Voltage gated inter-cation selective ion channels from graphene nanopores

Area of Science:

• Materials Science
• Nanotechnology
• Biophysics

Background:

• Biological ion channels control ionic flux, crucial for physiological processes.
• Graphene offers a promising solid-state alternative for artificial ion channels due to its unique properties.

Purpose of the Study:

• To demonstrate inter-cation selectivity in graphene nanopores.
• To investigate the mechanism behind the observed selectivity.
• To explore a novel fabrication approach for selective graphene membranes.

Main Methods:

• Fabrication of graphene membranes with nanopores (up to 50 nm).
• Characterization using liquid atomic force microscopy.
• Analysis of ion selectivity and gate voltage modulation.
• Molecular dynamics simulations of ion translocation.

Main Results:

• Graphene nanopores exhibited significant inter-cation selectivity (∼20× preference for K+ over divalent cations).
• Selectivity was modulated by an applied gate voltage.
• Surface nanobubbles near the pores were identified as the cause of selectivity.
• Ion translocation occurs via a water layer at the pore edge and nanobubble.

Conclusions:

• Graphene nanopores with surface nanobubbles can achieve high inter-cation selectivity.
• This approach provides a method for fabricating selective graphene membranes without requiring sub-nanometer pores.
• Demonstrates potential for solid-state artificial ion channels and filtration applications.