Metallic nanoparticles cobalt

In the early work on the thermolysis of metal complexes for the synthesis of metal nanoparticles, the precursor carbonyl complex of transition metals, e.g., Co2(CO)8, in organic solvent functions as a metal source of nanoparticles and thermally decomposes in the presence of various polymers to afford polymer-protected metal nanoparticles under relatively mild conditions [1-3]. Particle sizes depend on the kind of polymers, ranging from 5 to >100 nm. The particle size distribution sometimes became wide. Other cobalt, iron [4], nickel [5], rhodium, iridium, rutheniuim, osmium, palladium, and platinum nanoparticles stabilized by polymers have been prepared by similar thermolysis procedures. Besides carbonyl complexes, palladium acetate, palladium acetylacetonate, and platinum acetylac-etonate were also used as a precursor complex in organic solvents like methyl-wo-butylketone [6-9]. These results proposed facile preparative method of metal nanoparticles. However, it may be considered that the size-regulated preparation of metal nanoparticles by thermolysis procedure should be conducted under the limited condition. 

As a result of CNT synthesis, catalyst metal nanoparticles (iron, cobalt, nickel) together with amorphous carbon and fullerenes are unavoidably present in the CNT soot. 

Hydrocarbonyl compounds, lanthanide complexes, 4, 4 ( -Hydrocarbyl)bis(zirconocene), preparation, 4, 906 Hydrocarbyl-bridged cyclopentadienyl-amido complexes, with Zr(IV), 4, 864 Hydrocarbyl complexes bis-Cp Ti hydrocarbyls reactions, 4, 551 structure and properties, 4, 551 synthesis, 4, 542 cobalt with rf-ligands, 7, 51 cobalt with rf-ligands, 7, 56 cobalt with ]4-ligands, 7, 59 cobalt with rf-ligands, 7, 71 heteroleptic types, 4, 192 homoleptic types, 4, 192 into magnetic metal nanoparticles via ligand stabilization, 12, 87 via polymer stabilization, 12, 87 into noble metal nanoparticles... 

In contrast to aqueous methods, the polyol approach resulted in the synthesis of metallic nanoparticles protected by surface-adsorbed glycol, thus minimizing the oxidation problem The use of polyol solvent also reduces the hydrolysis problem of ultrafine metal particles, which often occurs in aqueous systems. Oxide nanoparticles can be prepared, however, with the addition of water, which makes the polyol method act more like a sol—gel reaction (forced hydrolysis). For example, 5.5-nm CoFe204 has been prepared by the reaction of ferric chloride and cobalt acetate in 1,2- propanediol with the addition of water and sodium acetate. 

When the CO disproportionation is catalyzed by cobalt, some ordered metastable structures are detected inside the active metal nanoparticles after the reaction. These structures are regular thin (approximately 5 atoms in thickness) alternating cobalt layers of different crystallographic modifications (Figure 4.17). Note that the appearance of such structures at thermodynamically equilibrium states of the catalyst substance is contrary to the Gibbs phase rule for the phase equilibria in solids. Thus, the metastable layered structures may be considered an analogue of spatial dissipative structures. 

Except gold, several other metal nanoparticles, also those of less noble metals, could be prepared, for instance, of silver, palladium, and cobalt, as well as sulfidic species like CdS or PbS. ... 

Many nanostructural possibilities for creating very effective nanomaterials for photocatalytic decontamination are possible. The doping (or docking) of transition metal ions of visible light chromophores (e.g., vanadinm, chromium, manganese, iron, or cobalt) into the backbone of nanostructured silica (SiO ), titania (TiOj), silica-titania, as well as POMs, has been demonstrated. Other possibilities, such as halogens, metal nanoparticles, or other POMs with particular tuned potentials could be stored in pores as special chromophores. 

