Nanoparticles protective

Extraction by an organic solvent or water can be used to separate metal nanoparticles soluble in an organic solvent or water. This technique can be used only for the nanoparticles protected by organic ligands or pol5mers. The solubility of protecting reagents with the solvent is crucially important in this technique. 

An LCD is a ubiquitous electronic display. Now, it is widely distributed among human daily life, like mobile phones, TV, and personal computers. The LCD has, however, a drawback, i.e., slower response than a plasma display or an electroluminescene display. Recently we have first succeeded in combination of a nanoparticle technology with the LCD technology, which realized fast response of the LCD [45,235,236]. Thus we have found a phenomenon, i.e., a frequency modulation of the LCD doped with metallic nanoparticles. Since the frequency modulation, or electro-optic property depends on the kind of metals, we have prepared AgPd bimetallic nanoparticles protected with a typical liquid crystal molecule, 4-cyano-4 -pentylbiphenyl (5CB) to investigate the electro-optic property [45,235,236]. 

Recently, platinum nanoparticles protected by N,N-dimethyl-N-cetyl-N-(2-hydro-xyethyl)ammonium chloride salt and modified with cinchonidine were investigated in the enantiomeric hydrogenation of ethyl pyruvate in pure biphasic liquid-liquid (water/substrate) media at room temperature [139]. For the first time, the aqueous phase containing Pt(0) nanocatalysts with an average size of 2.5 nm could be reused for successive hydrogenations, and with a total conversion of activity and enantioselectivity in (R)-(+)-ethyl lactate up to 55% (Scheme 9.12). 

Pd- and Pt-nanoparticles protected by PS-b-PMAA were used to perform catalytic hydrogenations of cyclohexene in ethanol as solvent It could be shown that such colloids are catalytically active and thus interesting for the development of catalysts tailored for special reactions. 

These Au nanoparticles, protected by a monolayer of thiolated ligands, display interesting properties, such as single-electron charging and molecule-like HOMO-LUMO energy gaps, and can be used in optical and chemical sensing [70, 71]. Their physicochemical properties are closely related to their size and size distribution. Therefore, the ability to synthesize nano particles in a size-controlled... 

Fig. 16 2D-cartoons of quasi-spherical nanoparticles protected with mesogenic or pro-mesogenic capping agents giving rise to liquid crystalline quasi-spherical nanoparticles. The three major approaches include the decoration with calamitic molecules in an end-on fashion (7), with dendrons featuring calamitic or polycatenar moieties at the termini (8), and with laterally substituted calamitic molecules in a side-on fashion (9). The concept shown for the quasi-spherical nanoparticle 7 was also successfully used for spindle-like nanoparticles [533, 534]... 

In general, thiols characterized by a hydrocarbon chain length of C5 to Cl 8 impart an extraordinarily high degree of stability to AuNPs, while nanoparticles protected by aromatic thiols, such as 4-mercaptophenol, have been reported to degrade slowly... 

In contrast to aqueous methods, the polyol approach resulted in the synthesis of metallic nanoparticles protected by surface-adsorbed glycol, thus minimizing the oxidation problem The use of polyol solvent also reduces the hydrolysis problem of ultrafine metal particles, which often occurs in aqueous systems. Oxide nanoparticles can be prepared, however, with the addition of water, which makes the polyol method act more like a sol—gel reaction (forced hydrolysis). For example, 5.5-nm CoFe204 has been prepared by the reaction of ferric chloride and cobalt acetate in 1,2- propanediol with the addition of water and sodium acetate. 

Thiinemann AF, Schiitt D, Kaufher L, Pison U, Mdhwald H (2006) Maghemite nanoparticles protectively coated with poly(ethylene imine) and poly(ethylene oxide)-Wocl -poly(glutamic acid). Langmuir 22 2351-2357... 

There have been fewer reports on the particle size dependence of catalysis by platinum-catalyzed redox reactions. A report by Sharma et al. [21] showed that platinum colloidal nanoparticles do not demonstrate the same dependence on particle size as gold nanoparticles do for the reduction of hexacyanoferrate (III) by thiosulfate [19]. Platinum nanoparticles protected by sodium di(2-ethylhexyl) sulfosuccinate (synthesized by a reverse micelle technique) exhibit an optimum size ( 38 nm) for the reduction of ferricyanide by thiosulfate (Fig. 18.2). The reason for an optimum particle size is not fully understood however, they proposed the following explanation a shift in the Fermi level occurs as the diameter is increased. 

Hydrogenation reactions have been the most extensively studies for measuring the catalytic activities of nanoparticles. Noble monometallic (Pd, Pt, Rh) nanoparticles protected by linear polymers like PVP or polyvinylalcohol have high catalytic activities for hydrogenation of olefins [142-144]. We applied PVP-protected Pd/Pt [79,80] and Au/Pd [86] bimetallic nanoparticles prepared by the simultaneous... 

In particular, highly stable Pd nanoparticles, protected by an imidazolium based ionic polymer in a functionalized IL, can be easily prepared. These Pd nanoparticles are excellent pre-catalysts for Suzuki, Heck and Stille coupling reactions and can be stored without undergoing degradation for at least two years. 

Uemura, T.,Ohba,M. and Kitagawa, S. (2004) Size and surface effects of Prussian blue nanoparticles protected by organic polymers. Inorg. Chem., 43, 7339-7345. 

Numerous articles of a general interest have appeared on photocatalytic chemistry. These include nanoparticles, protection of buildings, antibacterial properties, ageing of pigment blends, modified titanium dioxides, photocatalytic paints, stabilization of pigmented systems, sensitization of acid dyes " and clay masterbatches. Anatase has been found to have a detri-... 

Recently colloidal Pd nanoparticles protected with tetraalkylammonium salts have been attracting attention as active catalysts. They are used for Heck and Suzuki-Miyaura reactions without phosphine ligands [6,7]. Most simply, Pd(OAc)2 is used without a ligand, forming some kind of colloidal or soluble Pd(0) species in situ in reactions of active substrates such as aryl iodides and diazonium salts. Pd on carbon without phosphine is active for some Heck and other reactions, but not always. These Pd(0) catalysts without ligands are believed to behave as homogeneous catalysts [8]. 

PANl TiO A1 alloy aa2024t3 Potentiostatic deposition Potentio dynamic polarisation in 5 mM NaCl and 0.1 MNa SO The coating containing TiO nanoparticles protects the substrate against the corrosion better than pure PAN and coatings based on PAN containing ZrO particles. [49]... 

Chitosan/alginate nanoparticles of about 150-340 nm diameter were used to encapsulate a cationic a-cyclodextrin (a-CD) which complexed insulin. These nanoparticles protected, to some extent, insulin from degradation by pepsin while being able to release insulin. ... 

Mayer, A. B. R. and Mark, J. E. CoUoidal gold nanoparticles protected by water-soluble homopolymers and random copolymers. European Polymer Joumal,34( 1), 103-108 (1998). 

Chavany, C Saison-Behmoaras, X, Doan, XL., Puisieux, F., Couvreur, P. and Helene, C. (1994) Adsorption of oligonucleotides onto polyisohexylcyanoaciylate nanoparticles protects them against nucleases and increases their cellular uptake. Pharm. Res., 11, 1370-1378. 

Nuopponen M, Tenhu H. Gold nanoparticles protected with pH and temperature-sensitive diblock copolymers. Langmuir 2007 23 5352. 

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