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1.
Rare earth doped lead borate glasses and transparent glass-ceramics have been studied using optical spectroscopy. Based on
the absorption, emission and its decay and the Judd-Ofelt calculations, several radiative and laser parameters for Ln
3+ ( Ln = Pr, Nd, Eu, Dy, Er, Tm) were evaluated. The large values of luminescence lifetime, quantum efficiency of excited state
and room temperature peak stimulated emission cross-section suggest efficient laser transitions of Ln
3+ ions in lead borate glasses. The obtained results indicate that lead borate glasses and glass-ceramics containing Ln
3+ ions are promising host matrices for solid-state laser applications. 相似文献
2.
Radiationless energy transfer between rare-earth ions (Ln 3+) in solutions has some features: 1) the electronic transitions in Ln 3+ complexes causing the luminescence of energy donor and the absorption of energy acceptors are forbidden by Laporte's rule and are weakly intensive. Therefore the critical radius (R o) of energy transfer between the rare-earth ions for dipole-dipole mechanism is close to that for exchange-resonant mechanism. This fact presents difficulties for unequivocal interpretation of the energy transfer mechanism. 2) The plus-three lanthanide ions exist in solution as a set of complexes with different number of charged ligands in the inner coordination sphere and hence with different total charge of complexes. 相似文献
3.
Lanthanide(III)-cored complexes based on 2-thenoyltrifluoroacetone (TTA) ligand for near infrared (NIR) emission have been developed to investigate the energy transfer pathway from the antenna ligand to the Ln 3+ ion. Their photophysical studies indicate the sensitization of Ln 3+ luminescence by energy transfer through the excited triplet state of β-diketone ligand. Nanosecond (ns) transient absorption behavior of Ln 3+-[TTA] 3(terpy) complexes at room temperature is explored. The triplet-triplet absorption spectrum for Gd 3+-[TTA] 3(terpy) is observed under degassed condition, whereas it is hardly observed in Er 3+-[TTA] 3(terpy) complex. The sensitizing process in Er 3+-[TTA] 3(terpy), through the triplet state of TTA ligand to Er 3+ ion, is also independent on the presence of oxygen. It indicates that the energy transfer rate through the excited triplet state of β-diketone ligand to Er 3+ ion occurs approximately faster than that of the oxygen quenching rate. 相似文献
4.
For the first time, direct experimental evidence of a new mechanism for the quenching of fluorescence of organic ligands (L) in complex compounds with lanthanide ions (Ln3+) is obtained. By analogy with the mechanism of luminescence quenching upon pair interactions of Ln3+ ions in inorganic systems, this mechanism is called the cross-relaxation mechanism. The experiments are performed with complexes of Tb3+ with dianions of halogen-substituted fluoresceins (HSFs): 4,5-dibromo-and 4,5-diiodofluorescein, eosin B, eosin, erythrosin, and Rose Bengal in dimethyl sulfoxide. In accordance with this mechanism—exchange energy transfer, L2?(*S
1), Tb3+(7
F
6)→L2?(T
1), Tb3+(7
F
5, 4), allowed by the spin selection rules—an increase in the quantum yield of formation of the triplet state (ΦT) of a ligand L2? and a decrease in the quantum yield of fluorescence (Φfl) are found to take place upon complexation. The efficiency of this process amounts to ~1 in accordance with the equality Φfl+ΦT=1, valid for solutions of HSFs. The possibility of other processes leading to a similar effect, specifically, recharging of the system (as for complexes of HSFs with Eu3+ and 3+) is considered. An example of inductive resonance interactions in complexes of HSFs with Pr3+ is given. The manifestation of equilibrium between outer-sphere and inner-sphere complexes in the photophysics of complexes of metals with HSFs is discussed. 相似文献
5.
Currently, tripositive lanthanide (Ln 3+) ions doped wide band-gap semiconductor nanocrystals (NCs) have been the focus of research interest due to their distinct optical properties and potential applications in optical devices and luminescent biolabels. Because of the low absorptions of parity-forbidden 4f-4f transitions for Ln 3+, it is highly anticipated that the luminescence of Ln 3+ ions embedded in wide band-gap NC lattices can be sensitized efficiently via exciton recombination in the host. For this purpose, the successful incorporation of Ln 3+ into the lattices of semiconductor NCs is of utmost importance, which still remains intractable via conventional wet chemical methods. Here, the most recent progress in the optical spectroscopy of Ln 3+ ions doped wide band-gap semiconductor NCs is discussed. Much attention was focused on the optical properties including electronic structures, luminescence dynamics, energy transfer as well as the up-conversion emissions of Ln 3+ ions in ZnO, TiO 2, SnO 2 and In 2O 3 NCs that were synthesized in our laboratory using wet chemical methods. 相似文献
6.
