Electrostatic interaction between ion-penetrable membranes in a salt-free medium

A set of coupled equations is given which determines the distributions of the electric potential and counterions in a system of two interacting identical ion-penetrable membranes of thickness d at separation h immersed in a salt-free medium containing only counterions. The solution to these coupled equations also gives the electrostatic repulsive force between the membranes. It is shown that the interaction force remains finite at h-->0, unlike the case of the interaction between two planar charged surfaces (d-->0), and that the interaction force becomes independent of the membrane fixed charge and membrane thickness d at very large h. Finally, an approximate single transcendental equation giving the solution to the coupled equations is derived.     

Electrostatic interaction between two parallel cylinders

Explicit exact analytic expressions are obtained for the electric potential distribution and for the electrostatic interaction energy for the system of two parallel dissimilar cylinders in an electrolyte solution on the basis of the linearized Poisson-Boltzmann equation.     

Electrostatic interactions in the adhesion of an ion-penetrable and ion-impenetrable bacterial strain to glass

Deposition to glass of Streptococcus salivarius HB-C12 and Staphylococcus epidermidis 3399 in a parallel plate flow chamber has been studied as a function of ionic strength. Electrophoretic mobility measurements revealed that S. epidermidis 3399 possesses a thick ion-penetrable layer, probably associated with its encapsulation, while S. salivarius HB-C12 has an ion-impenetrable surface. Streaming potential measurements indicated that also the glass surface was covered with a relatively thin, ion-penetrable layer. Theoretical initial deposition rates of both strains to glass were obtained by numerically solving the convective-diffusion equation, while accounting for the ion-penetrability of the interacting surfaces. Experimentally, the initial deposition rate of the ion-penetrable strain S. epidermidis 3399 was found to be higher and less dependent on ionic strength than of the ion-impenetrable S. salivarius HB-C12, in accordance with theoretical expectations. Agreement between theoretical and experimental deposition rates could be obtained when glass was considered ion-penetrable when interacting with the ion-penetrable organism S. epidermidis 3399, while glass behaved as an ion-impenetrable surface when interacting with the ion-impenetrable S. salivarius HB-C12. Probably, interaction with an ion-impenetrable strain drives the diffuse double layer charges into the limited volume of the thin ion-penetrable layer on the glass, readily filling it up and making it appear ion-impenetrable. During interaction of glass with another ion-penetrable surface, as of S. epidermidis 3399, diffuse double layer charges move into both ion-penetrable surfaces, resulting in a much lower mobile charge density in the ion-penetrable layer on the glass which consequently continues to behave as ion-penetrable.     

Electrostatic interaction between a cylinder and a planar surface

 An exact analytical expression for the potential energy of the electrostatic interaction between a plate-like particle 1 and a cylindrical particle 2 of radius a ₂ immersed in an electrolyte solution of Debye–Hückel parameter κ is derived on the basis of the linearized Poisson–Boltzmann equation without recourse to Derjaguin's approximation. Both particles may have either constant surface potential or constant surface charge density. In the limit of κa ₂→0, in particular, the interaction between a plate with zero surface charge density and a cylinder having constant surface charge density becomes identical to the usual image interaction between a line charge (a charged rod of infinitesimal thickness) and an uncharged plate. Received: 22 September 1998  Accepted in revised form: 27 January 1999     

Electrostatic interaction of ion-penetrable membranes. Effects of ionic solubility

An analytic, approximate expression for the electrostatic interaction between two membranes immersed in an electrolyte solution is derived on the basis of a simple membrane model. This model assumes that the membrane has a surface layer in which charged groups are uniformly distributed and that electrolyte ions can penetrate into the surface layer. The partition coefficients of cations and anions between the solution and the surface layer, which are related to their solubilities in the surface layer, may be different from unity.The electrostatic interaction depends on the ionic partition coefficients between the solution and the surface layer, and the relative permittivity of the surface layer, as well as on the membrane-fixed charges, the electrolyte concentration in the solution, and the surface layer thickness. It is shown, in particular, that even where the charge layer has no fixed charges, the electrostatic interaction force can be produced if the solubilities of cations and anions are different in the surface layer.     

Electrostatic Interaction between Two Ion-Penetrable Charged Spheroids

The electrostatic interaction between two ion-penetrable, charged spheroidal particles is examined theoretically. These particles can assume different sizes and an arbitrary spatial orientation. The electrical potential distribution is derived analytically under the Debye–Huckle condition. The results for two interaction spheres, one spheroidal particle and a planar surface, and rigid particles covered by an ion-penetrable membrane can be recovered as the special cases of the present general problem. We show that, for a fixed center-to-center distance between two particles, regardless of their relative sizes, the interaction free energy is the greatest if their major axes lie on the same line (head-to-head), and the smallest if their major axes are perpendicular to each other but not on the same plane (perpendicular).     

