Dendrimer-encapsulated Pt nanoparticle

Activation of Dendrimer Encapsulated Pt Nanoparticles for Heterogeneous Catalysts... 

Dendrimer encapsulated Pt nanoparticles (DENs) were prepared via literature methods (1, 11). PtCl42 and dendrimer solutions (20 1 Pt2+ dendrimer molar ratio) were mixed and stirred under N2 at room temperature for 3 days. After reduction with 30 equivalents of BH4 overnight, dialysis of the resulted light brown solution (2 days) yielded Pt2o nanoparticle stock solution. The stock solution was filtered through a fine frit and Pt concentration was determined with Atomic Absorption Spectroscopy (11). Details on catalyst characterization and activity measurements have been published previously (11). 

L. Beakley, R. Cheng, S. Yost, andB. D. Chandler, Immobilization of dilute dendrimer encapsulated Pt nanoparticles in a sol-gel silica matrix, Appl. Catal. A Gen. 292, 124-129 (2005). 

The approach for preparing dendrimer-encapsulated Pt metal particles is similar to that used for preparation of the Cu composites chemical reduction of an aqueous solution of G4-OH(Pt +)n yields dendrimer-encapsulated Pt nanoparticles (G4-OH(Ptn)). A spectrum of G4-OH(Pt6o) is shown in Fig. 12 a it displays a much higher absorbance than G4-OH(Pt +)6o throughout the wavelength range displayed. This change results from the interband transition of the encapsulated zero-valent Pt metal particles. 

Zhao, M., and Crooks, R. M., Dendrimer-encapsulated Pt nanoparticles, synthesis characterization, and applications to catalysis, Adv. Mater. 11,217 (1999a). 

M. Zhao, R.M. Crooks, Dendrimer-Encapsulated Pt Nanoparticles Synthesis, Characterization, and Applications to Catalysis, Advanced Materials 11, 217, 1999. 

It was demonstrated that high Pt + coordination ratios (a) can result in dendrimer-encapsulated Pt nanoparticles with narrow size distribution, while low values of a lead to nonencapsulated nanoparticles. Furthermore, the coordination can be accelerated by increasing temperature to SO C [49]. 

Knecht MR, et al. Structural rearrangement of bimetallic alloy Pd-Au nanoparticles within dendrimer templates to yield core/shell configurations. Chem Mater 2008 20 1019-28. Yamamoto D, Watanabe S, Miyahara MT. Coordination and reduction processes in the synthesis of dendrimer-encapsulated Pt nanoparticles. Langmuir 2010 26 2339-45. 

Yang X, et al. Microbial fuel cell cathode with dendrimer encapsulated Pt nanoparticles as catalyst. J Power Sources 2011 196 10611-5. 

Yu T, et al. Dendrimer-encapsulated Pt nanoparticles an artificial enzyme for hydrogen production. J Phys Chem C 2012 116 10516-21. 

Ye, H. and R. M. Crooks. Electrocatalytic Oj reduction at glassy carbon electrodes modified with dendrimer-encapsulated Pt nanoparticles. J. Am. Chem. Soc. 127, 2005 4930-4934. 

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