Transition metal nanoparticles chemical reduction method

There have been a number of synthetic protocols for the preparation of transition-metal nanoparticles, for example, vapor condensation, sonochemical reduction, chemical liquid deposition, reflux alcohol reduction, decomposition of organometallic precursors, hydrogen reduction, etc. Of these, the colloidal reduction route provides a powerful platform for the ready manipulation of particle structure and functionalization. One excellent example is the biphasic Brust method, in which nanoparticles are formed by chemical reduction of a metal salt precursor in the presence of stabilizing ligands. In a typical reaction, a calculated amount of a metal salt precursor is dissolved in water, and the metal ions are then transferred into the toluene phase by ion-pairing with a... 

The two versions of the Miilheim electrochemical process provide colloidal solutions (e.g., in THF) of a variety of transition metal or bimetallic nanoparticles, and constitute a simple, clean and reliable alternative to chemical processes such as reduction by borohydrides in which the excess reducing agent and/or the oxidized form thereof have to be removed from the product (in fact, boron originating from boron hydrides is sometimes incorporated in the nanopaiticles) [26], But are these methods of any use in catalysis. One possibiUty is immobUization on soUd carriers, deUvering materials having islands of metal clusters of a predefined size. Moreover, they allow for the design of heterogeneous catalysts with well-defined compositional and structural features on a macroscopic and microscopic level. 

Numerous methods exist for the preparation of transition metal(O) nanoparticles as recently reviewed [19,41-43]. Briefly, there are two general approaches for the preparation of metal nanoparticles "top-down" and "bottom-up" approaches. The "top-down" approach involves the thermal, chemical, or mechanical disintegration of large particles of bulk metal into nanoparticles [44-46], while the more common and practical "bottom-up" approach involves first the generation of metal atoms from the reduction or decomposition of a precursor followed by... 

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