Mechanism of Electrostatic Gating at Conical Glass Nanopore Electrodes

White, Henry S.; Bund, Andreas

doi:10.1021/la801776w

Cited by 32 publications

(24 citation statements)

References 28 publications

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“…Previous simulations utilized σ of −0.001 to −1.5 e/nm 2 (−0.16 to −240 mC/m 2 ) and produced rectified current responses in good qualitative agreement with measured current-voltage curves. 2,28,35,46-48 Recent simulations determine σ on a nanopipette wall through fitting experimentally measured i-V curves with simulated i-V s and gave σ values from −170 to −240 mC/m 2 . 47,49 For most simulations, −1 e/nm 2 (−160 mC/m 2 ) has been used to consider effects of surface charge on current rectification.…”

Section: Resultsmentioning

confidence: 99%

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Rectification of Ion Current in Nanopipettes by External Substrates

et al. 2013

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We describe ion distribution and the current-voltage (i-V) response of nanopipettes at different probe-to-substrate distances (Dps) as simulated by finite-element methods. Results suggest electrostatic interactions between a charged substrate and the nanopipette dominate electrophoretic ion transport through the nanopipette when Dps is within one order of magnitude of the Debye length (~10 nm for a 1 mM solution as employed in the simulation). Ion current rectification (ICR) and permselectivity associated with a neutral or charged nanopipette can be reversibly enhanced or reduced dependent on Dps, charge polarity and charge density (σ) of the substrate. Regulation of nanopipette current is a consequence of the enrichment or depletion of ions within the nanopipette interior which influences conductivity of the nanopipette. When the external substrate is less negatively charged than the nanopipette, the substrate first reduces, and then enhances the ICR as Dps decreases. Surprisingly, both experimental and simulated data show that a neutral substrate was also able to reduce and reverse the ICR of a slightly negatively charged nanopipette. Simulated results ascribe such effects to the elimination of ion depletion within the nanopipette at positive potentials.

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Section: Resultsmentioning

confidence: 99%

“…White and Bund have reported the application of FEM solve mass transfer problems in nanoscale domains. 28,35 The accuracy of FEM was verified by solving simple equations with regular geometries ( e.g. , the electrical double layer at a flat substrate and electroosmosis within a capillary) where known analytical solutions exist.…”

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confidence: 99%

Rectification of Ion Current in Nanopipettes by External Substrates

et al. 2013

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“…The simulation geometry of a RNE (a = 12 nm, L = 30 nm) is shown in Figure 1a, which corresponds to a RNE based on a PS-b-PMMA-derived nanoporous film that was previously studied by our group (9,10,13). The nanopore radius is significantly larger than the sizes of water molecules and ions, making it possible to carry out computer simulations based on continuum theory (19). Simulated CVs were obtained for a reversible, uncharged redox species (at 3 mM), which corresponded to 1,1'-ferrocenedimethanol (D bulk = 6.4 x 10 -6 cm 2 /s (20)).…”

Section: Methodsmentioning

confidence: 99%

Finite-Element Computer Simulations on Cyclic Voltammograms Measured at Recessed Nanodisk-Array Electrodes

Tran-Ba

Ito

2013

ECS Trans.

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The characteristics of cyclic voltammograms (CVs) at recessed nanodisk-array electrodes (RNEs) were investigated using finiteelement computer simulations. Simulations were performed for RNEs based on planar electrodes coated with electricallyinsulating films comprising hexagonally-distributed, verticallyoriented cylindrical nanopores (12 nm in radius, 30 nm deep). CVs and concentration profiles of redox species were simulated by varying electrode spacing (2s) and the diffusion coefficient of a redox species within the nanopores (D pore ). For nm-scale s and large D pore , peak-shaped CVs with currents very similar to those at a film-free electrode were obtained due to the overlapping of diffusion layers extended from multiple electrodes. However, larger s and smaller D pore gave smaller peak currents, as the nanoscale electrodes limited the number of redox species to be reacted. Further increase in s offered sigmoidal CVs though s was small enough for the overlapping of diffusion layers. These trends were consistent with experimental CVs measured at RNEs.

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“…11−13 This effect occurs within conical-shaped pores due to the voltage dependent solution conductivity within the aperture. 11 The degree to which a conical-shaped pore exhibits an asymmetrical current−voltage response is based on the orifice size, surface charge, and Debye length. 12,14 This current rectification is maximized at intermediate bulk ion concentrations, decreasing from this maximum at high concentrations due to the electrical screening of the surface charge as well as at low concentrations due to a fixed number of charge-carrying ions.…”

Section: * S Supporting Informationmentioning

confidence: 99%

Decreasing the Limits of Detection and Analysis Time of Ion Current Rectification Biosensing Measurements via a Mechanically Applied Pressure Differential

Schibel

Ervin

2015

Anal. Chem.

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Improving on the analytical capabilities of a measurement is a fundamental challenge with all assays, particularly decreasing the limit of detection while maintaining a practical associated analysis time. Of late, ion current rectification (ICR) biosensing measurements have received a great deal of attention as an analyte-specific, label-free assay. In ICR biosensing, a nanopore coated with an analyte specific binding molecule (e.g., an antibody, an aptamer, etc.) is used to detect a target analyte based on the ability of the target analyte to alter the ICR response of the nanopore upon it binding to the aperture interior. This binding changes the local surface charge and/or size of the nanopore aperture, thus altering its ICR response in a time dependent manner. Here, we report the ability to enhance the transport of a target analyte molecule to and through the aperture of an antibody modified glass nanopore membrane (AMGNM) with the application of a mechanically applied pressure differential. We demonstrate that there is an optimal pressure that balances the flux of the target analyte through the AMGNM aperture with its ability to be bound and detected. Applying the optimal pressure differential allows for picomolar concentrations of the cleaved form of synaptosomal-associated protein 25 (cSNAP-25) to be detected within the same analysis time as micromolar concentrations detected without the use of the pressure differential. The methodology presented here significantly expands the utility of ICR biosensing measurements for detecting low-abundance biomolecules by lowering the limit of detection and reducing the associated analysis time.

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Mechanism of Electrostatic Gating at Conical Glass Nanopore Electrodes

Cited by 32 publications

References 28 publications

Rectification of Ion Current in Nanopipettes by External Substrates

Rectification of Ion Current in Nanopipettes by External Substrates

Finite-Element Computer Simulations on Cyclic Voltammograms Measured at Recessed Nanodisk-Array Electrodes

Decreasing the Limits of Detection and Analysis Time of Ion Current Rectification Biosensing Measurements via a Mechanically Applied Pressure Differential

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