Fabrication of Cu2O@Cu2O core–shell nanoparticles and conversion to Cu2O@Cu core–shell nanoparticles in solution

Cu 2 O@Cu 2 O core-shell nanoparticles (NPs) were prepared by using solution phase strategy. It was found that Cu 2 O@Cu 2 O NPs were easily converted to Cu 2 O@Cu NPs with the help of polyvinylpyrrolidine (PVP) and excessive ascorbic acid (AA) in air at room temperature, which was an interesting phenomenon. The features of the two kinds of NPs were characterized by XRD, TEM and extinction spectra. Cu 2 O@Cu NPs with different shell thicknesses showed wide tunable optical properties for the localized surface plasmon (LSP) in metallic Cu. But Cu 2 O@Cu 2 O NPs did not indicate this feature. FTIR results reveal that Cu + ions on the surface of Cu 2 O shell coordinate with N and O atoms in PVP and are further reduced to metallic Cu by excessive AA and then form a nucleation site on the surface of Cu 2 O nanocrystalline. PVP binds onto different sites to proceed with the reduction utill all the Cu sources in Cu 2 O shell are completely assumed.