Noble metal nanopartides

With these considerations in mind, synthetic chemists have begun to address the needs of metal particle research by developing the synthetic chemistry of nanosized metals, with a view to using the strategies of molecular chemistry to prepare well-defined metal nanopartides. The goal may be stated as ... the search for synthetic methods for metal nanopartides of narrow size distribution and, if possible, with shape-control. Furthermore, bimetallic spedes will be considered, either with core-shell architecture or in alloyed form. 

Metal colloid science can be said to have begun with the experiments of Michael Faraday on gold sols in the mid-nineteenth century [1]. In this case, deep red 

In general, the particle sizes found for these AuNPs and related metal nanoparticles may vary between about 2 to 100 nm, depending on preparative conditions, with most examples falling in the large-diameter range. 

Strongly binding neutral adsorbate, the particles can now collide and agglomerate under the influence of the van der Waals attractive forces. This phenomenon can easily be demonstrated by the addition of pyridine to a gold sol of the type mentioned above [6]. 

Electrostatic and steric stabilization are, in a sense, combined in the use of long-chain alkylammonium cations and surfactants, either in single-phase sols or in the reverse micelle synthesis of colloidal metals. 

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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. 

Haes, A.J.. Zou, S., Schatz, G.C., and Van Duyne, R.P. (2004) Nanoscale optical biosensor short range distance dependence of the localized surface plasmon resonance of noble metal nanopartides. Journal of Physical Chemistry E, 108, 6961-6968. 

Aerobic oxidation is not going to be limited to alcohol oxidation. Apparently we are closer to finding suitable catalysts for alcohol oxidation, but oxidation of alkenes, aromatic hydrocarbons, alkylaromatics, imines, amines, sulfur compounds etc. will require much work in the forthcoming years. In some cases, the presence of radical initiators, even though in minor quantities, may serve to promote the oxidation catalyzed by noble metal nanopartides, and gold in particular [56, 108]. Thus, there is no doubt that the next years will witness exciting developments in the field of metal nanopartides for aerobic oxidation. 

DNA Engineered Noble Metal Nanopartides Fundamentals and State-of-the-art-of Nanobiotechnology... 

C. Lamy, J.-M. Leger, Catalysis and electrocatalysis at nanoparticle surfaces, in Andrzej Wieckowski, Elena R. Savinova, Constantino G. Vayenas (Eds.), Electrocatalysis with Electron-Conducting Pol)fmers Modified by Noble Metal Nanopartides, CRC Press, 2003, http //dx.doi.org/10.1201/9780203912713.ch25. 

Mesoporous titania films were successfiJly employed as a support for noble metal nanopartides as well as directly as photocatalysts [77-79]. A titaniaphotocatalytic synthesis of L-pipecohnic acid from L-lysine [79]. The reaction rate in the microreactor was 70 times larger than that in a batch reactor with titania nanopartides with almost the same selectivity and enantiomeric excess. 

Photocatalytic preparation of noble metal nanopartides with use of ultrafine Ti02 particles. Journal of Chemical Er neerir of Japan, 35, 1270-6. 

The various applications of these noble metal nanopartides stem from the unique structural properties at the nanometer dimensions, which can be further related to the surface plasmon resonance (SPR) effect (see Section 11.1.2). 

Origin of Surface Plasmon Resonance in Noble Metal Nanopartides... 

Jain, P.K., Huang, X., El-Sayed, I. and El-Sayed, M.A. (2007) Review of some interesting surface plasmon resonance-enhanced properties of noble metal nanopartides and their applications to biosystems. Plasmonics, 2,107-18. 

Mizukoshi, Y., Makise, Y., Shuto, T., Hu, )., Tominaga, A., Shironita, S. and Tanabe, S. (2007) Immobilization of noble metal nanopartides on the surface of Ti02 by the sonodiemical method Photocatalytic production of hydrogen from an aqueous solution of ethanol. Ultrasonics Sonochemistry, 14(3), 387-92. 

As described above, noble metal nanopartides with narrow size distribution can be introduced in polymers homogeneously resulting in translucent composites. In particular these nanocomposite materials offer completely new anisotropic optical properties, when either anisotropic partides (e.g., nanorods, nanowires) are used or the partides are uniaxially oriented. 

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... 

This sub-chapter is divided into two parts. In the first part, attention is focused on particles, except for a few examples that consist mainly of noble metals. Nanoparticles of noble metals, in particular, have a long tradition and the fundamental synthetic strategies associated with these materials have long been known. Thus, the aim here is not to describe the vast number of synthetic pathways for metal nanopartides, but rather to summarize the recognized syntheses (although some novel procedures have been included in so far as they complement traditional procedures). 

FIGURE 4.6 Synthesis steps for Pt monolayer catalysts on nonnoble metal core-noble metal shell nanopartides. Reprinted with permission from Ref. [21]. Copyright 2005 American Chemical Society. 

Dotmnguez-Doimnguez, S., Berenguer-Murda, A., Cazorla-Amoros, D., and Linares-Solano, A. (2006) Semihydrogenation of phenylacetylene catalyzed by metallic nanopartides containing noble metals./. Catal., 243 (1), 74-81. 

Metal particles with dimensions on the nanometer scale are of great current interest for their unusual properties [1-3]. Fundamentally, the mean free path of an electron in a metal at room temperature is 10-100 nm, and one would predict that as the metallic particle shrinks to this dimension, unusual effects might be observed [3]. Indeed, gold nanopartides of diameter - 100 nm or less appear red (not gold) when suspended in transparent media [1-3] and gold nanopartides of diameter 3 nm are no longer noble and unreactive, but can catalyze chemical reactions [4]. 

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