Related Experiment Video
Updated: Jan 28, 2026
09:35
Fabrication of High Contact-Density, Flat-Interface Nerve Electrodes for Recording and Stimulation Applications
Published on: October 4, 2016
10.1K
Electrostatic potential and counterion partition between flat and spherical interfaces
Kalil Bernardino1, André Farias de Moura2
1Institute of Chemistry, University of São Paulo, São Paulo, SP, Brazil.
The Journal of Chemical Physics
|February 24, 2019
Summary
Molecular dynamics simulations reveal that while counterion adsorption differs between micelles and flat interfaces, the overall electrostatic potential remains similar. A significant repulsion barrier prevents micelles from approaching surfactant monolayers.
Area of Science:
- Physical Chemistry
- Colloid Science
- Surface Science
Background:
- Analytical models struggle with complex geometries of charged interfaces.
- Interface geometry influences counterion adsorption, electrostatic potential, and solvent organization.
- Molecular details are crucial for understanding these interactions.
Purpose of the Study:
- To assess the electrostatics of sodium dodecyl sulfate (SDS) micelles near SDS monolayers at the water-vapor interface.
- To investigate the impact of interface geometry on counterion adsorption and electrostatic potential.
- To quantify the repulsive forces between micelles and monolayers.
Main Methods:
- Molecular dynamics (MD) simulations were employed.
- Numerical evaluation of electrostatic potential.
- Decomposition of electrostatic potential contributions by species.
- Analysis of counterion adsorption and water reorientation.
Main Results:
- Counterion adsorption was stronger at flat interfaces due to sodium bridge formation.
- Water reorientation was more pronounced near the micelle.
- Opposing effects led to similar overall electrostatic potential changes for both geometries.
- A significant double-layer mediated repulsion (14 kJ/mol) was found between micelles and monolayers.
- Hydrophobic regions contributed significantly to electrostatic potential due to ordered methyl groups.
Conclusions:
- Interface geometry significantly impacts local electrostatics and molecular organization.
- A repulsive free energy barrier prevents micelle-monolayer association.
- MD simulations provide crucial molecular insights into complex interfacial electrostatics.
Related Concept Videos
01:23Spherical Coordinates
15.8K
Spherical coordinate systems are preferred over Cartesian, polar, or cylindrical coordinates for systems with spherical symmetry. For example, to describe the surface of a sphere, Cartesian coordinates require all three coordinates. On the other hand, the spherical coordinate system requires only one parameter: the sphere's radius. As a result, the complicated mathematical calculations become simple. Spherical coordinates are used in science and engineering applications like electric and...
15.8K
01:16Electrostatic Boundary Conditions
954
Consider an external electric field propagating through a homogeneous medium. When the electric field crosses the surface boundary of the medium, it undergoes a discontinuity. The electric field can be resolved into normal and tangential components. The amount by which the field changes at any boundary is given by the difference between the field components above and below the surface boundary.
The surface integral of an electric field is given by Gauss's law in integral form and is related to...
The surface integral of an electric field is given by Gauss's law in integral form and is related to...
954
02:04Protein-protein Interfaces
14.7K
Many proteins form complexes to carry out their functions, making protein-protein interactions (PPIs) essential for an organism's survival. Most PPIs are stabilized by numerous weak noncovalent chemical forces. The physical shape of the interfaces determines the way two proteins interact. Many globular proteins have closely-matching shapes on their surfaces, which form a large number of weak bonds. Additionally, many PPIs occur between two helices or between a surface cleft and a...
14.7K
01:27Electrostatic Boundary Conditions in Dielectrics
1.9K
When an electric field passes from one homogeneous medium to another, crossing the boundary between the two mediums imparts a discontinuity in the electric field. This results in electrostatic boundary conditions that depend on the type of mediums the field propagates through.
Consider a case where both the mediums across a boundary are two different dielectric materials. Recall that the electric field and electric displacement are proportional and related through the material's permittivity....
Consider a case where both the mediums across a boundary are two different dielectric materials. Recall that the electric field and electric displacement are proportional and related through the material's permittivity....
1.9K
01:27Gravity between Spherical Bodies
9.4K
Newton's law of gravitation describes the gravitational force between any two point masses. However, for extended spherical objects like the Earth, the Moon, and other planets, the law holds with an assumption that masses of spherical objects are concentrated at their respective centers.
This assumption can be proved easily by showing that the expression for gravitational potential energy between a hollow sphere of mass (M) and a point mass (m) is the same as it would be for a pair of extended...
This assumption can be proved easily by showing that the expression for gravitational potential energy between a hollow sphere of mass (M) and a point mass (m) is the same as it would be for a pair of extended...
9.4K
01:26Spherical and Cylindrical Capacitor
6.7K
A spherical capacitor consists of two concentric conducting spherical shells of radii R1 (inner shell) and R2 (outer shell). The shells have equal and opposite charges of +Q and −Q, respectively. For an isolated conducting spherical capacitor, the radius of the outer shell can be considered to be infinite.
Conventionally, considering the symmetry, the electric field between the concentric shells of a spherical capacitor is directed radially outward. The magnitude of the field,...
Conventionally, considering the symmetry, the electric field between the concentric shells of a spherical capacitor is directed radially outward. The magnitude of the field,...
6.7K