Nanoscaled metal synthesis

It is well established that ultrasmall metal clusters on supports have catalytic properties distinct from those properties of large bulk-like particles, as illustrated by the selective oxidation of propylene to propylene oxide by gold, alkene and arene hydrogenation catalysis,and CO oxidation. In these examples, the catalytic properties improve as the clusters become smaller. On the other hand, a reduction in size of the metal cluster can lead to less desirable catalytic properties as seen for ammonia synthesis on iron. Various explanations have been offered to account for the unique properties of nanoscaled metal catalysts, however, much remains to be understood. Clearly, experimental and theoretical studies will be required to develop an in-depth under-... 

Nanoscaled Metal (Hydroxide) Fluoride-Catalyzed Fine Chemical Synthesis (All-rac)-(x-tocopherol (vitamin E) synthesis 155... 

The classical sol-gel synthesis certainly is one of the most powerful synthesis routes in terms of the wide variety of synthesis approaches and techitical applications. For a long time, especially the aqueous (hydrolytic) sol-gel synthesis route, mainly forced by the development of sitica, has been the main focus of thousands of chemists and materials scientists worldwide. Thus, it is no wonder that many nanoscaled metal oxide-based catalysts have been intensively investigated and reviewed for many different catalytic reactions. 

However, due to recent developments of new synthesis approaches toward nanoscaled metal fluorides, the interest in metal fluoride-based catalysis has received a significant boost over the past few years. 

Although several slightly differing synthesis routes toward nanoscaled metal fluorides have been explored very recently (reviewed by, e.g., Fedorov et al. [4]), they are not sol-gel based but bear several drawbacks. However, besides and in fact earlier than the fluorolytic, another indirect sol-gel route - the TFA route - was developed that will be briefly mentioned as well. 

Nanoscaled Metal (Hydroxide) Fluoride—Catalyzed Fine Chemical Synthesis... 

However, these nanoscaled metal fluorides and hydroxide fluorides not only represent new, catalytically active classes of compounds with very high surface areas but are also excellent candidates to be used as supports for active components such as precious (e.g., Au, Pd, Pt) or nonprecious (e.g., Sn, Nb) metal deposition by incipient wetness impregnation or by in situ incorporation during the fluorolytic sol-gel synthesis. 

The top-down approach starts with a bulk material and attempts to break it down into nanoscaled materials through physical methods. Hence, most of these techniques are really forms of fabrication rather than synthesis. For nanostructured bulk phases, including powders, the common methods are milling, devitrification of metallic glass, and severe plastic deformation. For nanocrystalline thin films (films with nanosized crystallites), methods include thermal vaporization (under high vacuum), laser ablation, and sputtering (thermal plasma), all of which were... 

ZnO is being regarded as one of the important metal oxide semiconductors for future applications. Since its chemical and physical properties are highly dependent on composition and shape (defects), reliable methods are necessary to ensure control over the latter. The heterocubane (MeZnO Pr)4 was shown to be a suitable organometallic precursor for gas-phase CVS and solid-state synthesis of nanoscaled Interestingly, highly... 

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