Nanoparticles/nanostructures metallic

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. 

Abstract. IR pyrolysis of PAN and PAN based composites yields ordered graphitelike structure as well as several carbon nanostructures. Metal-carbon nanocomposites, in which the nanosized metal particles were introduced into the structure of carbon matrix in the course of IR pyrolysis of composite-precursor on the basis of PAN and metal (Gd, Pt, Ru, Re) compounds were prepared. The carbon phase of metal-carbon nanocomposites was shown to include different types of nano structured carbon particles. Bamboo-like CNT were observed in the structure of pyrolized at 910 and 1000°C composite-precursor based on PAN and GdCl3. At T=1200°C the solid carbon spheres with diameter in the range of 50-360 nm and octahedral carbon particles with the size in the range of 300-350 nm were observed. These nanostructured particles consist of carbon only or they include Gd nanoparticles incapsulated in carbon shell. IR pyrolysis of composite-precursor based on PAN as well as H2PtCl6 and RuC13 or NH4Re04 (Pt Ru(Re)=10 l) allows the preparation of Pt-Ru and Pt-Re alloys nanoparticles with 2[Pg.577]

One family of new materials with potential use in metal catalysis is that of metal nanostructures such as metal nanoparticles (see Metal Nanoparticles, Synthesis of and Metal Nanoparticles, Organization Applications of), nanoshells, nanowires, nanorods, nanotubes, nanobelts, and nanoplates. " For instance, it has been recently shown that Ag nanowires and nanoparticles can be produced by... 

To understand the importance of spectral overlap to metal-enhanced fluorescence, it is useful to review the basics of metal-enhanced fluorescence. Metal nanostructures can alter the apparent fluorescence from nearby fluorophores in two ways. First, metal nanoparticles can enhance the excitation rate of the nearby fluorophore, as the excitation rate is proportional to the electric field intensity that is increased by the local-field enhancement. Fluorophores in such "hot spots" absorb more light than in the absence of the metal nanoparticle. Second, metal nanoparticles can alter the radiative decay rate and nonradiative decay rate of the nearby fluorophore, thus changing both quantum yield and the lifetime of the emitting species. We can summarize the various effects of a nanoparticle on the apparent fluorescence intensity, Y p, of a nearby fluorophore as ... 

More publications were found related to carbides. First, Suslick s early report [64] that certain carbonyls sonicated in a decalin solvent under argon. For Fe and Co, nanostructured metals are formed for Mo and W, metal carbides (e.g., M02C) are produced. Molybdenum carbide was used later as a catalyst. The selectivity and catalytic activity of the Mo and W carbides was examined in the dehydrogenation of alkanes [140]. Another carbide that has already been mentioned is that of Pd [65], which was prepared by Maeda s group. Iron carbide was a byproduct that served as protective layer in Nikitenko s work on air-stable iron nanoparticles [70]. 

Wet Chemical Deposition of Metal Nanoparticles and Metal Oxide Nanostructured Films on Electrode Surfaces for Bioelectroanalysis... 

Nanostructured metal oxide film deposition can also be prepared by hydrothermal decomposition, film casting method (sonication of nanoparticles in aqueous solution (H20) or preparation of aqueous suspension of nanoparticles for spread on conducting glass plate) and nanosized metal nanoparticles prepared by controlled hydrolysis [16,18,19,21,26],... 

X-ray diffraction technique is a non-destructive analytical technique that reveals information about crystallographic structure, chemical composition and physical properties of nanostructured materials. UV/Vis spectroscopy is routinely used in the quantitative determination of films of nanostructured metal oxides. The size, shape (nanocomb and nanorods etc,) and arrangement of the nanoparticles can be observed through transmission electron microscope (TEM) studies. Surface morphology of nanostructured metal oxides can be observed in atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies. 

Because of the considerable variety of materials that can be classified as porous, the discussion will be limited to several groups porous silicates and aluminosilicates, porous metal oxides and related compounds, porous polyoxometalates, metal-organic frameworks, porous carbons, carbon nanotubes, and several hybrid materials. All these materials can be viewed as relatively homogeneous from the electrochemical point of view. Metal and metal oxide nanoparticles, organic metals, fullerenes, and dendrimers, which can also be regarded as nanostructured materials, also displaying distinctive electrochemical features, will not be treated here for reasons of brevity, although their appearance in hybrid materials as modifiers for microporous materials will be discussed. 

In the present paper, we report on observation of the pronounced enhancement of photoluminescence of semiconductor nanocrystals near nanostructured metal surfaces which is shown to depend essentially on nanocrystal-metal spacing. Unlike conventional SERS, the surface enhanced PL should exhibit non-monotonous character with distance between emitting dipole (QD) and metal surface (Au colloid). The reason is that at smallest distances when QDs and colloidal particles are in close contact, the QD emission should be damped due to resonant energy transfer (RET) from photoexcited QDs to metal colloidal nanoparticles. Enhancement of photoluminescence (PL) is possibly promoted by surface plasmons excited in the metal. So, at a certain distance the enhanced QD emission would exhibit a maximum. We use a polyelectrolyte multilayers as the most appropriate... 

Radiation methods occupy an important place in the production and investigation of new functional materials, devices, and systems of nanometer size (ion-track membranes, polymeric nanocomposites, 3D nanostructures, metal nanoparticles, carbon nanostructures, etc.). The recent trend towards electronic miniaturization places at the forefront the problem of fabrication of semiconductor nanostructures, which is possible only with the use of radiation lithographic methods. The radiation modification of graphene can play a key role in the development of a new generation of industrial microchips based on graphene transistors, which will lead to a sharp increase in the operation speed and recording density of modem computer and communication systems. 

The nanostructures synthesis from organometallic unstable precursors can occur under controlled conditions. As a result, the nanoparticles have been specified by size, its distribution, stoichiometry and shape. The choice of organometallic compounds ligands can not only define the character of resulting cationic complex inorganic phases, the morphology of future nanoparticles (spheres, rods, cubes, wires), but can also affect their self-organization in one-, two-and three-dimensional clusters [338]. This approach is fruitful for the synthesis of nanoparticles of metals and alloys, simple and multication oxides and other compounds that exhibit ferroic properties. 

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