Dendrimer–cyclodextrin assemblies as stabilizers for gold and platinum nanoparticles

摘要

Aqueous assemblies of adamantyl-derivatized poly(propylene imine) (PPI) dendrimers and β-cyclodextrin (β-CD)nhave been used as nanoreactors in the preparation of gold and platinum nanoparticles in water. These particles havenbeen formed by the reduction of aurate or platinate anions in the presence of the generation 4 (4u0001(β-CD)32) and 5n(5u0001(β-CD)40) assemblies. Lower generation assemblies did not provide stable nanoparticles. A kinetic model isnproposed in which the particles form inside the dendrimer assemblies owing to preferred nucleation as a result of thenelectrostatic attraction between the polycationic core and the metallate anions. The persistent shape of thenadamantyl-derivatized dendrimers and the dense shell of adamantyl-β-CD complexes provide a kinetic barrier fornnanoparticle escape thus prolonging their lifetime. Exchange of the dendrimers for a cationic disulfide providednstable, water-soluble metal nanoparticles without change of their size distribution.