Dehydration as a Universal Mechanism for Ion Selectivity in Graphene and Other Atomically Thin Pores

Abstract

Ion channels play a key role in regulating cell behavior and in electrical signaling. In these settings, polar and charged functional groups -- as well as protein response -- compensate for dehydration in an ion-dependent way, giving rise to the ion selective transport critical to the operation of cells. Dehydration, though, yields ion-dependent free-energy barriers and thus is predicted to give rise to selectivity by itself. However, these barriers are typically so large that they will suppress the ion currents to undetectable levels. Here, we establish that graphene displays a measurable dehydration-only mechanism for selectivity of ${\mathrm{K}}^{+}$ over ${\mathrm{Cl}}^{-}$. This fundamental mechanism -- one that depends only on the geometry and hydration -- is the starting point for selectivity for all channels and pores. Moreover, while we study selectivity of ${\mathrm{K}}^{+}$ over ${\mathrm{Cl}}^{-}$, we find that dehydration-based selectivity functions for all ions, i.e., cation over cation selectivity (e.g., ${\mathrm{K}}^{+}$ over ${\mathrm{Na}}^{+}$). Its likely detection in graphene pores resolves conflicting experimental results, as well as presents a new paradigm for characterizing the operation of ion channels and engineering molecular/ionic selectivity in filtration and other applications.

27 pages

References in corpus (5)

• Graphene: A sub-nanometer trans-electrode membrane
• Physical approaches to DNA sequencing and detection
• Quantized ionic conductance in nanopores
• Ionic selectivity and filtration from fragmented dehydration in multilayer graphene nanopores
• Comment on "Characterization of the tunneling conductance across DNA bases"

Cited by in corpus (11)

• Tuneable Sieving of Ions Using Graphene Oxide Membranes
• Size effect in ion transport through angstrom-scale slits
• Colloquium: Ionic phenomena in nanoscale pores through 2D materials
• Ionic selectivity and filtration from fragmented dehydration in multilayer graphene nanopores
• Optimal transport and colossal ionic mechano-conductance in graphene crown ethers
• Maxwell-Hall access resistance in graphene nanopores
• Induced Charge Anisotropy: a Hidden Variable Affecting Ion Transport through Membranes
• Golden aspect ratio for ion transport simulation in nanopores
• Diffusion Limitations and Translocation Barriers in Atomically Thin Biomimetic Pores
• Resonance-Driven Mechanisms of Ion Transport and Selectivity
• Entropic modulation of divalent cation transport