共查询到20条相似文献,搜索用时 15 毫秒
1.
R.R. Netz 《The European physical journal. E, Soft matter》2000,3(2):131-141
The electrostatic interaction of charged particles through or at a low-dielectric slab, such as a lipid bilayer immersed in
water or a self-assembled monolayer (SAM) on a metal substrate, is considered theoretically in the presence of salt within
the Gaussian approximation using a generalized Green's formalism. A number of separate situations are discussed: i) The presence
of a low-dielectric slab leads to pronounced interactions of a single charge with the slab via the formation of polarization
surface charges. For SAMs on metal substrates, there is an intricate crossover from image-charge attraction to the metal substrate
(for large distances) to image-charge repulsion from the SAM (for small distances) with a stable minimum at a distance of
roughly 20 times the thickness of the hydrophobic film. For bilayers in water, the interaction of a single charge is always
repulsive. ii) The surface potential of a SAM is calculated for the case when the hydrophobic layer contains dipole moments,
which might explain the recently observed long-ranged repulsion of hydrophobic scanning tips from PEG-terminated SAMs on gold.
iii) The interaction between charged particles through the bilayer is weakened. Oppositely charged particles still attract
each other through the membrane. The free-energy minimum occurs as a result of the competition between self-repulsion from
the slab and interparticle attraction and is located at a separation from the membrane surface which equals 15 times the membrane
thickness. iv) Surface charges on the two surfaces of a bilayer attract each other through the bilayer unless the surface
charge densities are the same, even if the signs are the same. v) All these effects are strongly influenced by the presence
of salt.
Received 25 January 2000 相似文献
2.
We demonstrate that small charged nanocages can undergo reversible changes of shapes by modifying the ionic conditions including salt concentration, pH, and dielectric permittivity of the medium. Using numerical simulations, we analyze structures with various charge stoichiometric ratios. At zero or low charge densities, the shape of the cage is determined by its elastic properties, and the surface charge pattern is dictated by the globally fixed geometry. As the charge density per molecule increases, the shape is strongly affected by the electrostatic forces. In this regime, the shape of the nanocage is controlled by the charge distribution. 相似文献
3.
This Letter describes dynamic self-assembly in a system of stainless steel spheres ( approximately 1 mm in diameter) rolling on a flat dielectric surface under the influence of an external magnetic field that rotates parallel to the plane of the surface. As the spheres move, they charge triboelectrically. Self-assembly is mediated by two types of electrostatic interactions among these charges: (i) attraction between negatively charged regions of the surface and positively charged spheres and (ii) repulsion between the like-charged spheres. The spheres organize into highly ordered rings as a result of these electrostatic interactions. 相似文献
4.
Electrostatic assembly of multilayered thin films through sequential adsorption of polyions in layer-by-layer fashion utilizes the strong electrostatic attraction between oppositely charged molecules. We perform molecular dynamics simulations of multilayers of flexible polyelectrolytes around a charged spherical particle. Our simulations establish that the charge reversal after each deposition step is a crucial factor for the steady layer growth. The multilayers appear to be nonequilibrium structures. 相似文献
5.
Zhang F Skoda MW Jacobs RM Zorn S Martin RA Martin CM Clark GF Weggler S Hildebrandt A Kohlbacher O Schreiber F 《Physical review letters》2008,101(14):148101
Negatively charged globular proteins in solution undergo a condensation upon adding trivalent counterions between two critical concentrations C and C, C 相似文献
6.
Molecular-scale structures of mica surfaces in electrolyte solutions reveal how ion and interfacial hydration control cation adsorption. Key differences are obtained for Rb+and Sr2+ using resonant anomalous x-ray reflectivity: Rb+ adsorbs in a partially hydrated state and incompletely compensates the surface charge, but Sr2+ adsorbs in both fully and partially hydrated states while achieving full charge compensation. These differences are driven by balancing the energy cost of disrupting ion and interface hydration with the electrostatic attraction between the cation and charged surface. 相似文献
7.
The electrostatic interaction of a charged spherical particle in the vicinity of an orifice plane has been investigated in this paper.The particle can creep along the axis of the orifice and is immersed in a bulk electrolyte.By solving the Poisson-Boltzmann problem,we have obtained the effective electrostatic interaction for several values of reduced orifice radius h,including the cases of h > 1,h = 1 and h < 1.Two kinds of boundary conditions of the orifice plane are considered.One is the constant potential model corresponding to a conducting plane,the other is the constant charge model.In the constant potential model,there is an electrostatic attraction between the particle and the orifice plane when they get close to each other,while there is a pure electrostatic repulsion in the constant charge model.The interactions in both boundary models are sensitive to the parameters of the reduced orifice radius,the reduced particle-orifice distance,surface charge densities of the particle and orifice plane,and the reduced Debye screen constant corresponding to the salt-ion concentration and ion valence. 相似文献
8.
