The Electrical Double Layer and the Theory of Electrocapillarity.

Grahame, David C.

doi:10.1021/cr60130a002

Cited by 2,992 publications

(1,828 citation statements)

References 26 publications

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“…This is evident from Eq. (12). An increase in two orders of magnitude of ion concentration (e.g., from 1mM to 0.1M), increases the average electrical incubation time for cylindrical NW sensors (D F = 1) by one order of magnitude while for planar sensors (D F = 2) by two orders of magnitude.…”

Section: Discussionmentioning

confidence: 96%

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Screening-Limited Response of NanoBiosensors

2008

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ABSTRACT:Despite tremendous potential of highly sensitive electronic detection of bio-molecules by nanoscale biosensors for genomics and proteomic applications, many aspects of experimentally observed sensor response (S) are unexplained within consistent theoretical frameworks of kinetic response or electrical screening. In this paper, we combine analytic solutions of Poisson-Boltzmann and reaction-diffusion equations to show that the electrostatic screening within an ionic environment limits the response of nanobiosensor such that ( ) ( ) ( ) ( ) [ ]

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Section: Discussionmentioning

confidence: 96%

“…Performance Limits of Sensors: The detection limits of nanoscale sensors in a diffusion limited regime are predicted by Eq. (12). However, screening due to the ions can significantly increase the average incubation times for achieving the same sensor response.…”

Section: Discussionmentioning

confidence: 99%

Screening-Limited Response of NanoBiosensors

2008

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“…To describe ion storage in the EDLs in the micropores in the carbon particles, see arise from electrostatic compression of the diffuse charge in the micropore or specific adsorption of ions on the surface [61][62][63][64]. Although the Stern capacity must eventually saturate or even decrease at high voltage, as the water dipoles become strongly aligned and/or adsorbed ions become crowded [50], our parabolic charge dependence of C St,vol is a reasonable first approximation for Grahame's celebrated electrocapillary data for mercury drop electrodes [61].…”

Section: Non-linear Theory -Porous Electrodesmentioning

confidence: 99%

Time-dependent ion selectivity in capacitive charging of porous electrodes

Zhao

Soestbergen

Rijnaarts

et al. 2012

Journal of Colloid and Interface Science

233

182

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In a combined experimental and theoretical study we show that capacitive charging of porous electrodes in multicomponent electrolytes may lead to the phenomenon of time-dependent ion selectivity of the electrical double layers (EDLs) in the electrodes. This effect is found in experiments on capacitive deionization of water containing NaCl/CaCl 2 mixtures, when the concentration of Na + ions in the water is 5 times higher than the Ca 2+ -ion concentration. In this experiment, after applying a voltage difference between two porous carbon electrodes, first the majority monovalent Na + cations are preferentially adsorbed in the EDLs, and later they are gradually replaced by the minority, divalent Ca 2+ cations. In a process where this ion adsorption step is followed by washing the electrode with freshwater under open-circuit conditions, and subsequent release of the ions while the cell is shortcircuited, a product stream is obtained which is significantly enriched in divalent ions. Repeating this process three times by taking the product concentrations of one run as the feed concentrations for the next, a final increase in the Ca 2+ /Na + -ratio of a factor of 300 is achieved. The phenomenon of timedependent ion selectivity of EDLs cannot be explained by linear response theory. Therefore, a nonlinear time-dependent analysis of capacitive charging is performed for both porous and flat electrodes. Both models attribute time-dependent ion selectivity to the interplay of the transport resistance for the ions in the aqueous solution outside the EDL, and the voltage-dependent ion adsorption capacity of the EDLs. Exact analytical expressions are presented for the excess ion adsorption in planar EDLs (Gouy-Chapman theory) for mixtures containing both monovalent and divalent cations.key-words: water desalination; porous electrode theory; capacitive (non-faradaic) electrochemical cells; electrostatic double layer theory.2

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“…Based on the model of Gouy and Chapman (26,27), the Grahame equation (28) describes the relation between surface charge and surface potential in terms of the ionic composition of the solution. Even though this equation is based on the simplistic assumption of smeared surface charges it has been shown that it rather well describes the surface potential of a plane with moderately spread out point charges (29) and thus that of most ion channels (15).…”

Section: Introductionmentioning

confidence: 99%

Extracellular Linkers Completely Transplant the Voltage Dependence from Kv1.2 Ion Channels to Kv2.1

Elinder

Madeja

Zeberg

et al. 2016

Biophysical Journal

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The transmembrane voltage needed to open different voltage-gated K (Kv) channels differs by up to 50 mV from each other. In this study we test the hypothesis that the channels' voltage dependences to a large extent are set by charged amino-acid residues of the extracellular linkers of the Kv channels, which electrostatically affect the charged amino-acid residues of the voltage sensor S4. Extracellular cations shift the conductance-versus-voltage curve, G(V), by interfering with these extracellular charges. We have explored these issues by analyzing the effects of the divalent strontium ion (Sr 2þ ) on the voltage dependence of the G(V) curves of wild-type and chimeric Kv channels expressed in Xenopus oocytes, using the voltage-clamp technique. Out of seven Kv channels, Kv1.2 was found to be most sensitive to Sr 2þ (50 mM shifted G(V) by þ21.7 mV), and Kv2.1 to be the least sensitive (þ7.8 mV). Experiments on 25 chimeras, constructed from Kv1.2 and Kv2.1, showed that the large Sr 2þ -induced G(V) shift of Kv1.2 can be transferred to Kv2.1 by exchanging the extracellular linker between S3 and S4 (L3/4) in combination with either the extracellular linker between S5 and the pore (L5/P) or that between the pore and S6 (LP/6). The effects of the linker substitutions were nonadditive, suggesting specific structural interactions. The free energy of these interactions was~20 kJ/mol, suggesting involvement of hydrophobic interactions and/or hydrogen bonds. Using principles from double-layer theory we derived an approximate linear equation (relating the voltage shifts to altered ionic strength), which proved to well match experimental data, suggesting that Sr 2þ acts on these channels mainly by screening surface charges. Taken together, these results highlight the extracellular surface potential at the voltage sensor as an important determinant of the channels' voltage dependence, making the extracellular linkers essential targets for evolutionary selection.

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The Electrical Double Layer and the Theory of Electrocapillarity.

Cited by 2,992 publications

References 26 publications

Screening-Limited Response of NanoBiosensors

Screening-Limited Response of NanoBiosensors

Time-dependent ion selectivity in capacitive charging of porous electrodes

Extracellular Linkers Completely Transplant the Voltage Dependence from Kv1.2 Ion Channels to Kv2.1

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