Effect of Co concentration and temperature on the energy transfer process between Mn2+ and Co2+ ions in Zn0.99-xMn0.01CoxTe nanocrystals

Abstract

In this paper, we report a P2O5 – ZnO – Al2O3 – BaO – PbO glass system study, nanostructured with Zn0.99-xMn0.01CoxTe nanocrystals (NCs), synthesized by a fusion method. Transmission electron microscopy (TEM) images confirm the formation and electron paramagnetic resonance (EPR) spectra confirm the substitutional incorporation of Mn2+ and Co2+ ions in these NCs. The overlap between the Mn2+ ion emission bands and the Co2+ ion absorption bands suggests that an efficient resonance energy transfer from Mn2+ to Co2+ ions can be expected in these NCs. Indeed, the increase in emission intensity of Co2+ ions and the decrease in emission intensity of Mn2+ ions, as well as the decrease in lifetime emission of Mn2+ ions, with increasing cobalt concentration, confirm the nonradiative energy transfer from Mn2+ to Co2+ ions. On the other hand, temperature dependent measurements show the thermally activated energy transfer process via carriers of the lower energy states for those of the low energy.