Luminescence of RE2+ (RE = Sm, Yb) in barium octoborate

The reduction process from trivalent to divalent state for Sm3+ and Yb3+ ions in barium berates (BaB8O13) prepared in air was observed. The luminescence properties of these divalent rare-earth ions were studied. Yb2+ shows an f-d broad emission band, due to the 4f(14) --> 4f(13)5d transition, while the Sm2+ ion shows an f --> f transition. From the spectra of Yb2+, and using the D-5(0) --> F-7(0) transition of Sm2+ as a structural probe, two crystallographic sites were found to be available for the cations in the host. Vibronic transitions of Sm2+ were observed at low temperature. BaB8O13 was found to be a good host for reducing the trivalent rare-earth ions to divalent state and to exhibit interesting spectroscopic properties,

Luminescence and energy transfer between Ce3+ and Mn2+ in alkaline earth borates

The luminescence of Ce3+ and Ce3+, Mn2+ co-doped BaB8O13 and SrB4O7 prepared in air is studied. The results show that tetravalent cerium ion can he reduced to trivalent state in the hosts and gives rise to efficient luminescence. Energy transfer between Ce3+ and Mn2+ is possible. Mn2+ ions can be efficiently sensitized by Ce3+ and exhibit green and red emissions which implied that Mn2+ occupied the crystallographic sites of cations and boron sites of the anoins, respectively. The intensity ratio of red to Been emission in matrix increases with the increasing of manganese concentration.

Valence change and luminescence of divalent samarium in strontium berates

The valence change of samarium from trivalent to divalent state in strontium berates (SrB6O10) prepared in air was observed. The high resolution spectra of Sm2+ in matrix were studied between 10 K and 300 K. The results showed that three crystallographic sites for Sm2+ were available in the host. Energy transfer among these sites was possible. The vibronic transition of D-5(0) --> F-7(0) of Sm2+ was studied at room temperature and the Huang-Rhys factor S was calculated. Due to the thermal population, D-5(1) --> F-7(0) transition at room temperature was observed.

Luminescence of unusual bismuth in barium berates BaB8O13 : Bi)

The luminescence of unusual divalent bismuth (Bi2+) in BaB8O13 is reported. The emission band with maximum peak at 592 nm corresponds to the P-2(3/2)-->P-2(1/2) transition of Bi2+ in the matrix and the excitation spectrum with two bands peaked at 470 and 580 nm respectively corresponds to two split crystal-field levels of P-2(3/2) state. The small Stokes shift (similar to 350 cm(-1)) reflects the rigid structure of the host for the Bi2+ ions.

Luminescence and energy transfer phenomena of several rare earth ions in the CaAl2B2O7

The luminescence properties of Ce3+, Gd3+, and Tb3+ have been investigated in the compound CaAl2B2O7. The single excitation band peaking at about 320 nm and single emission band peaking at about 384 nm for Ce3+, without the characteristic doublet, are attributed to the extensive crystal-field splitting of 4f ground state. The emission of Gd3+ consists of well-known sharp lines and two weak bands around 319.5 and 325 nm. These bands are due to the coupling of Gd3+ with BO33- groups. The green emission of Tb3+ is considerably sensitized by Ce3+. Energy transfer from Ce3+ to Tb3+ in CaAl2B2O7 is efficient. (C) 1997 Elsevier Science Ltd.

Luminescence of Pb2+ and energy transfer from Pb2+ to rare earth ions in silicate oxyapatites

The Pb2+ luminescence in a series of silicate oxyapatites Me(2)(Y, Gd)(8)(SiO4)(6)O-2, Me(4)Y(6)(SiO4)(6)O (Me = Mg: Ca, Sr) is reported and discussed in relation to the crystal structure. The maximum wavelengths of the excitation (S-1(0)-P-3(1)) and emission (P-3(1)-S-1(0)) bands of Pb2+ are independent of the Mc:Y ratio (2:8 or 4:6) but they have lower energies in MgY-oxyapatites than in CaY- and SrY-oxyapatites. The Stokes shift of Pb2+ luminescence amounts to 11 100 to 11 400 cm(-1): which does not depend strongly on the host composition. There exists a mutual energy transfer between Pb2+ and Gd3+ in Sr2Gd8(SiO4)(6)O-2. At last, the dependence of the energy transfer efficiency of Pb2+-Sm3+, Tb3+: Dy3+ in Sr-2(La: Gd)(8)(SiO4)(6)O-2 and Ca-2(Y, Gd)(8)(SiO4)(6)O-2 on their doping concentrations was studied in more detail.

