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When a surface is immersed in a solution containing electrolytes, it develops a net surface charge.This is often because of ionic adsorption. Aqueous solutions universally contain positive and negative ions (cations and anions, respectively), which interact with partial charges on the surface, adsorbing to and thus ionizing the surface and creating a net surface charge. [9]
[1] [5] The boundary conditions play an important role, and the surface potential and surface charge density ¯ and ¯ become functions of the surface separation h and they may differ from the corresponding quantities ψ D and σ for the isolated surface. When the surface charge remains constant upon approach, one refers to the constant charge ...
Phospholipids with certain head groups can alter the surface chemistry of a bilayer and can, for example, serve as signals as well as "anchors" for other molecules in the membranes of cells. [3] Just like the heads, the tails of lipids can also affect membrane properties, for instance by determining the phase of the bilayer.
If positive and negative charges are both present in equal amounts, then this is the isoelectric point. Thus, the PZC refers to the absence of any type of surface charge, while the IEP refers to a state of neutral net surface charge. The difference between the two, therefore, is the quantity of charged sites at the point of net zero charge.
Electrokinetic phenomena are a family of several different effects that occur in heterogeneous fluids, or in porous bodies filled with fluid, or in a fast flow over a flat surface. The term heterogeneous here means a fluid containing particles.
According to the double layer theory, all surface charges in fluids are screened by a diffuse layer of ions, which has the same absolute charge but opposite sign with respect to that of the surface charge. The electric field also exerts a force on the ions in the diffuse layer which has direction opposite to that acting on the surface charge.
Diagram showing the ionic concentration and potential difference as a function of distance from the charged surface of a particle suspended in a dispersion medium. Zeta potential is the electrical potential at the slipping plane. This plane is the interface which separates mobile fluid from fluid that remains attached to the surface.
This surface charge can be treated through a surface integral, or by using discontinuity conditions at the boundary, as illustrated in the various examples below. As a first example relating dipole moment to polarization, consider a medium made up of a continuous charge density ρ ( r ) and a continuous dipole moment distribution p ( r ).