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 originated from the stretching vibration of the Mn–O bonds in the Fourier transform infrared (FTIR) spectra. And the small changes about this peak compared with the previous reports at 500 cm-1 can be attributed to the formation of quantum dots. This method we utilized to synthesize ZnS: Mn QDs is very simple, low cost, and applicable for other semiconductor QD materials.