Current voltage curves in synthetic conical nanopores described by a simple Poisson / Nernst Planck model
نویسنده
چکیده
We have developed a theoretical model [1] for ionic transport through synthetic conical nanopores. The results have been compared with experiments obtained for single, goldcoated conical nanopores. The model [1] describes quantitatively the ionic transport through synthetic conical nanopores. It is based on the Poisson and Nernst-Planck (PNP) equations and allows the calculation of realistic profiles of average ionic concentration and electric potential along the pore. The only adjustable parameter is the surface charge density σ. Within this formalism, the concentration and potential profiles are computed together as self-consistent solutions of the PNP equations, in this way avoiding the assumption of a given potential distribution along the pore. We have compared the results provided by the PNP model with recent experimental data by Siwy et al. [2] obtained for two poly(ethylene terephthalate) (PET) filters containing single goldcoated conical nanopores. They were produced by chemically etching a PET foil containing a single heavy ion track (irradiated at UNILAC, GSI) and subsequently covering the pore walls with gold by electroless plating. After this procedure, the small radius of the pores was ≈ 5 nm and the wide radius ≈ 300 nm. The length of the pores was ≈ 12 μm. In the experimental setup, the membrane separated the two halves of an electrolytic cell, containing 0.1 M KF solutions. I-V curves were recorded at several pH values, for pores with differently modified surfaces. The results in Fig. 1a were obtained from a nanopore modified with 2mercaptopropionic acid, yielding a negative surface charge at pH = 6.6, and a neutral surface charge at pH = 3.5. In Fig. 1b, the nanopore surface contained mercaptoethylammonium groups and the measurements were conducted at pH = 6.6, yielding a positive surface charge. When the pore wall is uncharged, the IV curve is linear (full circles in Fig. 1a). When the surface becomes charged, the corresponding IV curves show rectification (open circles). For negative surface charge, the electric current is higher for V > 0 than for V < 0 (states on and off). If the charge on the pore wall becomes positive, the on and off states of the nanopore appear at V < 0 and V > 0, respectively. The theoretical results in Fig. 1 (dashed and full lines) are parametric in the surface charge density σ (e is the elementary charge). In all the calculations we used the (infinite dilution) diffusion coefficients D+ = 1.47· 10 cm/s, and D = 2.03· 10 cm/s of the ionic species. Figure 1: Experimental (circles) [2] and theoretical (curves) results for the negatively (a) and positively (b) charged nanopore. The curves are parametric in the surface charge density σ.
منابع مشابه
Rectification in synthetic conical nanopores: a one-dimensional Poisson-Nernst-Planck model.
Ion transport in biological and synthetic nanochannels is characterized by phenomena such as ion current fluctuations and rectification. Recently, it has been demonstrated that nanofabricated synthetic pores can mimic transport properties of biological ion channels [P. Yu. Apel, Nucl. Instrum Methods Phys. Res. B 184, 337 (2001); Z. Siwy, Europhys. Lett. 60, 349 (2002)]. Here, the ion current r...
متن کاملPoisson-Boltzmann-Nernst-Planck model.
The Poisson-Nernst-Planck (PNP) model is based on a mean-field approximation of ion interactions and continuum descriptions of concentration and electrostatic potential. It provides qualitative explanation and increasingly quantitative predictions of experimental measurements for the ion transport problems in many areas such as semiconductor devices, nanofluidic systems, and biological systems,...
متن کاملIon Current Rectification, Limiting and Overlimiting Conductances in Nanopores
Previous reports on Poisson-Nernst-Planck (PNP) simulations of solid-state nanopores have focused on steady state behaviour under simplified boundary conditions. These are Neumann boundary conditions for the voltage at the pore walls, and in some cases also Donnan equilibrium boundary conditions for concentrations and voltages at both entrances of the nanopore. In this paper, we report time-dep...
متن کاملM ar 2 00 8 A singular perturbation approach to the steady - state 1 D Poisson - Nernst - Planck modeling
The reduced 1D Poisson-Nernst-Planck (PNP) model of artificial nanopores in the presence of a permanent charge on the channel wall is studied. More specifically, we consider the limit where the channel length exceed much the Debye screening length and channel’s charge is sufficiently small. Ion transport is described by the nonequillibrium steady-state solution of the PNP system within a singul...
متن کاملPoisson-Nernst-Planck model of ion current rectification through a nanofluidic diode.
We have investigated ion current rectification properties of a recently prepared bipolar nanofluidic diode. This device is based on a single conically shaped nanopore in a polymer film whose pore walls contain a sharp boundary between positively and negatively charged regions. A semiquantitative model that employs Poisson and Nernst-Planck equations predicts current-voltage curves as well as io...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2006