Statistical mechanics and lifshitz theory for electrolytes. Part 1

Barnes, Clayton; Davies, Brian

doi:10.1039/f29757101667

Cited by 14 publications

(4 citation statements)

References 3 publications

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“…However, in systems containing electrolyte, the screening of van der Waals interactions has to be taken into account (20,(28)(29)(30)(31). Only the microwave term is affected by the presence of electrolyte.…”

Section: Resultsmentioning

confidence: 99%

Approximations for Calculating van der Waals Interaction Energy between Spherical Particles—A Comparison

Thennadil

García‐Rubio

2001

Journal of Colloid and Interface Science

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Section: Resultsmentioning

confidence: 99%

Approximations for Calculating van der Waals Interaction Energy between Spherical Particles—A Comparison

Thennadil

García‐Rubio

2001

Journal of Colloid and Interface Science

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“…Within the framework of a mean-field theory, namely, the Poisson−Boltzmann theory, the force between them would always be repulsive, except at the isoelectric point where it would cancel. The effects of the correlations between the fluctuations of charge in the solution are still a matter of current research. ,, They are known to reduce the repulsion and even possibly to induce an attraction between like charged surfaces at short separation distances and high surface charge densities. However, this effect is believed to be negligible for monovalent ions, because, as the Bjerrum length l B is on the order of magnitude of the size of an ion, the steric repulsion between two neighboring ions prevents their electrostatic energy of interaction from being noticeably larger than the thermal energy k B T …”

Section: Model and Discussionmentioning

confidence: 99%

Adsorption of a Cationic Polyelectrolyte on Escherichia coli Bacteria: 2. Interactions between the Bacterial Surfaces Covered with the Polymer

2001

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Quaternized polyvinylpyridine (PVPQ) was used as a cationic polymer to destabilize an Escherichia coli bacterial suspension. The optical density and the fraction of free cells, obtained by light scattering measurements, were recorded as a function of the introduced polymer amount, as a way to monitor the stability of the suspension. The flocculation was almost complete for polymer dosages ranging from about 28 to 47 mg of carbon of PVPQ per dry g of bacteria. These dosages correspond to still negatively charged cells, as shown by ζ potential measurements. At low polymer coverages, a less efficient flocculation is observed. At higher dosages, the suspension restabilizes. We interpret these results using our previous study on the adsorption of the polymer chains. We argue that the flocculation at low dosages is rendered possible by the strong inhomogeneities of charge on the bacterial surfaces because of the self-similar configuration of the adsorbed polymer layer and that the restabilization at large dosages is due to the small mesh size of the polymer network on the surface as well as to the Coulombic repulsion between the cells. The properties of the bacterial aggregates were investigated by light scattering. Destabilized suspensions produce aggregates with sizes decreasing as the quantity of adsorbed polymer increases. At the optimum of flocculation, the polydispersity of the aggregates is low, suggesting a diffusion-limited aggregation mechanism (DLA). The presence of the characteristic self-similar structure of DLA aggregates, with a fractal dimension on the order of 1.9, is suggested by some of the light diffusion experiments. On the other hand, at low coverages, that is, when only some regions on the surfaces are covered with polymers, the flocculation seems to obey a reaction-limited aggregation, with a large polydispersity in the size of the aggregates.

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“…In related studies, it has been shown that surface layers of mobile charges or dipoles also lead to modifications of the van der Waals interaction energy [17], which is relevant for interpreting measured forces between lipid bilayers [18]. A separate issue concerns the interplay between counter-ion distributions coupled to surface charges and the electric field fluctuations associated with van der Waals interactions, which has been studied in a number of publications [19,11,[20][21][22].…”

Section: Introductionmentioning

confidence: 96%

Static van der Waals interactions in electrolytes

Netz

2001

The European Physical Journal E

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Using a field-theoretic formalism, we calculate the static contribution to the van der Waals interaction between two dielectric semi-infinite half-spaces in the presence of mobile salt ions. The ions can be located in the slab, in one, or in both half-spaces. We include an excess polarizability of the salt ions, i.e., each (spherical) ion has a dielectric constant which in general is different from the surrounding medium. This leads to a modification of the effective dielectric constant of the medium hosting the ions. This shift can be large for high salt concentrations and therefore influences the Hamaker constant decisively. Salt ions in the slab screen the static van der Waals interaction, as was shown by Davies and Ninham. The salt-modified van der Waals interaction also contains salt-confinement and salt-correlation effects. This is clearly demonstrated by the fact that the interaction is non-zero even in the case when the dielectric constant is homogeneous throughout the system, in which case salt correlations are solely responsible for the interaction. If the salt ions are in one or both of the two half-spaces (and no ions in the slab), the van der Waals interaction is not screened but the effective Hamaker constant approaches a universal value for large slab thickness which is different from the value in the absence of salt ions and which is independent of the salt concentration and of the effective electrolyte dielectric constant. If both half-spaces contain salt, the asymptotic value of the Hamaker constant for large separation between the half-spaces is the one obtained for the interaction between two metallic half-spaces through an arbitrary dielectric medium, which is given by A −1.20. As is explicitly demonstrated, ion enrichment or depletion at the interfaces due to image-charge effects is already included on the one-loop level and therefore does not lead to a change of the screened van der Waals interaction as given by Davies and Ninham. For positive and negative ions with different valencies or different excess polarizabilities, we obtain different adsorbed surface excesses of positive and negative ions, leading to a non-vanishing surface potential, which is computed explicitly. All of these results are obtained on the linear one-loop level. For a special case we extend the calculation of the dispersion interaction to the two-loop level. We find the corrections to the one-loop results to be quite large for high salt concentrations or multivalent ions. PACS. 82.70.-y Disperse systems; complex fluids -61.20.Qg Structure of associated liquids: electrolytes, molten salts, etc. -82.45.+z Electrochemistry and electrophoresis

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Statistical mechanics and lifshitz theory for electrolytes. Part 1

Cited by 14 publications

References 3 publications

Approximations for Calculating van der Waals Interaction Energy between Spherical Particles—A Comparison

Approximations for Calculating van der Waals Interaction Energy between Spherical Particles—A Comparison

Adsorption of a Cationic Polyelectrolyte on Escherichia coli Bacteria: 2. Interactions between the Bacterial Surfaces Covered with the Polymer

Static van der Waals interactions in electrolytes

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