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Gating with Charge Inversion to Control Ionic Transport in Nanopores.
Wilfred S Russell1, Chih-Yuan Lin2, Zuzanna S Siwy1,2,3
1Department of Chemistry, University of California, Irvine, California 92697, United States.
ACS Applied Nano Materials
|December 30, 2022
Summary
Multivalent ions induce charge inversion at interfaces, switching surface charge. Nanoconfinement effects on this phenomenon, particularly pore diameter influence, were investigated, revealing tunable surface charge density and ionic transport.
Area of Science:
- Physical Chemistry
- Nanotechnology
- Surface Science
Background:
- Multivalent ions can alter solid/liquid interface properties, including surface charge polarity.
- Charge inversion, a switch from negative to positive surface charge, occurs with multivalent ions due to their accumulation and correlation at surfaces.
- The impact of nanoconfinement, specifically pore diameter, on charge inversion-induced surface charge density remains largely unexplored.
Purpose of the Study:
- To investigate the influence of pore opening diameter on effective surface charge density induced by charge inversion.
- To explore how nanoconfinement affects the accumulation and correlation of multivalent ions at charged interfaces.
- To understand the role of pore size in controlling ionic transport and selectivity in the presence of multivalent ions.
Main Methods:
- Utilized a series of nanopores with varying opening diameters (4-25 nm).
- Exposed nanopores to trivalent chromium ions in tris(ethylenediamine)chromium(III) sulfate solutions at different concentrations.
- Measured effective surface charge density and transmembrane current under varying salt concentrations and applied voltages.
Main Results:
- Effective positive charge density induced by charge inversion is dependent on pore diameter, salt concentration, and applied voltage.
- Correlated multivalent ions can enhance transmembrane current in nanopores down to 10 nm.
- Significant current blockage was observed in narrower pores (<10 nm).
Conclusions:
- Nanoconfinement, specifically pore diameter, significantly modifies the effective surface charge density generated by charge inversion.
- Multivalent ions offer a means to control ionic transport and selectivity at the nanoscale.
- Differently sized pores within the same material can exhibit distinct surface charge densities and ion selectivities under identical experimental conditions.
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