The Luminescence Properties and Intramolecular Energy Transfer of Rare Earth Complexes with Aromatic Carboxylic Acids

The triplet state energies of para aminobenzoic acid and nicotinic acid were determined by means of low temperature phosphorescence spectrometry. The energy matches between them and the resonant emitting energy levels of Eu 3+ , Tb 3+ , Sm 3+ , Dy 3+ were studied. The intramolecular energy transfer processes from the two aromatic carboxylic acid ligands to rare earth ions were also discussed on the basis of the measurement results of luminescence intensities, lifetimes and quantum efficiencies.

Studies on Intermolecular Energy Transfer and Relaxation Processes in Solid Rare Earth Complexes by Photoacoustic Spectroscopy

The photoacoustic spectra of Eu ( benz)(3) (.) ( phen)(2) ( benz: benzoate, phen: phenanthroline) and Eu-0.(8)Ln(0.2)(benz)(3)(.)(phen)(2)(Ln(3+) : La3+ or Nd3+) were reported. The intermolecular energy transfer processes were studied from the point of the nonradiative transitions. Combined with the fluorescence spectroscopy, photoacoustic spectroscopy reflects the variation of the luminescence efficiencies of solid samples. The luminescence efficiency increases when La3+ is introduced, but it decreases greatly when Nd3+ is added, which is due to the difference of intermolecular energy transfer processes. The models of intramolecular and intermolecular energy transfer and relaxation processes were established.

Improved anti-Stokes energy transfer between rare earth ions in Er(0.5)Yb(9.5):FOV oxyfluoride vitroceramics explains the strong color reversal

The widely used energy transfer theory is a foundation of luminescence, in which the rates of Stokes and anti-Stokes processes have the same calculation formula. An improvement on the anti-Stokes energy transfer to explain the fluorescence intensity reversal between the red and green fluorescence of Er（0.5）Yb（9.5）：FOV is reported in the present article. The range of the intensity reversal Z was measured to be 877. Dynamic processes for 16 levels were simulated. A coefficient, the improvement factor of the intensity ratio of Stokes to anti-Stokes processes in quantum Raman theory compared to classical Raman theory, is introduced to successfully describe the anti-Stokes energy transfer. A new method to calculate the distance between the rare earth ions, which is critical for the energy transfer calculation, is proposed. The validity of these important improvements is also proved by experiment.

Study on Spectral Overlap Model for Energy Transfer between J-Multiplets in Rare Earth-Doped Crystals

Based on the experimental data of KY 3F 10∶Tm 3+ reported by Diaf, K ushida′s spectral overlap model (SOM) of energy transfer between J-multipl ets was studied. Firstly, with the help of the Inokuti-Hirayama and Yokota-Tan imoto models, the luminescence decay curve of 3H 4 of Tm 3+ ion was fitted, and the fitted values of corresponding interaction parameters C D A of energy transfer and C DD of energy migration were obtained. Seco ndly, by compared with Kushida′s SOM in which the relevant Judd-Ofelt approxim ative transition rates are known, the average overlap integrals of S DD and S DA were obtained. For S DD, how to treat the contributi on of the electronic-dipole (ED) crystal field transition forbidden by C 4v site symmetry in the calculation of S DD was discussed. For S DA we suggested that, by including the contribution of the phonon sideba nds in the analysis of oscillator strength of transition, Kushida′s SOM of ED- ED resonant energy transfer rate can be extended to non-resonant phonon-assist ed D-A energy transfer. The strengths and widths of phonon sidebands in this ex ample were discussed, and the results were reasonably good.

Tunable Emission and Energy Transfer of the Novel KY_(1-x)(MoO_(4))_(2-y)(WO_(4))y:xLn^(3+)(Ln^(3+)=Dy^(3+),Eu^(3+),and Tm^(3+))Single-phase White Luminescence Phosphor for White LEDs

The phosphors of KY_(1-x)(MoO_(4))_(2-y)(WO_(4))y:xLn^(3+)(Ln^(3+)=Tm^(3+),Dy^(3+),Eu^(3+))were synthesized by using a sol-gel method.Then,the crystal structure,luminescence properties,energy transfer,and white emission of the prepared materials were researched.The molar ratio of the anion group on the photoluminescence(PL)emission and excitation intensity were investigated,revealing that the optimum intensity could be obtained by using=3:1.The optimal Dy^(3+) doping concentration of KY(MoO_(4))1.5(WO4)0.5was obtained.In addition,the color-tunable emissions of Dy^(3+)/Eu^(3+)-codoped KY(MoO_(4))1.5(WO4)0.5phosphors were observed because of the effective energy transfer(ET)from Dy^(3+)to Eu^(3+)ions.Finally,by doping appropriate concentrations of Tm^(3+),Dy^(3+),and Eu^(3+)and different concentrations of(WO_(4))^(2-),white light emitting phosphors KY_(0.92)(WO_(4))2:0.01Tm^(3+),0.06Dy^(3+),0.01Eu^(3+)with excellent color-rending properties were obtained.The chromaticity coordinate was calculated as(x=0.3238,y=0.3173),closing to the artificial daylight(D65,x=0.313,y=0.329)illuminant,and which indicates the potential application of near ultraviolet White light-emitting diodes(WLEDs).

