By using a specially designed cell, the Zeta potential of a flat surface can be measured through the same process as Zeta potential for particles in solution. While the flat solid surface does not contribute particles for measurement, the surface Zeta potential is measured by adding probe particles to a test solution. As with Zeta potential for particles, flat surface Zeta potential can be calculated from the measured electrophoretic mobility of the probe particles. The characterization of flat surface Zeta potential can lead to a better understanding of how a material such as thin films and coatings behave.

Typical Experimental Results:

solid surface

Electrosmosis plot for a flat solid surface

 

solid surface

Zeta potential distribution graph for a flat solid surface

Zeta Potential of Flat Solid Surfaces

Sample Teflon Plate Lint-Free Cloth Rubber Filtration Membrane A Filtration Membrane B
Zeta Potential (mV) -51.22 -34.67 -24.74 -34.21 -13.78

Applications:

Effect of Additives Electroosmotic Flow Electrophoretic Light Scattering
Isoelectric Point Particle Mobility pH Analysis
pH Titration Photo Correlation Spectroscopy Solid Surface
Stability and Shelf Life Surface Charge Surface Coatings
Temperature Effects Thin Film Membranes Zeta Potential of Flat Surface

 

For more information please read our application notes:
Zeta Potentials of Solid Surfaces

 

Instruments: Delsa Nano C Nano Particle Size and Zeta Potential Analyzer

particle size

Key Specifications:

Concentration Range 0.001%-40%
Max Heating Temp 90 degrees C
Max Cooling Temp 15 degrees C below ambient temp
pH Range 1-13
Zeta Potential Range -100 – +100mV
Scattering Angle 15, 30, 160 degrees
Flat Surface Cell Sample Requirements 33x14mm (min), 37x16x5mm (max)

 

Zeta Potentials of Solid Surfaces

 

The Delsa Nano C Particle and Zeta Potential Analyzer, supplied by Beckman Coulter, has a unique capability to measure Zeta potentials of solid surfaces, in addition to determining particle size and particle Zeta potential in a solution. The solid surface Zeta potential measurements are performed with a specially designed flat surface cell.

 

The procedure for measuring the Zeta potential of a solid surface is similar to a typical Zeta potential measurement for particles. The measurements are carried out through dynamic light scattering of charged probe particles under influences from both electroosmosis and electrophoresis. The true electroosmotic flow due to solid surface Zeta potential is obtained by subtracting the true electrophoretic mobility from the total apparent electroosmotic flow of the charged probe particles.

 

AppNote-31

 

Figure 1. Zeta potentials at different locations in a flat surface cell due to the total apparent electoosmotic flow of the probe particles, obtained during the measurement of the Zeta potential for a Teflon plate surface.

 

AppNote-32

 

The surface Zeta potentials for several solid samples measured using the Delsa Nano C are shown in Table 1. They were derived from the Zeta potential plots, similar to the plot depicted in Figure 1.

 

Surface Zeta potentials of solids are extremely useful in filtration membranes for gases, oils, clean and waste waters. Particles and solutes in fluids may have negative or positive charges. A membrane with the same or the opposite charges could increase or decrease passing-though or retaining efficiency of the membrane. Measurements of Zeta potentials of solid surfaces also play important roles in biomedical material developments. Understanding of the surface Zeta potential of implants and catheters may be very helpful in controlling the surface interactions with blood cells. Other applications that could be benefited from Zeta potential measurements of solids include microfludics, semiconductor wafer surfaces, coatings and thin films for hydrophobicity and hydrophilicity modifications, etc.