Metal nanoparticles nanoparticle stabilization

Application of amphiphilic block copolymers for nanoparticle formation has been developed by several research groups. R. Schrock et al. prepared nanoparticles in segregated block copolymers in the sohd state [39] A. Eisenberg et al. used ionomer block copolymers and prepared semiconductor particles (PdS, CdS) [40] M. Moller et al. studied gold colloidals in thin films of block copolymers [41]. M. Antonietti et al. studied noble metal nanoparticle stabilized in block copolymer micelles for the purpose of catalysis [36]. Initial studies were focused on the use of poly(styrene)-folock-poly(4-vinylpyridine) (PS-b-P4VP) copolymers prepared by anionic polymerization and its application for noble metal colloid formation and stabilization in solvents such as toluene, THF or cyclohexane (Fig. 6.4) [42]. 

Scanning tunneling microscopy (STM) has been used to determine the dimensions of metal nanoparticles stabilized by alkylammonium salt in combination with high-resolution TEM (51). The difference between the diameter determined by STM (cl in Fig. 9.1.6) and that determined by TEM (clM in Fig. 9.1.6) allows estimation... 

For example, the aggregated structures of the solutions containing polymer-metal complexes and the colloidal dispersions of metal nanoparticles stabilized by polymers have been analyzed quantitatively (64). SAXS analyses of colloidal dispersions of Pi, Rh, and Pt/Rh (1/1) nanoparticles stabilized by PVP have indicated that spatial distributions of metal nanoparticles in colloidal dispersions are different from each other. The superstructure (greater than 10.0 nm in diameter), with average size highly dependent on the metal element employed, is proposed. These superstructures are composed of several fundamental clusters with a diameter of 2.0-4.0 nm, as shown in Figure 9.1.13 for PVP-stabilized Pt nanoparticles. 

F. Mirkhalaf, J. Paprotny, and D. J. Schifhin, Synthesis of metal nanoparticles stabilized by metal-carbon bonds, J. Am. Chem. Soc., 128 (2006) 7400-7401. 

Starburst dendrimers have received considerable attention in the area of heterogeneous catalyst synthesis in the last decade. Although Tomalia et al. and Bosman et al. originally discovered these hyperbranched macromolecules and their host-guest properties in the mid-1980s. Crooks and coworkers were the first to demonstrate the ability of poly(amidoamine) (PAMAM) starburst dendrimers to act as metal nanoparticle stabilizers that could potentially aid in the synthesis of supported metal catalysts. The benchmark work of Crooks et al. and subsequent literature reports have underscored the advantages of successfully utilizing PAMAM dendrimer-nanocomposite precursors over conventional catalyst preparation methods. 

The photophysical properties of dye molecule in DDSNs can also be tuned by exploiting plasmonic effects, that is by growing the silica nanoparticle around a metal core. Experimentally, such sophisticated structures are achieved by carrying out the Stober synthesis in the presence of preformed metal nanoparticles stabilized... 

Metal/carbon nanocomposite (Me/C) represents metal nanoparticles stabilized in carbon nanofilm stractures [7-9]. In turn, nanofilm stractures are formed with carbon amorphous nanofibers associated with metal eon-taining phase. As a result of stabilization and assoeiation of metal nanoparticles with carbon phase, the metal chemically active particles are stable in the air and during heating as the strong complex of metal nanoparticles with carbon material matrix is formed. The test results of nanocomposites obtained are given in Table 2.1. 

Metal/carbon nanocomposite (Me/C) represents metal nanoparticles stabilized in carbon nanofilm structures [7, 8]. In turn, nanofilm structures are formed with carbon amorphous nanofibers associated with metal con-... 

Cardiac myoglobin detection was based on direct electron transfer between the Fe(III)-heme and the electrode surface that was modified with metal nanoparticles stabilized by didodecyldimethylammonium bromide and antibodies. Gold, silver, and copper nanoparticles were tested as catalysts of the Fe(III)/Fe(II) electrode process. Experiments were carried out with human blood plasma samples of healthy donors and patients with acute myocardial infarction. The method proposed does not require labeled secondary antibodies. The myoglobin immunosensor has a detection limit of 5 ngrnL and a broad range of working concentrations (Suprun et al., 2011). The whole procedure takes 20 min and can be used to establish the diagnosis of acute myocardial infarction. 

Metal nanoparticles stabilized by star-shaped polymers 548... 

Emulsion Catalysis Participated by Metal Nanoparticles Stabilized by Polymer... 

CuNPs) in Fig. 7 shows the monodisperse and uniformly distributed spherical particles of 10+5 nm diameter. The solution containing nanoparticles of silver was found to be transparent and stable for 6 months with no significant change in the surface plasmon and average particle size. However, in the absence of starch, the nanoparticles formed were observed to be immediately aggregated into black precipitate. The hydroxyl groups of the starch polymer act as passivation contacts for the stabilization of the metallic nanoparticles in the aqueous solution. The method can be extended for synthesis of various other metallic and bimetallic particles as well. 

Scheme 1 Illustration of the general synthetic method followed in our group for the synthesis of metal nanoparticles i decomposition of the precimsor, nucleation ii first growth process in ripening or coalescence leading to size and shape controlled objects through addition of stabilizers which prevent the full precipitation of the metal (iv)...

In the past five years, the use of nanoparticles in this active research area has received increased attention since some homogeneous catalysts have been shown to be nanoheterogeneous [24-26]. Today, soluble noble metal nanoparticles are considered as reference in monocyclic arene catalytic hydrogenation under mild conditions and several stabilized systems have been reported [27,28]. 

Finally, the term steric stabihzation coifid be used to describe protective transition-metal colloids with traditional ligands or solvents [38]. This stabilization occurs by (i) the strong coordination of various metal nanoparticles with ligands such as phosphines [48-51], thiols [52-55], amines [54,56-58], oxazolines [59] or carbon monoxide [51] (ii) weak interactions with solvents such as tetrahydrofuran or various alcohols. Several examples are known with Ru, Ft and Rh nanoparticles [51,60-63]. In a few cases, it has been estab-hshed that a coordinated solvent such as heptanol is present at the surface and acts as a weakly coordinating ligand [61]. 

ROsch N (1999) A Critical Assessment of Density Functional Theory with Regard to Applications in Organometallic Chemistry. 4 109-163 Roucoux A (2005) Stabilized Noble Metal Nanoparticles An Unavoidable Family of Catalysts for Arene Derivative Hydrogenation. 16 261-279... 

Stabilized Noble Metal Nanoparticles An Unavoidable Family of Catalysts for Arene Derivative Hydrogenation... 

The preparation and study of metal nanoparticles constitutes an important area of current research. Such materials display fascinating chemical and physical properties due to their size [62, 63]. In order to prevent aggregation, metal nanoparticles are often synthesized in the presence of ligands, functionalized polymers and surfactants. In this regard, much effort has focused on the properties of nanoparticles dispersed into LCs. In contrast, the number of nanoparticles reported that display liquid crystal behavior themselves is low. Most of them are based on alkanethiolate stabilized gold nanoparticles. 

Crystalline phases (truncated octahedra) of 5 nm silver particles, thiolate protected as well, have been detected by means of high-resolution transmission electron microscopy (HRTEM) [26-28]. Three-dimensional architectures of 5-6 nm thiolate-stabilized gold particles have also been described [29]. Several other reports on 3D superlattices of metal nanoparticles have become known during the last few years [30-33]. 

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