Anomalous Ion Transport in 2D Graphene Oxide Nanochannels Enabled by Hydration Mimicry with Confined Amino Acids.

Vilayatteri, Muhammed Afnas; El Meragawi, Sally; Mahofa, Eubert; Duncan, Tyler J; Shahbabaei, Majid; Ganesan, Venkat; Majumder, Mainak · Nano Lett · 2025

basic_science · Level V

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Abstract

Inspired by biological ion channels, we design graphene oxide (GO) membranes functionalized with aspartic acid to introduce ion-specific binding sites within angstrom-scale confinement. This leads to a notable suppression of monovalent ion mobility, contributing to unexpected selectivity for divalent calcium ions, with Ca<sup>2+</sup>/Li<sup>+</sup> and Ca<sup>2+</sup>/Na<sup>+</sup> selectivities of ∼9.8 and ∼4.8, respectively. With the combination of transition-state theory and molecular dynamics simulations, the complex interplay of hydration energy, spatial confinement, and ion-ligand coordination strength is highlighted, offering a mechanistic basis for designing membranes with nonclassical selectivity profiles.