Synthesis Using Dendrimer Stabilizers

PAMAM dendrimers can also be used as templating agents and nanoparticle stabilizers for the synthesis of bimetallic particles. The unique ability of dendrimers to host various metal precursors enables the simultaneous complexation of multiple metallic species at its various internal functional groups. The three primary methods of bimetallic nanoparticle synthesis through dendrimer stabilization are partial displacement, co-complexation, and sequential complexation. 

In an attempt to develop synthesis of QDs using dendrimers as template, amino-polyester dendrons were used for t plating and stabilizing of CdS nanoparticles on the surface of single-wall carbon nanotubes (SWNTs) (Fig. 6.19). Attachment to SWNTs can be achieved by focal group while the interior space of the dendron serves for nanoparlicle formation. The obtained CdS nanoparticles with diameter of 1.4 nm were stable for more than 90 days at 25°C. It has been suggested that these characteristics may be useful for fabricating molecular electronic devices [55]. 

Dendritic nanoreactors can be used as a template and/or stabilizer for synthesis of nanoparticles with definite size and disparity. Various kinds of mono and bimetallic nanoparticles, as well as QDs, have been prepared using dendrimers. 

Ratheesh Kumar, V. K. and K. R. Gopidas. Palladium nanoparticle-cored Gl-dendrimer stabilized by carbon-Pd bonds Synthesis, characterization and use as chemoselective, room temperature hydrogenation catalyst. Tetrahedron Lett. 52, 2011 3102-3105. 

It is worthwhile to point out that dendrimers can also be used as normal capping agents during the synthesis of nanoparticles that do not reside inside the cavities of dendrimers [59,60]. These dendrimer-stabilized nanoparticles, capped with several dendrimer molecules, are usually much bigger than DENs and will not be discussed in this book chapter. 

The use of dendrimers constitutes an attractive stabilization mode for the synthesis of metal nanoparticles for several reasons ... 

Dendrimers are a special class of arborescent monodisperse nanometer sized molecules that have been used in the synthesis of Au NPs as surface stabilizers or nanoreactor/templates for nanoparticle growth. Moreover, these hybrid nanomaterials have great potential for application in different fields such as sensors, imaging in cells, electrooptical devices, catalysis, drug delivery agents, and so on. 

The potential loading capacity of these hyperbranched polymers is similarly high as for dendrimers (5-14 mmol g ) and some hyperbranched polymers are even commercially available [13,121]. The use of these commercial materials as supports for organic synthesis, however, is hmited due to the chemical stability of the respective polymer backbone (e.g. polyamines, polyesters) and the relatively broad molecular weight distributions (typically PD>2) [13]. Therefore, new hyperbranched species have been developed. 

---