Debye-Hückel-Bjerrum theory for charged colloids

Instituto de Fı́sica, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, 91501-970 Porto Alegre (RS), Brazil
Physica A: Statistical Mechanics and its Applications (Impact Factor: 1.73). 09/1998; 258(3-4):341-351. DOI: 10.1016/S0378-4371(98)00238-6
Source: arXiv


We formulate an extension of the Debye-Hueckel-Bjerrum theory [M. E.
Fisher and Y. Levin, Phys. Rev. Lett. 71, 3826 (1993)] to the fluid
state of a highly asymmetric charged colloid. Allowing for the formation
of clusters consisting of one polyion and n condensed counterions, the
total Helmholtz free energy of the colloidal suspension is constructed.
The thermodynamic properties, such as the cluster-density distribution
and the pressure, are obtained by the minimization of the free energy
under the constraints of fixed number of polyions and counterions. In
agreement with the current experimental and Monte Carlo results, no
evidence of any phase transition is encountered.

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    • "Therefore, the ion mobilities beneath the slip plane at present can only be considered fitting parameters. In the limiting case of zero counterion mobility, the model of hydrodynamically immobile surface layer yields results similar to the model of counterion condensation [19]. By introducing a hydrodynamically immobile layer into the capillary space charge model, we are confronted with three additional fitting parameters, namely, the layer thickness and the mobilities of counterions and co-ions beneath the slip plane. "
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    Physica A: Statistical Mechanics and its Applications 11/1998; 268(1-2-268):24-49. DOI:10.1016/S0378-4371(99)00013-8 · 1.73 Impact Factor
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    ABSTRACT: Using a carefully justified development of Debye-Huckel theory for highly asymmetric electrolytes, one finds that a region of expanded phase instability, or miscibility gap, can appear for charge-stabilised colloidal suspensions at high charges and low ionic strengths. It is argued that this is offers a straightforward explanation for the observations of void structures and other anomalies in such suspensions in this region. The nature of the interface between coexisting phases, and general arguments that many-body attractions form a key part of the underlying physical picture, are also examined. The present analysis may also generate new insights into old problems such as coacervation in oppositely charged colloid or protein / polyelectrolyte mixtures, and suggests interesting new possibilities such as the appearance of charge density wave phases in colloidal systems in the vicinity of the critical solution points.
    The Journal of Chemical Physics 10/1999; 112(10). DOI:10.1063/1.481024 · 2.95 Impact Factor
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