Stabilizing agent, metal colloid preparation

After Faraday s seminal report on the preparation of transition metal clusters in the presence of stabilizing agents in 1857 [31], Turkevich [19-21] heralded the first reproducible protocol for the preparation of metal colloids and the mechanism proposed by him for the stepwise formation of nanoclusters based on nucleation, growth, and agglomeration [19] is still valid but for some refinement based on additional information available from modem analytical techniques and data from thermodynamic and kinetic experiments [32-41], Agglomeration of zero-valent nuclei in the seed or, alternatively, collisions of already formed nuclei with reduced metal atoms are now considered the most plausible mechanism for seed formation. Figure 3.1 illustrates the proposed mechanism [42],... 

A new method for the size- and morphology-selective preparation of metal colloids using tetraalkylammonium carboxylates of the type NR4 R C02 (R = octyl, R = alkyl, aryl, H) both as the reducing agent and as the stabilizer [Eq. (4)] was reported by Reetz and Maase [42]. 

Metal colloids have been known for years—red stained glass is gold in colloidal form in glass, for example. Aqueous colloids are preparations that contain metal particles of 20-1000 A diameter in which the metal does not precipitate because the surface of the particles is covered in a way that protects them from agglomeration the hydrophilic polymer polyvinylalcohol (PVA) is an effective stabilizing agent. In a typical preparation, an aqueous solution of a metal salt is reduced in the presence of PVA. Small metal clusters have a precisely defined nuclearity (number of metals) and structure, but colloid... 

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