Trigonal and hexagonal CuS (covellite) nanoflakes with controlled size (10-200 nm, and thickness of 3.6-5 nm) were synthesized through the reaction between copper acetylacetonate and sulfur in oleylamine. Size and shape of the products could be tuned by reaction parameters and reactant concentration. The as-prepared flakes have smooth surfaces and self-assemble face-to-face each other. High-resolution transmission electron microscopy and electron diffraction show that the nanoscale flakes were single-crystal hexagonal covellite. Formation mechanism of the nanoflakes is discussed. UV-vis spectra reveal that the samples have blue-shift absorbance onsets owning to the quantum size effects. (c) 2005 Elsevier B.V All rights reserved.