Metal nanopartides

Bimetallic nanoparticles, either as alloys or as core-shell structures, exhibit unique electronic, optical and catalytic properties compared to pure metallic nanopartides [24]. Cu-Ag alloy nanoparticles were obtained through the simultaneous reduction of copper and silver ions again in aqueous starch matrix. The optical properties of these alloy nanopartides vary with their composition, which is seen from the digital photographs in Fig. 8. The formation of alloy was confirmed by single SP maxima which varied depending on the composition of the alloy. 

Hakkinen, H., Moseler, M., Kostko, O., Morgner, N., Hoffmann, M.A. and Issendorff, B. v. (2004) Symmetry and Electronic Structure of Noble-Metal Nanopartides and the Role of Relativity. Physical Review Letters, 93, 093401-1-093401-4. 

The most spectacular results, in terms of comparison between CFPs- and carbon-supported metal catalysts, were likely provided by Toshima and co-workers [33,34]. As illustrated in Section 3.3.3, they were able to produce platinum and rhodium catalysts by the covalent immobilization of pre-formed, stabilized metal nanoclusters into an amine functionalized acrylamide gel (Scheme 5). To this purpose, the metal nanopartides were stabilized by a linear co-polymer of MMA and VPYR. The reaction between its ester functions and the amine groups of the gel produced the covalent link between the support and the... 

McLeod, M.C., McHenry, R.S., Beckman, E.J. and Roberts, C.B. (2003) Synthesis and stabilization of silver metallic nanopartides and premetallic intermediates in perfluoropolyether/C02 reverse micelle systems. Journal of Physical Chemistry B, 107 (12), 2693-2700. 

Hart, A.E. and Kitchens, C.L. (2011) Reverse micelle synthesis of monodispersed metallic nanopartides via a gas expanded liquid system. Presented at the AIChE 2011 Annual Meeting, Minneapolis, Minnesota, United States. 

Dupont, J., Fonseca, G.S., Umpierre, A.P., Fichtner, P.F.P. and Teixeira, S.R. (2002) Transition-metal nanopartides in imidazolium ionic liquids recycable catalysts for biphasic hydrogenation reactions. Journal of the American Chemical Society, 124 (16), 4228—4229. 

Willert, M., Rothe, R., Landfester, K. and Antonietti, M. (2001) Synthesis of inorganic and metallic nanopartides by miniemulsification of molten salts and metals. Chemistry of Materials, 13,4681-4685. 

Studies on the use of hydrothermal, microwave-assisted, and reflux synthesis methods for the development and application of nanomaterials have been reviewed. An important aspect of the green synthesis of metallic nanopartides involves techniques that make use of biological materials such as plant extracts and microorganisms. The design of nanomaterials and control of their desired properties have been reviewed. The unique properties of manufactured nanomaterials offer many potential benefits. 

Mo03 (bipy)] [Mo03 (H20) ] Inorganic Chemistry, 49, 6865—6873. Moreno-Manas, M. and Pleixats, R. (2003) Formation of carbon-carbon bonds under catalysis by transition-metal nanopartides. Accounts of Chemical Research, 36, 638—643. 

Kamat, P.V. (2002) Photophysical, photochemical and photocatalytic aspects of metal nanopartides. Journal of Physical Chemistry B, 106, 7729-7744. 

It is also possible to synthesize metallic nanopartides with k- and i-carrageenan [59]. Both Ag and Au nanoparticles have considerable potential for biochemical analysis [60]. The advantage of Ag nanoparticles is that the range of dyes which remain effective in biological media is much more extensive. On the other hand, in some biological systems, such as cell suspensions, Ag can react positively with the cell and it is well know as a bactericide. Au, Ag and Cu nanoparticles have the ability to... 

Feldheim, D.L. and Foss, C.A., Jr. (eds) (2002) Metal Nanopartides Synthesis, Characterization and Application, Marcel Dekker.New York. 

Transition-metal nanopartides are of fundamental interest and technological importance because of their applications to catalysis [22,104-107]. Synthetic routes to metal nanopartides include evaporation and condensation, and chemical or electrochemical reduction of metal salts in the presence of stabilizers [104,105,108-110]. The purpose of the stabilizers, which include polymers, ligands, and surfactants, is to control particle size and prevent agglomeration. However, stabilizers also passivate cluster surfaces. For some applications, such as catalysis, it is desirable to prepare small, stable, but not-fully-passivated, particles so that substrates can access the encapsulated clusters. Another promising method for preparing clusters and colloids involves the use of templates, such as reverse micelles [111,112] and porous membranes [106,113,114]. However, even this approach results in at least partial passivation and mass transfer limitations unless the template is removed. Unfortunately, removal of the template may re-... 

