The synthesis, characterization and properties of the metal and metal salt nanoclusters prepared in the presence of dendrimers

Synthesis and characterization of nanometer size metal particles and composites have attained great consideration owing to their optical, electric, and catalytic properties. In the preparation of these metal particles and composites, stabilizers play an important role in controlling particle size as well as dispersion stability. As a stabilizer, dendrimers have been attractive because they consist of a core molecule, hyperbranches which regularly extend from the core, and teriminal groups, having a defined molecular weight and size. In addition, dendrimers of higher generations take spherical shape and they can act as a template for preparing the metal or metal salt nanoparticles. All the reasons mentioned above motivate us to prepare the transitional metal and metal salt nanoclusters in the presence of dendrimers and other kind of polymer. Our research group began this research on 2000. Three main research developments will be discussed in this chapter: PAMAM dendrimers have a generation-dependent number of interior tertiary amines, so these are able to complex a range of metal ions including Ag⁺, Cu²⁺, Cd²⁺. The maximum number of metal ions that can be sorbed within the dendrimers and complexation between metal ions and PAMAM dendrimers depend on the metal ions, the dendrimer type, the dendrimer generation and pH value of the reaction solution. For example, a generation 5 PAMAM dendrimer can contain up to 34 Cd²⁺ ions, and a generation 4.5 PAMAM dendrimer can absorb only to 16 Cd²⁺ ions. It is easy for Cu²⁺ ions to be sorbed within the dendrimers, but the reaction between Ag⁺ ions or Cd²⁺ ions and PAMAM dendrimer are difficult, which result in the reaction time between Cu²⁺ ions and dendrimers being shorter than Ag⁺ ions and Cd²⁺ ions. The other coordination rules between mental ions (including Ag⁺, Cu²⁺, Cd²⁺) and PAMAM dendrimers are described in detail.