Red emitting nanophosphors of CaTiO3:Pr3+ with various particle sizes were prepared by sol−gel methods
and structurally characterized by X-ray diffraction and field emission scanning electron microscopy. The
fluorescent and phosphorescent properties of CaTiO3:Pr3+ nanoparticles as a function of particle sizes were
investigated by using photoluminescence and photoluminescence excitation spectra as well as time decay
patterns of fluorescence and phosphorescence. On the analysis of the longer lifetimes at 300 K as compared
to that at 77 K and the appearance of maximal photoluminescence, the dependence of photoluminescence on
phosphorescence is demonstrated. A very highly efficient phosphorescence recombination channel in the
nanophosphor is proposed and discussed. This work provides a promising method to develop novel phosphors
by manipulating the number of traps on the surface of nanophosphors through adjusting the particle size.
The effects of size and europium concentration on photoluminescence properties of La 2 O 2 S: Eu 3+ nanocrystals (∼20 nm) and the corresponding bulk were studied. The results indicate that in nanocrystals, the absorption edge largely shifted to blue in comparison to the bulk, which was mainly attributed to the variation of phononexcitation relaxation. Two excitation bands were observed, located at ∼250 and ∼330 nm, respectively, corresponding to the charge transfer (CT) transitions of Eu-O and Eu-S. Relative to the CT transition of Eu-O, that of Eu-S increased greatly with europium concentration. The dependence of photoluminescence intensity on concentration showed that in the nanocrystals and the bulk, Eu 3+ ions had two different quenching mechanisms, respectively, the exchange interaction and electric dipole-dipole interaction.
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