AufFan, M., Rose, J., Wiesner, M.R. and Bottero, J.Y. (2009) Chemical stability of metallic nanopartides a parameter controlling their potential cellular toxidty in vitro. Environ. Potlut., 157 (4), 1127-1133. 

In conclusion, exfoliated sheets of Mg-phyllo(organo)silicates containing pendant amino groups have been used to stabilize Au, Ag, Pd and Pt nanopartides. The nanoparticle-decorated day sheets can be easily dispersed in water. These metal nanopartides... 

A pioneer in the application of ultrasound to the formation of nanopartides of noble metals is Y. Maeda. In an earlier study his group [17] synthesized sonochemically metallic nanopartides of metals such as Ag, Pd, Au, Pt and Rh with a fairly narrow distribution (e.g., about 5 nm for Pd particles obtained from a 1.0 mM Pd(II) solution in polyethylene glycol monostearate solution). They suggested three different reduction pathways under sonication (i) reduction by H atoms, (ii) reduction by secondary reducing radicals formed by hydrogen abstraction from... 

The magnetic metals were also prepared by a method [25] based on the rapid expansion of supercritical fluid solutions (RESS) coupled with chemical reduction to produce nickel, cobalt, iron, and iron oxide nanopartides of reasonably narrow size distribution. Under the protection of a polymer stabilization agent, the largely amorphous metal nanopartides form stable suspensions in room-temperature solvents. 

A nonmetallic element, silicon, was prepared sonodiemically by reducing tetraethyl orthosilicate (TEOS) with a colloidal solution of sodium. The product was obtained as 2-5 nm sized, highly aggregated partides. The silicon exhibited a luminescence similar to that of porous silicon. This procedure is suggested as a general sonochemical reduction leading to the formation of metallic nanopartides [26]. 

Metallic nanopartides were deposited on ceramic and polymeric partides using ultrasound radiation. A few papers report also on the deposition of nanomaterials produced sonochemically on flat surfaces. Our attention will be devoted to spheres. In a typical reaction, commerdally available spheres of ceramic materials or polymers were introduced into a sonication bath and sonicated with the precursor of the metallic nanopartides. In the first report Ramesh et al. [43] employed the Sto-ber method [44] for the preparation of 250 nm silica spheres. These spheres were introduced into a sonication bath containing a decalin solution of Ni(CO)4. The as-deposited amorphous clusters transform to polyciystalline, nanophasic, fee nickel on heating in an inert atmosphere of argon at a temperature of 400 °C. Nitrogen adsorption measurements showed that the amorphous nickel with a high surface area undergoes a loss in surface area on crystallization. 

Wizel later extended her study and included another metallic nanopartide, cobalt, and an additional polymer, poly(methylmethacrylate), in her metal-polymer composite research [58]. A significant difference in the solubility of the iron-poly(methylacrylate) and cobalt-poly(methylacrylate) in various solvents was observed. While the iron-poly(methylacrylate) composite (FePMA) and iron-poly(methylmethacrylate) composite (FePMMA) dissolved in chloroform, acetone, and toluene at room temperature, the corresponding cobalt-poly(methylacrylate) composite (CoPMA) was insoluble in these solvents at room temperature. At elevated temperatures (45 °C), dissolution of CoPMA in these solvents was observed. This difference is accounted for by the stronger interaction existing between the cobalt and the surrounding polymer. For iron-poly(methylacrylate) this interaction is weakened due to the formation of an iron complex. The Mw of the various polymers and composites as a function of the metal-to-monomer weight ratio was measured and reported. 

Komarneni and coworkers [175] conducted a polyol reaction for the preparation of Pt and Ag nanopartides. The synthesis of the metal nanopartides [175] was conducted in a double-walled digestion vessel which has an inner liner and a cover made of Teflon PFA and an outer high-strength shell of Ultem polyetherimide. 

W. P. McConnell J. P. Novak L. C. Beousseau III R. R. Euierer R. C. Tenent D. L. Eeldheim, Electronic and Optical Properties of Chemically Modified Metal Nanopartides and Molecularly Bridged Nanopartide Arrays, f Phys. Chem. B 2000, 3 04, 8925-8930. 

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