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Rectification of Ion Current in Nanopores Depends on the Type of Monovalent Cations: Experiments and Modeling.

ABSTRACT: Rectifying nanopores feature ion currents that are higher for voltages of one polarity compared to the currents recorded for corresponding voltages of the opposite polarity. Rectification of nanopores has been found to depend on the pore opening diameter and distribution of surface charges on the pore walls as well as pore geometry. Very little is known, however, on the dependence of ionic rectification on the type of transported ions of the same charge. We performed experiments with single conically shaped nanopores in a polymer film and recorded current-voltage curves in three electrolytes: LiCl, NaCl, and KCl. Rectification degrees of the pores, quantified as the ratio of currents recorded for voltages of opposite polarities, were the highest for KCl and the lowest for LiCl. The experimental observations could not be explained by a continuum modeling based on the Poisson-Nernst-Planck equations. All-atom molecular dynamics simulations revealed differential binding between Li⁺, Na⁺, and K⁺ ions and carboxyl groups on the pore walls, resulting in changes to both the effective surface charge of the nanopore and cation mobility within the pore.

SUBMITTER: Gamble T

PROVIDER: S-EPMC4317049 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Rectification of Ion Current in Nanopores Depends on the Type of Monovalent Cations: Experiments and Modeling.

Gamble Trevor T Decker Karl K Plett Timothy S TS Pevarnik Matthew M Pietschmann Jan-Frederik JF Vlassiouk Ivan I Aksimentiev Aleksei A Siwy Zuzanna S ZS

The journal of physical chemistry. C, Nanomaterials and interfaces 20140414 18

Rectifying nanopores feature ion currents that are higher for voltages of one polarity compared to the currents recorded for corresponding voltages of the opposite polarity. Rectification of nanopores has been found to depend on the pore opening diameter and distribution of surface charges on the pore walls as well as pore geometry. Very little is known, however, on the dependence of ionic rectification on the type of transported ions of the same charge. We performed experiments with single coni ...[more]

PMID: 25678940

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Project description:The ionic current rectification (ICR) is a non-linear current-voltage response upon switching the polarity of the potential across nanopore which is similar to the I-V response in the semiconductor diode. The ICR phenomenon finds several potential applications in micro/nano-fluidics (e.g., Bio-sensors and Lab-on-Chip applications). From a biological application viewpoint, most biological fluids (e.g., blood, saliva, mucus, etc.) exhibit non-Newtonian visco-elastic behavior; their rheological properties differ from Newtonian fluids. Therefore, the resultant flow-field should show an additional dependence on the rheological material properties of viscoelastic fluids such as fluid relaxation time [Formula: see text] and fluid extensibility [Formula: see text]. Despite numerous potential applications, the comprehensive investigation of the viscoelastic behavior of the fluid on ionic concentration profile and ICR phenomena has not been attempted. ICR phenomena occur when the length scale and Debye layer thickness approaches to the same order. Therefore, this work extensively investigates the effect of visco-elasticity on the flow and ionic mass transfer along with the ICR phenomena in a single conical nanopore. The Poisson-Nernst-Planck (P-N-P) model coupled with momentum equations have been solved for a wide range of conditions such as, Deborah number, [Formula: see text], Debye length parameter, [Formula: see text], fluid extensibility parameter, [Formula: see text], applied electric potential, [Formula: see text], and surface charge density [Formula: see text] and [Formula: see text]. Limited results for Newtonian fluid ([Formula: see text], and [Formula: see text]) have also been shown in order to demonstrate the effectiveness of non-Newtonian fluid behaviour over the Newtonian fluid behaviour. Four distinct novel characteristics of electro-osmotic flow (EOF) in a conical nanopore have been investigated here, namely (1) detailed structure of flow field and velocity distribution in viscoelastic fluids (2) influence of Deborah number and fluid extensibility parameter on ionic current rectification (ICR) (3) volumetric flow rate calculation as a function of Deborah number and fluid extensibility parameter (4) effect of viscoelastic parameters on concentration distribution of ions in the nanopore. At high applied voltage, both the extensibility parameter and Deborah number facilitate the ICR phenomena. In addition, the ICR phenomena are observed to be more pronounced at low values of [Formula: see text] than the high values of [Formula: see text]. This effect is due to the overlapping of the electric double layer at low values of [Formula: see text].

Dataset Information

Rectification of Ion Current in Nanopores Depends on the Type of Monovalent Cations: Experiments and Modeling.

Publications

Rectification of Ion Current in Nanopores Depends on the Type of Monovalent Cations: Experiments and Modeling.

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