Figure 1.
The pH-dependent surface charge development on SPIONs at different ionic strengths (a). Zeta potential (calculated by Smoluchowski equation) proportional to the particle charge at shear plane and aggregation of SPIONs (DLS sizes reflecting the given kinetic state measured 2 min after sonication) as a function of pH and a photo of pH-adjusted series taken an hour after sonication (b). (The points of surface charge density versus pH curves (a) were calculated from the material balance of H+/OH− in the course of equilibrium acid–base titration considering the specific surface area of SPIONs of 105 m2 g−1.) (Online version in colour.)