Synthesis, Characterization, and Surface Immobilization of Metal Nanoparticles Encapsulated within Bifunctionalized Dendrimers

Abstract

Bifunctionalized poly(amidoamine) dendrimers having both quaternary ammonium groups and primary amines on their periphery were prepared. Pd and Pt nanoparticles were encapsulated within these dendrimers by extraction of the metal ions into their interior, followed by chemical reduction. The high positive charge on the surface of these dendrimers reduces the likelihood of agglomeration, and the unquaternized amine groups provide a reactive handle for immobilizing the dendrimer-encapsulated nanoparticles (DENs) onto surfaces. High-resolution transmission electron microscopy images reveal that both encapsulated Pd and Pt nanoparticles are nearly monodisperse with an average diameter of 1.7 ( 0.3 nm. Pd and Pt DENs were immobilized onto Au surfaces using an intermediary self-assembled monolayer as an adhesion layer. Only a small fraction of the resulting nanoparticle monolayer is lost when sonicated in an acidic aqueous solution or subjected to electrochemical cycling.

PAMAM Dendrimer Templated Nanoparticle Catalysts

“…Coordination of PtCl 4 2 − and reduction yields DENs within this matrix. Similarly, amine terminated Pt and Pd DENs have been immobilized on planar Au surfaces through self -assembled monolayer (SAM) chemistry [59,60] . Amine terminated dendrimers can also be deposited onto Au fi lms and then used to template Pt nanoparticles which are active electrocatalysts [61] .…”

Platinum–Dendrimer Nanocomposite Films on Gold Surfaces for Electrocatalysis

“…Besides, the attached nanoparticle should retain the electroactivity. Amine-terminated PAMAM and bifunctionalized PAMAM dendrimers have been linked to Au substrate through mercaptoundecanoic acid (MUA) monolayer with and without activation by ethyl chloroformate [36,37]. Activation by ethyl chloroformate aids the covalent linkage of dendrimers to the MUA monolayer.…”

Selective NO reduction using blue ferrocenyl cation

“…The carboxylic acid groups of MUA were activated by adding methyl morpholine and ethyl chloroformate. Methyl morpholine is added to generate the carboxylate anion which then reacts with ethyl chloro formate to give mixed anhydride which subsequently reacts with carboxyl groups of FCA or hydroxyl groups of ␤-cyclodextrin complexed with Fc to give an anhydride and ester linkage, respectively [11][12][13][14].…”