Wet-chemical synthesis of palladium nanosprings.

We report a methodology for synthesis of palladium (Pd) nanospring structures using an anodic aluminum oxide (AAO) membrane template and facile electrochemical deposition. The hydroxyl-terminated surfaces of alumina nanochannels and localized hydrogen evolution contribute to the growth of Pd atoms at peripheral positions of the alumina nanochannels in the presence of an effectual electric potential and a plating solution consisting of PdCl(2), CuCl(2), and HCl. Structural characterization including EDS line analysis and element mapping revealed Pd nanodomains curling up on the Cu nanorods. A clear Pd nanospring shape was observed after selectively removing Cu. The lengths of the nanosprings were dictated by the charges transported through electrodeposition, and the diameters of the nanosprings were tunable by altering the diameter of the alumina nanochannels. Screw dislocation is the most probable crystallographic defect responsible for the formation of coiled Pd nanostructures. Pd nanosprings have potential applications in nanomachines, nanosensors, nanoinductors, and metamaterials. We anticipate that our synthesis method will motivate and inform the synthesis of more advanced nanomaterials.