Malvern Zetasizer Nano Series, Руководство пользователя

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Ions close to the surface of the particle, will be strongly bound while ions that are
further away will be loosely bound forming what is called a
Diffuse layer .
Within the diffuse layer there is a notional boundary and any ions within this
boundary will move with the particle when it moves in the liquid; but any ions
outside the boundary will stay where they are – this boundary is called the
Slipping plane .
A potential exists between the particle surface and the dispersing liquid which
varies according to the distance from the particle surface – this potential at the
slipping plane is called the
Zeta potential .
Zeta potential is measured using a combination of the measurement
techniques: Electrophoresis and Laser Doppler Velocimetry , sometimes
called Laser Doppler Electrophoresis . This method measures how fast a
particle moves in a liquid when an electrical field is applied – i.e. its velocity.
Once we know the velocity of the particle and the electrical field applied we can,
by using two other known constants of the sample – viscosity and dielectric
constant, work out the zeta potential.
This technique will be further explained in chapter 15 - Zeta theory.
Why do we use it?
The zeta potential of the sample will determine whether the particles within a
liquid will tend to flocculate (stick together) or not.
Knowledge of zeta potential is therefore useful in many industries such as:
Ceramics :
A high zeta potential is required to ensure the ceramic particles are densely
packed. This gives added strength to the end product.
C H A P T E R 2
Z e t a s i z e r N a n o S e r i e s
P a g e 2 . 6
M A N 0 3 1 7
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Slipping plane
Ions strongly
bound to particle
Zeta potential
Diffuse layer
Ions loosely
attached
Negatively charged particle
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