Metal nanoparticles/nanoclusters

The size of metal nanoparticles obviously plays also a significant role considering the interaction with biosystems. The 1.4 nm gold nanoclusters interact irreversibly with DNA due to an extremely stable fixation in the major groves. These findings may lead to the development of novel cancer drugs, as can be concluded from a series of cell experiments. 

It should be mentioned here that Finke s group has added a whole plethora of significant contributions to the field of metal nanoclusters [295-299] including a recent study on the mechanism for the self-assembly of transition metal nanoparticles [294]. 

Finke has reported remarkable catalytic lifetimes for the polyoxoanion- and tetrabutylammonium-stabi-lized transition metal nanoclusters [288-292]. For example in the catalytic hydrogenation of cyclohexene, a common test for structure insensitive reactions, the lr(0) nanocluster [296] showed up to 18,000 total turnovers with turnover frequencies of 3200 h [293]. As many as 190,000 turnovers were reported in the case of the Rh(0) analogue reported recently. Obviously, the polyoxoanion component prevents the precious metal nanoparticles from aggregating so that the active metals exhibit a high surface area [297]. 

Many different topics are involved in the study of metallic nanoparticles and many fundamental issues can be present for example, which is the infiuence of the nanoparticle size, shape and composition on the chemical activity of heterogeneous catalysts Or, considering another problem, at what size does a small particle behave like the bulk material, for example, changing from an insulator to a semiconductor [9-12] An enormous amount of literature is published on metallic nanoclusters this review is focusing on the relevant problem concerning the characterization of metallic nanosized materials from the morphological and... 

In the XRD patterns of the unprotected metal nanoclusters prepared by the alkaline EG synthesis method, no signals derived from their corresponding oxides could be detected. XPS measurements also revealed that the prepared metals nanoparticles had the binding energies close to those of their corresponding zero valence species, 70.9 eV for Pt 4f7/2, 280.0 eV for Ru 3ds/2, 307.1 eV for Rh 3d5/2 and 50.0 eV for Os 4f7/2, respectively, indicating that the metal species were in a metallic state. 

Xin and co-workers modified the alkaline EG synthesis method by heating the metal hydroxides or oxides colloidal particles in EG or EG/water mixture in the presence of carbon supports, for preparing various metal and alloy nanoclusters supported on carbon [20-24]. It was found that the ratio of water to EG in the reaction media was a key factor influencing the average size and size distribution of metal nanoparticles supported on the carbon supports. As shown in Table 2, in the preparation of multiwalled carbon nanotube-supported Pt catalysts... 

Mao and Mao invented a method for synthesizing supported metal catalysts with small metal nanoparticles (1-3 nm) even at high metal loadings (30-50 wt.%) [25]. The obtained metal catalysts exhibited superior electrocatalytic performance in fuel cells. In this invention, the unprotected metal nanocluster colloids prepared according... 

Figure 1. Graphical model for the generation of size-controlled metal nanoparticles inside metallated resins, (a) Pd is homogeneously dispersed inside the polymer framework (b) Pd is reduced to Pd (c) Pd atoms start to aggregate in subnanoclusters (d) a single 3 nm nanocluster is formed and blocked inside the largest mesh present in that slice of polymer framework (Reprinted from Ref [5], 2004, with permission from Wiley-VCH.)...

Palladium metallic clusters have been prepared at room temperature by sonochemical reduction of Pd(OAc)2 and a surfactant, myristyltrimethylammonium bromide, in THE or MeOH [160[. It is noteworthy that nanosized amorphous Pd is obtained in THE, but in a crystalline form in MeOH. In this solvent, and in higher homologous alcohols, sonolysis of tetrachloropalladate(II) leads to Pd nanoclusters in which carbon atoms, formed by complete decomposition of the solvent, can diffuse. This results in an interstitial solid having the formula PdQ (0 < x < 0.15) [161]. Noble metal nanoparticles of Au, Pd, and Ag are obtained by sonicating aqueous solutions of the corresponding salts in the presence of a surfactant, which largely stabilise the naked col-... 

The fabrication of regular arrays of metallic nanoparticles by molecular templating is of great interest in order to prepare nanometre structures for future use in nanoelectronics, optical and chemical devices.43 A sensitive, rapid and powerful direct analytical method is required for the quantitative analysis of high purity platinum or palladium nanoclusters produced by biomolecular... 

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