Zeta Potential

Zeta Potential
Surface zeta potential of SiN wafers after cleaning by hydrofluoric acid, displayed as a function of pH.

Zeta potential measures the strength of net charge on particle and solid surfaces. The higher the magnitude of this potential, the stronger the surface interactions (repulsion and/or attraction) will be when the sample contacts other charged materials.

  • ELS zeta potential is highly sensitive, with ~ 100x the detection threshold of streaming potential measurement for macroscopic solids
  • Rapid and straightforward data collection
  • Numerous sample cells available to customize method for diverse sample types
  • Accurate Zeta Potential measurement in solid samples requires exact dimensions for the sample and capillary channel cross section
  • Zeta potential is only present when a material contacts a liquid
Example Outputs

Zeta potential distribution of carbon-black dispersed in toluene.

From: Anton Paar

Surface zeta potential of SiN wafers after cleaning by hydrofluoric acid, displayed as a function of pH.

From: Anton Paar
Instruments Used for
Anton Paar SURPASS 3

Anton Paar SURPASS 3

  • Streaming Potential Voltage: ± 2000 mV
  • Streaming Current: ± 2 mA
  • Cell Resistance: 5 Ω to 20 MΩ
  • pH Scan Range: 2 to 12
  • Temperature Range: 20 °C to 40 °C
Anton Paar Litesizer 500

Anton Paar Litesizer 500

  • Potential Range: ± 1000 mV
  • Particle Size Range: 3.8 nm to 100 μm
  • Temperature Range: 0 °C to 90 °C
Sample Requirements
  • For Solid Samples:
    • Minimum Particle Size (Powders): 25 μm
    • Sample Cells Available: Cylindrical, Adjustable-Gap, Clamping
    • Irregular sample geometries and nonplanar samples are not well suited for this measurement
  • For Liquid Samples:
    • Required Sample Volume: 2 mL
    • Particle Size Range: 3.8 nm to 100 μm
    • Maximum Sample Concentration: 70 % w/v
How Works

Particle Zeta Potential:

In particles, zeta potential is measured in solution-state using Electrophoretic Light Scattering (ELS). ELS is a variant methodology of Dynamic Light Scattering (DLS) and is likewise used to measure the speeds of solute particles.

Unlike standard DLS, ELS evaluates particle kinetics in response to an oscillating electric field. The field induces electrophoretic movement that yields a slight frequency shift in the scattering laser beam.

A collection of specialized detectors measures the magnitude and frequency of these shifts against a reference laser beam, and the resulting outputs are correlated to particle mobility and zeta potential.


Solid Zeta Potential

In solid (macroscopic) samples, instruments instead measure Streaming Potential to interpolate zeta potential. In this technique, a solid, electrochemically active material is mounted to form a capillary channel. Then, a solution of electrolytic ions is passed through the channel under the influence of a controlled pressure gradient.

As they flow, the ions induce electrophoretic effects in the slipping plane of the sample surface, causing charge carriers in this layer to rearrange.

The system measures the resulting change in electrical potential as a function of electrolyte strength and uses this data to calculate the zeta potential of the sample.

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