Doped Organic Electroluminescence from a Novel Rare Earth Complex Tb(3-metho)_3phen

A novel rare earth complex Tb(3 metho) 3phen was synthesized and characterized. The complex was doped into PVK to improve the conductivity and film forming property of Tb(3 metho) 3phen. A device with a structure of ITO/PVK∶Tb(3 metho) 3phen /Al was fabricated to study the electroluminescent properties of Tb(3 metho) 3phen. And the optoluminescent and AFM properties of this device were also studied, which proved the existence of energy transfer from PVK to Tb(3 metho) 3phen. As a result, a pure green emission with sharp spectral band at 547.5 nm was observed.

Photoluminescence and Energy Transfer Process in Bi³⁺/Sm³⁺Co-Doped Phosphate Zinc Lithium Glasses

Present paper reports on luminescence characteristics of individually doped Bi3+: PZL, Sm3+: PZL and co-doped (Bi3+/Sm3+): PZL (50P2O5-30ZnO-20LiF) glasses prepared by a melt quenching method. The results revealed that Bi3+: PZL glass exhibited a broad emission peak at 440 nm (3P1→1S0) under excitation wavelength 300 nm (1S0→3P1). Sm3+: PZL doped glass has shown a prominent orange emission at 601 nm (4G5/2→6H7/2) with an excitation wavelength 403 nm (6H5/2→4F7/2). Later on Bi3+ is added to Sm3+: PZL glass by increasing its concentrations from 0.1 - 1.5 mol%. By co-doping Bi3+ to Sm3+: PZL glass, Sm3+ emission intensity has been considerably enhanced till 1.0 mol% due to energy transfer from Bi3+ to Sm3+ and when its concentration exceeds this critical value (1.0 mol%) there has been a drastic decrease in Sm3+ emission which is explained accordingly from photoluminescence spectra, energy level diagram and lifetime measurements.

Multiple Energy Transfers in Rare Earth Complex-Doped SiO_2 Spheres

Silica spheres doped with Eu （TTFA）3 and/or Sm（TTFA）3 were synthesized by using the modified Stober method. The transmission electron microscope image reveals that the hybrid spheres have smooth surfaces and an average diameter of about 210 nm. Fluorescence spectrometer was used to analyze the fluorescence properties of hybrid spheres. The results show that multiple energy transfer processes are simultaneously achieved in the same samples co-doped with Eu （TTFA）3 and Sm（TTFA）3, namely between the ligand and Eu^3＋ ion, the ligand and Sm^3＋ ion, and Sm^3＋ ion and Eu^3＋ ion. Energy transfer of Sm^3＋→Eu^3＋ in the hybrid spheres leads to fluorescence enhancement of Eu^3＋ emission by approximately an order of magnitude. The lifetimes of the hybrid spheres were also measured.

A Theoretical Model of Energy Transfer between Rare Earth Ions in Crystals

The limitation of the random walk theory of energy transfer between rare earth ions in crystals published in literatures is pointed out in this paper. A modified model, which can be used in any level of rare earth ion concentration when the interaction between donor and acceptor is different from that between donors, is introduced. measured fluorescence lifetimes of Yb^3＋：YAl3（BO3）4 This model has been applied to analyze the with a series of Yb^3＋ concentrations.

Study on Luminescence Properties of a Novel Rare Earth Complex Eu(TTA)_2(N-HPA)Phen

A novel rare earth complex Eu（TTA）2（N-HPA）Phen （TTA = thenoyltrifluoroacetone, N-HPA = N-phenylanthranilic acid, and phen = 1,10-phenathroline ）, which contains three different ligands, was synthesized. The Eu complex was blended with poly N-vinylcarbazole （PVK） in different weight ratios and spin coated into films. The luminescence properties of films were investigated and energy transfer between PVK and the complex was discussed. Multilayer structural devices consisting of ITO/PVK： Eu （TTA）2 （N-HPA） phen/BCP/Alq3/Al were fabricated with PVK ： Eu （TTA）2（N-HPA） as light-emitting layer. Increasing the concentration of Eu in the PVK thin film would inhibit the emission of PVK to different degrees. Finally, the pure red luminescence of europium（ Ⅲ ） was observed when the doping weight ratio was approximately 1 ： 5, which indicated an effective energy transfer from PVK to rare earth complex.

