Modeling Pt2þ Coordination Process within Poly(amidoamine) Dendrimers for Synthesis of Dendrimer-Encapsulated Pt Nanoparticles

Dendrimer-encapsulated Pt nanoparticles can be synthesized by Pt2þ coordination with dendrimers followed by reduction. In the present study, we have systematically investigated the coordination kinetics of PtCl4 2 with fourth-generation hydroxyl-terminated poly(amidoamine) (PAMAM G4-OH) dendrimers using UV vis spectroscopy measurements. Our experimental investigation clarifies that Pt2þ coordination with dendrimers occurs after the H2O ligand exchange (aquation) of PtCl4 2 and that a resultant species PtCl2(H2O)2 predominantly coordinates with the dendrimers. From these results, we have proposed a simple dynamic model that describes the Pt2þ coordination as a consecutive reaction composed of the aquation reaction of PtCl4 2 and a subsequent coordination reaction of the resultant PtCl2(H2O)2 with the dendrimers. Our proposed model is in good agreement with the experimental results at a low concentration condition of PtCl4 2 , validating its performance. Furthermore, we suggest that the proposed scheme can be generalized and applied to metal species other than Pt2þ.