Nanoparticles polymer-protected

Evaporation of volatile byproducts and solvents is often used to obtain the solid metal nanoparticles. The residue may contain metal nanoparticles and protective reagents. When the nanoparticles are well protected by ligands or polymers, then the solid residues can be dispersed again without coagulation of the particles. When the nanoparticles are not well protected, however, the evaporation often results in aggregation of the nano-particles. 

Conventional filtration cannot be applied to the separation in purification of metal nanoparticles. If the metal nanoparticles are protected by polymer, however, the membrane filter, which can cut off the pol5mer with certain molecular weight, can be used to separate the polymer protected metal nanoparticles. Free metal nanoparticles which are not protected by polymer can pass through the membrane. Ion filter like cellulose can be used to separate ionic species from the reaction mixtures. 

Table 1 presents the mean diameters and standard deviations of Au nanoparticles synthesized at various TC BIP/Au molar ratios. Both the mean diameter and standard deviation decreased with an increase in the amount of the protective agent, TC BIP, which was also observed in the cases involving polymer-protected Pd [13], Pt [14,15], and Au nanoparticles [16]. For TC BIP (n = 8, 10, 12), Au nanoparticles smaller than 2nm could be... 

In the early work on the thermolysis of metal complexes for the synthesis of metal nanoparticles, the precursor carbonyl complex of transition metals, e.g., Co2(CO)8, in organic solvent functions as a metal source of nanoparticles and thermally decomposes in the presence of various polymers to afford polymer-protected metal nanoparticles under relatively mild conditions [1-3]. Particle sizes depend on the kind of polymers, ranging from 5 to >100 nm. The particle size distribution sometimes became wide. Other cobalt, iron [4], nickel [5], rhodium, iridium, rutheniuim, osmium, palladium, and platinum nanoparticles stabilized by polymers have been prepared by similar thermolysis procedures. Besides carbonyl complexes, palladium acetate, palladium acetylacetonate, and platinum acetylac-etonate were also used as a precursor complex in organic solvents like methyl-wo-butylketone [6-9]. These results proposed facile preparative method of metal nanoparticles. However, it may be considered that the size-regulated preparation of metal nanoparticles by thermolysis procedure should be conducted under the limited condition. 

Zhou Y, Itoh H, Uemura T, Naka K, Chujo Y (2002) Preparation, optical spectroscopy, and electrochemical studies of novel pi-conjugated polymer-protected stable PbS colloidal nanoparticles in a nonaqueous solution. Langmuir 18 5287-5292... 

Kato, Y., Sugimoto, S., Shinohara, K., Tezuka, N., Kagotani, T. et al, Magnetic properties and microwave absorption properties of polymer-protected cobalt nanoparticles, Mater. Trans., JIM, 2002, 43, 406. 

PEBBLEs are water-soluble nanoparticles based on biologically inert matrices of cross-linked polymers, typically poly(acrylamide), poly(decylmethacrylate), silica, or organically modified silicates (ORMOSILs), which encapsulate a fluorescent chemo-sensor and, often, a reference dye. These matrices have been used to make sensors for pH, metal ions, as well as for some nonionic species. The small size of the PEBBLE sensors (from 20 to 600 nm) enables their noninvasive insertion into a living cell, minimizing physical interference. The semipermeable and transparent nature of the matrix allows the analyte to interact with the indicator dye that reports the interaction via a change in the emitted fluorescence. Moreover, when compared to naked chemosensors, nanoparticles can protect the indicator from chemical interferences and minimize its toxicity. Another important feature of PEBBLEs, particularly valuable in intracellular sensing applications, is that the polymer matrix creates a separate... 

Shan J Tenhu H, Recent advances in polymer protected gold nanoparticles Synthesis, properties and applications, Chem. Commun., 2007,4580—4598. 

