Morphological Evolution of Single-Crystal Ag Nanospheres during the Galvanic Replacement Reaction with HAuCl₄

This paper presents a systematic study of the galvanic replacement reaction between 23.5 nm single-crystal Ag nanospheres and HAuCl4 in an aqueous medium. We have monitored both morphological and spectral changes as the molar ratio of HAuCl4 to Ag is increased. The replacement reaction on single-crystal Ag nanospheres results in the formation of a series of hollow and porous nanostructures composed of Au−Ag alloys. By varying the molar ratio of HAuCl4 to Ag, we are able to control the size and density of the pores. In addition, the localized surface plasmon resonance peaks of these nanostructures can be readily tuned from 408 to 791 nm as the product becomes increasingly more hollow and porous.