Size Effects in the Oriented-Attachment Growth Process: The Case of Cu Nanoseeds

Size effects in the oriented-attachment (OA) growth process of Cu nanoseeds were found. Monodispersed Cu nanoseeds with average diameters of 2.2, 3.4, and 5.2 nm were controllably synthesized by the reduction of copper acetate in a boiling solvent and using dodecanethiol (DT) as a stabilizer and sulfur source of sulfide. These Cu nanoseeds were then treated under solvothermal conditions. When the diameters of Cu nanoseeds were smaller than 5 rim, Cu2S nanorods with lengths of similar to 30-100 nm and diameters of similar to 2-4 nm were obtained at lower temperatures, and Cu2S nanodisks with diameters of similar to 6-13 nm and thicknesses of similar to 2-4 nm were obtained at higher temperatures. Once the diameter of Cu nanoseeds was larger than 5 nm, only irregular particles were obtained, regardless of other conditions. The uniformity, which related to the density of DT on the surface of Cu nanoseeds, was the key for success of self-assembly of the final nanocrystals, High-resolution transmission electron microscopy images demonstrated that these nanorods, nanodisks, and particles were formed by an OA process of Cu nanoseeds into 1D, 2D, and 3D aggregates, which recrystallized into single crystals.