The results of measuring the efficiencies of the formation of electronically excited states of the Ln 3+ lanthanide ions in aqueous solutions in the processes of radioluminescence and multibubble sonoluminescence are analyzed.
In both cases, electronic excitation occurs due to inelastic collisions of Ln 3+ ions with (for radioluminescence) charged ionizing particles in liquid and (for multibubble sonoluminescence) high-energy
particles, primarily electrons, in the gas phase of cavitation bubbles. In both processes, the efficiencies of exciting ions
whose luminescence states appear in the 4 f-5 d transitions (Ce 3+ and Pr 3+) are significantly lower (by an order of magnitude or larger) than the efficiencies of exciting ions whose luminescence states
appear in the 4 f-4 f transitions (Gd 3+ and Tb 3+). Therefore, the probability of the f- d transitions is lower than the probability of the f- f transitions in lanthanide ions excited by collisions with the charged particles and the relative probabilities of these transitions
are inverted in these processes as compared to photoexcitation.
Original Russian Text ? G.L. Sharipov, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007,
Vol. 85, No. 9, pp. 559–562. 相似文献
7.
The ligand 1-(2-naphthyl)-4,4,4-trifluoro-1,3-butanedionate (Htfnd) has been employed to synthesize six novel ternary-lanthanide complexes in which the synergic ligands were 1,10-phenanthroline-5,6-dione (dione) and 4,5-diazafluoren-9-one (dafone), respectively. Two series of complexes Ln(tfnd) 3dione and Ln(tfnd) 3dafone (Ln=Ho, Pr, Tm) were obtained. These complexes were characterized by elemental analysis, Fourier Transform Infrared spectra and diffused reflectance. After ligand-mediated excitation, Ln(tfnd) 3dione and Ln(tfnd) 3dafone all show the characteristic NIR luminescence of the corresponding Ln 3+ ions (Ln=Ho, Pr, Tm). This can be attributed to the efficient energy transfer from ligands to central Ln 3+ ions, via an antenna effect. The indirect energy transfer in the complexes has been investigated and the differences in the luminescence intensity between Ln(tfnd) 3dione and Ln(tfnd) 3dafone were discussed in detail. The excellent luminescent performances enable these NIR-luminescent complexes to have potential applications in optical amplification operating at 1300 or 1500 nm. 相似文献
8.
Dinuclear lanthanide (Ln=Tb 3+ or Eu 3+) complexes (Ln 2L2) of two octadentate macrocyclic polyaminopolycarboxylic ligands connected through a benzophenone (BP) moiety ( L2) have been synthesized. Sensitized luminescence properties of Ln 2L2 in water have been studied in comparison to those of BP-conjugated mononuclear Ln complexes (Ln L1). The luminescence intensity of Tb 2L2 is lower than that of Tb L1 because of lower triplet quantum yield of the BP moiety. In contrast, Eu 2L2 shows higher intensity than Eu L1. For both Eu complexes, energy level of triplet excited-state BP ( 3BP*) is only 3 kJ mol −1 higher than that of 5D 2 excited-state of Eu 3+. The 5D 2 state formed by a triplet-energy transfer (TET) from 3BP* is therefore deactivated by a back energy transfer (BET) to the ground-state BP, resulting in low luminescence intensity of Eu L1. In contrast, within Eu 2L2, TET from 3BP* to 5D 0 state of two Eu 3+ ions is accelerated, thus leading to higher luminescence intensity. Another notable feature of Eu 2L2 is the luminescence quantum yield independent of its concentration. In contrast, for Eu L1 system, an intermolecular BET occurs from 5D 2 state of Eu 3+ to the ground-state BP conjugated to another Eu L1 complex, resulting in a yield decrease with the concentration increase. 相似文献
9.
