Nanocluster formation

Figure 3. Double autocatalytic pathway for the metal nanocluster formation. (Reprinted from Ref. [299], 2005, with permission from American Chemical Society.)...

Figure 4. Homogeneous nucleation to be inhibited completely for highly dispersed nanocluster formation.

For molecular catalytic systems, it is remarkable to note that the conversion at short times (< 5 h), increases with increasing Pd/substrate ratio. Actually, the nanoclusters formation seems to be less probable, in contrast to analogous experiments carried out for other Pd-cata-lysed reactions like C-C Fleck couplings [58]. 

Watzky, M.A. and Finke, R.G., Transition metal nanocluster formation kinetic and mechanistic studies. A new mechanism when hydrogen is the reductant slow, continuous nucleation and fast autocat-alytic surface growth, J. Am. Chem. Soc., 119,10382,1997. 

Ritchie CM, Johnsen KR, Kiser JR, Antoku Y, Dickson RM, Petty JT (2007) Ag nanocluster formation using a cytosine oligonucleotide template. J Phys Chem C 111 175-181... 

Research has also been conducted on the ratios of GSH to cadmium for nanocluster formation. Clusters were formed at ratios as high as 1 1, but these reactions did not produce a uniform distribution of particles. In fact, the most reproducible... 

As expected, the formation of ZnS-(GSH) nanoclusters is analogous to CdS. Beginning with the Zn(II)(GSH)2 precursor complex, nanocluster formation is initiated by the addition of the sulfide. Mehra et al. has shown that the precursor Zn(II)GSH complex does indeed closely follow the synthetic route of CdS-(GSH) nanoparticles. Considering the similarities between the thiol chemistry of zinc and cadmium, studies to optimize ZnS nanocluster formation primarily focused on the ratio of zinc to sulfide ions in solution. Varying equivalents of sulfide (0.1-2.0) were studied for the formation of nanoclusters. An optimal ratio of Zn + S was obtained at 1 1. The average size of nanoparticles prepared at this ratio was shown to be about 3.45 0.5nm. Elution profiles from SEC highlighted the dispersity of nanoparticle populations synthesized in aqueous solutions. By size dependent absorption, the reaction mixtures revealed two cluster populations with an approximate diameter of 22.6 A and 19.54 A, respectively. Any excess of sulfide added greater than 1 equivalent was volatilized and not incorporated into the nanoclusters. ... 

Plowman, S.J., Ariotti, N., Goodall, A., Parton, R.G., and Hancock, J.F. (2008). Electrostatic interactions positively regulate K-Ras nanocluster formation and function. Mol Cell Biol 28 4377-4385. 

Figure 6.15. Schematic of the four-step mechanism for transition metal (e.g., Pt) nanocluster formation. Shown are (i) nucleation to a desired cluster size (ii) autocatalytic growth onto the cluster surface (hi) diffusive agglomerative growth of two nanoclusters and (iv) autocatalytic agglomeration into bulk metal particulates. Reproduced with permission from Besson, C. Finney, E. E. Einke, R. G. J. Am. Chem. Soc. 2005,127, an9. Copyright 2005 American Chemical Society.

For an excellent review of transition metal nanocluster formation and nomenclature, as well as the difference between colloids and nanoclusters, see Finke, R. G. Transition Metal Nanoclusters in Metal Nanoparticles Synthesis, Characterization, and Applications, Dekker New York, 2002. 

In this paper, the investigation of the process of Ge nanoclusters formation during the deposition of Ge-doped po -Si films is described. 

The lr(0) NP catalyzed H/D exchange, in which deuterium incorporation in the 2-H and 4-H positions of the imidazolium occurs only after an induction period (Scheme 6.4). The kinetics are well-fit by the analytical equations corresponding to the auto-catalytic mechanism which is a diagnostic of nanocluster formation [85]. 

Ionizing Radiation as a Tool for Silver Nanoclusters Formation... 

Both types of radiation can be applied for metal nanocluster formation in solution. In the first method, the reactive species formed in water radiolysis are the reducing agents, as they were formed in the process of water radiolysis. The water radiolysis reaction is presented in Eigure 20.5. 

Inorganic Nanoparticles with Fullerene-like Structure and Nanotubes 1247 Scheme of the suboxide nanoclusters formation. 

The simplest example of direct silicon nanocluster formation is the electrochemical reaction of SiO with Lb, which proceeds in much the same way as tin convertible oxides (TCOs). Li O formed in situ is known to be an appropriate inactive matrix for accommodating active metal particles, and it is a good ionic conductor for Lb. However, convertible silicon oxides have worse kinetic properties, because silicon is a semiconductor and the bulk conductivity of the resulting nanocomposite is several orders of magnitude less than in case of SnO... 

Another example for ex situ sihcon nanocluster formation was proposed by Lee et al. here the authors used a mechanochemically driven reaction... 

Nanoclusters formation synergetics is directly connected with the studied polymers structure macroscopic characteristics. As it has been noted above, the fractal structure, characterized by the dimension is formed as a result of nanoclusters reformations. In Fig. 15.7 the dependence for the considered polymers is adduced, from which increase at A. growth follows. This means, that the increasing of possible reformations number m, resulting to Aj reduction (Fig. 15.6), defines the growth of segments number in nanoclusters, the latter relative fraction cp j enhancement and, as consequence, d reduction [3-5]. 

Jiang, R, Liu, Z. R, Cai, S. M. In situ CdS nanocluster formation on scanning tunneling microscopy tips for reliable single-electron mnneling at room temperature. Appl Phys Lett 1999, 75, 3023-3025. 

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