Nanocrystal Synthesis Metals

Semiconductor and Metal Nanocrystals Synthesis and Electronic and Optical Properties, edited by Victor I. Klimov... 

S. Link, M. A. El-Sayed, in Semiconductor and Metal Nanocrystals Synthesis and Electronic and Optical Properties (Ed V. I. Klimov), New York Routledge, 2003,421-452. 

The properties of metal and semiconductor nanocrystals are briefly reviewed. The organization of metal and semiconductor nanocrystals into mesostructures is an important aspect of nanoscience. New methods of nanocrystal synthesis and functionalization relevant to mesoscopic assembly are described, with emphasis on procedures that deal with monodispersed nanocrystals. Programmed assemblies of nanocrystals in one, two and three dimensions are discussed together with attempts to measure the properties of such lattices. Future directions and potential applications of ordered assemblies are indicated. 

We begin our discussion of nanocrystals in this chapter with the most challenging problem faced in the field the preparation and characterization of nanocrystals. These systems present challenging problems for inorganic and analytical chemists alike, and the success of any nanocrystal synthesis plays a major role in the further quantitative study of nanocrystal properties. Next, we will address the imique size-dependent optical properties of both metal and semiconductor nanoeiystals. Indeed, it is the striking size-dependent colours of nanocrystals that first attracted... 

The general process of metal nanocrystal synthesis can be divided, for didactic purposes, into five steps. The first step (step I) consists of the reduction of the metallic precursor (M+X ), which results in metal atoms (M ). These metallic atoms, ions, and metallic clusters will interact (step II), resulting in a metallic cluster growth process. Steps I and II are reversible. When the cluster grows to a critical size (step... 

Based on the above analysis, the development of metal oxides of nanometric dimensions can result in devices and materials with superior performance. However, these developments are directly related to the development of synthetic methods that allow for controlled particle size, particle morphology, and deposition. Once again, the bottom-up methods of wet chemical nanocrystal synthesis are apparently the most viable approach to achieve such control. Compared with the control attained in the synthesis of metal and 11-lV semiconductor nanocrystals, the control of metal oxide nanocrystals is still incipient, particularly insofar as the synthesis of complex metal oxide nanocrystals (oxides formed of more than one cation) is concerned. 

The precursors used for the iron oxide nanocrystal synthesis via the heat-up method are various iron carboxylatc complexes, including the most widely used iron-oleate complex. Generally, when heated, metal carboxylatc complexes thermally decompose at temperatures near 300°C or higher to produce metal oxide nanocrystals along with some byproducts, such as CO, CO2, H2, water, ketones, esters, and various hydrocarbons. It is thought that the decomposition reaction proceeds via the formation of thermal See radicals liom metal carboxylatc (26, 27) ... 

In this coimection, a cryochemical solid-phase synthesis of metal-polymer systems is of special importance. As a result of such a synthesis, metal clusters and organometallic assemblies formed at low temperatures are buried in a polymer environment, which offers possibilities to stabilize and study these products over a large temperature range. This method was first offered and described in reference 10. The thermal rearrangement of the initial low-temperature system is governed by relaxation processes in polymer matrix. In particular, the aggregation of metal atom clusters to form metal nanocrystals in cryochemically produced metal-polymer systems yields new nanocomposite materials with valuable properties. The study of the mechanism of cluster aggregation, which depends on the characteristics of the polymer matrix, will allow the nanocomposite structure to proceed in the needed direction. Thus, it becomes possible to determine the methods of cryochemical synthesis of metal-polymer materials with predetermined properties. 

Rao CNR, Kulkami GU, Thomas PJ, Agrawal W, Gautam UK, Ghosh M (2003b) Nanocrystals of metals, semiconductors and oxides novel synthesis and applications. Curr Sci 85 1041-1045 Rao CNR, Kulkami GU, Thomas PJ (2005) Physical and chemical properties of nano-sized metal particles. In Nicolais L, Carotenuto G (eds) Metal-polymer nanocomposites. WUey, Hoboken, New Jersey, pp 1-36... 

Kwon, S.G. and Hyeon, T. (2008) Colloidal chemical synthesis and formation kinetics of uniformly sized nanocrystals of metals, oxides, and chalcogenides. Acc. Chem,... 

Synthesis of uniform-sized nanocrystals from thermal decomposition of metal-surfactant complexes... 

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