Kinetically Controlled Pt Deposition onto Self-Assembled Au Colloids:  Preparation of Au (Core)−Pt (Shell) Nanoparticle Assemblies

Assemblies of Au (core)−Pt (shell) nanoparticles were prepared by chemical deposition of Pt metal onto colloidal Au particles that self-assembled onto substrates, since PtCl 6 2 - may be reduced to Pt(0) by the mild reducing agent NH 2 OH in the presence of gold nanoparticles. It is shown that the Pt deposition is isotropic and uniform on each particle via the combination of scanning electron microscopy and atomic force microscopy analysis. And the linear dependence of the particle size on the deposition time suggests that the deposition procedure is kinetically controlled. What is more, the kinetics of this Pt deposition onto Au nanoparticles is analyzed, which further reveals that the growth rate of the core−shell nanoparticles depends on the concentration of PtCl 6 2 -, the molar mass and density of Pt metal, and a constant related to the surface reaction.