Photoluminescence of ZnS: Mn quantum dot by hydrothermal method

ZnS: Mn quantum dots (QDs) with the average grain size from 4.2 to 7.2 nm were synthesized by a hydrothermal method. All samples were cubic zinc blende structure (β-ZnS) measured using X-ray diffraction (XRD). And the main diffraction peaks of ZnS: Mn shifted slightly towards higher angle in comparison with the intrinsic ZnS because of the substitution of Mn2+ for Zn2+. Due to the small grain size (4-7 nm) effect, the poor dispersion and serious reunion phenomenon for the samples were observed from transmission electron microscopy (TEM). ZnS: Mn QDs had four peaks centered at 466, 495, 522, and 554 nm, respectively, in the photoluminescence (PL) spectra, in which the band at 554 nm absent in the intrinsic ZnS: Mn is attributed to the doping of Mn2+ in the lattice sites. As the concentration of Mn2+ increasing from 0% to 0.6 at%, the intensity of the PL emission also increased. But the concentration reached 0.9 at%, quenching of PL emission occurred. The peak in ZnS: Mn QDs observed at 490 cm-1 was origina...