Metal nanoparticle catalysis

S. Senkan, M. Kahn, S. Duan, A. Ly, C. Leidhom, High-throughput metal nanoparticle catalysis by pulsed laser ablation, Catal. Today 117 (2006) 291. 

Transition-metal Nanoparticle Catalysis in Imidazolium Ionic Liquids... 

Scholten, J.D., Leal, B.C. and Dupont, J., Transition metal nanoparticle catalysis in ionic liquids, ACS Catal 2,184-200 (2012). 

Dupont, J. and Silva D.D.O., Transition-metal Nanoparticle Catalysis in Imidazolium Ionic Liquids , in Nanoparticles and Catalysis, Ed. D. Astruc, Mley-VCH, Weinheim (2008), pp. 195-218. 

The coordination of ligands at the surface of metal nanoparticles has to influence the reactivity of these particles. However, only a few examples of asymmetric heterogeneous catalysis have been reported, the most popular ones using a platinum cinchonidine system [65,66]. In order to demonstrate the directing effect of asymmetric ligands, we have studied their coordination on ruthenium, palladium, and platinum nanoparticles and the influence of their presence on selected catalytic transformations. 

In summary, we found that Ugands indeed coordinate at the surface of nanoparticles and that they can be firmly or loosely attached to this surface according to their chemical nature. Furthermore, the hgands influence the reactivity of the metal nanoparticles. This is important in catalysis but, as we will see later in this paper, is also important for the control of the growth of metal nanoparticles of defined size and shape. 

Bimetallic nanoparticles (including monometallic ones) have attracted a great interest in scientific research and industrial applications, owing to their unique large sur-face-to-volume ratios and quantum-size effects [1,2,5,182]. Since industrial catalysts usually work on the surface of metals, the metal nanoparticles, which possess much larger surface area per unit volume or weight of metal than the bulk metal, have been considered as promising materials for catalysis. 

N. Toshima, Metal nanoparticles for catalysis, in L. M. Liz-Marzan, P. V. Kamat (eds.) Nanoscale Materials, Kluwer Academic Publishers, Dordrecht, 2003, 79. 

Advantages of small metal nanoparticles are (i) short range ordering, (ii) enhanced interaction with environments due to the high number of dangling bonds, (iii) great variety of the valence band electron structure, and (iv) self-structuring for optimum performance in chemisorption and catalysis. 

By using thermosensitive poly-acrylamides, it is possible to prepare cubic Pt nanocrystals (with predominant (1 0 0) facets) and tetrahedral Pt nanocrystals (rich in (111) facets). These Pt nanocrystals can be supported on oxide (alumina) and used as a catalyst in structure-sensitive reaction, NO reduction by CH4. The results proved that morphologically controlled metal nanoparticles supported on adequate support give us a novel tool to connect the worlds of surface science with that of real catalysis. 

The potential of morphologically controlled metal nanoparticles should be expanded by further improvement of their preparation method. It is highly required to develop preparation methods to obtain a better morphological control, i.e., perfect facet control on the particles of optional size. Better morphological control of metal nanoparticles is expected to be achieved in near future and the obtained metal particles will find new exciting applications, not only in catalysis but also in other technically important fields. 

Supported metal nanoparticles are of great interest in catalysis, because they offer the opportunity to combine the high reactivity and selectivity of the nanosized metals with the easy separation of the catalysts from the reaction mixture and recycling. 

In this chapter the potential of nanostructured metal systems in catalysis and the production of fine chemicals has been underlined. The crucial role of particle size in determining the activity and selectivity of the catalytic systems has been pointed out several examples of important reactions have been presented and the reaction conditions also described. Metal Vapor Synthesis has proved to be a powerful tool for the generation of catalytically active microclusters SMA and nanoparticles. SMA are unique homogeneous catalytic precursors and they can be very convenient starting materials for the gentle deposition of catalytically active metal nanoparticles of controlled size. 

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