Controllable fabrication and self-assembly of Cu nanostructures: the role of Cu²⁺ complexes

The controllable fabrication of low dimensional nanostructures and the assembly of nanostructures into hierarchical higher order structures at the atomic or molecular level have been two hot-spots of current nano research. In this work, the fabrication and self-assembly of Cu nanostructures were carried out by reducing Cu²⁺ complexes in a mixed aqueous solution of NaOH and hydrazine hydrate at a water bath temperature of 60 °C. The reduction products were characterized using a metalloscope, a scanning electron microscope, a transmission electron microscope and a powder X-ray diffractometer. It was found that the fabrication and self-assembly of Cu nanostructures can be easily realized by controlling the types of Cu²⁺ complexes such as [Cu(OH)₄]^2-, [Cu(EDA)₂]²⁺ and [Cu(EDA)(OH)₂]. The authors further analyzed the important roles of Cu²⁺ complexes in the fabrication and self-assembly of Cu nanostructures. It was concluded that the Cu²⁺ complexes in the aqueous solution would spontaneously arrange into a certain soft template according to the principle of "like dissolves like" and the action of electrostatic forces of positive and negative charges. The as-formed templates determine the fabrication and self-assembly routes and the final products of the Cu nanostructures. Therefore, it provides a controllable and universal method for both fabrication and self-assembly of Cu nanostructures, which may have potential applications in the fields of electronic and optoelectronic nanodevices in the future.