(470f) Silver Carboxylate Nanostructure Nucleation and Growth on Agbr Crystals | AIChE

(470f) Silver Carboxylate Nanostructure Nucleation and Growth on Agbr Crystals


Dong, J. - Presenter, University of Minnesota
Whitcomb, D. R. - Presenter, Eastman Kodak Company
McCormick, A. V. - Presenter, University of Minnesota
Davis, H. T. - Presenter, University of Minnesota

From Cryo-TEM
studies, we have found that the initial stage of the reaction (the first few minutes)
between an aqueous dispersion of sodium stearate (NaSt) and AgNO3
(aqueous solution) produces silver stearate micelles, [(C18H35O2)x(Nax-y)(Agy)(H2O)z],
and aggregates of these silver stearate (AgSt) micelles in the form of cubic,
pre-AgSt crystals. When cubic grains of 50 nm AgBr are added to the NaSt
dispersion prior to the AgNO3, the reaction proceeds to form the
silver stearate micelles, but not the aggregation of those micelles. Instead, the
{111} silver ion planes of the AgBr cubic crystal corners provide nucleation
sites for silver stearate micelle deposition and crystal growth. After nucleation,
the AgSt micelles form bud-like structures via an epitaxial interface on
one or several corners of each AgBr cubic crystal. Over time, the buds grow longer
and link their free ends from the same or different AgBr crystals. The linkage
builds the buds into doughnut-shaped structures, which grow through coalescence
or ripening processes. This talk will discuss the
characterization of the epitaxial interface between the AgBr and AgSt crystals
that is formed in the early stage of the reaction.