Numerical computation of the electrostatic interaction energy between methanol and the dyad water-imidazole

Summary The electrostatic interaction energy between methanol and the dyad water-imidazole has been computed numerically at three levels of approximation from 3D grids of the charge density of one partner and the electrostatic potential of the other. The minimum positions and energy values thus obtained compare well with those calculated analytically. The numerical procedure is especially interesting for the prediction of the stable conformers.     

通过静电相互作用制备CdTe/SiO2纳米复合物

以四乙氧基硅烷(TEOS)为原料,在乙醇相中制备了尺寸为80nmSiO₂纳米粒子,用3-氨基丙基三乙氧基硅烷对SiO₂纳米粒子进行了氨基化.以巯基乙酸为配体,在水相中合成了CdTe纳米晶.通过静电相互作用,CdTe纳米晶被吸附到氨基化的二氧化硅球的表面上.研究了两种粒子复合后引起的CdTe纳米晶发光光谱的变化.     

Electrical interaction between two cylinders with an ion-penetrable charged membrane in an oil/water interface

The electrical interaction between two long, parallel cylinders each is covered by an ion-penetrable charged membrane immersed in an oil/water interface is investigated. The effects of contact angle, radius of cylinder, and membrane thickness on the electrical interaction force are examined. The results of numerical simulation reveal that the following conditions lead to a greater electrical interaction force: (i) a larger contact angle, i.e. a larger fraction of a cylinder in the oil phase; (ii) a larger cylinder radius; and (iii) a thinner membrane. For a fixed ionic strength, the electrical interaction force is insensible to the type of electrolytes in the water phase, in general. However, if two cylinders are close enough, then the higher the valence of counterions the greater the electrical interaction force.     

Electrostatic interaction between a charge-regulated particle and a solid surface in electrolyte solution: effect of cationic electrolytes

The effect of cations on the electrostatic interaction between a negative charge-regulated particle and a solid surface of constant negative potential in electrolyte solution is analyzed. Here, we assume that the rate of approach of a particle to a solid surface is faster than that of the dissociation of the ionogenic groups on the surface of particle. In other words, the effect of the time-dependent dissociation of ionogenic groups on the surface of a particle is taken into account. The result of the present study reveals that, although the solid surface is negatively charged, the presence of cations in the suspension medium has a negative effect on the rate of adhesion. The qualitative behaviors in the variation of the interaction force between a particle and a solid surface as a function of separation distance between them predicted by a kinetic model and the corresponding equilibrium model and constant charge density model are entirely different. The rate of approach of a particle to a solid surface is on the order (constant charge density model)>(kinetic model)>(equilibrium model).     

Electrostatic interaction effect for human DNA separation with functionalized mesoporous silicas

This work describes the development of highly efficient human DNA separation with functionalized mesoporous silica (FMS) materials. To demonstrate the electrostatic interaction effect between the target DNA molecules and FMS, three aminofunctionality types comprised of a mono-, a di-, and a tri-amine functional group were introduced on the inner surfaces of mesoporous silica particles. Systematic characterization of the synthesized materials was achieved by solid-state ²⁹Si and ¹³C-NMR techniques, BET, FT-IR, and XPS. The DNA separation efficiency was explored via the function of the amino-group number, the amount used, and the added NaCl concentration. The DNA adsorption yields were high in terms of the use of triaminofunctionalized FMS at the 10 ng/L level, and the DNA desorption efficiency showed the optimum level at over 3.0 M NaCl concentration. The use of FMS in a DNA separation process provides numerous advantages over the conventional silica-based process.     

Interaction between an ion-penetrable particle and a solid particle. 1. Electrical double-layer interaction

Expressions are derived for the force and potential energy of the electrical double layer interaction between two parallel plates of different nature, i. e., an ion-penetrable plate and an ion-impenetrable plate. The latter may have either constant surface potential or constant surface charge density. It is shown that when the ion-impenetrable plate has a constant surface potential, the interaction force may, under certain conditions, become attractive even if the surface potentials of the two plates at infinite separation are of the same sign. In contrast, when the ion-impenetrable plate has a constant surface charge density, the interaction force may, under certain conditions, become repulsive even if the two plates at infinite separation are of opposite sign. This means that an ion-penetrable plate shows a dual behavior. That is, under certain conditions, it behaves like a solid plate with constant surface potential or surface charge density, depending on whether it interacts with a solid plate having a constant surface potential or a constant surface charge density.     

Approaches to separation interfaces: Electrostatic interaction and local structures of ions at zwitterionic interface

The interaction and separation of ions with zwitterionic layers are reviewed principally based on a series of the author's work. An electrostatic model has allowed us to discuss the chromatographic retention of ions on the zwitterionic stationary phase, and has revealed the ionic interaction occurring at the zwitterionic interface. Similar consideration is applicable to the ionic partition into zwitterionic micelles having the spherical dimension. In the electrostatic models, ion association and solvation changes of ions have been assumed to explain the selectivity in ion recognition. Both assumptions are applicable to polarizable large ions, whereas the former cannot account for the results obtained for small and well-hydrated ions (Cl⁻ and Br⁻). A special X-ray absorption finestructure (XAFS) measurement, which allows selective access to ions interacting with surface monolayers, has been developed, and applied to ions attracted by a zwitterionic monolayer. The X-ray absorption spectra suggest that Zn²⁺ attracted by the zwitterionic monolayer is still hydrated. In contrast, the direct interaction of Br⁻ has been confirmed, indicating that the electrostatic model involving either ion association or the solvation change of an ion does not properly explain the observed phenomena but both effects should be taken into consideration.     

