Metallic nanoparticle composites hydrogenation reactions

Y. Yoo, M. Tuck, R. Kondakindi, C.-Y. Seo, Z. Dehouche, K. Belkacemi, Enhanced hydrogen reaction kinetics of nanostructured Mg-based composites with nanoparticle metal catalysts dispersed on supports , J. Alloys and Compounds, 446-447 (2007) 84-89. 

Fig. 3. Schematic illustration of the synthesis of metal nanoparticles within dendrimer templates. The composites are prepared by mixing of the dendrimer and metal ion, and subsequent chemical reduction. These materials can be immobilized on electrode surfaces where they serve as electrocatalysts or dissolved in essentially any solvent (after appropriate end-group functionalization) as homogeneous catalysts for hydrogenation and other reactions...

The polymer resulting from oxidation of 3,5-dimethyl aniline with palladium was also studied by transmission electron microscopy (Mallick et al. 2005). As it turned out, the polymer was formed in nanofibers. During oxidative polymerization, palladium ions were reduced and formed palladium metal. The generated metal was uniformly dispersed between the polymer nanofibers as nanoparticles of 2 mm size. So, Mallick et al. (2005) achieved a polymer- metal intimate composite material. This work should be juxtaposed to an observation by Newman and Blanchard (2006) that reaction between 4-aminophenol and hydrogen tetrachloroaurate leads to polyaniline (bearing hydroxyl groups) and metallic gold as nanoparticles. Such metal nanoparticles can well be of importance in the field of sensors, catalysis, and electronics with improved performance. 

The LBL deposition of polymer layers incorporating metal nanoparticles was employed to study the electrochemical properties of the resultant composite films by using SECM. Wittstock and coworkers electrodeposited Pd and Pt nanoparticles in the matrix of LBL-deposited multilayers of polyelectrolytes, that is, polyfdiallyldimethylammonium) and poly(4-stylene sulfonate). The production of hydrogen peroxide during the ORR at the nanoparticle-incorporated LBL films was monitored in the SG/TC mode. The transient current at a 25 pm diameter Pt SECM tip was measured at various tip-substrate distances and quantitatively analyzed to determine effective rate constants 2, and k, for the following reactions at the film ... 

Protein nanocages can be used as a catalytic reaction space of metal particles [54, 64], For example, Ueno et al. have succeeded in the preparation of monodispersed Pd nanoparticles and the size-selective olefin hydrogenation catalyzed by the composite (Fig. 11b) [54]. Olefin snbstrates must penetrate the threefold channels of apo-Fr to react with the Pd particle, thus, larger substrates are less reactive than smaller snbstrates. 

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