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Beyond steric selectivity of ions using ångström-scale capillaries
Solleti Goutham1,2, Ashok Keerthi2,3, Abdulghani Ismail1,2
1Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester, Manchester, UK.
Nature Nanotechnology
|March 30, 2023
Summary
Artificial channels can now separate same-charge ions, overcoming limitations of size and charge-based methods. This breakthrough uses ion position in nanoconfined water, enabling advanced ion separation beyond traditional sieving.
Area of Science:
- Materials Science
- Nanotechnology
- Physical Chemistry
Background:
- Ion-selective channels are crucial for biological functions and technological applications.
- Mimicking biological ion selectivity in artificial solid-state channels, especially for same-charge ions, remains a significant challenge.
- Existing artificial nanoporous membranes primarily rely on hydrated ion size or charge for selectivity.
Purpose of the Study:
- To investigate the mechanism of ion selectivity in ångström-scale artificial channels.
- To develop artificial channels capable of distinguishing between same-charge ions with similar hydrated diameters.
- To move beyond steric and Coulombic exclusion principles for ion separation.
Main Methods:
- Fabrication of ångström-scale artificial channels using van der Waals assembly.
- Characterization of channel properties, focusing on minimal residual charge.
- Experimental investigation of ion transport and selectivity for same-charge ions.
Main Results:
- Demonstrated selectivity between same-charge ions with similar hydrated diameters in 2D ångström-scale capillaries.
- Identified ion position within nanoconfined water layers as the key selectivity mechanism.
- Showed that selectivity depends on ion-core size and differs for anions and cations.
Conclusions:
- Artificial channels can achieve ion selectivity beyond steric and charge-based mechanisms.
- The position of ions within nanoconfined water layers dictates selectivity.
- This mechanism offers new possibilities for advanced ion separation technologies.
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