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A facile method to describe the electron transfer and energy transfer processes among lanthanide ions is presented based on the temperature dependent donor luminescence decay kinetics. The electron transfer process in Ce3+-Yb3+ exhibits a steady rise with temperature, whereas the Ce3+-Tb3+ energy transfer remains nearly unaffected. This feature has been investigated using the rate equation modeling and a methodology for the quantitative estimation of interaction parameters is presented. Moreover, the overall consequences of electron transfer and energy transfer process on donor-acceptor luminescence behavior, quantum efficiency, and donor luminescence decay kinetics are discussed in borate glass host. The results in this study propose a straight forward approach to distinguish the electron transfer and energy transfer processes between lanthanide ions in dielectric hosts, which is highly advantageous in view of the recent developments on lanthanide doped materials for spectral conversion, persistent luminescence, and related applications. [ABSTRACT FROM AUTHOR]

Transparent inorganic materials showing persistent luminescence can act as cover layer and emergency lighting for security signs in the dark. Herein, we report a Mn2 +-activated glass and transparent glass ceramics containing spinel-type Z n 1 + xGa2 _ 2 xGexO4 (0 < x < 1) nano-crystals, which show multi-color persistent luminescence for more than 10 min. The color of persistent luminescence showed a remarkable change from red, to orange, greenish, and green with respect to the increase of annealing temperature. The effect has been explained due to the variation of crystal field strength surrounding the M n 2 + ions. [ABSTRACT FROM AUTHOR]

We have developed bright persistent phosphors of Ce3+-Cr3+-doped Y3Al5-xGaxO12 (x=2.5, 3, 3.5) ceramics with green luminescence (Ce3+:5d→4f) via blue-light excitation. The persistent luminance value 5min after ceasing blue-light excitation for the Ce3+-Cr3+-doped Y3Al2Ga3O12 sample is approximately 3900 times higher than that for a Ce3+-doped Y3Al2Ga3O12 sample and better than that from compact SrAl2O4:Eu2+-Dy3+ powders. The results are consequences of efficient carrier trap formation and effective excitation of the interior of the translucent ceramic samples. A series of Ce3+-Cr3+-doped garnet materials is the best candidate for the persistent phosphor under white-light emitting diode (LED) illumination consisting of blue LEDs and visible phosphors. [ABSTRACT FROM AUTHOR]

Intense 1.8?µm and efficient 1.47?µm infrared emissions have been recorded in Tm3+-doped alkali-barium-bismuth-tellurite (LKBBT) glasses with lower phonon energies under the excitation of a 792?nm diode laser. The maximum emission cross-sections for the 1.8 and 1.47?µm emission bands are derived to be 6.643 × 10?21and 3.551 × 10?21?cm2and the peak values are obviously higher than those in Tm3+-doped ZBLAN fluoride and TBSN tellurite glasses, respectively. In low concentration doping, the full-widths at half-maximum (FWHMs) of the two emission bands are 206?nm and 109?nm, respectively, and peak intensity ratio between them is about 2. When the doping concentration increases to 1?wt%, the peak intensity ratio exceeds 7 and the quantum efficiency of 3H4level is only 64.6% due to the cross-relaxation process [3H4, 3H6] ? [3F4, 3F4], which benefits to achieve powerful 1.8?µm emission. The efficient and broad 1.8 and 1.47?µm infrared emission bands indicate that Tm3+-doped LKBBT glasses are suitable materials in developing S- and U-band amplifiers and 1.8?µm infrared laser. [ABSTRACT FROM AUTHOR]

We report a new material, BaCN2:Eu2+ for a very sensitive optical pressure sensor, 50 times more sensitive than ruby. Photoluminescence spectra of the BaCN2:Eu2+ phosphor was measured under hydrostatic pressures from ambient pressure to 5.34 GPa at room temperature. The peak wavelength of the luminescence was drastically red-shifted at a rate of 19 nm GPa−1, which is approximately 50 times larger than that of the ruby, most commonly used as a pressure sensor in the high-pressure experiments. This large shift of the luminescence wavelength is suitable for application in optical pressure sensors for the high-pressure experiments without a high-resolution monochromator. [ABSTRACT FROM AUTHOR]

We report on red persistent phosphors of Y3Al5−xGaxO12:Cr3+ garnet (YAGG:Cr3+, x from 0 to 5). In these materials, Cr ions act as both emission centers and electron traps. The trap depth, which is regarded as the energy gap between the bottom of the conduction band and the electron trap, can be optimized by modifying the Ga3+ substitution content (x). After ceasing UV illumination, the persistent luminescence of the YAGG:Cr3+ (x = 3) phosphor was nearly 5 times higher than that of the widely used ZnGa2O4:Cr3+ red persistent phosphor. Such novel red persistent phosphors have great potential for an improved in vivo bioimaging application. [ABSTRACT FROM AUTHOR]

We report deep-red long-lasting persistent luminescence in Cr3+-doped LaAlO3 perovskite phosphor synthesized by solid-state reaction. The LaAlO3:Cr3+ sample showed persistent luminescence peaking at a very long wavelength of 734 nm due to Cr3+:2E → 4A2 transition after ultraviolet excitation. The Sm3+ ion was found to be a good codopant for increasing the persistent luminescence intensity more than 35-fold. For the Cr3+–Sm3+-codoped LaAlO3 sample, the radiance of persistent luminescence in mW sr−1 m−2 unit was higher than or comparable to that of ZnGa2O4:Cr3+ phosphor, which is a candidate phosphor with a peak luminescence at 694 nm for in vivo imaging application. [ABSTRACT FROM AUTHOR]

We have developed a yellow persistent phosphor of Ce3+–Cr3+-codoped Gd3Al2Ga3O12 transparent ceramics prepared by a solid-state reaction. The yellow persistent luminescence due to the Ce3+: 5d–4f transition was observed even after 460 nm blue-light excitation as well as after UV excitation. The chromaticity coordinate of the persistent luminescence in the ceramic phosphor is located at , which appears really yellow compared with the color coordinate of the well-known SrAl2O4:Eu2+–Dy3+ or other conventional blue or green persistent phosphors. The luminance values for the transparent ceramic sample 1, 5, and 30 min after the blue excitation was ceased are 731, 63, and 8 mcd/m2, respectively. [ABSTRACT FROM AUTHOR]