Nano-clusters

SAMs of alkanethiols on an Au(l 11) surface are widely used to control surface properties, electron transfer processes and to stabilize nano-clusters [6, 7]. SAMs are formed by chemical bond formation between Sand Au when an Au(l 11) substrate is immersed in a solution containing several mM of alkanethiols for hours to days. Various functions have been realized by using SAM s of alkanethiols on Au substrates as listed in Table 16.1. 

Choudhary TV, Goodman DW. 2002. Oxidation catalysis by supported gold nano-clusters. Top... 

Jitianu A., Altindag Y., Zaharescu M., Wark M., New Sn02 nano-clusters obtained by sol-gel route, structural characterization and their gas sensing applications, J. Sol-Gel Sci. Technol. 2003 26 483-488. 

Scheme 9.5 Synthesis of Rh(0) nanoclusters from (1,5-COD)RhP2W15Nb3Oj polyoxoanion-supported nano-cluster-forming precatalyst (space-filling representation). (Adapted from [63].)...

Lu, P. et al., Polymer-protected Ni/Pd bimetallic nano-clusters preparation, characterization and catalysis for Hydrogenation of Nitrobenzene, J. Phys. Chem. B, 103, 9673, 1999. 

Considerable work in the area of general research on fuel cells, materials and components was reported by Australia, where the government-sponsored fuel cell R D program has made efficiency improvements in fuel cell electrodes by the formation of platinum nano-clusters in porous carbon by high density plasma sputter mechanisms. Initial experiments on the plasma sputter deposition of platinum onto a porous film has shown great promise and aggregates of platinum were detected in the film with a density profile which decreased away from the surface exposed to the plasma. 

Abstract The present paper discusses classification of nano-objects, which is based on their size, morphology and chemical nature. The subject of nanochemistry includes those nano-objects whose chemical properties depend on size and morphology, such as spheroidal molecules, anisotropic (2D) and isotropic (ID) nanoparticles, nano-clusters and nanophases. Nanophase is a nano-dimensional part of the microphase whose properties depend on its size. The potential health hazards of nano-objects are associated with their capability of penetrating the body through inhalation, digestion or the skin. 

Nano-clusters are also nano-dimensional objects. They can be neutral (atomic or molecular) or charged (ionic or ionic-molecular) complexes or ensembles of molecules, atoms and ions. 

In this communication we have reported the synthesis and characterization of different types of surface modified MCM-41 type pure-silicate and alumino-silicate materials. Simultaneous incorporation of thio- and amino-propyl groups was also achieved. There is tremendous potential in this field as these materials itself can be used as supra-molecular ligand in complexation with a metal ion. They can also be potentially used as host for different nano-cluster stabilization. 

Nano-Clusters, Enantioselective Catalysis and Molecular Recognition Contrast Agents in MCM-41. Part I. 

Most of our discussion thus far has involved some rather extreme synthetic environments of laser, arc, or pyrolysis. However, a preferred route toward nano-clusters/nanoparticles of metals and their compounds is through use of relatively mild conditions - often taking place at room temperature on the benchtop. This is not possible for carbon nanoallotropes, since the precursor e.g., graphite) contains... 

The primary advantage being that this techniqne offers the ability to study in situ the changes to both electronic and short range atomic order in the nano-clusters and other complex reaction centers with element specificity under conditions of actual fuel cell operation. 

The XAS data can thus be normalized to the average number of surface atoms for these nano-clusters. 

G. Bauer F. Pittner T. Schalkhammer, Metal nano-cluster biosensors. Mikrochim. Acta 1999, 333, 107-114. 

Here the first term is a pair-potential repulsive term and the second term corresponds to the band-structure term. N is the total number of atoms, rM is the distance between atoms i and j of the species a and p, respectively, (a and p stand for A1 and Ni) and the sum j is extended up to fifth neighbours. Numerical values of the constants A, , p, q and r0 are given in [16], MMC simulations of this type have been carried out in the past to investigate the surface configurations of isolated nano-clusters of NixAly alloys [17],... 

This predicted surface composition is thus in very good agreement with the BET measurement. Interestingly, the nano-cluster actually contains enough Al atoms to provide a 69 at.% surface coverage of Al. However, this would entail Al-Al bonding which is not energetically favourable [17],... 

Figure 4 Isolated NiAl nano-cluster 54 atoms in diameter (equating to a...

Both the optical and the electrical trapping have already been demonstrated separately. The double evanescent wave trap for atoms has been proposed in Ref. [Ovchinnikov 1991] and has been demonstrated in Ref. [Hammes 2002] for Cs atoms. Bezryadin and coworkers [Bezryadin 1997] have reported a method of fabrication for nanoscale controllable break junctions, in which the polarized nano-clusters, such as Pd clusters, have been trapped between the electrodes. The nano-clusters were self-assembled in the region of the maximum field in order to produce a wire connecting the tips [Bezryadin 1997],... 

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