Tetrachloroaurate ion

Bond and coworkers [521] have described Au(III) electroreduction and Au(0) oxidation stripping processes in dilute aqua regia utilizing platinum, rhodium, iridium, gold, and glassy carbon electrodes. Sorption of tetrachloroaureate ions on carbon paste electrode modified with montmorillonite has been performed as a preconcentration step in the determination of gold in pharmaceutical preparation [522]. 

The stability of the tetrachloroaurate ion AuCl - is responsible for the ability of aqua regia, a mixture of nitric and hydrochloric acids, to dissolve gold, which is not significantly soluble in the acids sepa-... 

The polymer resulting from oxidation of 3,5-dimethyl aniline with palladium was also studied by transmission electron microscopy (Mallick et al. 2005). As it turned out, the polymer was formed in nanofibers. During oxidative polymerization, palladium ions were reduced and formed palladium metal. The generated metal was uniformly dispersed between the polymer nanofibers as nanoparticles of 2 mm size. So, Mallick et al. (2005) achieved a polymer- metal intimate composite material. This work should be juxtaposed to an observation by Newman and Blanchard (2006) that reaction between 4-aminophenol and hydrogen tetrachloroaurate leads to polyaniline (bearing hydroxyl groups) and metallic gold as nanoparticles. Such metal nanoparticles can well be of importance in the field of sensors, catalysis, and electronics with improved performance. 

Coreduction of Mixed Ions. Coreduction of mixed ions is the simplest method to synthesize bimetallic nanoparticles. However, this method cannot be always successful. Au/Pt bimetallic nanoparticles were prepared by citrate reduction by Miner et al. from the corresponding two metal salts, such as tetrachloroauric(III) acid and hexachloroplatinic(IV) acid (24). Reduction of the metal ions is completed within 4 h after the addition of citrate. Miner et al. studied the formation of colloidal dispersion by ultraviolet-visible (UV-Vis) spectrum, which is not a simple sum of those of the two monometallic nanoparticles, indicating that the bimetallic nanoparticles have an alloy structure. The average diameter of the bimetallic nanoparticles depends on the metal composition. By a similar method, citrate-stabilized Pd/Pt bimetallic nanoparticles can also be prepared. 

Coreduction of Au and Pt ions by refluxing alcohol in the presence of PVP gives the colloidal dispersions of Au-core/Pt-shell structured bimetallic nanoparticles, as mentioned before. The formation of this bimetallic nanoparticles was traced by in situ UV-Vis spectra (68). The spectral change is shown in Figure 9.1.15, in which the peaks ascertained to be the metal ions disappear at first, and then the broad tailing peaks due to the colloidal dispersions appear. More precisely speaking, the tetrachloroauric(III) acid (at —320 nm) is reduced first, followed by reduction of hexachloroplatinic(IV) acid (at —265 nm). This order of reduction is consistent with the standard redox potential of the two metal ions. After the reduction of two... 

Reactions of gold(III) [tetrachloroaurate(III)] ions To study these reactions use a 0-33m solution of commercial gold(III) chloride, which in fact is hydrogen tetrachloroaurate(III), H[AuC14]. 3HzO. 

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