Colloidal metal particle dispersions fabricating

It was shown in [5 3,54] that there are two methods to fabricate the homogeneous polymer-immobilized dispersions of colloidal metal particles (Fe, Co, Cr, Mo, W, Mn, Re, Ni, Pd, Pt, Ru, Rh, Os, Ir) using the precursors thermal decomposition. In the former case an active polymer solution (containing amino-, amido-, imino-, nitrilo-, hydroxy-, and other functional groups) is used. In an inert solvent a labile metal compound is gradually added to the solution (this operation creates the favorable conditions for the chemisorption interaction) followed by the suspension thermal decomposition at 370-440 K or by radiation. 

The use of colloidal metallic nanoclusters deposited onto solid substrates can provide a higher degree of control over the SPs spectral properties state-of-the-art results in the chemical synthesis showed, in fact, the possibility to grow nano-objects with high uniformity and low size dispersion [36-38], This can allow to fabricate extended substrates, in which the local morphology, and thus the resulting MEF effect, can be controlled with good precision [19, 39], As a counterpart, still some randomness is unavoidable in this approach, since it is not simple to define the position of the nanoclusters on the substrate with micrometer precision to realize, for instance, ordered arrays of metallic particles. 

Kim et al. [64] analyzed porous carbon by using colloidal sUica particles as templates. Carbon with micro, meso and macropores were obtained modifying the initial pH of the carbon precursor solutions. This fabrication method produces materials with narrow pore size distribution in a broad range of pore size. The fuel cell test showed better DMFC performance for carbons with high meso-macropore area with large pore than that with micropores. Again, this effect was attributed to the fact that meso and macropores produce a favorable dispersion of PtRu metal species and allow the access of perfluorosulfonate ionomer for the formation of the triple phase boundary. 

Interfacial phenomena at metal oxide/water interfaces are fundamental to various phenomena in ceramic suspensions, such as dispersion, coagulation, coating, and viscous flow. The behavior of suspensions depends in large part on the electrical forces acting between particles, which in turn are affected directly by surface electrochemical reactions. Therefore, this chapter first reviews fundamental concepts and knowledge pertaining to electrochemical processes at metal oxide powder (ceramic powder)/aqueous solution interfaces. Colloidal stability and powder dispersion and packing are then discussed in terms of surface electrochemical properties and the particle-particle interaction in a ceramic suspension. Finally, several recent examples of colloid interfacial methods applied to the fabrication of advanced ceramic composites are introduced. 

The simulation protocol for the formation of Pt-decorated primary C particles (PPCs) mimics catalyst dispersions obtained by pertinent fabrication techniques. In practice, two methods are used to obtain PPCs (1) impregnation of carbon nanoparticles with Pt precursor or (2) adsorption of Pt oxide or Pt metal colloids onto the carbon surface (Antolini, 2003 Antolini et al., 2002). In the case of impregnation with Pt precursor, diffusion into the pores of each individual support particle can occur. For the second mechanism, colloidal Pt or Pt oxide particles adsorb on the external surface of the support particles as a result of size exclusion, the accessibility of the inner pores is limited and, therefore, Pt particles are mostly formed on the surface of CNPs. 

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