HR: 08:20h
AN: B31F-02 INVITED    [Abstracts]
TI: Structural and Chemical Transformations in Nanocrystals
AU: * Alivisatos, P
EM: alivis@berkeley.edu
AF: University of California, Berkeley, One Cyclotron Rd., MS66-246, Berkeley, CA 94720, United States
AB: Structural and Chemical transformation of nanocrystals from one state to another can proceed rapidly and with remarkably simplified kinetics compared to bulk solid state transformations. We have investigated the Wurtzite to rock salt pressure induced solid-solid structural transformation in CdSe nanorods of 4 nm diameter as a function of rod length. Rods of length less than 10 nm transform reversibly, while rods greater than 10 nm in length fracture during the structural transformation. Two other recent examples we have investigated are the formation of hollow nanocrystals via addition reactions and cation exchange reactions. Hollow nanocrystals of many transition metal oxides and sulfides have been studied, and from these we are learning how to predict the shell thickness. Cation exchange from CdSe to Ag2Se proceeds completely, but is reversible, and the number of anions per nanocrystal remains invariant. Above a critical size, the nanocrystals retain non-equilibrium shapes over multiple cycles of cation exchange.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting