Nanoparticles organometallic approach

In summary, we have described our approach towards the synthesis of novel nano-objects consisting of a metal core and a surface that may be functionalized by addition of organic ligands. TEM pictures of the metal core of these nanoparticles appear similar to those of particles commonly used in heterogeneous catalysis or to colloids prepared by well-known reduction methods. However, the organometallic approach displays several specificities which can be summarized as follows ... 

Finally, the groups of Chaudret and Choukroun have demonstrated that PVP-protected native Rh nanoparticles synthesized by an organometallic approach are active in the hydrogenation of benzene in a biphasic mixture. 

An alternative approach to stabilize nanoparticles is to use polyoxoanions (see Scheme 9.5). Finke and coworkers described polyoxoanion- and ammonium-stabilized rhodium zerovalent nanoclusters for the hydrogenation of classical benzene compounds [95, 108]. This organometallic approach allows reproducible preparation of stable nanoparticles starting from a well-defined complex in terms of composition and structure (see Section 9.3.5). 

In summary, Dupont and coworkers have developed an organometallic approach for the stabilization of various zero-valent nanoparticles in the ionic liquid BMI PFe. Transition metal nanoparticles of 2.0-3.0 were obtained with... 

Finally, Jessop and coworkers describe an organometallic approach to prepare in situ rhodium nanoparticles [78]. The stabilizing agent is the surfactant tetrabutylammonium hydrogen sulfate. The hydrogenation of anisole, phenol, p-xylene and ethylbenzoate is performed under biphasic aqueous/supercritical ethane medium at 36 °C and 10 bar H2. The catalytic system is poorly characterized. The authors report the influence of the solubility of the substrates on the catalytic activity, p-xylene was selectively converted to czs-l,4-dimethylcyclohexane (53% versus 26% trans) and 100 TTO are obtained in 62 h for the complete hydrogenation of phenol, which is very soluble in water. 

Scheme 1 Schematic representation of the organometallic approach for the synthesis of metal nanoparticles from Ru(C8Hio)(CaHi2).

Finally, sulfides were also obtained through an organometallic approach for other purposes. For example, nanoparticles of M0S2, an important compound for applications in catalysis and lubrification, of 10-30 nm mean diameter were synthesized through decomposition of Mo(CO)6 at 140°C in the presence of sulfur. ... 

Chaudret s team has developed the use of organometallic complexes as precursors for the synthesis of metal nanoparticles. The main advantage of this organometallic approach is the mild reaction conditions followed, the synthesis being mostly performed at room temperature and under low gas pressure (1-3 bar H2 for example). Ideal precursors are complexes bearing olefins as ligands since... 

The preparation of unsupported metal nanoparticles was therefore achieved following an organometallic approach since this does not employ drastic reaction conditions and avoids surface contamination. In addition, the size, the shape and the surface state of the particles can be controlled using various stabilizing agents. Besides catalysis, such work can find applications in different areas such as chemical sensors [141, 142] or magnetic properties [143]. 

Other Metal Magnetic Nanopartides Synthesized by Methods of Colloidal Chemistry In the previous sections, the coUoidal synthesis of Co and CoPts nanocrystals and the great potential of an organometallic approach in the preparation of high-quality magnetic nanoparticles have been discussed. Yet, these synthetic... 

In order to avoid such surface contaminations and their drastic effects on magnetic properties, an organometallic approach could be advantageous since controlled decomposition under mild conditions can be achieved. Through intensive prospective work, we determined that amido precursors such as Fe[N(SiMe3)2]2(THF) (Me = CH3, THF = tetrahydrofurane) [43] or the dimer (Fe[N(SiMe3)2]2 2 [44] can yield unoxidized iron metal nanoparticles (MNPs) under mild conditions. These precursors exhibit a good compromise between stability (to be stored once prepared) and reactivity( to be decomposed under mild and reductive conditions). 

Chaudret, B. Organometallic approach to nanoparticles synthesis and self-organization. CR Phys 2005, 6,117-131. 

In summary, the organometallic approach is also efficient to prepare bimetallic nanoparticles. By precisely selecting the reaction conditions (precursor, stabilizer, reactant), we could access to ruthenium-based bimetallic nanoparticles displaying a controlled chemical order, i.e. alloy, core-shell, or even nanoparticles decorated with a second metal such as platinum, iron, or tin. These nanoparticles, which display different surface properties, can pave the way towards synergetic and selective catalytic performances. 

Philippot, K. and B. Chaudret. 2003. Organometallic approach to the synthesis and surface reactivity of noble metal nanoparticles. C. R. Chim. 6 (8-10) 1019-1034. 

We have described four significant catalytic systems consisting of stabilized metal nanoparticles in the hydrogenation of monocyclic aromatic compounds. Four noble metals are efficient in this reaction Rh, Ru, Ir, and Pt. Several stabilization methods have been described which represent typical nanoparticle stabihzers polymers, surfactants, polyoxoanions and ionic liquids. Two approaches are developed for the preparation of nanocatalysts which provide interesting results in catalytic apphcations the reduction starting with an organometalhc precursor or a metal salt. The organometallic... 

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