Preparation of Ag(Shell)–Au(Core) nanoparticles by anti-Galvanic reactions: Are capping agents the “real heroes” of reduction?

• Unconventional Aucore – Agshell NPs were prepared by a simple and convenient method.
• Ag+ ions were reacted with pre-formed dodecylamine or dodecanethiol capped Au NPs.
• Reaction with dodecylamine capped Au NPs resulted in Aucore – Agshell structures.
• Reaction with dodecanethiol capped Au NPs resulted in individual Ag and Au NPs.
• Aucore – Agshell NPs formation by this route critically depends on the ligand nature.

The formation of Ag(shell)–Au(core) nanoparticles by the reduction of Ag+ ions on preformed Au NPs, mediated by the capping agents like dodecylamine is described. We clearly established that while monodisperse Ag(shell)–Au(core) structures can be formed in presence of weak surface binding ligands such as amines, strong binding ligands such as thiols, lead to formation of separate monometallic Au and Ag particles. Apart from highlighting the influence of metal-ligand binding strength on the formation of core–shell nanoparticle architectures, our study also provides an easy means to produce Ag(shell)–Au(core) structures.

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