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

Abstract

This paper presents a systematic study of the galvanic replacement reaction between 23.5 nm singlecrystal Ag nanospheres and HAuCl 4 in an aqueous medium. We have monitored both morphological and spectral changes as the molar ratio of HAuCl 4 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 HAuCl 4 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.

25th Anniversary Article: Galvanic Replacement: A Simple and Versatile Route to Hollow Nanostructures with Tunable and Well‐Controlled Properties

“…This result is in contrast with the galvanic replacement reaction between Ag cuboctahedrons and HAuCl 4 (Figure 2 ), [ 23,70 ] in which is to introduce an ionic species to facilitate the reaction. In addition to their role to change the reduction potentials of the metal/ ion pairs and thus shift the equilibrium towards the direction of galvanic replacement, the ionic species can also increase the reaction kinetics.…”

“…For example, when Ag cuboctahedrons of 24 nm in size were used as the templates, the products underwent a shape transformation into octahedrons. [ 70 ] This transformation from cuboctahedral to octahedral shape can be attributed to both the selective deposition of Au on {100} facets, and the relatively small size of the templates.…”

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“…2D). The measured interplanar spacing for the lattice fringes is 0.23 nm, which corresponds to the (1 1 1) lattice plane of Ag [32]. Meanwhile, the TEM image of Fig.…”

Shape-Controlled Synthesis of Silver Nanoparticles for Plasmonic and Sensing Applications

“…As both structures are single crystals, the synthetic method for silver nanospheres is very similar to that of silver nanocubes. Trace amounts of NaCl are added to promote oxidative etching of all twinned structures, but in this case, the reaction is stopped before the single-crystal seeds can grow to large sizes and be stabilized by PVP [31,32].…”