title: A Systematic Investigation ofp-Nitrophenol Reduction by Bimetallic Dendrimer Encapsulated Nanoparticles.
abstract: We demonstrate that the reduction ofp-nitrophenol top-aminophenol by NaBH4is catalyzed by both monometallic and bimetallic nanoparticles (NPs). We also demonstrate a straightforward and precise method for the synthesis of bimetallic nanoparticles using poly(amido)amine dendrimers. The resulting dendrimer encapsulated nanoparticles (DENs) are monodisperse, and the size distribution does not vary with different elemental combinations. Random alloys of Pt/Cu, Pd/Cu, Pd/Au, Pt/Au, and Au/Cu DENs were synthesized and evaluated as catalysts forp-nitrophenol reduction. These combinations are chosen in order to selectively tune the binding energy of thep-nitrophenol adsorbate to the nanoparticle surface. Following the Brønsted-Evans-Polanyi (BEP) relation, we show that the binding energy can reasonably predict the reaction rates ofp-nitrophenol reduction. We demonstrate that the measured reaction rate constants of the bimetallic DENs is not always a simple average of the properties of the constituent metals. In particular, DENs containing metals with similar lattice constants produce a binding energy close to the average of the two constituents, whereas DENs containing metals with a lattice mismatch show a bimodal distribution of binding energies. Overall, in this work we present a uniform method for synthesizing pure and bimetallic DENs and demonstrate that their catalytic properties are dependent on the adsorbate's binding energy.
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: Zachary D
authors.initials: ZD
authors.lastname: Pozun
authors.forename: Stacia E
authors.initials: SE
authors.lastname: Rodenbusch
authors.forename: Emily
authors.initials: E
authors.lastname: Keller
authors.forename: Kelly
authors.initials: K
authors.lastname: Tran
authors.forename: Wenjie
authors.initials: W
authors.lastname: Tang
authors.forename: Keith J
authors.initials: KJ
authors.lastname: Stevenson
authors.forename: Graeme
authors.initials: G
authors.lastname: Henkelman