The assembly of quantum dot (QD) on the surface of multi-walled carbon nanotubes (MV/NT) in aqueous solution leading to QD-MWNT hybrid structures is demonstrated. The assembly of QDs on the MWNTs surface occurs through interaction of the amine groups on the MWNTs with the mercaptoacetic acid modified QDs. Furthermore, QD-MWNT hybrid material shows an excellent solubility in aqueous solution, this will be significant for its potential application in bioassay, bioconjugation, and biosensors. (c) 2005 Elsevier B.V. All rights reserved.