Influence of crystal structure on the luminescence properties of bismuth(III), europium(III) and dysprosium(III) in Y2SiO5

The luminescence properties of Bi3+, EU(3+), Dy3+ and energy transfer from Bi3+ to Dy3+ and EU(3+) have been studied in two modifications of Y2SiO5 (low-temperature X(1) type and high-temperature X(2) type) and discussed in relation to their crystal structures. The Bi3+ ion luminesces in the blue region of the spectrum in X(1)-Y2SiO5 but in the UV region in X(2)-Y2SiO5. Two obviously different luminescent centres have been observed for Bi3+ and Eu3+ ill X(1)-Y2SiO5, but only one has been seen in X(2)-Y2SiO5. The Stokes shift (9200 cm(-1)) for Bi3+ in X(1)-Y2SiO5 is much larger than that (5000 cm(-1)) in X(2)-Y2SiO5. This suggests that the host lattice is more rigid in X(2)-Y2SiO5 than in X(1)-Y2SiO5. As a result, the Bi3+, EU(3+) and Dy3+ ions show higher emission intensity in the former than in the latter type. X(1)-Y2SiO5 is more suitable for Bi3+ --> EU(3+) energy transfer and X(2)-Y2SiO5 is more suitable for Bi3+ --> Dy3+ energy transfer.

LUMINESCENCE AND ENERGY MIGRATION IN THE OXYAPATITE CA2GD8(SIO4)6O2 DOPED WITH SEVERAL RARE-EARTH AND MERCURY-LIKE IONS

Energy transfer phenomena have been observed by activating the oxyapatite host-lattice Ca2Gd8(SiO4)6O2 with Eu3+, Tb3+, Dy3+, Sm3+. This is based on the energy migration in the Gd3+ sublattice and trapping by the activators. The trapping efficiency for G

INVESTIGATION ON THE LUMINESCENCE PROPERTIES OF DY3+ AND EU3+ IN M3LN2(BO3)4 (M=CA, SR, BA, LN= LA, GD, Y)

In this paper, the luminescence properties of Dy3+ and Eu3+ in M3Ln2 (BO3)4 (M = Ca,Sr,Ba; Ln = La, Gd, Y) were systematically studied. The hypersensitive transitions of Dy3+ and Eu3+ were investigated in relation to the host compositions; the relationship between the energy of Eu3+ charge-transfer band and M2+ ion was discussed, and the concentration quenching of Dy3+ luminescence was reported.

A homogeneous DNA hybridization system by using a new luminescence terbium chelate

Homogeneous DNA hybridization assay based on the luminescence resonance energy transfer (LRET) from a new luminescence terbium chelate, N,N,N-1,N-1-[2,6-bis(3'-aminomethyl-1'-pyrazolyl)-4-phenylpyridine]tetrakis(acetic acid) (BPTA)-Tb3+ (lambda(ex) = 325 nm and lambda(em) = 545 nm) to an organic dye, Cy3 (A,. = 548 nm and A,. = 565 nm), has been developed. In the system, two DNA probes whose sequences are complementary to the two different consecutive sequences of a target DNA are used; one of the probes is labeled with the Tb3+ chelate at the T-end, and the other is with Cy3 at the 5'-end. Labeling of the Tb3+ chelate is accomplished via the linkage of a biotin-labeled DNA probe with the Tb3+ chelate-labeled streptavidin. Strong sensitized emission of Cy3 was observed upon excitation of the Tb3+ chelate at 325 run, when the two probe DNAs were hybridized with the target DNA. The sensitivity of the assay was very high compared with those of the previous homogeneous-format assays using the conventional organic dyes; the detection limit of the present assay is about 30 pM of the target DNA strand.

