Noble Metal Nanoparticle

K-Sites on Carbon Surface as Anchors for Metal Nanoparticles Noble metals, both in zerovalent and in ionic states (in particular in the low-oxidation state), are prone to form stable 7r-complexes with multiple C-C bonds of organic compounds [53]. The stability of the 7r-complexes increases if the ligand contains electron acceptor groups (for example, oxygen-containing or aryl) in close proximity of the >C—C< bond. 

Noble metal nanoparticles dispersed in insulating matrices have attracted the interest of many researchers fromboth applied and theoretical points of view [34]. The incorporation of metallic nanoparticles into easily processable polymer matrices offers a pathway for better exploitation of their characteristic optical, electronic and catalytic properties. On the other hand, the host polymers can influence the growth and spatial arrangement of the nanoparticles during the in situ synthesis, which makes them convenient templates for the preparation of nanoparticles of different morphologies. Furthermore, by selecting the polymer with certain favorable properties such as biocompatibiHty [35], conductivity [36] or photoluminescence [37], it is possible to obtain the nanocomposite materials for various technological purposes. 

The application of ly transition metal carbides as effective substitutes for the more expensive noble metals in a variety of reactions has hem demonstrated in several studies [ 1 -2]. Conventional pr aration route via high temperature (>1200K) oxide carburization using methane is, however, poorly understood. This study deals with the synthesis of supported tungsten carbide nanoparticles via the relatively low-tempoatine propane carburization of the precursor metal sulphide, hi order to optimize the carbide catalyst propertira at the molecular level, we have undertaken a detailed examination of hotii solid-state carburization conditions and gas phase kinetics so as to understand the connectivity between plmse kinetic parametera and catalytically-important intrinsic attributes of the nanoparticle catalyst system. 

Porter LA, Choi HC, Ribbe AE, Buriak JM (2002) Controlled electroless deposition of noble metal nanoparticle films on Germanium surfaces. Nano Lett 2 1067-1071... 

Thiols are known to be excellent hgands for the stabilization of gold and platinum nanoparticles. In this respect, we did not observe any Iluxional behavior [31,52] in solution NMR experiments for thiols coordinated to the surface of noble metal particles (Fig. 8). However, in the case of rutheniiun, we foimd the slow catalytic formation of alkyl disulfides [31]. After exclud-... 

In the past five years, the use of nanoparticles in this active research area has received increased attention since some homogeneous catalysts have been shown to be nanoheterogeneous [24-26]. Today, soluble noble metal nanoparticles are considered as reference in monocyclic arene catalytic hydrogenation under mild conditions and several stabilized systems have been reported [27,28]. 

ROsch N (1999) A Critical Assessment of Density Functional Theory with Regard to Applications in Organometallic Chemistry. 4 109-163 Roucoux A (2005) Stabilized Noble Metal Nanoparticles An Unavoidable Family of Catalysts for Arene Derivative Hydrogenation. 16 261-279... 

Stabilized Noble Metal Nanoparticles An Unavoidable Family of Catalysts for Arene Derivative Hydrogenation... 

Enhanced electric-field distribution is illustrated schematically in Figure 3.8, based on reported electromagnetic simulations, for a dimer of a noble metal spherical nanoparticle. The optical field enhancement at the gap site occurs only when the incident polarization is parallel to the interparticle axis of the dimer. 

To summarize, we have shown here that enhanced electric-field distribution in metal nanoparticle assemblies can be visualized on the nanoscale by a near-field two-photon excitation imaging method. By combining this method and near-field Raman imaging, we have clearly demonstrated that hot spots in noble metal nanoparticle assemblies make a major contribution to surface enhanced Raman scattering. 

In this chapter, we have provided an overview of near-field imaging and spectroscopy of noble metal nanoparticles and assemblies. We have shown that plasmon-mode wavefunctions and enhanced optical fields of nanoparticle systems can be visualized. The basic knowledge about localized electric fields induced by the plasmons may lead to new innovative research areas beyond the conventional scope of materials. 

The nature of the element under investigation is certainly of some relevance, but not decisive for related elements, say noble metals. On the other hand, it is still not yet known how far the properties of two metal nanoparticles of different elements, but identical size really differ with respect to their quantum size behaviour. 

The size of metal nanoparticles plays also a role in a quite different field of nanoscience the interaction with biosystems with nanoparticles in general, here especially with metal nanoparticles. Chapter 4 will deal with some very recent aspects considering the interaction of noble metal nanoparticles with biomolecules and living cells. 

There exist numerous reports on the interaction of noble metal nanoparticles, especially those of gold, with DNA. The reason for this intense work in most cases is the use of gold nanoparticles for the analysis of nucleic acids, or proteins. In any case, the interactions between the two... 

Nanoparticles of the noble metals have been prepared extensively by the polyol or the modified polyol methods because of the ease of reduction of their salts (Figure 9). 

Noble metal ions can be easily reduced to the corresponding zero-valent metal atoms. Therefore, bimetallic nanoparticles consisting of two different noble metals have been extensively investigated for purpose of novel catalysts and optical materials. A simultaneous reduction of two noble metal ions with alcohol is a simple and useful technique to prepare bimetallic nanoparticles. The alcohol reduction of metal ions M + is followed by Equation (1). 

Late transition metal or 3d-transition metal irons, such as cobalt, nickel, and copper, are important for catalysis, magnetism, and optics. Reduction of 3d-transition metal ions to zero-valent metals is quite difficult because of their lower redox potentials than those of noble metal ions. A production of bimetallic nanoparticles between 3d-transi-tion metal and noble metal, however, is not so difficult. In 1993, we successfully established a new preparation method of PVP-protected CuPd bimetallic nanoparticles [71-73]. In this method, bimetallic hydroxide colloid forms in the first step by adjusting the pH value with a sodium hydroxide solution before the reduction process, which is designed to overcome the problems caused by the difference in redox potentials. Then, the bimetallic species... 

Pt/Ru bimetallic nanoparticles. In the case of dye-sensitized photochemical water splitters, to which much attention has been received recently, noble metal nanoparticles are often used for the active centers to produce hydrogen gas from water. Bimetallic nanoparticles will be easily replaced by these metal nanoparticles for the sake of saving resources. 

Interpretation of the Electronic Structure of Transition and Noble Metal Nanoparticles... 

Thus, silver nanoparticles grow gradually during UV light irradiation (processes al-a3 in Figure 2). Nanoparticles of other noble metals such as gold, copper, platinum, and palladium can also be deposited by this method. 

In this Section we want to present one of the fingerprints of noble-metal cluster formation, that is the development of a well-defined absorption band in the visible or near UV spectrum which is called the surface plasma resonance (SPR) absorption. SPR is typical of s-type metals like noble and alkali metals and it is due to a collective excitation of the delocalized conduction electrons confined within the cluster volume [15]. The theory developed by G. Mie in 1908 [22], for spherical non-interacting nanoparticles of radius R embedded in a non-absorbing medium with dielectric constant s i (i.e. with a refractive index n = Sm ) gives the extinction cross-section a(o),R) in the dipolar approximation as ... 

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