title: Shape- and size-selective electrochemical synthesis of dispersed silver(I) oxide colloids.
abstract: Silver(I) oxide (Ag2O) micro- and nanoparticles were electrochemically synthesized by anodizing a sacrificial silver wire in a basic aqueous sulfate solution. Ag2O particles were released from the silver electrode surface during synthesis producing a visible sol "stream". The composition of these particles was established using selected area electron diffraction, X-ray diffraction, and X-ray photoelectron spectroscopy. The shape of Ag2O crystallites could be adjusted using the potential of the silver wire generator electrode. The generation of a dispersed Ag2O sol and the observed shape selectivity are both explained by a two-step mechanism involving the anodic dissolution of silver metal, Ag0 --> Ag+(aq) + 1e-, followed by the precipitation of Ag2O particles, 2Ag+ + 2OH- --> Ag2O(s) + H2O. Within 100 mV of the voltage threshold for particle growth, cubic particles with a depression in each face ("hopper crystals") were produced. The application of more positive voltages resulted in the generation of 8-fold symmetric "flower"-shaped particles formed as a consequence of fast growth in the <111> crystallographic direction. The diameter of flower particles was adjustable from 250 nm to 1.8 microm using the growth duration at constant potential.
authors.affiliation: Department of Chemistry and Institute for Surface and Interface Science, University of California, Irvine, Irvine, California 92697-2025, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Murray
authors.forename: Q
authors.initials: Q
authors.lastname: Li
authors.forename: J T
authors.initials: JT
authors.lastname: Newberg
authors.forename: E J
authors.initials: EJ
authors.lastname: Menke
authors.forename: J C
authors.initials: JC
authors.lastname: Hemminger
authors.forename: R M
authors.initials: RM
authors.lastname: Penner