Modulation of K⁺/Na⁺ Selective Transport Kinetics via Charge and Alkyl Chain Length of Edge-modified Carbon Nanotubes

Abstract

The respective and coupled contributions of electrostatic charge and steric hindrance at the nanopore entrance to ion transport remain poorly understood. Molecular dynamics simulations were employed to investigate potassium and sodium ion transport through edge-functionalized carbon nanotubes, focusing on how charge and chain length of grafted groups modulate ion permeation. It turns out that positively charged short chains promote chloride transport; strong sodium-chloride pairing drives sodium ions backward while potassium migrates forward, achieving complete spatial separation. For negatively charged groups, a four-state selectivity progression emerges from competition between ion hydration and group coordination. Long chains enhance potassium selectivity by disrupting hydration shells more effectively. This work provides atomic-level design principles for functionalized carbon nanotube ion channels and offers insights into transport mechanisms in confined nanofluidic systems.

Keywords

Carbon nanotube (CNT) / Molecular dynamics / Real first interface

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Jilin University, The Editorial Department of Chemical Research in Chinese Universities and Springer-Verlag GmbH