High-quality monodisperse Cu2S nanocrystals (sizes from 2 nm to 20 nm) have been successfully synthesized by the reaction of copper stearate (CuSt(2)) and dodecanethiol (DDT) in 1-octadecene (ODE). The nanocrystals were characterized using X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), and transmission electron microscopy (TEM). These as-prepared Cu2S nanocrystals with certain sizes have been found with good self-assembly behaviors, and they were easily to assemble into two-dimensional and three-dimensional superlattice structures. DDT served as both Sulfur source and capping ligand, and was found a key factor to affect the growth and the self-assembly behaviors of the Cu2S nanocrystals. (C) 2008 Elsevier Inc. All rights reserved.