Luminescence and Energy Transfer Properties of Ca_2Gd_8(SiO_4)_6O_2∶A(A=Pb^(2+), Tm^(3+))Phosphors

Ca_2Gd_8(SiO_4)_6O_2∶ A(A=Pb^(2+), Tm^(3+))phosphors were prepared through the sol-gel process. X-ray diffraction(XRD), scanning electron microscopy(SEM)and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicate that the phosphors crystallized completely at 1000 ℃. SEM study reveals that the average grain size is 300～1000 nm. In Ca_2Gd_8(SiO_4)_6O_2∶Tm^(3+) phosphors, the Tm^(3+) shows its characteristic blue emission at 456 nm(~1D_2—~3F_4)upon excitation into its ~3H_6—^(1)D_2(361 nm), with an optimum doping concentration of 1mol% of Gd^(3+) in the host lattices. In Ca_2Gd_8(SiO_4)_6O_2∶Pb^(2+), Tm^(3+) phosphors, excitation into the Pb^(2+) at 266 nm(~1S_0—~3P_1)yields the emissions of Gd^(3+) at 311 nm(~6P—~8S)and Tm^(3+) at 367 nm(~1D_2 —~3H_6)and 456 nm(~1D_2—~3F_4), indicating that energy transfer processes of Pb^(2+)—Gd^(3+) and Pb^(2+)—Tm^(3+) have occurred in the host lattices.

Synthesis and Photoluminescence Properties of Rare Earth Complexes with 3-Allyl-2, 4-Pentanedione

In order to combine the merits of rare earth organic complexes with excellent material performances of polymers, a polymerizable chelating agent, 3-allyl-2, 4-pentane dione (APD), was synthesized by phase transfer catalysis and its rare earth complexes were prepared. The compounds were characterized by EA, IR and (()~1H NMR.) Their UV spectra and fluorescence spectra were investigated. The effects of allyl on the luminescence properties of the complexes were studied. The results show that the sensitization of APD is changed by allyl in comparison with that of acetyl acetone (acac), and it becomes an ideal novel ligand of Eu. In addition, intramolecular energy transfer mechanism in the luminescence process in the complexes was also discussed in detail.

Luminescence Characteristic of a New Novel Coprecipitate Rare Earth Complexes

The Tb 3+ ion was introduced in the Tb x Eu 1- x (BSA) 3phen as a bridge to make the energy transfer process from ligand to the Eu 3+ complex more efficient. The characteristics of the device used Tb x Eu 1- x (BSA) 3phen as the emission material with the different ratio of x were discussed. When x is 0.5, the device emits pure red color with the maximal brightness of 100 cd·m -2 and has good commutation property. The role of the Tb 3+ ion in the energy transfer process between the ligand and the Eu 3+ ion and the mechanism of energy transfer process were also discussed.

Synthesis, luminescence properties and energy transfer of binary and ternary rare earth complexes with aromatic acids and 1,10-phenanthroline

A series of binary and ternary rare earth (Gd, Eu, Tb) complexes with ortho hydroxyl benzoic acid, pam aminobenzoic acid, nicotinic acid and 1,10-phenanthroline were synthesized. Phosphorescence spectra and lifetimes of Gd complexes were measured and the lowest triplet state energies of gadolinium binary complexes end the intramolecular energy transfer efficiencies were determined. The luminescence properties and energy transfer process of Eu3+ and Tb3+ complexes were discussed.

Roles of crystal defects in the persistent luminescence of Eu^(2+), Dy^(3+) co-doped strontium aluminate based phosphors

The roles of different point defects in persistent luminescence of SrAl2O4：Eu,Dy phosphors were investigated. The research results showed that Dyer plays an important role in the persistent luminescence of SrA1EO4：Eu, Dy phosphors. It can serve as the electron trap of suitable depth for persistent luminescence. V~ does not serve as the electron trap of suitable depth, but its existence can increase the depth of electron traps. There is interaction between the Dy^3＋（ DySr ） and the Eu^2＋（Eu^x Sr ）, and only if the distance between the Dy^3＋（DySr） and the Eu^2＋ （Eu^x Sr） is close enough, the Dyer can work as an effective electron trap. The point defect of V＂ Sr can be hole trap, but the change of its density in crystal matrix does not arouse the obvious change of persistent luminescence.

