Nanoparticle dendrimer

Taratula O, Garbuzenko O, Savla R, Wang YA, He H, Minko T (2011) Multifunctional nanomedicine platform for cancer specific delivery of siRNA by superparamagnetic iron oxide nanoparticles-dendrimer complexes. Curr Drug Deliv 8 59-69... 

Besides rings, spontaneous formation of nanoparticle strip patterns has been observed on dewetting a dilute film of polymer coated nanoparticles floating on a water surface [577]. Hybridization of branched DNA trimers and Au nanoparticle DNA conjugates have been employed to produce discrete self-assembled nanoparticle dendrimers [578]. Self-assembly of triangular and hexagonal CdS nanocrystals into complex structures such as rods and arrows has been observed [579]. Furthermore, self-assembly of CdSe nanoparticle-copolymer mixtures has been observed wherein the copolymers assemble into cylindrical domains that dictate the distribution of the nanoparticles [580]. 

Esumi K (2003) Dendrimers for Nanoparticle Synthesis and Dispersion Stabilization. 227 31-52 Famulok M, Jenne A (1999) Catalysis Based on Nucleid Acid Structures. 202 101-131 Fechter MH, see de Raadt A (2001) 215 327-345... 

There is currently considerable interest in processing polymeric composite materials filled with nanosized rigid particles. This class of material called "nanocomposites" describes two-phase materials where one of the phases has at least one dimension lower than 100 nm [13]. Because the building blocks of nanocomposites are of nanoscale, they have an enormous interface area. Due to this there are a lot of interfaces between two intermixed phases compared to usual microcomposites. In addition to this, the mean distance between the particles is also smaller due to their small size which favors filler-filler interactions [14]. Nanomaterials not only include metallic, bimetallic and metal oxide but also polymeric nanoparticles as well as advanced materials like carbon nanotubes and dendrimers. However considering environmetal hazards, research has been focused on various means which form the basis of green nanotechnology. 

Esumi K (2003) Dendrimers for Nanoparticle Synthesis and Dispersion Stabilization. 227 31-52... 

These P-CD/adamantyl pseudorotaxane-terminated dendrimers can be used as nanoreactors in the preparation of gold and platinum nanoparticles in water... 

Spherical vaterite crystals were obtained with 4-mercaptobenzoic acid protected gold nanoparticles as the nucleation template by the carbonate diffusion method [51]. The crystallization of calcium carbonate in the absence of the 4-MBA capped gold nanoparticles resulted in calcite crystals. This indicates that the polymorphs of CaCOj were controlled by the acid-terminated gold nanoparticles. This result indicates that the rigid carboxylic acid structures can play a role in initiating the nucleation of vaterite as in the case of the G4.5 PAMAM dendrimer described above. 

Figure 8.30 Synthesis of dendrimer-functionalized gold nanoparticles.

Similarly, Pd, Ag, and Pd-Ag nanoclusters on alumina have been prepared by the polyol method [230]. Dend-rimer encapsulated metal nanoclusters can be obtained by the thermal degradation of the organic dendrimers [368]. If salts of different metals are reduced one after the other in the presence of a support, core-shell type metallic particles are produced. In this case the presence of the support is vital for the success of the preparation. For example, the stepwise reduction of Cu and Pt salts in the presence of a conductive carbon support (Vulcan XC 72) generates copper nanoparticles (6-8 nm) that are coated with smaller particles of Pt (1-2 nm). This system has been found to be a powerful electrocatalyst which exhibits improved CO tolerance combined with high electrocatalytic efficiency. For details see Section 3.7 [53,369]. 

Dendrimer-protected colloids are capable of adsorbing carbon monoxide while suspended in solution, but upon removal from solution and support on a high surface area metal oxide, CO adsorption was nil presumably due to the collapse of the dendrimer [25]. It is proposed that a similar phenomena occurs on PVP-protected Pt colloids because removal of solvent molecules from the void space in between polymer chains most likely causes them to collapse on each other. Titration of the exposed surface area of colloid solution PVP-protected platinum nanoparticles demonstrated 50% of the total metal surface area was available for reaction, and this exposed area was present as... 

Activation of Dendrimer Encapsulated Pt Nanoparticles for Heterogeneous Catalysts... 

Dendrimer encapsulated Pt nanoparticles (DENs) were prepared via literature methods (1, 11). PtCl42 and dendrimer solutions (20 1 Pt2+ dendrimer molar ratio) were mixed and stirred under N2 at room temperature for 3 days. After reduction with 30 equivalents of BH4 overnight, dialysis of the resulted light brown solution (2 days) yielded Pt2o nanoparticle stock solution. The stock solution was filtered through a fine frit and Pt concentration was determined with Atomic Absorption Spectroscopy (11). Details on catalyst characterization and activity measurements have been published previously (11). 

Supported, intact DENs do not bind CO and are not active catalysts. Presumably, in the absence of solvent, the dendrimer collapses onto the nanoparticles preventing even small substrates from accessing the metal surface (11,12). This means that the organic dendrimer must be removed in order to prepare active catalysts. 

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