Cu-doped ZnS (ZnS:Cu) quantum dots were prepared in de-ionized water by femtosecond laser ablation of a bulk ZnS: Cu target. The obtained quantum dots exhibit good colloidal stability and water solubility, showing narrow and symmetric Cu-related emission, which is analogous to the well-known blue emission from bulk ZnS: Cu. The mean size of the quantum dots varies from 2.1 to 4.0 nm by changing the laser fluence, resulting in a redshift of the emission peak from 375 to 400 nm. The experimental results demonstrate that femtosecond laser ablation is an effective method for preparing doped quantum dots. (C) 2008 Published by Elsevier B.V.