CuAg纳米结构表面共存和Ag表面对甘氨酸的新吸附行为

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

在异质纳米结构表面发生的新现象是当前研究的热点 .最近发现 ,尽管甘氨酸在纯Ag表面只能作物理吸附 ,蒸镀在Cu表面的单层Ag岛却能在Cu的帮助下 ,出现对甘氨酸作化学吸附的能力 ,这种现象是溢流效应的一种反映 .蒸镀在Ag表面的Cu岛也能帮助附近裸露的Ag表面获得化学吸附甘氨酸的能力 ,虽然这里已不是单原子层的银了 .结果说明这种溢流现象来源于CuAg在表面的纳米结构共存 ,而不只是这种共存的某个结构所特有的 .但是 ,由于Cu的表面能大于Ag,所以即使是在室温下 ,Cu岛也会逐渐地被一单层Ag原子完全覆盖 ,从而失去溢流的能力 .这说明要利用异质纳米结构系统的新的物质特性时 。

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-coexistance of Cu and Ag on the surface, rather than any specific structure of the coexistance, 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.