Abstract

Understanding ion transport in nano/angstrom scale channels has practical relevance in applications such as membrane desalination, blue energy, supercapacitors and batteries, as well as in understanding ionic flow through biological channels. Synthetic Å-channels are now a reality with the emergence of several cutting-edge bottom-up and top-down fabrication methods. In particular, the use of atomically thin 2D-materials and nanotubes as components to build fluidic conduits has pushed the limits of fabrication to the Å-scale. In this talk, I will discuss about angstrom (Å)-scale capillaries, which can be dubbed as “2D-nothing”. The Å-capillary is an antipode of graphene, created by what is left behind after extracting one-atomic layer out of a crystal [1]. What is intriguing here is, the dimensions of these channels being comparable to the size of a water molecule. The Å-capillaries have helped probe several intriguing molecular-scale phenomena experimentally, including: water flow under extreme atomic-scale confinement [1,2] complete steric exclusion of ions a concentration gradient) and discuss the importance of ionic parameters that are often overlooked in the selectivity between ions. specular reflection and quantum effects in gas reflections off a surface [5], voltage gating of ion flows [6] translocation of DNA [7]. I will present ionic flows induced by stimuli (electric, pressure, concentration gradient) and discuss the importance of ionic parameters that are often overlooked in the selectivity between ions.

References: [1] B. Radha et al., Molecular transport through capillaries made with atomic-scale precision. Nature 538, 222 (2016). [2] Y. You, A. Ismail et al., arXiv:2203.13027, to appear in Annual Reviews of Materials Research (2022). [3] A. Esfandiar et al., Size effect in ion transport through angstrom-scale slits. Science 358, 511 (2017). [4] K. Gopinadhan et al., Complete ion exclusion and proton transport through monolayer water. Science 363, 145 (2019). [5] A. Keerthi et al., Ballistic molecular transport through two-dimensional channels, Nature (2018), 558, 420. [6] T. Mouterde et al., Molecular streaming and voltage gated response in Å-scale channels. Nature 567, 87 (2019). [7] W. Yang et al., Translocation of dna through ultrathin nanoslits. Advanced Materials 2007682, (2021).