One-Pot Synthesis of Pd Nanorings Using a Soft Template of Spindle-Shaped Amphiphilic Molecular Assembly

Metallic nanorings have attracted much attention of researchers owing to their unique optical, electrical, and magnetic properties, and now, simple and large-scale synthesis methods must be developed for their practical application in various fields. Here, we report the one pot synthesis of ultrathin Pd nanorings through a simple and novel soft-template approach based on wet-chemical synthesis. A spindle-shaped assembly of a long-chain amidoamine derivative(C18AA) served as the soft template of Pd nanorings that were prepared in an aqueous solution containing the Pd precursor and a suitable amount of C18AA and toluene, and the chemical reduction of the Pd precursor in the aqueous solution produced an array of almost circular Pd nanorings covering the assembly. Pd nanorings that were parallel to the amine group, which is the head group of C18AA, appeared on the assembly surface. The amount of toluene strongly affected the formation of the spindle-shaped assembly and Pd nanorings. Furthermore, transmission electron microscope images were obtained at several points in time during the reaction; they revealed that the Pd nanorings were produced by the fusion of Pd nanoparticles formed on the spindle-shaped molecular assembly during an early stage of the reaction. The Pd nanorings were also found to have high structural stability against organic solvents, high temperatures, and high and low pH.