Metal salts Nanocrystals

An interesting approach to synthesize metal alloy nanocrystals is the use of simultaneous salt reduction and thermal decomposition processes. Sun et al. [18] reported on the synthesis of iron-platinum (FePt) nanoparticles through the reduction of platinum acetylacetonate by a diol, and decomposition of iron pentacarbonyl (Fe(CO)5) in the presence of a surfactant mixture (oleic acid and oleyl amine). On the basis of a similar approach, Chen and Nikles [217] synthesized ternary alloy nanoparticles (FC cCo3,Ptioo x-y), using a simultaneous reduction of acetylacetonate and platinum acetylacetonate and thermal decomposition of Fe(CO)5 and obtaining an average particle diameter of 3.5 nm and narrow particle size distribution. 

The chemical synthesis of metal oxide nanocrystals based on hydrolysis falls into two major groups hydrolysis of metal alkoxides hydrolysis of metal halides, and other inorganic salts. Metal alkoxide compounds are defined as compounds that have metal-oxygen-carbon bonds. Si(OC2H5)4 (tetraethyl orthosUicate or TEOS), for instance, is an alkoxide compound. This class of compound is highly reactive with water. Because the hydroxyl ion (OH ) becomes bonded to the metal of the organic precursor, this reaction is called hydrolysis. Equation (50) shows a typical hydrolytic reaction of an alkoxide compound [100] ... 

Besides the common features of most metal oxides as chemically stable and mechanically robust materials, this class of compounds can also provide unique functions for ceramics, high refractive index and magnetic materials, catalysis, and biocompatibility. A wide range of porous metal oxide materials have been synthesized over the last decade. In general three distinct pathways have been undertaken a sol-gel synthesis of the metal alkoxide infiltration with an appropriate metal salt and subsequent conversion or infiltration or codeposition with preformed metal oxide nanocrystals. 

The same preparative approach - that is, the dissolution of a metal salt in water in the presence of a stabilizing thiol - yielded nanocrystals of CdSe [132], CdTe [133-136], HgTe [137], ZnSe [138], CdHgTe [139-141], ZnCdSe [142], and CdSeTe [143] (for recent reviews on this subject, see also Refs [144, 145]). The thiols used included 1-thioglycerol, 2-mercaptoethanol, l-mercapto-2-propanol, l,2-dimercapto-3-propanol, thioglycolic acid, thiolactic acid, and cysteamine [146]. 

C02-expanded ethanol, porous hollow metal oxide nanoparticles have been prepared using a carbon template by Sun and co-workers.A metal salt, such as C0 j(NO3)3,(CO3)z(OH) , wHaO, can be prepared from the corresponding metal nitrate in COa-expanded ethanol and deposited on the surface of template carbon colloids. Thermal treatment in nitrogen affords CoO nanocrystals. When calcined in air, these can be transformed to C03O4. Electron microscopy images of these dense hollow porous nanostructures are shown in Fig. 9. The improved performance of this material as an anode in Li-02 battery has also been demonstrated, along with the capacity to generate FeO NiO and MnO, nanocomposites. 

Nanocrystals are zero-dimensional particles and can be prepared by several chemical methods, typical examples being reduction of salts, solvothermal synthesis and the decomposition of molecular precursors, among which the first method is the most commonly used in the case of metal nanocrystals. Metal oxide nanocrystals are generally prepared by the decomposition of precursor compounds such as metal acetates, acetylacetonates and cupferronates in appropriate solvents, often under solvothermal... 

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