Transition from core-shell to Janus chemical configuration for bimetallic nanoparticles

In order to determine the possibilities to control the chemical configuration of bimetallic nanoparticles, we have considered CuAg nanoparticles synthesized by a physical route as a model in this study. The synthesis was made by pulsed laser deposition under ultra-high vacuum conditions, via a sequential deposition procedure. We show that the temperature of the substrate and the absolute quantity of Ag in a particle are the main parameters that drive the chemical configuration. To explain the transition from a core-shell configuration to a Janus configuration as a function of Ag quantity, we have conducted density-functional theory calculations and atomistic molecular dynamics simulations to investigate the stability of this system. The results are presented together with the experimental observations. Energy filtered micrographs showing the transition between core-shell and Janus bimetallic configurations.