Ion Transport In Sub-nm Pores And Ion-electron Coupling Transport At Solid-liquid Interface

Nanofluidics,as a natural extension of microfluidics to a smaller scale,has received extensive attention and research in recent decades and gradually become an independent field.A decade ago,such limited-scale exploration faced significant technical obstacles because nanoscale channels could not be manufactured manually.Nowadays,because of the progress of manufacture technology,people has been able to overcome the challenge of sub-nm scale fabrication,and realize the preparation of artificial equipments at zero dimension,one-dimensional or two-dimensional geometric restrictions.Special effects that do not exist at the micro scale,such as dielectric anomalies,ionic Coulomb blockade,and ultrafast water transport,appear at the nanoscale and sub-nm scale.However,the majority of the current research in nanofluidics is built on continuum and mean field equations.Although the methods are effective down to a few nanometers,they eventually fail as ionic correlations,dielectric anomalies,and other subcontinuum effects come into play.The experimental research and mechanism of ion transport on sub-nm scale are still an unresolved issue.The resolution of this issue has a profound impact on the development of membrane science and ionic electronics,as well as the design and application of minimal artificial systems in biological processes.Our work focuses on the ion transport of single layer two-dimensional sub-nm pores and ion-electron coupling transport at solid-liquid interface.We experimentally investigate the ion transport in sub-nm pores,including ionic Coulomb blockade,gating,and ion-electron coupling transport.Furthermore,we comprehend the underlying physical principles using computational simulations and sub-continuous fluid mechanics.The following three components make up the primary contents:The first part concerns the ion transport in a single-layer MoS₂ sub-nm pore.We found ionic conductance oscillation.We regulated the surface charge density of MoS₂ sub-nm pores by photoelectric effect and observed the ionic Coulomb blockade and ionic conductance oscillation.By investigating the ion concentration,ion valence state,and border aperture,we think that the cause of the ionic conductance oscillation is the many-body Coulomb interaction between charged particles.Using the molecular dynamics simulation and sub-continuous fluid mechanics,we restore the physical image of Coulomb interaction of ion-ion and ion-pore charge,revealing the mechanism of ionic conductance oscillation and ionic Coulomb blockade.The second section concentrated on the ion transport of single-layer graphene sub-nm pores which exhibited channel behavior akin to that of biological ion gating-dynamic and ramdom ionic conductance switching between high and low states.It was found that gating behavior of graphene sub-nm pores is electric field dependent and concentration dependent.So,we speculated that dynamic ionic Coulomb blockade is a possible mechanism of gating behavior.By molecular dynamics simulation,we found that the Coulomb interaction caused by random adsorption/desorption of cations on sub-nm pores is the main reason for gating behavior.This discovery provides a new way to understand the physical mechanism of material transport in biological ion channels and construct artificial ion systems.The third part focuses on the ion-electron coupling transport at solid-liquid interface.We experimentally investigated the dynamic ion-electron coulomb interaction at the monolayer graphene membrane-ionic solution interface,and observed that the electric current was generated in an opposite direction of the ion current.By changing the electronic properties of the material and the ion current,correspondingly,the induced current can be controlled.Through ab initio molecular dynamics simulation（AIMD）,we found that the induced current is maybe caused by a limited Coulomb interaction between ions and electrons at the solid-liquid interface.The ion migration drives electronic mobile through Coulomb drag mechanism.This discovery provides a new opportunity for controlling ion-electron coupling transport and expanding artificial nanofluid systems.