One step synthesis of bright luminescent core/shell CdTe_xS_1−x/ZnS quantum dots emitting from the visible to the near infrared

Highlights: • A one-pot aqueous route was developed to prepare core/shell CdTe_xS_1−x/ZnS QDs. • The influence of the synthesis conditions on the PL emission was studied. • The PL can be tuned for the visible region to the near infrared. • CdTe_xS_1−x/ZnS QDs exhibit low cytotoxicity and can be used for live-cell imaging. - Abstract: A one-pot synthetic approach was developed to prepare water-dispersible core/shell CdTe_xS_1−x/ZnS QDs using CdCl₂, Zn(OAc)₂, NaHTe and 3-mercaptopropionic acid (MPA) as starting materials. Sulfide S^2- ions produced from the partial decomposition of MPA associate to CdTe nuclei to form an alloyed CdTe_xS_1−x core before reacting with Zn²⁺ ions to generate the ZnS shell. The photoluminescence (PL) of CdTe_xS_1−x/ZnS QDs QDs can be adjusted from the green to the near-infrared region by varying the ratio of precursors or the reaction time. The formation of core/shell CdTe_xS_1−x/ZnS structure was confirmed by high resolution transmission electron microscopy and X-ray diffraction studies. The highly luminescent QDs (PL quantum yields up to 35%) exhibit good stability in aqueous solution and low cytotoxicity towards Kluyveromyces bulgaricus cells. Bioconjugation of CdTe_xS_1−x/ZnS QDs with (D)-(+)-galactose was successfully applied for the fluorescent imaging of the yeast cells.