Three-dimensional cluster networks

The chemical tailoring of the charging energy in three dimensional networks of metal clusters has recently been described. The basic idea was to increase the 

As described above, the charging energy Eq, which is dependent on the cluster size and on the inter-particle capacitance C, can be determined directly from the temperature-dependence of the dc conductivity. Previous investigation of the electrical properties of these clusters has shown that even at high temperatures thermally activated electron hops instead of hops of variable range dominate charge transport through the samples. 

Whereas compact packing of the cluster material results in an activation energy of 20 meV, insertion of the spacer molecules increases this to 50 meV. The corresponding capacitance decreases from an initial value of 4.0 x 10 F to 1.6 x 10 F. The specific conductivity follows the same trend, the volume fraction of the metal in the total sample volume decreases. Comparable results where obtained by Schiffrin et who investigated 2.2- and 8.8-nm colloidal gold nanoparticles 

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Contrary to the 6-12 mixed halide phase, the three-dimensional cluster network of this structure is based on chlorine bridges only. As detailed in [17] an interesting relationship exists between this 6-13- and the [(Zr6B)Cli4] ([Nb6Cli4]) structure [19], which is shown in Fig. 5.6. The transformation of Nb6Cli4... 

The important feature is that a three-dimensional gel network comes from the condensation of partially hydroly2ed species. Thus, the microstmcture of a gel is governed by the rate of particle (cluster) growth and their extent of crosslinking or, more specifically, by the relative rates of hydrolysis and condensation (3). 

Even dynamic measurements have been made on mixtures of carbon black with decane and liquid paraffin [22], carbon black suspensions in ethylene vinylacetate copolymers [23], or on clay/water systems [24,25]. The corresponding results show that the storage modulus decreases with dynamic amplitude in a manner similar to that of conventional rubber (e.g., NR/carbon blacks). This demonstrates the existence and properties of physical carbon black structures in the absence of rubber. Further, these results indicate that structure effects of the filler determine the Payne-effect primarily. The elastomer seems to act merely as a dispersing medium that influences the magnitude of agglomeration and distribution of filler, but does not have visible influence on the overall characteristics of three-dimensional filler networks or filler clusters, respectively. The elastomer matrix allows the filler structure to reform after breakdown with increasing strain amplitude. 

In the case of water and ice, such a model might be realistic in treating the nucleation of liquid or solid from supersaturated vapour, as it occurs in the upper atmosphere. It seems doubtful, on the other hand, whether the model of stepwise molecular condensation can realistically be applied to the liquid - solid transition, because liquid water itself is already extensively associated and exists as a three-dimensional distorted network of hydrogen-bonded molecules, not too dissimilar from ice. Any mechanistic model of ice nucleation, based on the condensation of individual water molecules onto clusters of molecules with the properties of ice, should therefore be treated with caution. 

Forms a hexagonal two-dimensional surface structure, a tetrahedral three-dimensional molecular network, or clusters which influence the mutual (in)solubility significantly chaotropic compounds lower the order by H-bond breaking. 

Self-assembled coordination supramolecular structures encompass both discrete and polymeric types in a range of synthetic areas. Although coordination polymers, two- and three-dimensional coordination networks, polynuclear metal clusters (with primarily metal-metal or /r-oxo or... 

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