Polyelectrolyte metal nanoparticles

Feldheim, D.L., et al.. Electron transfer in self-assembled inorganic polyelectrolyte/ metal nanoparticle heterostructures. J Amer Chem Soc, 1996. 118 p. 7640-7641. 

In general, the protocol for electrostatic attachment of metal nanoparticles proceeds through a preliminary deposition of polyelectrolytes, which also establishes whether the tubes are positively or negatively charged cationic poly(diallyldimethyl-... 

Formation of metal nanoparticles in ultra thin polyelectrolyte systems was carried out using polydiallyldimethyl ammonium chloride (PDADMAC) by the layer-by-layer deposition method. PDADMAC was purchased from Aldrich (Mw = 400 000 - 500 000). The structure of PDADMAC is shown in Fig. 4. 

Preformed metal oxide nanoparticles have been successfully coated on polymer spheres by the use of the layer-by-layer method. This involves the coating of the template spheres with polyelectrolyte layers, which are oppositely charged to the metal oxide nanoparticles to be deposited. Alternating the polyelectrolyte and nanoparticle deposition has led to the successful formation of silica [67,68] and titania [69] coated PS spheres. Using this approach preformed crystalline nanoparticles can be deposited on the organic spheres and crystalline hollow spheres can be obtained without the need of calcination. On removal of the template and the polymer interlayers by heating, hollow spheres of the inorganic material can be obtained [68-70]. This procedure is described in detail in the chapter by Dr Frank Caruso. 

SPHERICAL POLYELECTROLYTE BRUSH BASED METALLIC NANOPARTICLES... 

The focus of this chapter is the use of both the spherical polyelectrolyte brashes and microgel particles as carrier systems for novel metal nanoparticles, which can be used for catalysis in aqueous media, that is, under very mild conditions. Thus, the composite systems of metallic nanoparticles and polymeric carrier particles allows us to do green chemistry and conduct chemical reactions in a very efficient way. This approach can open new possibilities for catalytic application of metal composite particles in different reactions and represents a typical example of mesotechnology Nanoscopic objects with catalytic properties are judiciously combined with polymeric carriers to serve for a given, well-defined purpose. 

SPHERICAL POLYELECTROLYTE BRUSH BASED METALLIC NANOPARTICLES 9 TABLE 1.2. Heck Reaction Promoted by Pd SPB in Aqueous Media"... 

The composite particles of metal nanoparticles and spherical polyelectrolytes present robust systems that can be employed in catalysis More importantly, such metal nanoparticles can be used as effective catalysts in a green fashion, " that is, low temperature, easy removal of the catalyst, and low leaching of heavy metal into the product. 

Here we have reviewed our recent studies on metallic nanoparticles encapsulated in spherical polyelectrolyte brushes and thermosensitive core-shell microgels, respectively. Both polymeric particles present excellent carrier systems for applications in catalysis. The composite systems of metallic nanoparticles and polymeric carrier particles allow us to do green chemistry and conduct chemical reactions in a very efficient way. Moreover, in the case of using microgels as the carrier system, the reactivity of composite particles can be adjusted by the volume transition within the thermosensitive networks. Hence, the present chapter gives clear indications on how carrier systems for metallic nanoparticles should be designed to adjust their catalytic activity. 

Highly anisotropic ID nanostructures composed of closely packed nanoparticles have been prepared using linear macromolecular or supramolecular templates such as polyelectrolytes [2, 3], carbon nanotubes [2-5], DNA [6-9], peptide nanofibrils [10, 11], tubulin [12, 13] and bacteriophage and tobacco mosaic virus rods [14, 15]. Moreover, ID arrays are produced by spontaneous alignment of nanoparticles with intrinsic electric dipoles to form anisotropic chains of metallic nanoparticles, driven by heterogeneities in the surface chemistry and polarity of the nanoparticles [16]. These methods have been recently used to obtain defined nanostructures, predominantly in many steps and not defect free, with inhomogeneous metallic nanoparticle distribution. 

Two chemical ways were used to include metal nanoparticles inclusion in the microcapsule shell. It was photoreduction of silver under of UV-irradiation and chemical reduction of silver by acetaldehyde oxidation (reaction of a "silver mirror"). The polystyrene latex and calcium carbonate were used as a template for the formation of polyelectrolyte shells. 

It was shown that polyelectrolyte microcapsules containing metallic nanoparticles in their walls could be remotely activated inside living cells to release encapsulated material inside them (Figure 3.4.). These metal nanoparticles served as absorption centers for the energy supplied by a laser beam. These absorption centers caused local heating that disrupted the polyelecrolyte shell and allowed the encapsulated material to leave the interior of the capsule. Fluorescently labeled polymers were used as a model system of encapsulated material. 

The integrity of microcapsule shells or their ultrasonic sensitivity depends upon the influence time, the capacity of ultrasound and the shell structure of microcontainers, i.e. upon the number of polyelectrolyte layers in shell, the presence or absence of different metal nanoparticles and the volume fraction of these nanoparticles. At the same time only the destruction of microcapsule shell integrity under the ultrasonic waves occurs without changing their thickness and composition of microcapsules. Also the degree of microcapsules damage rises according to the increase of sonication time while the size of shell fragments decreases (Fig.3.6.). ... 

Co-assembly of neutral-ionic blocks, 2009 [42] graft, random copolymers with oppositely chaiged species in aqueous solution synthetic (co)polymers of various architectures biopolymers multivalent ions metallic nanoparticles surfactants polyelectrolyte block copolymer micelles metaUo-supramolecular polymers... 

Keywords Interpolyelectrolyte complexes Interpolyelectrolyte reactions Macromolecular co-assembly Metal nanoparticles MetaUo-containing interpolyelectrolyte complexes Nanostructures Polyelectrolytes Polymer-inorganic hybrids... 

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