Multiplication of electronic excitations in nanophosphors Lu2O3:Eu3+ and Lu2O3:Tb3+

Luminescence properties of Lu2O3:Eu3+ and Lu2O3:Tb3+ nanocrystalline powders with the particle size varying from 46 to 6 nm were studied under excitation by synchrotron radiation in the photon energy range (up to ∼22.5 eV) covering the region where the processes of multiplication of electronic excitation occur. It was found that the excitation spectra of Tb3+ emission from all Lu2O3:Tb3+ nanopowders have similar behavior, whereas the shape of the excitation spectra of Eu3+ emission from Lu2O3:Eu3+ nanopowders strongly depends on the particle size. The difference in the behavior of Lu2O3:Eu3+ and Lu2O3:Tb3+ nanophosphor systems was explained by different mechanisms of the energy transfer from the host to Eu3+ or Tb3+ ions (either the hole or electron recombination mechanism, respectively), which are differently influenced by losses of electronic excitations near the particle surface.