Particle synthesis: mechanisms nucleation

There have been many recent studies in support of this mechanistic approach. Stepwise reductive formation of Ag3+ and Ag4+ clusters has been followed using spectroscopic methods by Henglein [33], Reduction of copper (II) to colloidal Cu protected by cationic surfactants (NR4+) through the intermediate Cu+ prior to nucleation of the particles [36] as monitored by in situ x-ray absorption spectroscopy is another example. The seed-mediated synthesis also serves as evidence in support of this mechanism [38-41],... 

The formation of highly dispersed particles or crystallites in the synthesis process of, for example, a supported metal catalyst, is governed by nucleation and growth mechanisms (vide supra) that have been described in the literature [15, 16, 21-23]. For sintering or redispersion (spreading and film formation) to occur, particles or atoms, molecules or clusters of the active... 

Dispersions of metallic nanoparticles can be obtained by two main methods (i) mechanic subdivision of metallic aggregates (physical method) or (ii) nucleation and growth of metallic atoms (chemical method). The physical method yields dispersions where the particle size distribution is very broad. Traditional colloids are typically larger (>10nm) and not reproducibly prepared, giving irreproducible catalytic activity. Chemical methods such as the reduction of metal salts is the most convenient way to control the size of the particles. Today, the key goal in the metal colloid area is the development of reproducible nanoparticle (or modem nanocluster) syntheses in opposition to traditional colloids. As previously reported, nanoclusters should be or have at least (i) specific size (1-10 nm), (ii) well-defined surface composition, (iii) reproducible synthesis and properties, and (iv) be isolable and redissolvable ( bottleable )- ... 

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