HR: 10:35h
AN: B11E-02    [PDF]
TI: Surface modification of lattice dynamics in ZnS nanoparticles
AU: * Gilbert, B
EM: bgilbert@eps.berkeley.edu
AF: University of California, Earth & Planetary Sciences 455 McCone Hall UC-Berkeley, Berkeley, CA 94720 United States
AU: Huang, F
EM: fhuang@seismo.berkeley.edu
AF: University of California, Earth & Planetary Sciences 455 McCone Hall UC-Berkeley, Berkeley, CA 94720 United States
AU: Zhang, H
EM: heng@seismo.berkeley.edu
AF: University of California, Earth & Planetary Sciences 455 McCone Hall UC-Berkeley, Berkeley, CA 94720 United States
AU: Banfield, J F
EM: jill@seismo.berkeley.edu
AF: University of California, Earth & Planetary Sciences 455 McCone Hall UC-Berkeley, Berkeley, CA 94720 United States
AB: Ligand binding is frequently observed to limit the growth and aggregation of both synthetic and environmental nanoparticles. Surface ligands can have significant consequences on nanoparticle structure, either driving transformations to alternate structures, or modifying the detailed structure relative to the equivalent bulk phase. The shortest interatomic distances in a structure are bond-lengths, accurately measured by extended X-ray absorption fine structure (EXAFS) spectroscopy. Bond-length expansions and contractions have been observed, depending on the choice of ligand. However, a more complete description of nanoparticle structure is observed with the longer-range distances, obtained from wide-angle X-ray scattering (WAXS). By comparing WAXS data for bulk ZnS and 3 nm ZnS nanoparticles coated with mercaptoethanol, we reveal a structural contraction that becomes more evident at larger distances. Temperature-dependent EXAFS measurements show that this structural modification is associated with a substantial increase in the vibration frequency of the Zn-S bond, relative to bulk ZnS. This pair of observations shows that organic ligands on nanoparticles can cause lattice modification and stiffening, emphasizing that nanoparticles may have surprisingly different materials properties relative to the bulk.
DE: 0400 Biogeosciences
DE: 3909 Elasticity and anelasticity
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
SC: Biogeosciences [B]
MN: 2003 Fall Meeting