What is Gouy-Chapman length?

What is Gouy-Chapman length?

The Gouy-Chapman length, ℓGC, is inversely proportional to σ. For strongly charged membranes, ℓGC is rather small, on the order of a tenth of nanometer. In their pioneering work of almost a century ago, Debye and Hückel introduced. the important concept of screening of the electrostatic interactions between two.

What is Gouy-Chapman theory?

The Gouy-Chapman theory describes a rigid charged surface, with a cloud of oppositely charged ions in the solution, the concentration of the oppositely charged ions decreasing with distance from the surface. This is the so-called diffuse double layer.

How do you calculate the potential of Gouy-Chapman model?

Potential ψx and counterion density [Na+]x profiles away from a surface with surface charge density σ = −0.0922 C m−2, ψ0 = −75 mV, as resulting from the Grahame equation (2.18) and the Gouy-Chapman model (2.22). Note that counterion concentration decreases much faster than potential away from the surface.

What causes the formation of the double layer?

During the process of adsorption of surfactant ions at a liquid-fluid interface, the surface electric potential and charge density increase with time. This leads to the formation of an electric double layer inside the solution.

What is IHP and OHP?

The IHP refers to the closest approach of specifically adsorbed ions (generally anions) and the OHP refers to that of the nonspecifically adsorbed ions. The OHP is also the plane where diffuse layer begins. d is the double-layer distance described by the Helmholtz model.

What is the scaling length of electric double layer?

The Electric Double Layer In a metallic electrode the thickness is around 0.1 nm and is a function of the electron density due to the stationary nature of atoms in solids. In the electrolyte the thickness varies more, in a range of . 1 to 10 nm.

How do you calculate electrical double layer?

Surface charge is also reduced, where σ* = σ/(kTε/ed). Three pore widths of 2 nm (x* = 4.706), 5 nm (x* = 11.77), and 10 nm (x* = 23.53) are considered, each at surface charges of 0.000 C/m2 (σ* = 0.000), 0.050 C/m2 (σ* = 1.19), 0.100 C/m2 (σ* = 2.23), and 0.160 C/m2 (σ* = 3.81).

What is zeta potential in colloids?

Zeta potential, or ζ potential, is an abbreviation for electrokinetic potential in colloidal systems. From a theoretical viewpoint, zeta potential is the electric potential in the interfacial double layer of a dispersed particle or droplet versus a point in the continuous phase away from the interface.

What is the effect of concentration of electrolyte on the thickness of electric double layer?

The thickness of the diffuse region of the electric double layer depends on the concentration of ions in the solution: the lower the ion concentration, the thicker the diffuse layer.

What is Stern double layer?

The Stern Layer is the first (internal) layer of the electric double layer, which forms at a charged surface in an ionic solution. The Stern Layer is immobile relative to the surface and is comprised of a layer of ions charged oppositely to the surface which attach to the surface.

How is Debye length calculated?

After determining Kappa, Debye length can be calculated by taking the reciprocal (1/K) of the Kappa. Lamda = 1/Kappa The unit of Kappa is inverse meter and the unit of Debye length is meter.

What is OHP and IHP?

How do you calculate CDL on CV?

Take the current width of the CV (in amps, pick a point in the CV where there is no faradaic process occurring) and divide that by the scan rate of the CV (V/s). Amps is Coulombs/s divided by Volts/s = Coulombs / Volt which is Farrads.

Why is zeta potential an important indicator?

The magnitude of the zeta potential gives an indication of the potential stability of the colloidal system. If all the particles in suspension have a large negative or positive zeta potential then they will tend to repel each other and there will be no tendency for the particles to come together.

What is Helmholtz Perrin model?

Helmholtz–Perrin model (or) Parallel Plate condenser model Helmholtz considered the double layer consisting of two oppositely charged layers at a fixed distance a part. It can be compared to a parallel plate condenser of constant capacity.

What does Debye length depend on?

Debye length depends on the square root of the diffusion coefficient according to Eq. (2.23), which would reduce uncertainty in determining Debye length to the scale of only 10%. If the diffuse layer extends right to the surface, Eq. (2.24) can then be used to relate the surface charge to the surface potential.

What is the Debye length of a 1/1 electrolyte?

From the Gouy-Chapman theory for a 1:1 electrolyte it follows that (139)qd=−2ε0RTFεκ sinhFϕd2RT, where κ, the Debye length, is: (140)κ=2F2c0εε0RT

What is the Stern layer in the Gouy Chapman model?

A finite ion size, though, would limit the distance between them and the particle. Stern modified the Gouy-Chapman model by introducing a layer of thickness, δs, known as the Stern Layer, in which there is no charge and which separates the counterion charge from the charge of the particle surface [150, Chapter 5].

What are the limitations of Gouy-Chapman theory?

3.5.2Limitations of the Gouy-Chapman Theory and the Stern Layer The Gouy-Chapman theory, outlined here, is based on several assumptions, some of which do not accurately represent the real situation. This theory provides a general conceptual model for the gross interaction of clay particles but fails to explain certain aspects of that interaction.

What is the Gouy-Chapman model?

The Gouy–Chapman model is helpful to analyze the experiments of dye leakage induced by peptides in GUVs. Tamba and Yamazaki used this theory to calculate the partition constant of peptides to GUVs and evaluate the fraction of magainin 2 bound to the GUVs interface [135].