Synthesis, characterization and photoluminescence studies of Mn doped ZnS nanoparticles

The present paper reports the synthesis, characterization and photoluminescence (PL) studies of Mn doped ZnS nanoparticles prepared by chemical precipitation method using mercaptoethanol as a capping agent. The nanoparticles were characterized by X-ray diffraction (XRD), field emission gun scanning electron microscope (FEGSEM), and high resolution transmission electron microscope (HRTEM). When the concentrations of capping agent (merceptoethanol) used are 0 M, 0.01 M, 0.025 M, 0.040 M, and 0.060 M, the sizes of the nanoparticles are 2.98 nm, 2.80 nm, 2.61 nm, 2.20 nm and 2.10 nm, respectively. Two peaks are obtained in the PL spectra of ZnS:Mn nanoparticles for the excitation wavelength of 220 nm, in which the first peak shifts from 400 nm to 388 nm with decreasing size of nanocrystals, and the second peak lies at 583 nm and it does not shift with reducing size of nanocrystals. The PL spectra of ZnS:Mn nanoparticles were measured for different concentrations of merceptoethanol used. The concentration of Mn was kept 1.2%, in which two peaks were found for each sample of ZnS:Mn nanocrystals. The intensities of both the PL peaks increase with reducing size of the nanoparticles. The PL emission centered at 583 nm is the characteristics emission of Mn-ion which can be attributed to a T-4(1) -> (6)A(1) transition. However, the blue emission around 400 nm is very broad and originates from the radiative recombination involving defect states in the ZnS nanocrystals. Expressions derived for the dependence of PL intensities of peak-I and peak-II on the size of nanopartides are in good agreement with experimental results. (C) 2015 Elsevier Ltd. All rights reserved.