PMMA with Long-Persistent Phosphors and Its Behavior of Luminescence

A new kind of rare earth material with high efficient long-persistent phosphors, such as SrAl2O4: Eu, Dy, has been developed in recent years. The PMMA with long-persistent phosphors is typical one of applications for the phosphors. In this work, we try to probe into the affection of the manufacture process on the PMMA with long-persistent phosphors, to analyze its performance, and its luminescence behavior, especially to study the self-excitation of the PMMA with long-persistent phosphors.

Three-photon-excited upconversion luminescence of YVO4 single crystal by infrared femtosecond laser irradiation

We report on the upconversion luminescence of a pure YVO4 single crystal excited by an infrared femtosecond laser. The luminescent spectra show that the upconversion luminescence comes from the transitions from the lowest excited states T-3(1), T-3(2) to the ground state (1)A(1) of the VO43-. The dependence of the fluorescence intensity on the pump power density of laser indicates that the conversion of infrared irradiation to visible emission is dominated by three-photon excitation process. We suggest that the simultaneous absorption of three infrared photons promotes the VO43- to excited states, which quickly cascade down to lowest excited states, and radiatively relax to ground states, resulting in the broad characteristic fluorescence of VO43-. (c) 2005 Optical Society of America.

Infrared luminescence properties of bismuth-doped barium silicate glasses

Infrared (IR) luminescence covering 1.1 to similar to 1.6 mu m wavelength region was observed from bismuth-doped barium silicate glasses, excited by a laser diode at 808 nm wavelength region, at room temperature. The peak of the IR luminescence appears at 1325 nm. A full width half-maximum (FWHM) and the lifetime of the fluorescence is more than 200 nm and 400 mu s, respectively. The fluorescence intensity increases with Al2O3 content, but decreases with BaO content. We suggest that the IR luminescence should be ascribed to the low valence state of bismuth Bi2+ or Bi+, and Al3+ ions play an indirect dispersing role for the infrared luminescent centers.

Broadband infrared luminescence from transparent glass-ceramics containing Ni2+-doped beta-Ga2O3 nanocrystals

Transparent Ni2+-doped beta-Ga2O3 glass-ceramics were synthesized. The nanocrystal phase in the glass-ceramics was identified to be beta-Ga2O3 and its size was about 3.6 nm. It was confirmed from the absorption spectra that the ligand environment of Ni2+ ions changed from the trigonal bi-pyramid fivefold sites in the as-cast glass to the octahedral sites in the glass-ceramics. The broadband infrared emission centering at 1270 nm with full width at half maximum (FWHM) of more than 250 nm was observed. The fluorescence lifetime was about 1.1 mu s at room temperature. The observed infrared emission could be attributed to the T-3 (2g) (F-3) -> (3)A (2g) (F-3) transition of octahedral Ni2+ ions. It is suggested that the Ni2+-doped transparent beta-Ga2O3 glass-ceramics with broad bandwidth and long lifetime have a potential as a broadband amplification medium.

Transparent Ni2+-doped ZnO-Al2O3-SiO2 system glass-ceramics with broadband infrared luminescence

We report transparent Ni2+-doped ZnO-Al2O3-SiO2 system glass-ceramics with broadband infrared luminescence. After heat-treatment, ZnAl2O4 crystallite was precipitated in the glasses, and its average size increased with increasing heat-treatment temperature. No infrared emission was detected in the as-prepared glass samples, while broadband infrared luminescence centered at 1310 nm with full width at half maximum (FWHM) of about 300 nm was observed from the glass-ceramics. The peak position of the infrared luminescence showed a blue-shift with increasing heat-treatment temperature, but a red-shift with an increase in NiO concentration. The mechanisms of the observed phenomena were discussed. These glass-ceramics are promising as materials for super broadband optical amplifier and tunable laser. (c) 2006 Elsevier Ltd. All rights reserved.