Nanopore/electrode structures for single-molecule biosensing

Ayub, Muhammad Adnan; Ivanov, Aleksandar P.; Instuli, Emanuele; Cecchini, Michael P.; Chansin, G.; McGilvery, Catriona M.; Hong, Jongin; Baldwin, Geoff; McComb, David W.; Edel, Joshua B.; Albrecht, Tim

doi:10.1016/j.electacta.2010.03.051

Cited by 35 publications

(51 citation statements)

References 54 publications

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“…For a cylindrical nanopore, for example, where the length is equal to the membrane thickness, L , r(z) is constant at r 0 and the bulk nanopore conductance is

G_{bulk} = π K r_{0}^{2} ∕ L

, ignoring corrections due to end effects 21 . In the bulk limit, the nanopore conductance decreases linearly as the electrolyte conductivity decreases with reduced electrolyte concentration 19,22 . Experimental results and theoretical studies of nanoscale channels, including nanopores, however, have shown that when the surface is charged, the conductance falls less rapidly as the electrolyte concentration is reduced 18-19,22-28 .…”

Section: Theorymentioning

confidence: 99%

“…We focus on small, r 0 ≤ 10nm, nanopores for which the nanopore access resistance is a negligible contribution to the measured conductance 17 , and which is moreover the length scale of greatest interest for a large number of applications 1 . This length scale faces the most significant challenges in terms of pore-to-pore fabrication reproducibility 19 and thus a straightforward, complete sizing method would have tremendous benefit. We focus, in addition, on nanopores that are symmetric about the membrane midpoint, so that an experimental measurement of their conductance, with identical electrolyte composition on either side of the membrane, will yield a conductance independent of the applied voltage polarity.…”

Section: Introductionmentioning

confidence: 99%

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Conductance-Based Determination of Solid-State Nanopore Size and Shape: An Exploration of Performance Limits

Frament

Dwyer

2012

J. Phys. Chem. C

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Knowledge of nanopore size and shape is critical for many implementations of these single-molecule sensing elements. Geometry determination by fitting the electrolyte-concentration-dependence of the conductance of surface-charged, solid-state nanopores has been proposed to replace demanding electron microscope-based methods. The functional form of the conductance poses challenges for this method by restricting the number of free parameters used to characterize the nanopore. We calculated the electrolyte-dependent conductance of nanopores with an exponential-cylindrical radial profile using three free geometric parameters; this profile, itself, could not be uniquely geometry-optimized by the conductance. Several different structurally simplified models, however, generated quantitative agreement with the conductance, but with errors exceeding 40% for estimates of key geometrical parameters. A tractable conical-cylindrical model afforded a good characterization of the nanopore size and shape, with errors of less than 1% for the limiting radius. Understanding these performance limits provides a basis for using and extending analytical nanopore conductance models.

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“…For a cylindrical nanopore, for example, where the length is equal to the membrane thickness, L , r(z) is constant at r 0 and the bulk nanopore conductance is

G_{bulk} = π K r_{0}^{2} ∕ L

Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Conductance-Based Determination of Solid-State Nanopore Size and Shape: An Exploration of Performance Limits

Frament

Dwyer

2012

J. Phys. Chem. C

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“…Designing the chemical adapter is more challenging than in an STM configuration: To bind each DNA base as the strand passes along, the binding kinetics has to be carefully optimized. Strong electric fields inside the nanopore can lead to decomposition of molecular adsorbates and even corrosion of metallic layers on or embedded in the membrane 91 . Finally, careful consideration needs to be applied to the surface chemistry used to bind the adapter to the electrode.…”

Section: Small-molecule Sensing By Tunnelling Currentsmentioning

confidence: 99%

Electrochemical tunnelling sensors and their potential applications

Albrecht

2012

Nat Commun

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the quantum-mechanical tunnelling effect allows charge transport across nanometre-scale gaps between conducting electrodes. application of a voltage between these electrodes leads to a measurable tunnelling current, which is highly sensitive to the gap size, the voltage applied and the medium in the gap. applied to liquid environments, this offers interesting prospects of using tunnelling currents as a sensitive tool to study fundamental interfacial processes, to probe chemical reactions at the single-molecule level and to analyse the composition of biopolymers such as Dna, rna or proteins. this offers the possibility of a new class of sensor devices with unique capabilities. E lectrochemical sensors based on measuring the tunnelling current across nanoscale electrode junctions in solution are emerging as a new class of single-molecule sensors. They combine extremely high spatial resolution with sensitivity to the electronic structure of the analyte. This opens up perspectives towards the label-free detection of small molecules, the characterization of catalytic or enzymatic processes at the single-molecule level as well as the analysis of biopolymers with sub-molecular resolution, Fig. 1. To this end, label-free, fast and inexpensive RNA and DNA sequencing may be in reach, potentially revolutionizing the way we perform gene sequencing today.Charge transfer by quantum-mechanical tunnelling is one of the most ubiquitous elementary processes in nature and features in areas as diverse as electron or hydrogen transfer in enzymatic reactions, interfacial charge transfer at metal electrodes in solution, thin-layer devices in electronics, charge transfer between crystal defects and radioactive α-decay 1 . Important applications exploiting tunnelling transport include the Esaki tunnelling diode and the scanning tunnelling microscope (STM)-both recognized with the Nobel Prize in Physics for their inventors, namely Esaki in 1973 (jointly with Josephson), and Binnig and Rohrer in 1986, respectively.'Tunnelling' refers to the transport of electrons (or other light charge carriers) across a nanometre-sized gap, a molecule or even an insulating layer between two electrodes. Upon application of a bias voltage V bias between the two electrodes, negatively charged electrons are more likely to be transported towards the positively biased electrode and a so-called 'tunnelling current' I t is detected. The latter depends exponentially on gap size, which is the reason for the high spatial resolution of STM, the applied voltage V b and the electronic structure of the medium in the gap. To this end, the electrode junction may be represented by a transmission function that characterizes the probability of electrons moving from one electrode across the gap into the second electrode, summarized over all energy levels.Hence, the more accessible the energy levels in the junction, and the better their electronic coupling to the electrodes, the higher current across the junction. This also implies that the tunnelling current is sensitive to ...

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“…Nanoscale pores and pore arrays can be produced in silicon, silicon oxide and silicon nitride membranes by focused-ion beam (FIB) [4,27] or electron beam (E-beam) [36] milling, or lithography and etch techniques [40,65,19,12,39]. Combinations of beam lithography and etching are also used [32,75].…”

Section: Fabrication Of Nanoporesmentioning

confidence: 99%