Multi-walled carbon nanotubes (MWNTs) were coated with metal sulfide such as US, Ag2S and HgS by an in situ synthetic method via non-covalent functionalization of MWNTs with sodium dodecyl sulfate (SDS), which were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM) and photoluminescence spectroscopy. The coating layer was composed of metal sulfide nanoparticles with size of less than 30 nm. This method offers MWNTs/metal sulfide composites without significantly affecting the energy states of the MWNTs. (c) 2005 Elsevier B.V. All rights reserved.