A facile method to synthesize high-quality ZnS(Se) quantum dots for photoluminescence

Colloidal zinc sulfide (ZnS) quantum dots are synthesized by a solvothermal route from Zn(Ac)₂·2H₂O, sulfur powder and oleylamine at 120-240 °C. Microstructural, morphological, and optical properties of the as-synthesized ZnS quantum dots are characterized by X-ray diffraction analysis, transmission electron microscopy, UV-vis absorption spectroscopy, and photoluminescence spectroscopy. Results indicate that the obtained ZnS quantum dots distribute uniformly, the particle size is in the range between 1.7 nm and 3.1 nm, and the band gap decreases from 4.16 eV to 3.90 eV with an increase of the particle size. The size-dependent photoluminescence exhibits a strongly broadened peak accompanied by a pronounced blue-shift. It is also found that the size of the ZnS nanocrystals can be effectively controlled by adjusting synthesis temperature. It is shown that the present method is also applicable to synthesize other binary II-VI semiconductor materials, such as ZnSe quantum dots.