Aqueous suspensions of ferrihydrite nanoparticles form complex aggregate structures, with important consequences for environmental transport and bioavailability. We combine nanoparticle synthesis, Cryo-Transmission Electron Microscopy (Cryo-TEM) and Small Angle X-Ray Scattering (SAXS) information to determine factors that impact nanoparticle formation, aggregate structure, and aggregate stability. Cryo-TEM utilizes rapid quenching to preserve nanostructures with vitreous ice, allowing for direct, high resolution imaging of structures in solution that would be impossible using traditional electron microscopy conditions. Cryo-TEM is also utilized to obtain 3D tomographic reconstructions of selected aggregate structures. Our results reveal a tendency for ferrihydrite nanoparticles to form extended aggregate networks of low fractal dimension. Variations in ionic strength can be used to induce aggregation, or to induce densification of preexisting aggregates. The correlation between these results and concurrent nanoparticle transport experiments will be discussed.

Using Cryo Transmission Electron Microscopy to characterize nanoparticle aggregate structure

242nd National Meeting (2011)

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