Up-Conversion Luminescence of Mn2+ in ZnS:Mn2+ nanoparticles
Wei Chen*, a, Alan G. Jolyb, Jin Z. Zhangc
aNomadics, Inc., 1024 South Innovation Way, Stillwater, OK 74074, USA bPacific Northwest National Laboratory, P. O. Box 999, Richland, WA 99352 cDepartment of Chemistry, University of California, Santa Cruz, CA 95064
For the first time, a strong up-conversion luminescence of Mn2+ is observed in ZnS:Mn2+ nanoparticles. The up-conversion emission band excited at 767 nm is red-shifted from the photoluminescence emission excited at 300 nm with the bulk and the particles encapsulated in zeolite-USY as exceptions. In the nanoparticles, the decay lifetimes of the up-conversion emission excited at 767 nm are shorter than the 300 nm excited photoluminescence lifetimes, while in the bulk, the two decays are almost identical. When the Stokes emission is obtained by excitation at 383.5 nm, which is the sum energy of two-photons at 767 nm, the emission spectra and the lifetimes of the two types of luminescence are almost identical. Also, the temperature dependence of the photoluminescence emission at 383.5 nm excitation is almost the same as that of the up-conversion emission at 767 nm excitation, while is different from that of the photoluminescence at 300 nm excitation. The power dependence of the
photoluminescence is linear, while that of the up-conversion emission is quadratic. Based on those observations, it is concluded that two-photon excitation is responsible for the up-conversion luminescence of Mn2+ in ZnS:Mn2+ nanoparticles.
Nomadics, Inc., 1024 South Innovation Way, Stillwater, OK 74074, USA