Experimental Determination of Particle Size-Dependent Surface Charge Density for Silica Nanospheres

Abstract

Surface charge densities of spherical silica nanoparticles of varied size spanning from 4.1 to 495.7 nm in NaCl solution with a concentration from 0.003 to 1.2 mM at a pH value of 8.0 were determined by converting their corresponding measured zeta potential with Poisson–Boltzmann model. The magnitude of the derived surface charge density (negative) at a given NaCl concentration of 0.225 mM decreases monotonically with the increasing particle size and reaches almost a steady value when the size exceeds 30 nm, revealing clearly the effect of the nanoparticle curvature on the surface charge density. The experimental data provide a consensus for the validity of different models describing the relation between the surface charge density and the electric potential, that is, the surface complexation model and the Poisson–Boltzmann model for the charged nanospheres in electrolyte solution. We found that if the former includes the curvature-dependent deprotonation constant of the surface silanol groups, both models would give a consistent result.

Interactions between nanoparticles in nanosuspension

“…For metal oxide, e.g. TiO 2 , nanoparticles a decrease of size results in the shift of the point of zero charge (PZC) to higher pH values [62], whereas surface charge density increases [63]. Similar results were obtained also in numerical simulations [64,65].…”

Evaluation of sonication on stability-indicating properties of optimized pilocarpine hydrochloride-loaded niosomes in ocular drug delivery

“…Overall, there was more impact on the zeta potential of the Span 60 formulation than the Tween 60 formulation. This is possibly due to the occurrence of only minimal changes in size with the Tween 60 formulation, suggesting that there might be some relationship between changes in particle size and zeta potential (Shi et al 2018 ). Formulation K8's behaviour was explained by Nakatuka et al ( 2015 ) stating that smaller particles are more easily affected by surrounding particles and random fluid flow movement in a Brownian diffusion effect, hence there is easy collision with other particles.…”

The role of human serum and solution chemistry in fibrinogen peptide–nanoparticle interactions

“…Although anisotropy techniques do not provide detailed insight into the binding mechanism, these results, combined, are consistent with other studies of similar peptides binding to silica NPs via positively charged amino acids and hydrogen bonds. 24,[39][40][41] Silica NP charge and surface curvature change with size, 22,61 suggesting that these results may also vary with silica NP size and surface coating.…”