Stable, small, and water-soluble Cu-doped ZnS quantum dots prepared via femtosecond laser ablation

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.