Ion condensation in the electric double layer and the corresponding Poisson-Boltzmann effective surface charge

1995 ◽  
Vol 99 (38) ◽  
pp. 14174-14181 ◽  
Author(s):  
Phil Attard
Keyword(s):  
Surface Charge ◽  
Double Layer ◽  
Electric Double Layer ◽  
Effective Surface ◽  
Poisson Boltzmann

scholarly journals Debye-Hückel Free Energy of an Electric Double Layer with Discrete Charges Located at a Dielectric Interface

Membranes ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 129
Author(s):  
Guilherme Volpe Bossa ◽  
Sylvio May
Keyword(s):  
Free Energy ◽  
Double Layer ◽  
Electric Double Layer ◽  
Low Dielectric Constant ◽  
Surface Charges ◽  
Dielectric Interface ◽  
Charge Densities ◽  
Low Dielectric ◽  
Poisson Boltzmann ◽  
The Continuum

Poisson–Boltzmann theory provides an established framework to calculate properties and free energies of an electric double layer, especially for simple geometries and interfaces that carry continuous charge densities. At sufficiently small length scales, however, the discreteness of the surface charges cannot be neglected. We consider a planar dielectric interface that separates a salt-containing aqueous phase from a medium of low dielectric constant and carries discrete surface charges of fixed density. Within the linear Debye-Hückel limit of Poisson–Boltzmann theory, we calculate the surface potential inside a Wigner–Seitz cell that is produced by all surface charges outside the cell using a Fourier-Bessel series and a Hankel transformation. From the surface potential, we obtain the Debye-Hückel free energy of the electric double layer, which we compare with the corresponding expression in the continuum limit. Differences arise for sufficiently small charge densities, where we show that the dominating interaction is dipolar, arising from the dipoles formed by the surface charges and associated counterions. This interaction propagates through the medium of a low dielectric constant and alters the continuum power of two dependence of the free energy on the surface charge density to a power of 2.5 law.

scholarly journals Influence of the Ionic Composition of Fluid Medium on Red Cell Aggregation

1973 ◽  
Vol 61 (5) ◽  
pp. 655-668 ◽  
Author(s):  
Kung-Ming Jan ◽  
Shu Chien
Keyword(s):  
Ionic Strength ◽  
Surface Charge ◽  
Double Layer ◽  
Surface Potential ◽  
Electric Double Layer ◽  
Divalent Cations ◽  
Ionic Composition ◽  
Cell Aggregation ◽  
Fluid Medium ◽  
Induced Aggregation

The effects of ionic strength and cationic valency of the fluid medium on the surface potential and dextran-induced aggregation of red blood cells (RBC's) were investigated. The zeta potential was calculated from cell mobility in a microelectrophoresis apparatus; the degree of aggregation of normal and neuraminidase-treated RBC's in dextrans (Dx 40 and Dx 80) was quantified by microscopic observation, measurement of erythrocyte sedimentation rate, and determination of low-shear viscosity. A decrease in ionic strength caused a reduction in aggregation of normal RBC's in dextrans, but had no effect on the aggregation of neuraminidase-treated RBC's. These findings reflect an increase in electrostatic repulsive force between normal RBC's by the reduction in ionic strength due to (a) a decrease in the screening of surface charge by counter-ions and (b) an increase in the thickness of the electric double layer. Divalent cations (Ca++, Mg++, and Ba++) increased aggregation of normal RBC's in dextrans, but had no effect on the aggregation of neuraminidase-treated RBC's. These effects of the divalent cations are attributable to a decrease in surface potential of normal RBC's and a shrinkage of the electric double layer. It is concluded that the surface charge of RBC's plays a significant role in cell-to-cell interactions.

Modeling of Electroosmotic Nanoflows With Overlapped Double Layer

2011 ◽  
Author(s):  
Reza Nosrati ◽  
Mehrdad Raisee ◽  
Ahmad Nourbakhsh
Keyword(s):  
Zeta Potential ◽  
Double Layer ◽  
Electric Double Layer ◽  
Potential Distribution ◽  
Present Model ◽  
Ionic Concentration ◽  
Channel Height ◽  
Parabolic Profile ◽  
Poisson Boltzmann ◽  
Volume Method

In the present paper a new model is proposed for electric double layer (EDL) overlapped in nanochannels. The model aimed to obtain a deeper insight of transport phenomena in nanoscale. Two-dimensional Nernst and ionic conservation equations are used to obtain electroosmotic potential distribution in flow field. In the proposed study, transport equations for flow, ionic concentration and electroosmotic potential are solved numerically via finite volume method. Moreover, Debye-Hu¨ckle (DH) approximation and symmetry condition, which limit the application, are avoided. Thus, the present model is suitable for prediction of electroosmotic flows through nanochannels as well as complicated asymmetric geometries with large nonuniform zeta potential distribution. For homogeneous zeta potential distribution, it has been shown that by reduction of channel height to values comparable with EDL thickness, Poisson-Boltzmann model produces inaccurate results and must be avoided. Furthermore, for overlapped electric double layer in nanochannels with heterogeneous zeta potential distribution it has been found that the present model returns modified ionic concentration and electroosmotic potential distribution compare to previous EDL overlapped models due to 2D solution of ionic concentration distribution. Finally, velocity profiles in EDL overlapped nanochannels are investigated and it has been showed that for pure electroosmotic flow the velocity profile deviates from the expected plug-like profile towards a parabolic profile.

Effective surface charge for symmetric electrolytes in the primitive model double layer

1996 ◽  
Vol 41 (14) ◽  
pp. 2115-2124 ◽  
Author(s):  
Jonathan Ennis ◽  
Stjepan Marčelja ◽  
Roland Kjellander
Keyword(s):  
Surface Charge ◽  
Double Layer ◽  
Effective Surface ◽  
Primitive Model
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