The controlled synthesis of Cu(OH)2 nanowires and nanoribbons in a solution phase has been realized with high yield at low cost by simply dropping KOH and ammonia solutions into an aqueous solution of CuSO4 at ambient temperature. It is demonstrated that the morphology of nanostructured Cu(OH)2 is significantly influenced by the feeding manner of the alkaline solutions. A rational mechanism based on coordination self-assembly and oriented attachment is proposed for the selective formation of the polycrystalline Cu(OH)2 nanowires and single-crystalline Cu(OH)2 nanoribbons. In the presence of a polymeric additive, poly(acrylic acid) (PAA), ordered assemblies of Cu(OH)2 nanorods can be readily obtained. Furthermore, well-defined CuO nanostructures, such as CuO nanoplatelets, nanoleaflets, and nanowires, were produced by thermal dehydration of the as-prepared Cu(OH)2 nanostructures in solution or in the solid state. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the products.

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Using oxalate as a stabilizing agent, stable colloidal solutions of platinum nanoparticles of different shape distributions were prepared by reducing K2[Pt(C2O4)2], K2PtCl6, or K2PtCl4 with hydrogen. The mean diameters of the Pt nanoparticles prepared from these precursors are 6.5, 3.5, and 7.9 nm, respectively. UV-vis absorption spectroscopy and transmission electron microscopy studies on the preparation processes and the products indicate that not only the rate of reduction and particle size but also the shape distributions of the prepared Pt nanoparticles depend on the used precursors. The reduction of K 2[Pt(C2O4)2] in water at room temperature is quite slow, while adding suitable amounts of CaCl2 or increasing temperature can accelerate the reduction process. Pt nanoparticles prepared from K2[Pt(C2O4)2] have quite narrow size and shape distributions, and the selectivity of cubic nanoparticles is greater than 90%. Adding CaCl2 in the reaction system does not obviously affect the size and shape distributions of the prepared nanoparticles. Oxalate-stabilized Pt colloid is sensitive toward oxygen; during aging in air, oxidation decomposition of oxalate is catalyzed by the Pt nanoparticles, which leads the Pt nanoparticles to aggregate into linear aggregations. After exposure to air for long times and treatment with hydrogen, these linear aggregations transform into Pt nanowires.