Calculation of electrostatic interaction forces between ellipsoidal particles

An analytical expression is presented for describing the electrostatic interaction forces between various shaped particles having mutual orientations. The expression is derived by applying the surface integration method, which is a generalization of the Derjaguin summation procedure. Based on previous theoretical considerations it is possible to calculate the electrostatic interaction force between regularly shaped bodies (both convex or concave in the vicinity of their contact point) by multiplying the interaction energy derived for paralled plates with the corresponding geometric factor. The forces acting between two equal shaped ellipsoids are described and discussed, considering three different limiting orientations, the parallel, the perpendicular, and the contact of the edges' orientation.     

Hybrid Hydrogels Toughened by Chemical Covalent Bonding and Physical Electrostatic Interactions

Polystyrene nanoparticles with negative charges(n-PSs) were synthesized using styrene(St) and sodium styrene sulfonate(NaSS) as initial materials by surfactant-free emulsion polymerization. Subsequently, a hybrid hydrogel was prepared using acrylamide(AAm) and methacryloyloxyethyltrimethyl ammonium chloride(DMC) as co-monomers with N,N'-methylenebisacrylamide(MBA) as a chemical crosslinker and n-PSs as a physical electro-static interaction agent. The resulting hybrid hydrogels exhibited excellent tensile strength and elongation at break. The tensile stress of hybrid hydrogels was seven times greater than that of hydrogels without n-PSs. The elongation at break of hydrogels reached 700%, which was much higher compared to those of the hydrogels without n-PSs. Furthermore, swelling measurements of the hydrogels indicate that there is an overshoot in the swelling process and the extent of overshoot decreases with the increasing n-PSs. Therefore, the work presented here provides a method for improving the mechanical properties of hydrogels via the introduction of polymeric nanoparticles.     

静电层层组装的微量热研究

利用静电层层组装技术,在CaCO3微球表面交替沉积带相反电荷的聚电解质制备多层膜。在静电层层组装过程中伴随热效应出现,借助微量热仪对该热效应进行精确测定,从而为层层组装过程提供一种新的表征手段。     

细胞色素C电化学反应的静电作用模型

首次发现,简单的阴离子Ⅰ~-是细胞色素c电化学反应的良好促进剂。在碘离子修饰的金电极上能观察到细胞色素c的准可逆电化学反应。根据细胞色素c的结构特点和碘离子的吸附特性,提出了一个以静电作用为基础的细胞色素c的电化学反应的模型。     

Electrostatic repulsion between two parallel plates covered with polymer brush layers

An expression for the electrostatic repulsive force is obtained for two parallel similar plates immersed in an electrolyte solution at separation h covered with a uniformly charged polymer brush layer of intact thickness d _o under compression (h<2d _o) after the two brushes come into contact. It is assumed that when the two brushes come into contact, they are squeezed against each other but do not interdigitate. The electrostatic repulsive force is found to increase with decreasing h as 1/h for highly charged brushes and as 1/h ² for weakly charged brushes. This is in contrast to the interaction force between the brush layers before contact (h≥2d _o), which is essentially proportional to exp[−κ(h−2d _o)] (where κ is the Debye–Hückel parameter). It is also shown that the interaction force for highly charged brushes, which becomes independent of the electrolyte concentration, can be comparable in magnitude to the steric repulsive forces between the brushes resulting from osmotic repulsion and the elastic energy of the brushes. Received: 21 October 1998 Accepted in revised form: 25 December 1998     

Matrix-isolation-FTIR spectroscopy with an integrating sphere

The use of an integrating sphere for the measurement of absorption spectra of thin films is described. The thin film (for example a rare gas matrix) is grown directly on the inside surface of the sphere. Multiple reflections inside the integrating sphere lead to significant enhancement of weak absorptions of the film, increasing the sensitivity of such measurements.     

Electrostatic interaction between soft particles

Electrostatic interaction between two soft particles (i.e., polyelectrolyte-coated particles) in an electrolyte solution is discussed. An approximate analytic expression for the interaction energy between two dissimilar soft spheres is derived by applying Derjaguin's approximation to the corresponding interaction energy between two parallel dissimilar soft plates for the case where the density of fixed charges within the polyelectrolyte layer is low. The obtained expression covers various limiting cases that include hard sphere/hard sphere interaction, spherical polyelectrolyte/spherical polyelectrolyte interaction, soft sphere/spherical polyelectrolyte interaction, soft sphere/hard sphere interaction, and spherical polyelectrolyte/hard sphere interaction.