Dendrimer-Mediated Immobilization of Catalytic Nanoparticles on Flat, Solid Supports

Abstract

Sixth-generation poly(amidoamine) (PAMAM) dendrimers have been used to explore methods for immobilizing Pd nanoparticles on atomically flat surfaces. Two methods are investigated. In the first method, dendrimer-encapsulated metal nanoparticles (DEMNs) are prepared using a PAMAM dendrimer with hydroxyl terminal groups. These particles are then deposited on a mica surface. Tapping-mode AFM images reveal a monodispersed size distribution of DEMNs that has an average composition of 40 Pd atoms per dendrimer. When thermal combustion in an O2 stream is used to remove the dendrimer host at 630 °C, Pd particles aggregate via surface diffusion, resulting in an increase in particle diameter. In the second method, the step edges of a HOPG surface are first oxidized in an oxygen atmosphere. A PAMAM dendrimer with amine terminal groups is then allowed to adsorb selectively on the step edges, followed by immobilization of Pd particles via surface chemical reactions. The Pd particles prepared by this method are shown to be catalytically active for electroless copper deposition.