30th Annual SSRL Users' Meeting — October 9-10, 2003

Investigations into the Surface Structure and Chemistry of ZnS Nanoparticles

B. Gilbert, F. Huang, H. Zhang, and J. F. Banfield

Department of Earth and Planetary Science, University of California at Berkeley, Berkeley, CA 94720 USA

The structure of nanoparticles, and surface structure in particular, can respond dynamically to surface environment changes at room temperature. Uncoated 3 nm ZnS nanoparticles undergo reversible structural change associated with methanol desorption and rewetting. Water addition causes a profound, non-reversible rearrangement to a more crystalline structure. Unexpected differences (relative to bulk ZnS) in the structural dynamics of ZnS nanoparticles capped with an organic ligand can be linked to the observation of surface reconstruction. Hence, solvent or ligand interactions can alter the structure, and potentially the reactivity of small nanoparticles at the interface with their environment. We combine vibrational and electronic spectroscopies with molecular dynamics modelling to investigate the structure of the nanoparticle surface, and nature of surface chemical interactions. We seek to determine how surface molecules, e.g. water, can drive substantial atomic reorganization, and to identify the reactive surface sites of the nanoparticles.