside and outside vesicles.

Abstract

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).