Terahertz-Light Induced Structural Transition and Superpermeation of Confined Monolayer Water

Abstract

The confined monolayer water between atomic-gapped graphene-based membranes has broad and promising applications in seawater desalination and water purification, which benefits from the fast transport of water and subsequent low energy cost. However, it is still unclear whether there are approaches to further improve the transport of water across membranes. Herein, based on molecular dynamics simulations, we propose that a light stimulus with the frequency of 31.5 ± 1.0 THz can nonthermally enhance the permeation of confined monolayer water across a graphene-based membrane by 37-fold, followed by a transition to the super permeation state of confined water. The underlying mechanism is disclosed to involve a THz light-induced structural phase transition of the monolayer water, but not bulk water, from quasi-two-dimensional (2D) ice to 2D liquid at room temperature due to resonance of the electromagnetic wave with the vibration mode of confined water. These findings are expected to improve the understanding of molecular transport at the atomic scale and potential physics in biology and to promote the applications of terahertz technology in desalination and biomedical science.

Confinement-Controlled Aqueous Chemistry within Nanometric Slit Pores

“…195 The dynamics of water in slit pores keeps being investigated, in particular the way in which it may be affected by the asymmetry of the confining surfaces, 196 meaning hydrophilic and hydrophobic surfaces at each side of the water lamella, and also how it can be controlled or enhanced by the application of light pulses. 197 Other computational studies are aimed at ion solvation, 198 ion separation, and transport properties of slit pores 199,200 and their possible control by the use of flexible confining surfaces 201 or by their functionalization. 202 Finally, we note that most simulations are still done with force fields, in particular employing water models that have been optimized to describe bulk properties rather than water in narrow slit pores including its peculiar wall interactions.…”

“…We note that the concern about the use of the proper expressions for computing the dielectric response of water in confinement and the acknowledgement of its anisotropic character as elaborated in Section is growing . The dynamics of water in slit pores keeps being investigated, in particular the way in which it may be affected by the asymmetry of the confining surfaces, meaning hydrophilic and hydrophobic surfaces at each side of the water lamella, and also how it can be controlled or enhanced by the application of light pulses . Other computational studies are aimed at ion solvation, ion separation, and transport properties of slit pores , and their possible control by the use of flexible confining surfaces or by their functionalization .…”

Molecular-Level Insights into Unique Behavior of Water Molecules Confined in the Heterojunction between One- and Two-Dimensional Nanochannels

“…On the other hand, there have been also a great variety of simulations on water molecules confined in two-dimensional (2-D) layered materials up to now, ,− where water molecules can display different structures and dynamics properties from those in 1-D materials. Graphene, as one of the most promising 2-D crystal nanostructures, has been a prototypical model for investigating water molecules in 2-D materials.…”

“…Their simulations revealed that the adjacent two hydrolayers within the mixed region show greater disparities in water orientation and HB behavior, which may be responsible for the rapid transport of water across graphene oxide membranes. More recently, Song and co-worker introduced a terahertz electromagnetic light stimulus into their MD simulations, leading to a permeation behavior of waters confined in a graphene-based membrane owing to the structural transition of water molecules from solid ice to liquid.…”

Heating anomaly of cold interfacial water under irradiation of mid-infrared pulses

“…It is known that the interfacial properties of the materials are responsible for many interesting anomalous phenomena of water that can be seen, for instance, by the 2-dimensional (2D) ice at the room temperature under various interfacial confinements [4,5] and a water droplet formed bizarrely on a water monolayer because of the interface beneath it [6]. Moreover, there are also lots of fascinating phenomena in confined water arising from the interplay with electromagnetic fields, including the phase transition of confined 1D or 2D water to superpermeation [7,8], ice-liquid phase transition of the monolayer water due to applied electric field [9], and water freezing on a pyroelectric surface during a heating-up process [10], etc. These anomalous properties enrich the knowledge on the water complexity, as many features of the confined nano-water can be different drastically from those of bulk water.…”