Ag⁺-Keggin ion colloidal particles as novel templates for the growth of silver nanoparticle assemblies

In the work reported in this paper, we demonstrate that Ag ⁺-Keggin ion colloidal particles are excellent templates for the synthesis of organized assemblies of silver nanoparticles, wherein the Keggin ion host plays the role of a UV-switchable reducing agent. More specifically, we investigate the formation of aqueous colloidal particles of Ag⁺ ions complexed with phosphotungstate (PW₁₂O₄₀) ^3- Keggin ions and show that they may be used as a new class of inorganic scaffolds in the synthesis of silver nanoparticle assemblies. The crystalline Keggin ion host may be reduced photochemically resulting in electron transfer to the entrapped silver ions and consequent formation of silver nanoparticle assemblies on the underlying colloidal particle surface. Treatment with alkali results in dissolution of the colloidal particle template leaving behind the silver nanoparticle network reasonably intact.