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The step energy transfers from Pr3+ 4f5d state to Ce3+ 5d state followed by energy back transfer from Ce3+ 5d state to Pr3+ 1D2 level are studied. The Ce3+→Pr3+ energy back transfer upon Pr3+ 4f5d excitation is found to be more efficient than the normal Ce3+→Pr3+ energy transfer upon Ce3+ 5d excitation. The efficient energy back transfer is attributed to preferential excitation of the Ce3+ ion with an adjacent Pr3+ surrounding in Pr3+→Ce3+ energy transfer of the first step, whereas Ce3+ is excited randomly in the normal energy transfer. The efficiencies of Ce3+→Pr3+ energy back transfer as a function of Ce3+ and Pr3+ concentration are evaluated, respectively.

The Ce3+-activated, Tb3+-activated, and Ce3+ and Tb3+ co-activated phosphors 2SrO–nB2O3–(1−n)P2O5 were synthesized by the solid-state reaction. The structures, photoluminescent spectra and dynamics of them were systemically studied. The results demonstrate that the structure of the samples with n=0.10–0.50 belongs to the hexagonal phase. When n is beyond this range, the structures are the mixed phases of α-Sr2P2O7 and Sr2B2O5. The optimum composition is determined to be n=0.25 for the 2SrO–nB2O3–(1−n)P2O5 phosphors. As n varies from 0.01 to 0.50, the lifetime of Ce3+ ion increases gradually, while the lifetime of Tb3+ ion decreases, indicating that the energy transfer efficiency decreases with the increase of n. The ET efficiency between Ce3+ and Tb3+ in the optimum composition reaches to 70%. The present results demonstrate that the Ce3+ and Tb3+ co-activated hexagonal 2SrO–0.25B2O3–0.75P2O5 powders can possibly be applied as the newly developed green efficient phosphors in the field of lighting and display.

The ZnO@ZnWO4:Eu3+ core–shell composites were prepared by a two-step hydrothermal method and the photoluminescence properties of the composites were studied in contrast to the corresponding hexagonal ZnO and monoclinic ZnWO4: Eu3+ nanocrystals prepared by the one-step hydrothermal method. The results demonstrate that in the nanocomposites the Eu3+ ions in the ZnWO4 phase occupy two symmetry sites, one a well-crystalline inner site and one a disordered surface site; while in the ZnWO4: Eu3+ nanocrystals, the local environments surrounding Eu3+ ions are relatively disordered for both the inner and the surface sites. This indicates that in the composites, the crystallinity of the ZnWO4 becomes better, which have positive influence on the improvement of photoluminescence. The temperature stabilities for both the emissions of ZnO and Eu3+ ions are improved in contrast to the pure ZnO or ZnWO4:Eu3+ nanocrystals.

In this paper, TiO 2 :Sm 3+ (0.75 mol%) nanoparticles doped with different amounts of Br − were prepared by an improved sol–gel method and were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), VG ESCALAB MKIIX-ray photoelectron spectrometer (XPS) and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS). Their photoluminescence (PL) properties were investigated at room temperature. The emissions of 4 G 5/2 – 6 H J ( J =5/2, 7/2, 9/2) transitions of Sm 3+ ions were observed under the excitation wavelength at 350 nm and the emission intensity depended strongly on the doping amount of Br − . TiO 2 :Sm 3+ (0.75 mol%) nanoparticles doped with 1 mol% of Br − calcined at 700 °C exhibit highest intensity of luminescence, which is nearly three times than the undoped one. The mechanism of photoluminescence in the co-doped system was discussed.

In this work, the luminescence properties of samarium ions-doped titanium dioxide prepared by the sol–gel process were studied. A strong orange red emission (4G5/2−6H7/2 (orange) and 4G5/2–6H9/2 (red)) ascribed to the electron transitions in 4f5 configuration of Sm3+ ions was observed upon excitation into TiO2 host. The energy transfer from TiO2 to Sm3+ was verified and the relevant mechanism was discussed. In addition, the impacts of metal ion codopants upon the TiO2:Sm3+ luminescence properties were studied. The results indicated that the central excitation band shifted to blue in the bismuth-codoped materials (0.5–4% in molar ratio), while it shifted to red in the zirconium-codoped materials. Such materials may find applications in white light-emission diode (LED) and tunable solid lasers.

Sub-micrometer-sized fibers of europium-doped yttria (Y 2 O 3 :Eu 3+ ) were prepared by electrospinning followed by high-temperature calcinations for the first time. The fibers were with diameters of 200–400 nm and lengths of several 10 μm and cubic in phase. The spectral properties of the Y 2 O 3 :Eu 3+ fibers were studied, in contrast with those of bulk powders. The results indicated that in the present Y 2 O 3 :Eu 3+ fibers the excited charge transfer band had slightly blue shift in comparison with that in the bulk due to weaker covalence of Eu–O bonds. In addition, both of the lifetimes of the 5 D 1 and 5 D 0 states in the fibers became shorter than that in the bulk due to improved nonradiative transition rates.

Pure hexagonal-phased YBO 3 :Eu 3+ nanocrystals (NCs) including nanosheets (NSs), bundles of nanobelts (NBs) and quasi-spheres composed of nanotubes (NTs) were prepared by hydrothermal method. The results indicate that in NCs, there exist two symmetry sites of Eu 3+ ions, the interior (A) and the surface (B), while there exists only one interior site (A) in the bulk. It is important to observe that the electronic transition rate of 5 D 0 -Σ j 7 F J of Eu 3+ at the surface site is improved 3-5 times than that of the interior site.

ZnO nanorods with hexagonal structures were synthesized by the hydrothermal method at different conditions. Their room-temperature emission spectra and fluorescent dynamics were studied. The ultraviolet emissions of excitons (3.2 eV) and visible emissions (2.0 eV) from deep levels (DLs) of defects were observed. The results demonstrate that preparation condition pH influences the intensity ratio of the exciton emissions and DLs, as well as the decay time constant of DLs emissions.

One dimensional Gd 2 O 3 :Eu nanowires with diameters of ∼100 nm were fabricated by anodic aluminum oxide (AAO) template method. Excitation and emission spectra, fluorescence dynamics of Gd 2 O 3 :Eu/AAO were studied. The results showed that the charge transfer band of Eu 3+ in Gd 2 O 3 :Eu/AAO blue shifted with increasing annealing temperature and time. The decay time constant of 5 D 0 – 7 F 2 transition became longer with the increasing annealing temperature in Gd 2 O 3 :Eu/AAO. The 5 D 0 – 7 F 1 transition of Eu 3+ ions in cubic phase had longer lifetime than that in amorphous phase. In contrast to the lifetime of 5 D 0 – 7 F J in the bulk powder, that in Gd 2 O 3 :Eu/AAO composite films increased.