The energy transfer from the S 1 levels of p-phenylbenzoyltrifluoroacetone (PhBTA) and dyes to different Ln 3+ ions is studied in nanoparticles (NPs) composed of complexes of this diketone with Ln 3+ and 1,10-phenanthroline (phen) and doped with dye molecules. The quenching rate constants in the NPs consisting from complexes of Pr 3+, Nd 3+, Sm 3+, Eu 3+, Ho 3+, Er 3+, and Tm 3+ are determined from the data on the quenching of sensitized (cofluorescence) and ordinary fluorescence of coumarin 30 (C30) and rhodamine 6G (R6G). The quenching rate constants vary from ≤5 × 10 11 to 10 13 s ?1 for the fluorescence quenching of PhBTA by different Ln 3+ ions, while the quenching of dye fluorescence occurs at rates of the order of 10 9 s ?1. In the case of complexes with the Pr 3+ ions, the fluorescence quenching of PhBTA in NPs composed of its complexes is accompanied by sensitized luminescence of Pr 3+. The quenching observed is due to a nonradiative energy transfer from the S 1 states of ligands and dyes to these ions. It is shown that in NPs composed of complexes with Eu 3+, Yb 3+, and Sm 3+ the cofluorescence of C30 is quenched via the electron-transfer mechanism. The study of quenching of cofluorescence and fluorescence of dyes in NPs composed of mixed complexes of La 3+ and Nd 3+ (Ho 3+) shows that the observed quenching of fluorescence and cofluorescence is governed mainly by the quenching of the S 1 state of dyes when the Nd 3+ (Ho 3+) content does not exceed 5–10% and by the quenching of the S 1 state of a ligand when the Nd 3+ (Ho 3+) content exceeds 50%. It is assumed that the high rate constant of energy transfer from the S 1 level of ligands to ions Pr 3+, Nd 3+, Ho 3+, Er 3+, and Tm 3+ in NPs composed of beta-diketonate complexes is caused by exchange interactions. 相似文献
10.
Sensitized luminescence behavior of lanthanide (Ln=Eu 3+, Tb 3+) macrocyclic cyclen (1,4,7,10-tetraazacyclododecane) complexes bearing one or four benzophenone (BP) moieties as antenna (Ln L1 and Ln L4) has been studied in water. Despite higher molar extinction coefficient of Eu L4 owing to four antennae, it shows only one-thirtieth the luminescence intensity of Eu L1. Energy level of triplet excited-state of BP antenna ( ET) is only a few kJ mol −1 higher than that of 5D 2 excited-state of Eu 3+, thus promoting a back energy transfer (BET) from 5D 2 of Eu 3+ to ground-state BP antennae. On Eu L4 bearing four antennae, BET occurs more rapidly than that on Eu L1, thus exhibiting much weaker luminescence. For Tb complexes, the energy gap between ET of BP antenna and 5D 4 excited state of Tb 3+ is large enough (>13 kJ mol −1), such that practically no BET occurs. The luminescence intensity of Tb L4 is, however, lower (two-third) than that of Tb L1. Time-resolved luminescence measurement reveals that hydration number of Tb 3+ within Tb L4 is twice that within Tb L1. This is because the structural distortion of ligands on Tb L4, caused by an intramolecular dipole-dipole interaction among the BP antennae, allows coordination of higher number of H 2O molecules to Tb 3+, thus leading to a strong Tb luminescence quenching via O-H oscillators. 相似文献
11.
We investigate the luminescent properties of potassium wolframylphosphate glasses doped with Eu 3+, Tb 3+, and Dy 3+ ions whose luminescence is excited by donor-acceptor interaction between the active WO
2
2+
and Ln 3+ ions, as well as the migration of energy in the subsystems of each type of the active ions. Comparison of the obtained data
with the results of investigation of the spectroscopic properties of Ln 3+ in uranylphosphate materials shows that a sufficiently high degree of the ionicity of bonds of Ln 3+ with the atoms of its first coordination sphere is preserved in wolframylphosphate matrices. We show that three stages of
the decomposition of electron excitations are typical of the WO
2
2+
ions in wolframylphosphate glasses doped with Ln 3+ and two stages in nonactivated glasses. The electron excitation energy transfer in the WO
2
2+
−Ln 3+ system occurs due to induction-resonance interaction.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 620–625, September–October, 1997. 相似文献
12.
