Recent Research Developments

Index of Recent Research News
November 12, 2003
    Size Dependent Reactivity of Iron Oxyhydroxide Nanoparticles
    Amy J. Anschutz, R. Lee Penn
    Department of Chemistry, University of Minnesota

    Nanoparticle reactivity is critically important to the geochemical cycling of both natural and anthropogenic chemical species. Iron oxides and oxyhydroxides are common and important materials in the biogeochemical cycle of iron and other metals and molecular species at the Earth's surface. These materials commonly occur as nanoparticles in the 3-10 nm size range (e.g., goethite nanoparticles as in Penn et al., Geology, 2000). Our work shows that the rate of redox using hydroquinone as the reducing agent and iron oxyhydroxide nanoparticles as reductant is strongly particle size and phase dependent. For example, redox reactions using ~3.5 nm 6-line ferrihydrite nanoparticles, ~9x70 nm needle-shaped goethite nanoparticles, and ~30x350 nm needle-shaped goethite particles (figure 1) show that the surface-area normalized rates of redox are fastest (by as much as 100x) in experiments using the 6-line ferrihydrite. Furthermore, the surface-area normalized rates of redox for the ~9x70 nm needle-shaped goethite nanoparticles is up to fourteen times faster than the rates of redox for the ~30x350 nm needle-shaped goethite particles (figure 2).

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