*4.3.1 Zeta potential*

The zeta potential is the electric potential at the interfacial double layer between the dispersed particle and the liquid layer surrounding it, and can be determined by electrophoretic light scattering, where the particle migrates toward the electrode of opposite charge with a velocity that is proportional to the magnitude of the zeta potential [23]. Regarding stability, it is important to ensure that the zeta potential values of the nanosystems are greater than ±30 mV, as this guarantees the strong electrostatic repulsion forces that prevent the occurrence of aggregation phenomena among the particles [50]. In addition to evaluating the stability of nanodevices, zeta potential measurements can also confirm the coating or adsorption of a specific material on the nanocapsules surface, which is useful specifically in the layer-by-layer technique described in Section 3.3 [24].
