Preparation of stable, water-soluble, highly luminescence quantum dots with small hydrodynamic sizes.

This work presents a simple method to prepare water-soluble alloyed CdSe-ZnS quantum dots, which photoluminescence are tunable from green to red continuously, through replacing the hydrophobic oleic acid stabilizers with hydrophilic thiol molecules. 3-Mercaptopropionic acid and 2-mercaptoethylamine have been used respectively as the surface substitutes to obtain water-soluble quantum dots with negative and positive surface charges. The methods achieved highly efficient phase transfer (approximately 100%) of quantum dots from non-polar media to water. Different techniques including photoluminescence, ultraviolet-visible absorption, Fourier transform infrared spectra, hydrodynamic diameter and zeta potential have been employed to characterize the products of phase transfer. And the results demonstrate that the obtained quantum dots exhibit a remarkably colloidal stability and have a relatively small hydrodynamic diameter with quantum yield up to 30%, which could benefit the applications of luminescent quantum dots carried out in aqueous media, such as bioimaging, metal ions sensors and photocatalysis.