Colloidal Nanoparticles: Electrokinetic Characterization


Hideo Matsumura National Institute of Advanced Industrial Science and Technology

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A charged colloidal particle suspended in an electrolyte solution is surrounded by a cloud of counterions. The set of the surface charges and countercharges is called the electrical double layer. The electrical double layer plays an essential role in various interfacial electrical phenomena on the particle surface and in the particle–particle interaction of colloid suspension.

Generally, it is almost impossible to measure the surface potential on colloid particles. However, we can measure the potential near the particle surface. It is called the zeta (ζ) potential. The zeta potential is the potential at the hydrodynamic slipping plane in the electrical double layer, hence its value is not precisely the same as that of making a stable suspension because the total interaction potential between two particles a bit distant from their surface is essential for a stable dispersion. The ζ-potential has been considered to provide useful information necessary for preparing stable colloidal suspensions in many application fields including food preparation, agriculture, pharmaceuticals, paper industry, ceramics, paints, coatings, photographic emulsions, etc. The concept of the zeta potential is also very important in such diverse processes as environmental transport of nutrients, sol–gel synthesis, mineral recovery, waste water treatment, corrosion, and many more.