Figure 8.

Evolution of hydrodynamic radius and MNP aggregation and gelation. (a) Evolution of the average hydrodynamic radius of dominant size class of MNPs as a function of time for RNIP (Fe⁰/Fe₃O₄), magnetite, and hematite at pH 7.4. The particle size distribution for RNIP and magnetite becomes bimodal at the last measured point due to gelation of aggregates. (b) Rapid MNP aggregation and subsequent chain-like gelation: rapid aggregation of MNP to form micron-sized clusters (first regime) and chain-like aggregation and gelation of the micron-sized aggregates (second regime). Copyright 2007 American Chemical Society. Reprinted with permission from [73].