HR: 08:00h
AN: U51C-01 INVITED     [Abstracts]
TI: Concerning the ferrous-ferric charge distribution in magnetite nanoparticles
AU: * Rosso, K M
EM: kevin.rosso@pnl.gov
AF: Pacific Northwest National Laboratory, Environmental Molecular Sciences Laboratory, Richland, WA 99352, United States
AB: Nanoparticles of iron oxides are abundant environmental constituents that, when bearing structural Fe(II), can serve as a source of electrons for reducing metals such as U(VI) or Cr(VI). Iron oxides such as magnetite possess the characteristic of facile charge redistribution by thermally activated Fe(II/III) valence interchange reactions, in this case by transfer of minority spins within the octahedral sublattice. This characteristic in combination with the finite dimensions of nanoparticles leads to the possibility of a ferrous-ferric charge distribution that differs substantially from bulk magnetite. I will present the results of density functional theory calculations focused on determining the sensitivity of the ferrous-ferric charge distribution to the reduction of periodicity from three dimensions, to two, to one, and finally nanoparticles. In addition, we will discuss the effects of surface hydration on the charge distribution. Hydrated two-dimensional (100) surfaces show a charge distribution that is different than bulk magnetite. Nanoparticles in particular partition the trivalent charge to the surface and the divalent charge to the core to reduce the total electrostatic energy. This redistribution affects the magnetic structure of the nanoparticles as well. The findings imply that electron availability for surface chemistry on magnetite nanoparticles is strongly size and shape dependent.
DE: 0793 Biogeochemistry (0412, 0414, 1615, 4805, 4912)
DE: 1000 GEOCHEMISTRY
DE: 1042 Mineral and crystal chemistry (3620)
DE: 1540 Rock and mineral magnetism
DE: 4825 Geochemistry
SC: Union [U]
MN: 2007 Joint Assembly