Nanoparticles formation

Figure 3. Schematic illustration of core/shell nanoparticle formation via redox transmetalation process. Metal ions (Mu) of reactant metal complexes (Mn-L ) are reduced on the surface of Mi nanoparticles while neutral Mi atoms are oxidized to Mi " by forming a Mi-ligand complex (Mi-Lj) as a resultant reaction byproduct. Repeating this process results in the complete coverage of shell layers on core metals. (Reprinted from Ref [145], 2005, with permission from American Chemical Society.)...

Nanoparticle Formation by Ion Etching of Island Thin Films... 

Figure 4. Scheme of nanoparticle formation during ion etching. (Reprinted from Ref. [123], 2003, with permission from Springer.)... 

Scheme 3. Reaction mechanism of Au-Ag alloy nanoparticle formation.

If only adsorbed complexes take part in the formation of nanoclusters, metal loading, the quantity of nanoclusters formed on the surface, is only proportional to the amount of the adsorption. Hence, the loading is quite small, even if so large amount of complexes is located in solution phase. So, the solute species should be deposited directly onto sites for nanoparticle formation, in order to establish high loading of nanoclusters on the surface. In addition, the resultant nanoclusters are expected smaller and higher dispersed, compared with the particles formed only via surface reaction between adsorbed species, as shown in Figure 3. 

Gold Nanoparticles Formation by Living Alfalfa Plants... 

V. Armendariz, Bioreduction of Gold(III) to Gold(O) and Nanoparticle Formation by Oat and Wheat Biomasses The Use of Plants in Nanobiotechnology. Master Thesis, the University of Texas at El Paso, Chemistry Department, El Paso, TX, 2005, p. 107. 

Nanoparticles show great promise as devices for the controlled release of drugs, provided that the choice of material for nanoparticle formation is made with the appropriate considerations of the drug cargo, administration route, and the desired site of action. The use of nano- and microparticles as controlled drug-delivery devices has recently been extensively reviewed [97]. 

Fig. 6.9 The absorbance versus time plot indicates that the rate of Au nanoparticle formation is significantly greater than the rate of Ag nanoparticle formation [37]...

Fig. 5.10 TEM micrographs of gel and nanoparticle formation of iron-loaded K-carrageenan at (A) pH 2 and (B) pH 13. In both casestheiron loadingwas 100%. ([57], CopyrightSpringer-Verlag 2000. With kind permission of Springer Science and Business Media).

Gardea-Torresdey, J. 2003. Use of XAS and TEM to determine the uptake of gold and silver and nanoparticle formation by living alfalfa plants. Abstracts of Papers of the American Chemical Society 225 U837-U837. 

Liu et al. prepared palladium nanoparticles in water-dispersible poly(acrylic acid) (PAA)-lined channels of diblock copolymer microspheres [47]. The diblock microspheres (mean diameter 0.5 pm) were prepared using an oil-in-water emulsion process. The diblock used was poly(t-butylacrylate)-Wock-poly(2-cinna-moyloxyethyl) methacrylate (PtBA-b-PCEMA). Synthesis of the nanoparticles inside the PAA-lined channels of the microspheres was achieved using hydrazine for the reduction of PdCl2, and the nanoparticle formation was confirmed from TEM analysis and electron diffraction study (Fig. 9.1). The Pd-loaded microspheres catalyzed the hydrogenation of methylacrylate to methyl-propionate. The catalytic reactions were carried out in methanol as solvent under dihydro-... 

S. Xu and M. Yonese, in Charge Densities and Nanoparticle Formation of Complexes Composed of Acid Polysaccharides and Protein, Nagoya, Japan, 1998, p. E1076. 

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]. 

Kinetic Studies of Indium Nanoparticle Formation The Autocatalytic Mechanism 377... 

Scheme 15.5 The pseudo-elementary step concept proposed by Finke and coworkers to monitor transition-metal nanoparticle formation.

An interesting additional experiment to follow the iridium nanoparticles formation was demonstrated by Watzky and Finke ]30], who used a direct method of monitoring by gas-hquid chromatography (GLC) the evolution of cyclo-octane... 

Hence, two methods are available that can be applied to follow nanoparticles formation and growth (i) an indirect method that utilizes the consumption of molecular hydrogen pressure versus time and (ii) a direct method that follows the loss of precursor by the 1 1 conversion of its cyclo-octadiene ligand to cyclo-octane by GLC measurements. The mechanism developed by Watzky and Finke suggests that the nanoparticles act as Hving-metal polymers -a concept that could be used to obtain particles with defined sizes simply by adding the appropriate amounts of catalyst precursors [32]. 

Kinetic Studies of Iridium Nanoparticle Formation The Autocatalytic Mechanism 379... 

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