Lubor Lejček 《Czechoslovak Journal of Physics》2001,51(8):805-818
The notion of an electrostatic charge of (±2)-twist disclinations is used to approximate the evaluation of the electrostatic interaction energy among disclinations forming arrays in finite samples of ferroelectric chiral smectic C liquid crystals. Screening effects of free charges in a material surrounding the disclination are taken into account by introducing a phenomenological depolarisation factor.The electrostatic interaction energy is important in chiral smectic C materials with high values of the spontaneous polarisation when screening effects of free charges are small. Then the electrostatic interaction leads to elimination of disclinations from the sample. When there is a high concentration of free charges in the sample (smaller value of depolarisation factor), the electrostatic interaction energy is of the order of the elastic interaction energy of disclinations what influences the equilibrium of disclination arrays in the sample. Two disclination configurations are considered. In the Brunet-Williams configuration the disclinations of opposite topological charge have also the opposite electrostatic charge so their attraction is augmented. This attraction can be balanced by the helical structure in the central part of the sample when the sample thickness is rather high.On the contrary, in the Glogarová-Pavel configuration the disclinations of opposite topological charge have the electrostatic charge of the same sign. The equilibrium in this configuration is either a balance of elastic attraction and electrostatic repulsion if elastic and Coulomb forces are of the same order or it is governed by the value of the anchoring energy when electrostatic interaction prevails over the elastic one. 相似文献
9.
Two charged dust particles inside a cloud of charges are considered as Debye atoms forming a Debye molecule. Cassini coordinates
are used for the numerical solution of the Poisson-Boltzmann equation for the charged cloud. The electric force acting on
a dust particle by the other dust particle was determined by integrating the electrostatic pressure on the surface of the
dust particle. It is shown that attractive forces appear when the following two conditions are satisfied. First, the average
distance between dust particles should be approximately equal to two Debye radii. Second, attraction takes place when similar
charges are concentrated predominantly on the dust particles. If the particles carry a small fraction of total charge of the
same polarity, repulsion between the particles takes place at all distances. We apply our results to the experiments with
thermoemission plasma and to the experiments with nuclear-pumped plasma. 相似文献
10.
A self-consistent density-functional approach has been employed to study the structure of an electric double layer formed from a charge-asymmetric (2:l) electrolyte within the restricted primitive model which corresponds to charged hard sphere ions and a continuum solvent. The particle correlation due to hard-core exclusions is evaluated by making use of the universality of the density functionals and the correlation function of the uniform hard sphere fluid obtained through the integral equation theory with an accurate closure relation whereas mean spherical approximation is employed for the electrical contribution. Numerical results on the diffuse layer potential drop, ionic density profile, and the mean electrostatic potential near the electrode surface at several surface charge densities are found to be in quantitative agreement with the available simulation data. 相似文献
11.
Using a molecular theory, we investigate the temperature-dependent self-assembly of single-stranded DNA(ss DNA)tethered to a charged nanoparticle surface. Here the size, conformations, and charge properties of ss DNA are taken into account. The main results are as follows: i) when the temperature is lower than the critical switching temperature, the ss DNA will collapse due to the existence of electrostatic interaction between ss DNA and charged nanoparticle surface; ii)for the short ss DNA chains with the number of bases less than 10, the switching of ss DNA cannot happen, and the critical temperature does not exist; iii) when the temperature increases, the electrostatic attractive interaction between ss DNA and charged nanoparticle surface becomes weak dramatically, and ss DNA chains will stretch if the electrostatic attractive interaction is insufficient to overcome the elastic energy of ss DNA and the electrostatic repulsion energy. These findings accord well with the experimental observations. It is predicted that the switching of ss DNA will not happen if the grafting densities are too high. 相似文献
12.
In the fourth order of smallness in the amplitude of a periodic capillary-gravitational wave travelling over the uniformly
charged free surface of an ideal incompressible conducting liquid of a finite depth, analytical expressions for the evolution
of the nonlinear wave, velocity field potential of the liquid, electrostatic field potential above the liquid, and nonlinear
frequency correction that is quadratic in a small parameter are derived. It is found that the dependence of the amplitude
of the nonlinear correction to the frequency on the charge density on the free liquid surface and on the thickness of the
liquid layer changes qualitatively when the layer gets thinner. In thin liquid layers, the resonant wavenumber depends on
the surface charge density, while in thick layers, this dependence is absent. 相似文献
13.
Würger A 《The European physical journal. E, Soft matter》2006,19(1):5-15
We study the electrostatic properties of charged particles trapped at an
interface in a water-in-oil microemulsion. The electrostatic potential and the
counterion distribution in the water droplet are given in terms of the ratio
of the Debye screening length κ-1 and the droplet radius R. In the
limit R→∞ we recover the well-known results for a flat
interface. Finite-size corrections are obtained in terms of the small
parameter 1/κR. Part of the counterions spread along the interface and
form a charged layer of one Debye length thickness. In particular, there is a
uniform surface charge contribution. We derive explicit expressions for the
electric field, the mobile charge density, and the charge-induced pressure on
the interface. 相似文献
14.
