Galvanic replacement-mediated synthesis of hollow Cu2O-Au nanocomposites and Au nanocages for catalytic and SERS applications

The galvanic replacement reaction (GRR) involves a corrosion process that is driven by the difference in the electrochemical potentials of two species. Here we demonstrate the synthesis of hollow Cu2O-Au nanocomposites via a GRR process between Cu2O and HAuCl4, and subsequent conversion of the hollow Cu2O-Au nanocomposites into Au nanocages that are actually assembled of similar to 10 nm Au nanoparticles. It is interesting to find that Cu2O nanocubes produced from reductive solution chemistry are actually transformed from Cu(OH)(2) nanowire precursors, and the Cu2O particle size is inversely proportional to the reaction temperature. A time-dependent TEM study of the GRR process between Cu2O and HAuCl4 indicates that this reaction involves evolution of an internal hollow core and surface precipitation of Au nanoparticles, which allows the formation of hollow Cu2O-Au nanocomposites. Comparing the properties of hollow Cu2O-Au nanocomposites and Au nanocages, it is determined that the hollow Cu2O-Au nanocomposites are more catalytically active in the reduction of 4-nitrophenol into 4-aminophenol in the presence of NaBH4, and Au nanocages are two orders of magnitude more sensitive in SERS detection of the target molecule, methylene blue. We believe the findings in this work may render a better understanding of the preparation and GRR process of Cu2O nanomaterials.