NaLaP 2O 7 and NaGdP 2O 7 powder samples are prepared by solid-state reactions at 750 and 600 °C, respectively, and the VUV-excited luminescence properties of Ln 3+ (Ln=Ce, Pr, Tb, Tm, Eu) in both diphosphates are studied. Ln 3+ ions in both hosts show analogous luminescence. For Ce 3+-doped samples, the five Ce 3+ 5d levels can be clearly identified. As for Pr 3+ and Tb 3+-doped samples, strong 4f-5d absorption band around 172 nm is observed, which matches well with Xe-He excimer in plasma display panel (PDP) devices. As a result, Pr 3+ can be utilized as sensitizer to absorb 172 nm VUV photon and transfer energy to appropriate activators, and Tb 3+-doped NaREP 2O 7(RE=La, Gd) are potential 172 nm excited green PDP phosphors. For Tm 3+ and Eu 3+-doped samples, the Tm 3+-O 2− charge transfer band (CTB) is observed to be at 177 nm, but the CTB of Eu 3+ is observed at abnormally low energy position, which might originate from multi-position of Eu 3+ ions. The similarity in luminescence properties of Ln 3+ in both hosts indicates certain structural resemblance of coordination environment of Ln 3+ in the two sodium rare earth diphosphates. 相似文献
13.
Time-gated luminescence detection technique using lanthanide complexes as luminescent probes is a useful and highly sensitive
method. However, the effective application of this technique is limited by the lack of the target-responsive luminescent lanthanide
complexes that can specifically recognize various analytes in aqueous solutions. In this work, a dual-functional ligand that
can form a stable complex with Tb 3+ and specifically recognize Hg 2+ ions in aqueous solutions, N,N,N
1
,N
1
-{[2,6-bis(3′-aminomethyl-1′-pyrazolyl)-4-[ N,N-bis(3″,6″-dithiaoctyl)-aminomethyl]- pyridine]} tetrakis(acetic acid) (BBAPTA), has been designed and synthesized. The luminescence
of its Tb 3+ complex is weak, but can be effectively enhanced upon reaction with Hg 2+ ions in aqueous solutions. The luminescence response investigations of BBAPTA-Tb 3+ to various metal ions indicate that the complex has a good luminescence sensing selectivity for Hg 2+ ions, but not for other metal ions. Thus a highly sensitive time-gated luminescence detection method for Hg 2+ ions was developed by using BBAPTA-Tb 3+ as a luminescent probe. The dose-dependent luminescence enhancement of the probe shows a good linearity with a detection
limit of 17 nM for Hg 2+ ions. These results demonstrated the efficacy and advantages of the new Tb 3+ complex-based luminescence probe for the sensitive and selective detection of Hg 2+ ions. 相似文献
14.
Energy transfer and photoextinction from Ln 3+ to Tb 3+ and Eu 3+ in aqueous chloride solutions were studied by absorption, emission and excitation spectra. The energy gaps below the luminescent terms of Gd 3+, Tb 3+ and Eu 3+ are spanned by 10, 5 and 4 quanta, respectively, of the highest energy vibration in aqueous solution, and luminescence is observed in each case. This is not so for other Ln 3+ where nonradiative deactivation dominates over luminescence. It was verified that only Gd 3+ could transfer energy to Tb 3+ and Eu 3+ ions in aqueous or acid solutions. The ions Pr 3+, Nd 3+, Sm 3+, Dy 3+, Ho 3+ and Er 3+ exhibited strong competitive absorption at certain wavelengths, resulting in the photoextinction of Tb 3+ and Eu 3+ emission. 相似文献
15.
Fluorescence emission of Ln 3+ doped nanoparticles is influenced by many factors. Enhancement of fluorescence emission of Ln 3+ doped nanoparticles can be achieved either through an external approach or an internal adjustment. The external approaches mainly include application of core/shell configuration and metal or semiconductor nanoparticles. Varying the crystal phase of the nanoparticle or introducing a codopant sensitizer are the internal approaches frequently used to obtain fluorescence enhancement, which are through inner adjustments to change the local structure, local symmetry and interaction with active ions. In the current work, efforts to obtain luminescence enhancement in Ln 3+ doped nanoparticles through external or internal approaches are reviewed. The important roles of local symmetry and asymmetric interactions with optically active ions are extensively discussed. 相似文献
16.
Lanthanide complexes Ln(bta) 3L 2 (Ln 3+: Eu 3+, Tb 3+ and Ho 3+; bta: benzoyltrifluoroacetonate; L: N-octadecyl-2-hydroxy-4-tetradecyloxybenzal- dimine) are synthesized. Their photoacoustic
(PA) spectra are reported and interpreted. In the region of ligand absorption, PA intensity increases for Eu(bta) 3L 2, Tb(bta) 3L 2 and Ho(bta) 3L 2, respectively. It is found that the PA intensity of the ligand bears a relation to the intramolecular energy transfer process.