A.W.C. Lau P. Pincus 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(1):175-180
We consider the electrostatic interaction between two rigid membranes, with different surface charge densities of opposite
sign, across an aqueous solution without added salt. Exact solutions to the nonlinear Poisson-Boltzmann equation are obtained
and their physical meaning discussed. We also calculate the electrostatic contribution to the free energy and discuss the
renormalization of the area per head group of the charged lipids arising from the Coulomb interaction.
Received 13 October 1998 相似文献
15.
We investigate the phenomenon of multilayer formation via
layer-by-layer deposition of alternating charged polyelectrolytes.
Using mean-field theory, we find that a strong short-range
attraction between the two types of polymer chains is essential for
the formation of multilayers. For strong enough short-range
attraction, the adsorbed amount per layer increases (after an
initial decrease), and finally it stabilizes in the form of a
polyelectrolyte multilayer that can be repeated hundreds of times.
For weak short-range attraction between any two adjacent layers, the
adsorbed amount (per added layer) decays as the distance from the
surface increases, until the chains stop adsorbing altogether. The
dependence of the threshold value of the short-range attraction as
function of the polymer charge fraction and salt concentration is
calculated. 相似文献
16.
José Rafael Bordin Rudolf Podgornik Christian Holm 《The European physical journal. Special topics》2016,225(8-9):1693-1705
Coarse-grained implicit solvent Molecular Dynamics (MD) simulations have been used to investigate the structure of the vicinal layer of polarizable counterions close to a charged interface. The classical Drude oscillator model was implemented to describe the static excess polarizability of the ions. The electrostatic layer correction with image charges (ELCIC) method was used to include the effects of the dielectric discontinuity between the aqueous solution and the bounding interfaces for the calculation of the electrostatic interactions. Cases with one or two charged bounding interfaces were investigated. The counterion density profile in the vicinity of the interfaces with different surface charge values was found to depend on the ionic polarizability. Ionic polarization effects are found to be relevant for ions with high excess polarizability near surfaces with high surface charge. 相似文献
17.
The balanced field equations [1] of general relativity have been used for presenting a model for a sphere of charged dust having different densities of matter and charge. The Schwarzschild's and Penney's solutions are the particular case of the solution arrived at herein. Further equations are solved to get a model in which gravitational attraction and electrical repulsion balance each other. 相似文献
18.
Zoltán ádám Tamus István Kiss Norbert Szedenik Mónika Keindl 《Journal of Electrostatics》2009,67(2-3):267-270
Due to their very high energy propagating brush discharges are the most dangerous electrostatic discharges. As it is known, they usually occur on thick insulating layers on which significant charge can be accumulated. Discharge energy is a function of several parameters, like the surface charge density (influenced by the thickness of the layer and its relative permittivity), the size of the charged surface, etc. This paper represents a laboratory model to examine the energy of propagating brush discharges. Based on these measurements list of results were evaluated to estimate the energy of the generated propagating brush discharges. This energy is especially important to determine how incentive these discharges are. By the help of the model the effect of the polarity of the original charging, the surface charge density of the sample and the geometry of the sample have been examined. 相似文献
19.
固液界面的表面电荷会影响微纳流体系统的流体阻力,因此如何测量固液界面的表面电荷密度以及分析表面电荷的产生机理对于研究表面电荷对流体阻力的影响具有较大的意义。提出了一种基于接触式AFM的固液界面表面电荷密度测量方法。基于该方法测量了浸在去离子水和0.01 mol/L的NaCl溶液中的高硼硅玻璃和二氧化硅样本的表面电荷密度,并研究了溶液pH值对表面电荷的影响。研究结果表明高硼硅玻璃和二氧化硅由于表面硅烷基的电离带负电。溶液pH值和离子浓度的增加都会增加浸在去离子水和0.01 mol/L的NaCl溶液中高硼硅玻璃和二氧化硅的表面电荷密度的绝对值。 相似文献
20.
O.V. Borisov F. Hakem T.A. Vilgis J.-F. Joanny A. Johner 《The European physical journal. E, Soft matter》2001,6(1):37-47
We present a scaling theory for the adsorption of a weakly charged polyelectrolyte chain in a poor solvent onto an oppositely
charged surface. Depending on the fraction of charged monomers and on the solvent quality for uncharged monomers, the globule
in the bulk of the solution has either a spherical conformation or a necklace structure. At sufficiently high surface charge
density, a chain in the globular conformation adsorbs in a flat pancake conformation due to the Coulombic attraction to the
oppositely charged surface. Different adsorption regimes are predicted depending on two screening lengths (the Debye screening
length monitored by the salt concentration and the Gouy-Chapman length monitored by the surface charge density), on the degree
of ionization of the polymer and on the solvent strength. At low bulk ionic strength, an increase in the surface charge density
may induce a transition from an adsorbed necklace structure to a uniform pancake due to the enhanced screening of the intra-chain
Coulombic repulsion by the counterions localized near the surface.
Received 12 April 2001 相似文献