Metal colloid synthesis decomposition

In the chemical preparation of unprotected metal colloids, the metal concentration usually has a significant influence on the particle size of obtained metal nanoclusters. For example, when increasing Pd concentration from 0.1 to 1.0 mM in the preparation of Pd metal colloids by the thermal decomposition of Pd acetate in methyl isobutyl ketone, the average Pd particle size increased from 8 to 140nm [6,7]. However, in the alkaline EG synthesis method, the size of metal nanoclusters was only slightly dependent on the metal concentration of the colloidal solution. The colloidal Pt particles prepared with a metal concentration of 3.7 g/1 had an average diameter of... 

Other Methods. Other reductants like hydrazine, sodium metal, etc. can be used for the reduction of metal ions. Decomposition of metal salts or complexes by heat treatment is sometimes used for synthesis of fine particles as well. In this case the valence of metals in the fine particles should be carefully examined. Recently, irradiation of ultrasonic wave was applied to the synthesis of colloidal dispersions of metal fine particles. 

The earliest routes for forming ceramics from sol-gel solutions involved the precipitation of metal oxide particles from solutions. These form a true colloidal suspension a sol. Upon destabilization of this sol, aggregation takes place and a rigid network is formed a gel. A gel is intermediate between a solid and a liquid. The term sol—gel has since been used by the materials science community to describe, albeit erroneously, virtually all chemical processing of ceramics from solutions (e.g., metal oxide particle precipitation or metalorganic decomposition). This discussion focuses on the gel aspects of sol—gel synthesis and not on the sol aspects, which are treated separately in this book. 

Paek et al. (2007)reported the synthesis of colloidal nanorings and nanoplates of several rare earth metal oxides from thermal dehydration of hydrolyzed metal precursor-surfactant aggregates (Figure 21). The Gd (acac)3 precursor was hydrolyzed at a low temperature of 90 °C and latter, the hydrolyzed precursor-surfactant aggregates were heated to 320 °C for thermal decomposition. Colloidal cubic R2O3 nanorings and nanoplates were obtained. 

Initial reports for the synthesis of bi-metallic, nanosized PtRu catalysts involved a number of steps. A well-known synthesis of bi-metallic carbon-supported Pt/Ru catalysts of high surface area (ca. 80 m g Pt + Ru) is the Watanabe method [9]. They first formed colloidal Pt02 from platinic acid (H2PtCl6) with the reduction of NaHSOs and oxidative decomposition with H2O2 at a fixed pH of 5, according to the following, possible reaction scheme [10] ... 

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