By comparison with luminescence spectra, the energy transfer process and phase transition of lanthanide complexes are studied
from two aspects: radiative and nonradiative processes. 相似文献
17.
Binuclear rare earth complexes Ln2L3phen2 (LnIII?=?NdIII, SmIII, EuIII, TbIII, DyIII, YbIII and YIII) with bis-CAPh type ligand - tetramethyl N,N′-(2,2,3,3,4,4-hexafluoro-1,5-dioxopentane-1,5-diyl)bis(phosphoramidate) (H2L) and 1,10-phenanthroline (phen) were synthesized and characterized by elemental analysis, IR, NMR, absorption and luminescence spectroscopy. Luminescence measurements were performed for all the complexes in solid state and for the EuIII, TbIII and YIII complexes - in solution in DMSO as well. The effective energy transfer from organic ligands to LnIII ions strongly sensitizes the LnIII ions emission and under excitation by UV light, the complexes exhibited bright characteristic emission of lanthanide metal centers. It was found that the energy level of the ligands lowest triplet state in the complexes matches better to resonance level of EuIII rather than TbIII ion. Depending on temperature the emission decay times of solid europium and terbium complexes were in the range of 1.5–2.0 ms. In solid state at room temperature the EuIII complex possess intense luminescence with very high intrinsic quantum yield 91% and decay time equal 1.88 ms. 相似文献
18.
The inhibitory effects of lanthanide ions on the generation of free radicals from the reaction of Fe 3+ and Fe 2+ with tert-butyl hydroperoxide ( tBuOOH) were investigated by electron spin resonance (ESR) utilizing 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap.
Peroxyl, alkoxyl, and carbon-centered free radicals generated from Fe 3+- tBuOOH system were successfully trapped by DMPO, whereas peroxyl radicals were not trapped in Fe 2+- tBuOOH system. Peroxyl and alkoxyl radicals are initial radical species generated from Fe 3+ and Fe 2+ systems, respectively. The carbon-centered radicals ( ⋅CH 3) might be attributed to β-scission reaction of these alkoxyl radicals. The ESR signals of DMPO adducts of these radicals
were quenched in the presence of lanthanides (Ln 3+ or [Ln(cit) 2] 3−), in concentration-dependent fashion. Moreover, the quenching effect of Ln 3+ is closely related to the time the Ln 3+ was added into the free-radical-triggered systems. The results reveal that there might be various mechanisms responsible
for inhibiting generation and transformation of the free radicals. If Ln 3+ and iron react with peroxide simultaneously, the complex formation of Ln 3+ with tBuOOH will be the main mechanism of the competitive inhibitory effect of Ln 3+. Whereas if Ln 3+ is added after iron, the inhibitory effect on the ESR signal of DMPO adducts might be interpreted preferentially by the coordination
and magnetic dipole-dipole interaction between Ln 3+ and DMPO adducts. 相似文献
19.
The crystal structure and luminescence properties of CaY 2Ge 3O 10:Ln 3+ (Ln = Eu, Tb) germanates synthesized via a conventional solid-state reaction and an ethylenediaminetetraacetic acid complexing process are studied. The CaY 2 ? x Ln x Ge 3O 10 (Ln = Eu, Tb; x = 0–1.0, 2.0; Δ x = 0.1) solid solutions have a monoclinic structure (space group P2 1/ c, Z = 4), in which dopant ions occupy three nonequivalent noncentrosymmetric sites with different Ca 2+/Ln 3+ ratios. The effect of the synthesis methods, dopant concentrations, and excitation wavelengths on the luminescence properties of the compounds obtained is determined. 相似文献
20.
Undoped and Eu 3+ activated Ln 3BWO 9 (Ln=Y, La, Gd) were prepared by the Pechini method and characterized with X-ray diffraction (XRD) and ultraviolet (UV) spectroscopy. All the samples have the hexagonal phase after heat treatment in the range of 850–1000 °C. The Eu 3+ doped samples emit high-purity red light with peak maximum at about 617 nm under excitation of UV light (~285 nm) at room temperature. When the doping concentration of Eu 3+ is about 20–30%, luminescence intensity reaches the maximum. Luminescence decay curves indicate that Ln 3BWO 9:Eu 3+ exhibits a fast decay time of about 0.5 ms. A possible luminescence mechanism has also been proposed. It is worth noting that both the absorption of host lattice and the charge transfer (CT) transition of Eu 3+ are of great importance to the promising luminescent performance of Ln 3BWO 9:Eu 3+. 相似文献
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