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_(1.75)S 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.
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