Synthesis and photoluminescence of water-soluble Mn:ZnS/ZnS core/shell quantum dots using nucleation-doping strategy

The water-soluble Mn:ZnS/ZnS (core/shell) quantum dots were synthesized through nucleation-doping strategy in aqueous solutions in air, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and photoluminescence (PL) spectra. It was found that the Mn2+4T1 → 6A1 emission intensity of Mn:ZnS d-dots significantly increased with the increase of Mn2+ concentration, and showed a maximum when Mn2+ doping content was 1.0%. If Mn2+ concentration continued to increase, namely more than 1.0%, the Mn2+4T1 → 6A1 emission intensity would decrease. By the growth of an additional ZnS shell on Mn:ZnS d-dots, the emission intensity of Mn2+ in Mn:ZnS/ZnS core/shell d-dots were enhanced due to the elimination of the surface defects. Mn:ZnS/ZnS (core/shell) d-dots were not at all air sensitive, while Mn:ZnS d-dots were strongly air sensitive.