Temperature behaviour of the orange and blue emissions in ZnS:Mn nanoparticles

The temperature dependences of the orange and blue emissions in 10, 4.5, and 3 nm ZnS:Mn nanoparticles were investigated. The orange emission is from the ⁴T₁-⁶A₁ transition of Mn²⁺ ions and the blue emission is related to the donor-acceptor recombination in the ZnS host. With increasing temperature, the blue emission has a red-shift. On the other hand, the peak energy of the orange emission is only weakly dependent on temperature. The luminescence intensity of the orange emission decreases rapidly from 110 to 300 K for the 10 nm sample but increases obviously for the 3 nm sample, whereas the emission intensity is nearly independent of temperature for the 4.5 nm sample. A thermally activated carrier-transfer model has been proposed to explain the observed abnormal temperature behaviour of the orange emission in ZnS:Mn nanoparticles.