Effects of SrO/Al_2O_3 Molar Ratio on the Luminescent Characteristics of Rare-Earth Strontium Aluminate Phosphors

The study on the effects of SrO/Al 2O 3 molar ratio on the crystalline phases and photoluminescence characteristics of strontium aluminate phosphors co-activated with Eu 2+ and Dy 3+ were conducted by X-ray powder diffractometry, fluorescence spectrometer and photometer. The strontium aluminate luminescent materials with different SrO/Al 2O 3 molar ratio emit the visible lights with different color tone after removal of excitation. The peak wavelengths of the emission spectra drift in the direction of short wave, the quantity of Sr 4Al 14O 25 crystalline phase increases and the afterglow time lengthens with the SrO/Al 2O 3 reduction. The results show that when the SrO/Al 2O 3 molar ratio is near 1, the photoluminescence materials have high luminescent intensity, and when it is near 0.75, they have long afterglow time. However, when SrO/Al 2O 3 molar ratio is more than 1, the luminescent materials appear strong alkaline in water solution; when SrO/Al 2O 3 molar ratio is much less than 0.75, the samples need a higher temperature to be sintered.

Effects of 4f Electron Characteristics and Alternation Valence of Rare Earths on Photosynthesis: Regulating Distribution of Energy and Activities of Spinach Chloroplast

Chloroplasts were isolated from spinach treated with taCl3, CeCl3, and NdCl3. Because of owning 4f electron characteristics and alternation valence, Ce treatment presented the highest enhancement in light absorption, energy transfer from LHC Ⅱ to PS Ⅱ, excitation energy distribution from PS Ⅰ to PS Ⅱ, and fluorescence quantum yield around 680 nm. Compared with Ce treatment, Nd treatment resulted in relatively lower enhancement in these physiological indices, as Nd did not have alternation valence. La treatment presented the lowest enhancement, as La did not have either 4f electron or alternation valence. The increase in activities of whole chain electron transport, PS ⅡDCPIP photoreduction, and oxygen evolution of chloroplasts was of the following order： Ce〉Nd 〉La〉 control. However, the photoreduction activities of spinach PS I almost did not change with La, Ce, or Nd treatments. The results suggested that 4f electron characteristics and alternation valence of rare earths had a close relationship with photosynthesis improvement.

Energy Transfer from PVK to Europium Complex in Electroluminescence

The spectra of solutions, films and light emitting diodes of rare earth complexes were studied. It is shown that the absorption spectra of PVK dopping rare earth complexes can be red shifted to the visible region and overlap with the emission spectrum of PVK, which makes the energy transfer possible from PVK to the rare earth ion.

Nd^(3+)/Yb^(3+) co-doped mid-infrared luminescence fluorobromide glass with energy transfer and zero-thermal-quenching IR emission

Nd^(3+)/Yb^(3+)co-doped fluorobromide glass samples were prepared by melt quenching.The mid-infrared(MIR)luminescence of the Nd^(3+)/Yb^(3+)co-doped fluorobromide glass was investigated by Br-doping reduces the phonon state density of the matrix.The 3.9μm MIR luminescence of the samples excited at 793 and 980 nm pump excitation was investigated in detail.There is an effective mutual energy transfer process between Nd^(3+)and Yb^(3+).It is proved under 793 nm excitation that the luminescence of Nd^(3+)at 3.9μm is reduced by effective energy transfer from,Nd^(3+):2 H11/2→Yb^(3+):2 F5/2,At the same time,it is proved that the effective energy transfer from Yb^(3+):2 F5/2→Nd^(3+):2 H11/2 under the excitation of 980 nm enhances the luminescence of Nd^(3+)at 3.9μm.In addition,it is found that the samples still have good infrared(IR)luminescent properties when the temperature changes.The emission cross-sectional area and the absorption cross-sectional area areσem(3.87×10^(-20)cm^(2))andσabs(4.25×10^(-20)cm^(2)).The fluorescence decay characteristics of the sample at 3.9μm at the 2 H11/2 level were investigated and the fluorescence lifetime was calculated.The gain performance of the sample was calculated and analyzed,which can reach 4.25×10^(-20)cm^(2).Those results prove that Nd^(3+)/Yb^(3+)co-doped fluorobromide glass is the potential mid-infrared laser gain material.

Emission of Rare Earth Complex Tb_(0.5)Eu_(0.5) (asprin)_3phen

The coprecipitate Tb 0.5 Eu 0.5 3phen was synthesized. By doping the rare earth complex into polymer PVK, the EL device was fabricated with the structure of ITO/PVK∶RE/PBD/Al. Compared with the device using PVK/Eu(asprin) 3phen blend as the light emitting layer, the emission of Eu 3+ in the PVK/Tb 0.5 Eu 0.5 (asprin) 3 phen blend is greatly enhanced along with the quenching of the emission of PVK.