Up-conversion luminescence of Mn2+ in ZnS : Mn2+ nanoparticles - art. no. 041202

Strong up-conversion luminescence of Mn2+ is observed in ZnS:Mn2+ bulk and nanoparticles. The upconversion emission band excited at 767 nm is redshift ed from the photoluminescence emission excited at 300 ran with the bulk and the particles encapsulated in zeolite ultrastable zeolite-Y as exceptions. In the nanoparticles, the decay lifetimes of the up-conversion emission ex cited at 767 nm are shorter than the 300-nm excited luminescence lifetimes, while in the bulk, the two decays are almost identical. When the photolumi nescence is obtained by excitation at 383.5 nm, which is the sum energy of two photons at excitation at 767 nm, the emission spectra and the lifetimes of the two types of luminescence are almost identical. The power dependenc e of the photoluminescence is linear, while that of the up-conversion emiss ion is quadratic. Based on these observations along with the temperature de pendence of the up-conversion luminescence intensity, it is concluded that two-photon excitation is responsible for the up-conversion luminescence of Mn2+ in ZnS:Mn2+ nanoparticles.