Influence of Polyvinyl Pyrrolidone on Absorption and Radiation Transitions of Mn$^{2 + }$ ions in Mn-doped ZnS Nanoparticles

Abstract

ZnS:Mn nanoparticles were synthesized by co-precipitation method from the precursors solutions of 0.1M Zn(CH$_{3}$COO)$_{2}$, Na$_{2}$S and Mn(CH$_{3}$COO)$_{2}$ then were capped with polyvinyl pyrrolidone. The XRD patterns showed that the ZnS:Mn nanoparticles possessed the $T_d^2 - F4\bar {3}m$ cubic structure with the average crystallite size of several nanometers. At 300~K, the obtained photoluminescence spectra showed only a wide yellow-orange band centered at 603 nm, which should be attributed to the radiation transition of [$^{4}$T$_{1}(^{4}$G)$\to ^{6}$A$_{1}(^{6}$S)] of Mn$^{2 + }$(3d$^{5})$ cations in the ZnS matrix. The excitation spectra recorded at 300 K on the other hand featured a strong photoluminescence band around 310-334 nm, which were assigned to the near band-edge absorption transition of ZnS host lattice, in addition with three weaker bands relating to the absorption transitions of [$^{6}$A$_{1}(^{6}$S) $\to$ $^{4}$T$_{2}(^{4}$D)]: 430 nm, [$^{6}$A$_{1}(^{6}$S) $\to$ $^{4}$A$_{1}(^{4}$G) -- $^{4}$E($^{4}$G)]: 468 nm, and [$^{6}$A$_{1}(^{6}$S) $\to  ^{4}$T$_{2}(^{4}$G)]: 498 nm of Mn$^{2 + }$(3d$^{5})$ cations. It was shown that the capping affected only the intensities of emissions bands.