Coexistence of Cu and Ag in surface nano-structure and the new behavior of glycine adsorption on silver surfaces

Novel properties of surfaces with hetero-nano-structures are of considerable interest in recent years. Although glycine can only be physisorbed on pure silver surfaces, our recent results show that monolayer-silver islands deposited on copper surfaces, with the help from the nearby nude copper surface areas, have the ability of chemisorption of glycine. In the present study we find that, on the other way round, copper islands deposited on the Ag(111) surface can also make glycine being chemisorbed on the nude silver areas, although in the latter case the surface of a silver bulk is involved. This result demonstrates that it is the nano-coexistence of Cu and Ag on the surface, rather than any specific structure of the coexistence, that gives rise to the novel chemical property of the silver surfaces. Furthermore, we also find that all deposited copper islands will gradually be covered by a monolayer of Ag atoms, even at the room temperature, and thus lose the ability of helping the silver surface to gain the novel chemical property. This indicates that in order to take advantage of the novel properties of hetero-nano-structures, we have to consider their long-term stability and very often it is possible to choose the stable ones.EI0103447-34525