Excitation energy dependence of the life time of orange emission from Mn-doped ZnS nanocrystals

Mn-doped ZnS nanocrystals were prepared by co-precipitation method. X-ray diffraction analysis indicates pure cubic zinc blende structure. We report for the first time experimental observation of the dependence of the decay time of Mn2+ emission from Mn-doped ZnS nanocrystals on excitation energy. Photon energy smaller than the ZnS bandgap induces faster decay time compared to the one equal to the bandgap energy. In addition, while the decay spectra of orange emission indicate both sub mu s and ms, the time-resolved luminescence measurement suggests that the sub mu s component belongs to the tail of the blue emission.