Organometallic compound decomposition, nanoparticle

The most intensive development of the nanoparticle area concerns the synthesis of metal particles for applications in physics or in micro/nano-electronics generally. Besides the use of physical techniques such as atom evaporation, synthetic techniques based on salt reduction or compound precipitation (oxides, sulfides, selenides, etc.) have been developed, and associated, in general, to a kinetic control of the reaction using high temperatures, slow addition of reactants, or use of micelles as nanoreactors [15-20]. Organometallic compounds have also previously been used as material precursors in high temperature decomposition processes, for example in chemical vapor deposition [21]. Metal carbonyls have been widely used as precursors of metals either in the gas phase (OMCVD for the deposition of films or nanoparticles) or in solution for the synthesis after thermal treatment [22], UV irradiation or sonolysis [23,24] of fine powders or metal nanoparticles. 

Metal nanoparticles can be prepared in a myriad of ways, e.g., by pulse radiolysis [110], vapor synthesis techniques [111], thermal decomposition of organometallic compounds [112], sonochemical techniques [113,114], electrochemical reduction [115,116], and various chemical reduction techniques. Some of the most frequently used reducing agents include alcohols [117,118], citrate [119,120], H2 [121], borohydrides [122], and, more recently, superhydride [123]. The chosen experimental conditions determine the size, size distribution, shape, and stability of the particles. Because naked metal particles tend to aggregate readily in solution, stabilizing the nanoparticles is the key factor for a successful synthesis. Sometimes the solvent can act as a stabilizer, but usually polymers and surfac-... 

Other procedures for the synthesis of CNTs use a gas phase for introducing the catalyst, in which both the catalyst and the hydrocarbon gas are fed into a furnace, followed by a catalytic reaction in the gas phase. The method is suitable for large-scale synthesis, because nanotubes are free from catalytic supports and the reaction can be operated continuously. A high-pressure carbon monoxide reaction method, in which the CO gas reacts with iron pentacarbonyl to form SWNTs, has been developed [38]. SWNTs have been synthesized from a mixture of benzene and ferrocene in a hydrogen gas flow [55]. In both methods, catalyst nanoparticles are formed through thermal decomposition of organometallic compounds, such as iron pentacarbonyl and ferrocene. 

The decomposition combined with oxidation occurs when both the oxidant and the surfactant are added to the solution. Using organometallic compounds with two or more cations, like (ri -C5H5)CoFe2(CO)9, the CoFe204 nanoparticles of 4.9 nm size can be obtained [325]. 

Decomposition of organometallic compounds with subsequent synthesis of nanostructures is often accompanied by so-called self-assembly (Self-assembling) phenomenon. The example here is above synthesis on mesoporous template. Many papers studying self-assembly and self-organization of nanoparticles have been published during last decade. Some of them belong to nanoferroics. 

Two of the most common methods for preparing highly dispersed iron oxide nanoparticles are thermal decomposition of iron organometallic compounds and co-precipitation of aqueous iron salts (chlorides, nitrates, etc) in basic media. On the one hand, one of the most representative syntheses within the first group is the one reported by Sun et al. to prepare nanoparticles of Fe, Co and Mn ferrites through the decomposition of the corresponding acetylacetonate precursors in benzyl ether in the presence of oleylamine and oleic acid. Since the final aim is to use the nanoparticles in... 

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. ... 

Although several reports exist describing a variety of synthetic approaches for isotropic palladium nanoparticles, a major challenge exists in the ability to produce well-defined and monodisperse Pd nanoparticles. For wet-chemical methods used in the preparation of palladium nanoparticles, both organic and inorganic Pd compounds have been used as precursors. The oxidation state of the Pd compounds largely dictates the reaction conditions under which the synthetic procedure will ensue. For example, the decomposition of zerovalent organometallic Pd complexes is usually performed in an air-free environment with well-controlled... 

---