The Zetasizer is a highly important device for nanoanalytics, as it provides information about the size distribution of nanoparticles and their surface charge.

Dynamic light scattering (DLS) is used to determine the hydrodynamic radius by measuring the diffusion coefficient of the particles. Thereby, a laser beam is directed towards a diluted sample and scattering by the particles is detected over time. Since particle movements occurs due to the Brownian motion, this provides information about the velocity of the particles in the sample and can, if the refractive index and viscosity of the solvent are known, be used to calculate the hydrodynamic radius. As the Stokes-Einstein equation is employed during these calculations, the  resulting sizes are only applicable for spherical particles.

Additionally, when working with surface modified nanoparticles, the surface charge is of crucial importance. The ζ-Potential is measured by exposing the sample to an electric field . In this approach, the mobility of the particles is measured and can be used to determine the surface charge.