Quantification of Zeta-Potential and Electrokinetic Surface Charge Density for Colloidal Silica Nanoparticles Dependent on Type and Concentration of the Counterion: Probing the Outer Helmholtz Plane

Abstract

Electrokinetic data were measured for dilute aqueous dispersions of amorphous silica nanoparticles of various size via capillary electrophoresis with borate buffers containing either Li + , Na + , K + , or guanidinium as a counterion. Taking the mobility-dependent relaxation effect into account (modified analytic approximation developed by Ohshima), reliable values are obtained for the electrokinetic potential and the electrokinetic charge density dependent on the type of cation and the concentration of buffer. The reliability was confirmed by comparison of the results obtained for the nanoparticles with those values obtained for the planar-limiting case (fused-silica capillary inner wall/electrolyte interface). Regarding the inner part of the electrical double layer as a (mono)layer of unspecifically adsorbed counterions, we calculate (together with data gained by Brown et al. on the same type of nanoparticles via in situ photoelectron spectroscopy and potentiometric titration) the charge density at the outer Helmholtz plane and the fraction of charge included in the Stern layer for electrolytes containing the alkali ions Li + , Na + , or K + . This approach explains differences in the electrokinetic charge density as a result of differences in the properties of the Stern layer due to differences in the size of the hydrated cation and the hydration state of the silica surface.

Geochemical evidence for the application of nanoparticulate colloidal silica gel forin situcontainment of legacy nuclear wastes

“…When mixing the colloidal silica with a saline solution (1.4 M NaCl or 0.175 M CaCl2 as the accelerant, at a colloidal silica:accelerant ratio of 5:1) gelling is induced. 12,13 Cations within the saline accelerant cause a reduction in the negative ζ-potential of the silica nanoparticles [49][50][51][52][53] through surface complexation with deprotonated silanol sites 52 and a decrease in the thickness of the (electric) diffuse layer associated with negatively charged…”

Mapping Surface Charge Distribution of Single-Cell via Charged Nanoparticle

“…According to the Gouy−Chapman theory [ 32 ], zeta potential represents the cell and particle’s surface charge density in a solution. The relation between the net charge density and the zeta potential can be described by the Gouy−Chapman equation [ 9 , 15 , 32 , 33 , 34 , 35 ]: where σ charge is the surface charge density, c is the ion concentration, N A is the Avogadro constant, ε r is the relative dielectric permittivity of the solution, ε 0 is the vacuum permittivity, κ B is the Boltzmann constant, e is the charge on a proton, ξ is zeta potential, and T is the absolute temperature.…”

Magnetic Materials and Systems: Domain Structure Visualization and Other Characterization Techniques for the Application in the Materials Science and Biomedicine

“…The two layers that compose the EDL are the Stern layer, which is closer to the surface, and the diffuse layer [237]. The Stern layer is primarily formed by ions/molecules with opposite charge to that of the particle, while the diffuse layer is made up of both same and opposite charged ions/molecules (Figure 21) [238]. While the charge of the Stern layer is stable as it is due to direct chemical interactions with the particle, the peculiarity of the diffuse layer is that it is dynamic as its composition is influenced by various factors (e.g., concentration, ionic strength, and pH).…”