De-alloying behaviour of metal nanoclusters in SiO2 upon irradiation and thermal treatments

Bimetallic Au–Cu and Au–Ag nanometer sized clusters obtained by sequential ion implantation in silica have an elemental selective de-alloying process upon thermal annealing in oxidizing atmosphere or irradiation with smaller atomic mass ions. In the case of Au–Cu alloy, the first process promotes preferentially copper extraction due to the chemical interaction (oxidation) with the incoming oxygen atoms. Irradiation with light ions promotes on the contrary a preferential extraction of gold from the alloy (either Au–Cu or Au–Ag), resulting in the formation of Au-enriched ‘satellites’ nanoparticles around the original cluster.