Ag dewetting in cu@ag monodisperse core-shell nanoparticles

We report on the synthesis of monodisperse Cu and Cu@Ag nanocrystals. Using the same synthetic procedure in three different temperature ranges, Cu@Ag show very different stability pathways which we interpret as three different growth mechanisms: galvanic displacement at low temperature, metal assisted growth, and overgrowth of Ag at high temperature. At middle range temperature, Ag shell is shown to be stable over several months and efficiently passivates the Cu core. In the two other cases, combined dynamic light scattering (DLS) and high-resolution transmission electron microscopy (HRTEM) demonstrate the diffusion processes of Ag taking place at the surface of Cu and the dewetting of Ag shell from the surface of Cu to form spherical Ag nanocrystals. This result is a nice example of aging of core/shell nanostructure, and the chemical rearrangement is put in perspective of previously reported theoretical calculations and applications to printed electronics.