Phase-Selective Synthesis and Self-Assembly of Monodisperse Copper Sulfide Nanocrystals

Single-crystalline, monodisperse copper sulfide nanocrystals with controlled sizes, shapes, and phases were successfully synthesized via a simple, low-cost, and environmentally friendly chemical reaction of CuCl₂ and S in oleylamine at 100−180 °C. It was found that the molar ratios of [CuCl₂]:[S] played the critical role for the control of the sizes, shapes, and phases of copper sulfide nanocrystals. The hexagonal CuS nanodisks, hexagonal CuS nanoribbons consisting of face-to-face stacked nanodisks, and monoclinic Cu_1.75S nanoribbons consisting of face-to-face stacked nanodisks were obtained when the molar ratios of [CuCl₂]:[S] were 1:1, 2:3, and 2:1, respectively. It was believed that the van der Waals force and dipole−dipole interaction were responsible for the self-assembly of copper sulfide nanodisks. Finally, the copper sulfide nanocrystals were characterized by transmission electron microscopy, high-resolution transmission electron micrscopy, X-ray diffraction, and Fourier transform infrared, and its growth mechanism was primarily discussed.