Measurement of the zeta potential. Brief review of the main methods

Some Methodological Aspects in Studies of Metal Nanoparticles’ Toxicity towards Cultured Cells

“…As for the nanoparticles, it is easy to guess that, for the corresponding particle sizes this condition cannot be fulfilled, and therefore the Smoluchowski equation is, in principle, invalid. The same conclusion was made recently in the review of the methods used for zeta potential determination [21]. As an illustration we give here an example of the calculation of criterion Rel for the nanoparticles stabilized with anionic or cationic surfactant bearing dissociating groups fully ionized at the neutral pH in the diluted salt solution; the relevant expressions for the calculation of κ and φ s may be found elsewhere [37,39,41].…”

“…However, as shown by the more general theories of electrophoresis developed in the past century [13][14][15][16][17][18][19][20], there are practically significant combinations of conditions (small particle size, not very small charge, and low ionic strength of the medium) where the assumptions used in the Smoluchowski theory do not work. As shown in the review [21] and explained also in our monograph ( [11], p. 191) the Smoluchowski theory is not valid for the charged nanoparticles in the whole nanodimensional range (1-100 nm). Therefore, zeta potential values found by the Smoluchowski equation cannot be regarded as correct measure of the nanoparticle charge and the more general theories should be applied.…”