Water’s motions in x–y and z directions of 2D nanochannels:Entirely different but tightly coupled  

作　　者：Shouwei Liao Qia Ke Yanying Wei Libo Li 

机构地区：[1]Guangdong Provincial Key Lab of Green Chemical Product Technology,School of Chemistry&Chemical Engineering,South China University of Technology,Guangzhou 510640,China [2]State Key Laboratory of Pulp and Paper Engineering,South China University of Technology,Guangzhou 510640,China

出　　处：《Nano Research》2023年第5期6298-6307,共10页纳米研究（英文版）

基　　金：the National Natural Science Foundation of China(Nos.22078104,22022805,and 22078107);the National Key Research and Development Program(No.2021YFB3802500);the financial support from the Science and Technology Key Project of Guangdong Province(No.2020B010188002);State Key Laboratory of Pulp and Paper Engineering(No.2022PY04);Fundamental Research Funds for the Central Universities(No.2022ZYGXZR010).

摘　　要：Two-dimensional(2D)material-based membrane separation has attracted increasing attention due to its promising performance compared with traditional membranes.However,in-depth understanding of water transportation behavior in such confined nanochannels is still lacking,which hinders the development of 2D nanosheets membranes.Herein,we investigated water confined in graphene or MoS_(2)nanochannels by molecular dynamics(MD)simulations and found water’s diffusivity always varied linearly with their mean square displacement along z direction(Δz^(2))when system variables(e.g.,water molecules’number,channel height,nonbonded interaction parameter,harmonic potential constraining water’s z-coordinate)changed.Such linear correlation applies to different water models and different force fields(FFs)of channel walls(e.g.,different Lennard–Jones parameters or even flexible FF),no matter whether water molecules form 3-,2-,or quasi-2-layer structure in the nanochannel.This indicates,though water molecules’motion along z direction(z-fluctuation,confined within 1 nm)and that in xy plane(xydiffusion)are entirely different,they are tightly coupled:Violent z-fluctuation would produce more transient void to facilitate xydiffusion,which is to the sharp contrary of bulk water,where motions in x,y,z directions are symmetric,but independent.Our work could help design high performance 2D nanochannels and discover more novel principles in nano-fluidics and membrane separation fields.

关 键 词：graphene membranes NANOCHANNEL nanofluidics water diffusion 

分 类 号：TB383[一般工业技术—材料科学与工程]