Metal nanostructures synthesis

Chen HM, Liu RS (2011) Architecture of metallic nanostructures synthesis strategy and specific applications. J Phys Chem C 115 3513... 

In this chapter the potential of nanostructured metal systems in catalysis and the production of fine chemicals has been underlined. The crucial role of particle size in determining the activity and selectivity of the catalytic systems has been pointed out several examples of important reactions have been presented and the reaction conditions also described. Metal Vapor Synthesis has proved to be a powerful tool for the generation of catalytically active microclusters SMA and nanoparticles. SMA are unique homogeneous catalytic precursors and they can be very convenient starting materials for the gentle deposition of catalytically active metal nanoparticles of controlled size. 

Murphy CJ, Sau TK, Gole A, Orendorff CJ (2005) Surfactant-directed synthesis and optical properties of one-dimensional plasmonic metallic nanostructures. MRS Bull 30 349-355... 

Readers interested in more specific details about synthesis strategies, mechanisms of nanorod formation, characterization, or factors influencing the morphology of noble metal nanorods are referred to a comprehensive review by Sau and Rogach [185]. Reviews by Kijima and Zhang et al. will provide additional, detailed information on the synthesis of other one-dimensional metal nanostructures (including nanowires and nanotubes) [186, 187]. 

One family of new materials with potential use in metal catalysis is that of metal nanostructures such as metal nanoparticles (see Metal Nanoparticles, Synthesis of and Metal Nanoparticles, Organization Applications of), nanoshells, nanowires, nanorods, nanotubes, nanobelts, and nanoplates. " For instance, it has been recently shown that Ag nanowires and nanoparticles can be produced by... 

Consequently, CVD is now the method-of-choice for the synthesis of CNTs. As discussed in Chapter 4, these methods consist of the decomposition (typically thermal) of a hydrocarbon precursor on the surface of catalytic metal nanostructures. Methane and acetylene have been used most extensively as precursors other alternatives now include CO, C2H4, and methanol/ethanol. As with any CVD approach, this method is easily scaleable, and is used to generate kilogram quantities of CNTs for an ever-increasing laundry list of applications. 

Synthesis of metal nanostructures with tunable properties (optical, magnetic, electronic, catalytic, etc.), in specific physicochemical environments, is today of great importance from a fundamental as well as an applied point of view. Since the physicochemical properties of nanostructures are strongly dependent not only on the size but also on the shape, controlling the architecture of metal nanoparticles... 

Xia, Y. N. and Halas, N. J. (2005). Shape-controlled synthesis and surface plasmonic properties of metallic nanostructures. Mrs Bulletin 30 338-344. 

Two different nanomaterials, namely colloidal core / shell Quantum Dots (QDs) and Quantum Rods (QRs) were synthesized as described in [51]. In the case of CdSe / ZnS QDs, the synthesis yielded samples emitting at Inux = 580 nm widi a spectral width of the fluorescence emission of 40 nm. CdSe quantum rods showed an emission peak centered at l x = 567 nm with similar linewidth. The NCs were subsequently dispersed in PMMA and deposited onto the substrate by spin-coating. In order to study tiie influence of the average fluorophore-metallic surface distance on the MEF efi t, several thicknesses of the active layer were investigated, finding an o(Aimum value of 35 nm, as measured from the surface of the metallic nanostructures. 

In the Pt-doped hexagonal mesophase formed from CPCI (cetyl pyridinium chloride), platinum ions are adsorbed at the surface of the surfactant cylinders. They are reduced radiolytically into a metal layer as a nanotube of around 10 nm diameter and a few hundred nm long (Fig. 3f). Extraction of all these nanostructures is achieved by dissolution of the soft template using alcohol. This possible easy extraction constitutes a marked advantage over the synthesis in hard templates, such as mesoporous silica or carbon nanotubes, the dissolution of which is more hazardous for the metal nanostructures. 

G. Schmid), Wiley-VCH, Weinheim, 2004 (c) Metal Nanoparticles Synthesis, Characterization and Applications (Eds. D. L. Feldheim, C. A. Foss, Jr.), Marcel Dekker, New York, 2001 (d) Nanoparticles and Nanostructured Films. Preparation, Characterization and Applications (Ed. J. H. Fendler), Wiley-VCH, Weinheim, 1998 (e) G. Schmid, in Nanoscale Materials in Chemistry (Ed. ... 

The nanostructures synthesis from organometallic unstable precursors can occur under controlled conditions. As a result, the nanoparticles have been specified by size, its distribution, stoichiometry and shape. The choice of organometallic compounds ligands can not only define the character of resulting cationic complex inorganic phases, the morphology of future nanoparticles (spheres, rods, cubes, wires), but can also affect their self-organization in one-, two-and three-dimensional clusters [338]. This approach is fruitful for the synthesis of nanoparticles of metals and alloys, simple and multication oxides and other compounds that exhibit ferroic properties. 

Chen H, Wang Y, Dong S. An effective hydrothermal route for the synthesis of multiple PDDA-protected noble-metal nanostructures. Inorganic Chem 2007 46(25) 10587-93. 

Fig. 12 (a) Mussel-inspired templating synthesis of noble metal nanostructures on the electrospun PVA-g-ct nanofibers, (b) SEM images of PVA nanofibers after incubation with a 0.2 mM AgNOa in methanol for 40 min. (c, d) SEM images of PVA-g-ct nanofibers after incubation in the same solution for (c) 20 and (d) 40 min. Adapted with pmnission from [108]. Copyright (2012)... 

Metal nanostructures Chemical and electrochemical reduction of metal salts in solution and at liquidlliquid interface [67- 74, 84] Electrochemical synthesis from sacrificial anode [59, 95, 96]... 

Chemical reduction of metal salts represents the most popular method for the synthesis of metallic nanostructures, in particular consisting of Au, Pt, and Ag [122-126]. The synthesis of nanostractures can be described, to a first approximation, by three subsequent steps (1) reduction of the suitable metal salt, (2) nucle-ation, and (3) growth of the nuclei. The second step leads to the formation of stable nuclei ( seeds ) that subsequently grow to the final NP size. The second and third steps can follow two different pathways (1) autocatalytic pathway, where the reduction of the metal ions occurs at the surface of the NPs, or (2) collision pathway, where the formation of the nuclei occurs by collision between metal atoms from the previous reduction step. However, the exact reaction mechanism is poorly defined even in the most extensively investigated systems, owing to the high number of different chemical species involved and to the high reaction rate. 

There are a number of procedures for simultaneous formation of metal and metal oxide nano-objects and relevant deposition onto electrode surfaces [189-192]. In the case of metal nanostructures, the processes involve chemical or cathodic reduction of the corresponding metal salts (Fig. 6.19) and may generate an electrode surface modified by pristine nano-objects (Fig. 6.19a) or by hybrid coatings (Fig. 6.19b, c). The synthesis of nano-objects at the same time as deposition onto the electrode surface provides quick and easy formation of nano-structured surfaces. However, although many authors claim that the size of the resulting nanostructures can be controlled by suitable choice of the deposition parameters, the resulting size distribution is generally quite broad. 

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