Hollow Magnetic Nanocrystals Hollow nanoscale stmctures were first obtained by Y. Yin during the sulfurization of cobalt nanocrystals at elevated temperatures [145]. This process was found to lead to the formation of hollow cobalt sulfide nanocrystals such that, depending on the size of the cobalt nanocrystals and the cobalt sulfur molar ratio, different stoichiometries of hollow cobalt sulfide could be obtained. Hollow nanostmctures are usually formed through the nanoscale Kirkendall effect, which is based on the difference in diffusion rates of two species, and results in an accumulation and condensation of vacancies [146]. This phenomenon was first observed by Kirkendall at the interface of copper and zinc in brass in 1947 [147]. As a typical example of the nano-Kirkendall effect, the controllable oxidation of iron nanoparticles by air can lead to the formation of hollow iron oxide nanostructures, as shown in Figure 3.137. During the course of metal nanoparticle oxidation, the outward diffusion of metal occurs much faster in... 

Two systems were used by Chen et al. [428] for synthesis of cobalt metal nanoparticles. One of them was the well-known system AOT/isooctane/aqueous solution. Two reverse microemulsions (w = 11) were prepared with 0.3M C0CI2 or 0.6M NaBH4 dissolved in water as the aqueous phase. The microemulsions, when mixed, yielded a black colloid. Removal of the isooctane led to the formation of a paste containing Co particles in AOT. The surfactant was removed by washing with water. The product in this form, or as a powdery material, yielded 3-4 nm sized Co particles. Heating at 550°C/2 h produced crystalline Co. 

Other non-precious metal chalcogenides centers containing cobalt have been also synthesized following the template depicted in Fig. 9. In this woik, the in sitn free-surfactant method for carbon supported COxXy (X = S, Se) based on the decomposition of cobalt carbonyls was obtained. To control the growth of the metal nanoparticles and to prevent agglomeration, the use of stabilizers, e.g., donor hgands, polymers and surfactants, i.e., oleic acid (OA), trioctylphosphine oxide (TOPO), trioctyl-phosphine (TOP) and triphenylphosphine (TPP) are necessary. ... 

Metallic nanoparticles are very interesting materials with unique electronic and electrocatalytic properties which depends on their size and morphology [63, 64]. The efiftciency of electronic and electrochemical redox properties becomes these classes of nanostructured materials very interesting for technological applications. In particular, gold nanoparticles (AuNPs) are much explored materials as components for biosensors development due to the capability to increase electronic signal when a biological component is maintained in contact with nanostructured surface. On the other hand, silver, platinum, palladium, cooper, cobalt and others... 

Several metal nanoparticles (NPs) (such as silver, gold or cobalt NPs) were successfully incorporated into polymer fibers via direct dispersion electrospinning. However, we point out that metal NPs are more commonly generated through an in situ procedure (see Sect. 2.2) that allows to achieve a more uniform dispersion of small size particles. 

Kem and coworkers have also explored controllable, uniform metal deposition by employing TMV as a biotemplate. In their studies, the addressable amino acid side chains that function as metal nncleation sites are first activated with a metal complex, followed by incubation with the desired metal for metallization and its subsequent chemical reduction to form metal nanoparticles. By employing this approach of electroless deposition, discrete nickel, silver, and cobalt nanoclusters were selectively formed on the interior or exterior of the virus by controlling the pH and the activation complex used in the reaction. In addition... 

Conversion reactions may circumvent these limitations and calculated theoretical capacities are above those of lithium cobalt oxide, lithium iron phosphate, or graphite by a factor of 5 to 10. This is due to a complete electrochemical reduction with the transfer of several electrons per 3d transition metal ion t3qjically leading to metal nanoparticles which are embedded in a host matrbc of the lithium compound. 

Bennett RA, Stone P, Bowker M (1999) Scanning tunnelling microscopy studies of the reactivity of the TiO2(110) surface re-oxidation and the thermal treatment of metal nanoparticles. Faraday Discuss 114 267-277 Bezemer GL, Bitter JH, Kuipers HP, Oosterbeek H, Holewijn JE, Xu X, Kapteijn F, Van Dillen A, De Jong KP (2006) Cobalt particle size effects in the Fischer-Tropsch reaction studied with carbon nanofiber supported catalysts. J Am Chem Soc 128 3956-3964... 

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