Similar to Ag, the Cu nanoparticles obtained from RESOLV with the microemulsion as solvent for the rapid expansion formed a stable suspension in ethanol under PVP polymer protection, which was essentially indistinguishable from a typical homogeneous solution. The nanoparticles were air-sensitive in both the suspension and the solid state to form copper oxide in the presence of oxygen. Thus, an inert atmosphere had to be maintained via purging nitrogen gas to prevent the nanoparticles from oxidation. Shown in Figure 3 is the absorption spectrum of... 

Fig. 3.17 Catalysis process on the surface of polymer-protected metal nanoparticles,...

Y. Zhou, H. Itoh, T. Uemura, K. Naka, Y. Chujo, Preparation of H-Conjugated Polymer-Protected Gold Nanoparticles in Stable Colloidal Form. Chem. Commun. 2001,613-614. 

Polymer-immobilized bimetallic Pt-Co colloids exhibit high selectivity (up to 99.8%) in the reaction of hydrogenation of cinnamaldehyde to the corresponding alcohol. The application of polymer-protected nanoparticles is expected to lead to the discovery of new specific effects in catalysis. The cluster Pfti5(CO)3o] fixed on Sephadex is used to catalyze of the hydrogenation of selective redox-active cofactors. ... 

The use of polymer-protected nanoparticles can contribute new features to catalysis. A platimun sol as well as Pt on AI2O3 are well-known enantioselective hydrogenation catalysts. The possible uses of hybrid nanocomposites in catalysis are far from all realized. ... 

Stable platinum colloids were prepared by reducing dihydrogen hexachloroplatinate H2PtCl in the presence of protective polymers. In this chapter, we report the results for several nonionic polymers and cationic polyelectrolytes and their ability to stabilize such platinum colloids. The sizes of the platinum particles were investigated by transmission electron microscopy (TEM) and found to be in the nanometer size range. The catalytic activity of these systems was tested by the hydrogenation of cyclohexene, dsp-cyclooctene, and 1-hexene. A variety of polymer-protected platinum nanoparticles showed catalytic activity, and conversions of 100 % were obtained in most cases. 

The polymer-protected metal nanoparticles are usually prepared by in-situ reactions, such as chemical reductions, photolyses, and thermal decompositions of metal sah precursors within the polymer matrix (J-8). 

Catalytic Hydrogenations. Table IV shows some results for the catalytic hydrogenation of cyclohexene, and a selection of results obtained for the hydrogenation of cis-cyclooctene and 1-hexene is given in Table V. The results show that a variety of polymer-protected platinum nanoparticles are catalytically active, and conversions of 100 % were obtained in most cases. The catalysts could be employed either directly as a colloidal dispersion or as a solid after the evaporation of the solvent and the subsequent redissolving in the mixture for liquid-phase hydrogoiation. Unlike most catalysts systems, they could be stored in air for several weeks/months and still showed very good catalytic activity. 

Zhang Z, Yan B, Liu K, Liao Y, Liu H (2009) CE-MS analysis of heroin and its basic impurities using a charged polymer-protected gold nanoparticle coated capillary. Electrophoresis 30(2) 379-387... 

Bmshes grafted to latex particles [279, 280] polymer-protected gold nanoparticles [281, 282] various copolymers [45, 49, 55,259] drug delivery, tissue engineering [45], thermoresponsive gels [130]... 

ShanJ, Tenhu H Recent advances in polymer protected gold nanoparticles synthesis, properties and apphcations, Chem Commun 44 4580-4598, 2007. 

Gao, J., Sun,Y., Zhou, J., Zheng, Z., Chen, H.,Su,W. and Zhang,Q. (2007) Preparation of Ag nanoparticles termini-protected side-chain liquid crystalline azobenzene polymers by RAFT polymerization ,/. Polym. Sci. Polym. Chem., 45,5380. 

Matsuura K, Ohno K, Kagaya S, Kitano H. Carboxybetaine polymer-protected gold nanoparticles high dispersion stability and resistance against non-specific adsorption of proteins. Macromol Chem Phys 2(X)7 208 862—873. 

Figure 34 UV-Vis absorption spectra of the Ag nanoparticles in PVP polymer-protected suspension prepared via RESOLV. Solid line, as-prepared dashed line, after dialysis against freshwater.

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