Luminescence characteristics of ZnS nanoparticles co-doped with Ni2+ and Mn2+

ZnS nanoparticles doped with Ni2+ and Mn2+ have been prepared by co-precipitation from homogeneous solutions of Zn, Ni and Mn salt compounds, with S2- as precipitating anion formed by decomposition of thioacetamide (TAA). X-ray diffraction analysis shows that the average crystalline particle size of the doped and undoped ZnS nanometer scale samples is about 2-4 nm. A novel luminescent property has been observed in the photoluminescence (PL) spectra of the ZnS nanoparticles co-doped with Ni2+ and Mn2+. The ZnS nanoparticles can be doped with Ni2+ and Mn2+ during synthesis without altering the X-ray diffraction pattern. However, the emission wavelengths (with a color range from blue to green, lambda(em) = 475-540 nm) and PL intensities of the co-doped samples vary with changing the impurity mole ratios of Ni2+ and Mn2+ in the co-doped samples. When the mole ratios of Ni2+ and Mn2+ in the co-doped sample are 0.3% and 2.0%, respectively, the relative fluorescence intensity of the co-doped samples is about four times of that of un-doped ZnS nanocrystals. The PL properties of the co-doped samples are dramatically different from those of Ni2+- and Mn2+-doped ZnS nanocrystals. (C) 2003 Elsevier B.V. All rights reserved.