Gate modulation of proton transport in a nanopore (original) (raw)
Related papers
pH-Regulated nanopore conductance with overlapped electric double layers
Electrochemistry Communications, 2015
There has been a significant growth of interest in single nanopore ionic devices that could control the transport of ions and rectify ionic current. To improve the advance of relevant nanofluidic devices, a model is derived for the first time to investigate the zeta potential and ionic conductance of a cylindrical nanopore with overlapped electric double layer as functions of pH, salt concentration as well as the Stern layer capacitance. The developed model is validated by the experimental data of the nanopore conductance. Results show that in addition to the magnitudes, the relevant behaviors of zeta potential and conductance of the nanopore might be significantly influenced by the Stern layer.
Modeling of pH-Switchable Ion Transport and Selectivity in Nanopore Membranes with Fixed Charges
The Journal of Physical Chemistry B, 2003
The pH-switchable ion transport and selectivity in nanopore membranes with fixed charges is theoretically analyzed using a model based on the Nernst-Planck flux equations. The ionization state of the weak polyelectrolyte groups attached to the pore surface appears to be a crucial factor in order to understand the conductive properties of the pore. The model allows for the calculation of the fluxes of all of the ionic species involved and the membrane potential. Comparison of the theoretical results with the experimental data by 5271-5) for surface modified nanopores with fixed charges shows that the model can describe qualitatively the changes of the permeate ion flux and the membrane potential with the pH and the solute concentration of the external solutions. The effect of applying an electric potential to the nanopore walls is also studied. Some of the main characteristics that allow a simple description of pH-switchable effects on nanopore membranes with fixed charges are clearly shown.
Theoretical description of the ion transport across nanopores with titratable fixed charges
Cell Biochemistry and Biophysics, 2006
Recently developed nanometer-sized synthetic pores display several properties so far believed to be distinctive features of a large variety of biological wide ion channels. Thus conductance in the pS-nS range, pH-dependent ion selectivity, fluctuations of current between open and closed states, flux inhibition caused by protons or divalent cations, current rectification, and the ability to perform selective macromolecule sizing and counting are found in synthetic and biological channels alike. Despite other differences such as pore size and geometry, the similarities open a new field for exploring specific technological applications via the chemical modification of synthetic pores with biological molecules. This article reviews some of the basis concepts and theories relevant to ion transport in nanopores with titratable charges stressing the analogies between synthetic pores and biological ion channels. The ultimate goal is to show that continuum theories may account for the essential features of these systems. A simple electrodiffusion model and its comparison with experimental results are chosen as a case study.
Descreening of field effect in electrically gated nanopores
Applied Physics Letters, 2010
This modeling work investigates the electrical modulation characteristics of field-effect gated nanopores. Highly nonlinear current modulations are observed in nanopores with non-overlapping electric double layers, including those with pore diameters 100 times the Debye screening length. We attribute this extended field-effect gating to a descreening effect, i.e. the counter-ions do not fully relax to screen the gating potential due to the presence of strong ionic transport. *
Controlling ion transport through nanopores: modeling transistor behavior
Physical Chemistry Chemical Physics, 2018
We present a modeling study of a nanopore-based transistor computed by a mean-field continuum theory (Poisson–Nernst–Planck, PNP) and a hybrid method including particle simulation (Local Equilibrium Monte Carlo, LEMC) that is able to take ionic correlations into account including the finite size of ions.
Control of ionic transport through gated single conical nanopores
Analytical and Bioanalytical Chemistry, 2009
Control of ionic transport through nanoporous systems is a topic of scientific interest for the ability to create new devices that are applicable for ions and molecules in water solutions. We show the preparation of an ionic transistor based on single conical nanopores in polymer films with an insulated gold thin film "gate." By changing the electric potential applied to the "gate," the current through the device can be changed from the rectifying behavior of a typical conical nanopore to the almost linear behavior seen in cylindrical nanopores. The mechanism for this change in transport behavior is thought to be the enhancement of concentration polarization induced by the gate. Control of ionic transport through nanoporous systems is a topic of scientific interest for the ability to create new devices that are applicable for ions and molecules in water solutions. We show the preparation of an ionic transistor based on single conical nanopores in polymer films with an insulated gold thin film "gate." By changing the electric potential applied to the "gate," the current through the device can be changed from the rectifying behavior of a typical conical nanopore to the almost linear behavior seen in cylindrical nanopores. The mechanism for this change in transport behavior is thought to be the enhancement of concentration polarization induced by the gate.
Nanopore Electrochemistry: A Nexus for Molecular Control of Electron Transfer Reactions
ACS Central Science
Pore-based structures occur widely in living organisms. Ion channels embedded in cell membranes, for example, provide pathways, where electron and proton transfer are coupled to the exchange of vital molecules. Learning from mother nature, a recent surge in activity has focused on artificial nanopore architectures to effect electrochemical transformations not accessible in larger structures. Here, we highlight these exciting advances. Starting with a brief overview of nanopore electrodes, including the early history and development of nanopore sensing based on nanopore-confined electrochemistry, we address the core concepts and special characteristics of nanopores in electron transfer. We describe nanopore-based electrochemical sensing and processing, discuss performance limits and challenges, and conclude with an outlook for nextgeneration nanopore electrode sensing platforms and the opportunities they present.
Cell Biochemistry and Biophysics, 2006
Recently developed nanometer-sized synthetic pores display several properties so far believed to be distinctive features of a large variety of biological wide ion channels. Thus conductance in the pS-nS range, pH-dependent ion selectivity, fluctuations of current between open and closed states, flux inhibition caused by protons or divalent cations, current rectification, and the ability to perform selective macromolecule sizing and counting are found in synthetic and biological channels alike. Despite other differences such as pore size and geometry, the similarities open a new field for exploring specific technological applications via the chemical modification of synthetic pores with biological molecules. This article reviews some of the basic concepts and theories relevant to ion transport in nanopores with titratable charges stressing the analogies between synthetic pores and biological ion channels. The ultimate goal is to show that continuum theories may account for the essential features of these systems. A simple electrodiffusion model and its comparison with experimental results are chosen as a case study.
Directional ion selectivity in a biological nanopore with bipolar structure
Journal of Membrane Science, 2009
Ion transport features of a biological nanopore, the bacterial porin OmpF from Escherichia coli, have been investigated by patch-clamp experiments performed at the single channel level. Membrane potential measurements done under asymmetric conditions of pH and electrolyte concentration provide important evidences about the charge regulation exerted by the channel that cannot be extracted from the rectification displayed in current-voltage curves. The pH gradient imposed across the pore induces an asymmetric fixed-charge distribution that resembles the structure of synthetic bipolar membranes. This particular arrangement demonstrates that the ionic selectivity of a non-uniformly charged structure is not an intrinsic quality of the system but depends crucially on several external factors. Amazingly, changing the direction of the salt concentration gradient can turn a cation selective channel into an anion selective one.
The Effects of Concentration Polarization on Molecule Translocation in a Nanopore Device
2008
Nanopores offer the potential for label-free detection of individual proteins [1] and have been identified as a key potential technology for low cost DNA sequencing.[2] To date, most studies of nanopore electrokinetic transport [1,3,4] have neglected the effects of concentration polarization (CP) especially in systems with nonoverlapped electric double layers (EDLs). We present a combined computational and experimental study of conical nanopores with tip diameters of 40-100 nm. Our modeling and experimental work shows that for typical (mM) buffer concentrations, even non-overlapped EDLs fundamentally affect key transport characteristics such as the rate of molecular translocations.