Zeta potential

Zeta potential
The zeta potential (?-potential) is the potential difference across phase boundaries between solids and liquids. It s a measure of the electrical charge of particles that are suspended in liquid. Since zeta potential is not equal to the electric surface potential in a double layer or to the Stern potential, it is often the only value that can be used to describe double-layer properties of a colloidal dispersion. Zeta potential, also known as electrokinetic potential, is measured in millivolts (mV).
In colloids, zeta potential is the electric potential difference across the ionic layer around a charged colloid ion. Another way; it s the potential in the interface double layer at the slipping plane. Typically, the higher the zeta-potential, the more stable the colloid. Zeta potential that is less negative than -15 mV typically represents the beginnings of agglomeration of particles. When the zeta-potential equals zero, the colloid will precipitate into a solid.
In the colloidal chemistry literature, it is usually denoted using the Greek letter zeta (?), hence ?-potential. The usual units are volts (V) or millivolts (mV). From a theoretical viewpoint, the zeta potential is the electric potential in the interfacial double layer (DL) at the location of the slipping plane relative to a point in the bulk fluid away from the interface. In other words, zeta potential is the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed particle.
The zeta potential is caused by the net electrical charge contained within the region bounded by the slipping plane, and also depends on the location of that plane. Thus it is widely used for quantification of the magnitude of the charge. However, zeta potential is not equal to the stern potential or electric surface potential in the double layer, because these are defined at different locations. Nevertheless, zeta potential is often the only available path for characterization of double-layer properties.
The zeta potential is a key indicator of the stability of colloidal dispersions. The magnitude of the zeta potential indicates the degree of electrostatic repulsion between adjacent, similarly charged particles in a dispersion. For molecules and particles that are small enough, a high zeta potential will confer stability, i.e., the solution or dispersion will resist aggregation. When the potential is small, attractive forces may exceed this repulsion and the dispersion may break and flocculate. So, colloids with high zeta potential (negative or positive) are electrically stabilized while colloids with low zeta potentials tend to coagulate or flocculate as outlined in the table.