Investigation of photophysical properties of ZnS: Mn2+ nanoparticles

Pure, capped and Mn2+ -doped ZnS nanoparticles have been synthesized by chemical precipitation method. Influence of the capping agent polyvinyl alcohol and doping of Mn2+ ions on the structural, optical and morphology of the nanoparticles have been studied using X-ray diffraction, UV-Vis spectrometer, photoluminescence, Fourier transform infrared spectrometer, high-resolution electron microscope and atomic force microscope. All the prepared samples possess cubic sphalerite crystal structure with lattice constant alpha = 5.33 angstrom. The size of the particles is found to be within 2-6 nm for all the cases. It has been observed that the particle size of the ZnS nanoparticle decreases when capped with polyvinyl alcohol and doped with Mn2+. Fourier transform infrared spectrum of the samples strongly supports the formation of ZnS/PVA and ZnS: Mn2+. The prepared Mn2+ -doped sample shows efficient photoluminescence emission in 585-nm region. The samples show bright luminescence at about 585 nm, characteristic of T-4(1) (excited)-(6)A(1) (ground) transition of Mn2+ ion. High-resolution electron microscope micrograph shows a spherical shape and nearly well-distributed nanoparticle with an average particle size of ranges between 4 and 10 nm. The samples show agglomeration of ZnS nanoparticles. The rate of aggregation of the particles is reduced due to polyvinyl alcohol capping and Mn2+ doping.