Supervisor: Davide Gardini

The size and zeta potential analyzer for nanoparticles supplied to CNR-ISTEC is a light-diffusion-based instrument that determines the particle-size distribution of nanoparticles dispersed in a liquid medium (Dynamic Light Scattering technique) and their zeta potential (Electrophoretic Light Scattering technique).

Main characterizations

  • Particle-size distribution.
  • Zeta potential dependence on pH (isoelectric point determination).
  • Zeta potential dependence on the concentration of an additive (determination of the optimal concentration).

Particle-size distribution – The light of a laser beam hits the cell containing the dilute suspension and is diffused by the particles in Brownian motion in all the directions; the intensity of the diffuse light is collected by a detector placed at 173° with respect to the incident light (backscattering). A correlator correlates the intensity of the diffused light collected at successive times by generating a correlation curve. From the interpolation of this curve with a suitable model, the translational diffusion coefficient of the particles is derived and from it, through the Stokes-Einstein relationship, the hydrodynamic diameter of the particles is obtained.

Zeta potential – The charged particles are put in motion by electrophoresis under the action of an electric field and their velocity determined by the Laser Doppler Velocimetry (LDV) technique by comparing the phase of the diffused light at 17° with that of a reference beam that do not cross the sample. From the velocity and the intensity of the electric field applied, the electrophoretic mobility is obtained. From such property the zeta potential is derived on the basis of a suitable model depending on the thickness of the electrical double layer (Smoluchowski, Hückel, Henry).

Malvern Zetasizer Nano ZSP

  • Size range: 0.3 nm – 10 µm.
  • Temperature range: 0 – 90 °C.
  • Suspension concentration: about 0.1-10 mg/mL.
  • Automatic titration system: MPT-2.
  • Available cells: cells for the measurement of the particle-size distribution in water (in polystyrene, DTS0012) and in organic solvents (in glass, PCS8501); U-capillary cells for the measurement of the zeta potential in water (in polystyrene, DTS1070).
Malvern Zetasizer Nano ZSP with titrator MPT-2