Mixed SnO2−RuO2 oxides were prepared by high-energy mechanical alloying of various proportions of pure SnO2 and RuO2 powders. The physicochemical characterization of the resulting materials was conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and electrochemical surface analysis. It is shown through XRD analysis that a single-phase (tetragonal) (Sn−Ru)O2 solid solution is formed over the whole composition range, in which the Sn4+ and Ru4+ ions share the same cationic sub-lattice of the rutile-like structure. The surface of the compounds was analyzed by XPS and shows a deficit of Ru atoms, with [Ru]surface = 36 at. % for an equimolar SnO2−RuO2 concentration in the bulk of the sample. In the case of pure nanocrystalline RuO2, the total surface charge, q T*, the most easily accessible surface charge, q O*, and the less easily accessible surface charge, q I*, are 35.3, 29.0, and 6.3 mC cm-2 mg-1, respectively. These surface charges vary linearly with the Ru content at the surface of the electrode, indicating that the surface electrochemical properties of the compounds are dominated by the redox properties of the Ru4+ cation. The ratio q O*/q T* is close to 0.8 and independent of the surface composition, suggesting that all compounds have a similar morphology.

Stable PtAu alloy colloids with a wide range of compositions were prepared using pulsed laser ablation on single metal-mixture targets in water. The concentration of Pt in the alloys can be tuned by varying the Pt/Au ratio in the targets, which are made by compression molding a mixture of Pt and Au powders at different ratios. Such fabricated PtAu alloy nanoparticles (NPs) show a face-centered cubic structure, and their composition basically follows that of their corresponding targets. The effect of aqueous solution pH and ablating laser fluence on the formation and structure of alloy NPs was further investigated. It is found that PtAu alloy colloids of identical composition can be achieved over a pH range extending from 4.0 to 11.0 and at fluences varying from 4 to 150 J cm–2 as long as the targets of the same composition are used. This finding suggests that alloy formation is essentially insensitive to both factors in certain ranges, and the method developed herein for the alloy NP formation is quite robust. Moreover, the surface composition, estimated from electrochemical measurements, is identical to the overall composition of the NPs estimated from Vegard’s law and X-ray diffraction data, which is a strong indication of the uniform composition on the surface and in the interior of these alloy NPs.

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