Size effect in ion transport through angstrom-scale slits

Abstract

In the field of nanofluidics, it has been an ultimate but seemingly distant goal to controllably fabricate capillaries with dimensions approaching the size of small ions and water molecules. We report ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal. The atomically flat angstrom-scale slits exhibit little surface charge, allowing elucidation of the role of steric effects. We find that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility. The confinement also leads to a notable asymmetry between anions and cations of the same diameter. Our results provide a platform for studying the effects of angstrom-scale confinement, which is important for the development of nanofluidics, molecular separation, and other nanoscale technologies.

Nanofluidic Ion Transport and Energy Conversion through Ultrathin Free‐Standing Polymeric Carbon Nitride Membranes

“…[5] Tw o-dimensional materials, [6] for example graphene and graphene oxide (GO), would be the ultimate step for such membranes,a nd nanosheets with similar 2D structures have been assembled into nano-channeled membranes,ahot topic of scientific research. [9] These nanosheet membranes already have demonstrated the desired advantages,s uch as outstanding separation performance,flexibility,and interesting nanoscale fluidic properties. [8] Recently,G eim et al described the ions transportation properties through angstrom-scale graphene slits.…”

“…[8] Recently,G eim et al described the ions transportation properties through angstrom-scale graphene slits. [9] These nanosheet membranes already have demonstrated the desired advantages,s uch as outstanding separation performance,flexibility,and interesting nanoscale fluidic properties. [6] Tw od imensional carbon nitride (C 3 N 4 ) materials are another obvious choice with inherent lateral porosity,and it already attracting broad interest with its broad applications in sensing,b io-imaging,n ovel solar energy exploitation, as well as photocatalysis.…”

Elucidating Ultrafast Molecular Permeation through Well‐Defined 2D Nanochannels of Lamellar Membranes

“…Mass transfer through nanoconfined pores,s lits,t ubes,o r channels is vital to many applications,s uch as catalysis,f uel cell systems,a nd membrane separation. [1] Recently,2 D lamellar membranes with highly efficient mass transfer ability exhibit distinct superiority in hydrogen production, water purification, organic recycling,and desalination, as compared to the state-of-the-art polymeric membranes. [2] However,the underlying molecular-level origin is rarely explored.…”

“…In contrast, nonpolar molecules with disordered configuration in both hydrophilic and hydrophobic nanochannels have comparable permeance.T wo phenomenological transport models correlate the permeance with the mass transport mechanism of molecules that display ordered and disordered configuration.Mass transfer through nanoconfined pores,s lits,t ubes,o r channels is vital to many applications,s uch as catalysis,f uel cell systems,a nd membrane separation. [1] Recently,2 D lamellar membranes with highly efficient mass transfer ability exhibit distinct superiority in hydrogen production, water purification, organic recycling,and desalination, as compared to the state-of-the-art polymeric membranes. [2] However,the underlying molecular-level origin is rarely explored.…”

β‐Cyclodextrin Functionalized Nanoporous Graphene Oxides for Efficient Resolution of Asparagine Enantiomers

“…[4] On the other hand, graphene oxide contains plentyo fr eactive oxygen groups (À COOH, ÀOH, carbonyl, and epoxy), which provides possibility for chemical modificationa nd produces functional materials for aw ide range of applications. [5] In particular,t hese GOs have been demonstrated to efficiently separate various materials such as cations, [6] gases, [7] and organic molecules [8] because of their properties such as large surfacea rea, tunable interactive sites, as well as adjustable interlayer spacing. [9] Chiral molecules, including polymers [10] and biomolecules, [11] have also been utilized to functionalize these graphene oxides and show typical enantioselective interaction towardg uest enantiomers.…”