HR: 0800h
AN: MR11A-0919    [Abstracts]
TI: Kinetic analysis of room temperature structural transformations in zinc sulfide nanoparticles using simultaneously collected SAXS/WAXS
AU: * Goodell, C M
EM: goodell@eps.berkeley.edu
AF: University of California, Berkeley, 307 McCone Department of Earth and Planetary Sciences, Berkeley, CA 94720-4767 United States
AU: Gilbert, B
EM: bgilbert@eps.berkeley.edu
AF: University of California, Berkeley, 307 McCone Department of Earth and Planetary Sciences, Berkeley, CA 94720-4767 United States
AU: Wiegand, S
EM: weigansj@northwestern.edu
AF: DND-CAT Synchrotron Research Center, APS/ANL Building 432A 9700 S. Cass Ave., Argonne, IL 60439-4857 United States
AU: Zhang, H
EM: heng@eps.berkeley.edu
AF: University of California, Berkeley, 307 McCone Department of Earth and Planetary Sciences, Berkeley, CA 94720-4767 United States
AU: Huang, F
AF: University of California, Berkeley, 307 McCone Department of Earth and Planetary Sciences, Berkeley, CA 94720-4767 United States
AU: Banfield, J
EM: jill@eps.berkeley.edu
AF: University of California, Berkeley, 307 McCone Department of Earth and Planetary Sciences, Berkeley, CA 94720-4767 United States
AB: Natural inorganic nanoparticles are always subject to ligand or solvent surface interactions and are frequently aggregated. In previous work, we have shown that such surface effects can drive significant changes in interior nanoparticle structure. For example, water addition to nanoparticle surfaces drives a solid-state transformation in zinc sulfide (ZnS) nanoparticles and reversible aggregation-driven transformations can be observed at room temperature. In general, changes in surface interaction may be accompanied by changes in aggregation state, so we have developed an approach for the simultaneous collection of in-situ small-angle and wide-angle x-ray scattering (SAXS and WAXS, respectively). We used this method to distinguish the kinetics of the structural transformation and aggregation of ZnS nanoparticles in methanol when water is added. The rate of structural transformation exhibits a marked temperature dependence over the range of 20 - 60 øC. However, the rate of nanoparticle aggregation increases only slightly over the same temperature range. Longer-range aggregate structure, as quantified by the fractal dimension derived from the SAXS data, is weakly changed following water addition. Thus, we conclude that water adsorption and not aggregation is driving the structural transformation and that either water adsorption or interior nucleation is the rate-limiting step for the transformation. These experiments were conducted at the APS on the DND-CAT beamline 5 ID-D.
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting