Search

Ce3+, Tb3+ and Ce3+-Tb3+ activated Ba3Y2(B2O5)3 phosphors were synthesized by a sol-gel pyrolysis method. The synthesized phosphors were investigated using X-ray diffraction (XRD) analysis, photoluminescence emission and excitation spectra and luminescence decay curves. In the Ce3+ activated Ba3Y2(B2O5)3 samples, two different Ce3+ centers (marked as Ce(1) and Ce(2)) could exist. The Ba3Y2(B2O5)3:Tb3+ phosphor shows some emission peaks at ∼350–650 nm among which the green emission peak at 540 nm is the strongest. For the Ba3Y2(B2O5)3:Ce3+, Tb3+ co-doped phosphor, the existence of energy transfer process from Ce3+ center to Tb3+ center is confirmed and the interaction mechanism between Ce3+ and Tb3+ in Ba3Y2(B2O5)3:Ce3+,Tb3+ system is dipole-dipole interaction based on Inokuti–Hirayama (I H) model.

Optical thermometry based on the adjacent thermally coupled levels of rare earth ions has been widely studied in the high temperature range, and shows unobvious effect at low temperature range. In this work, we propose a new method to achieve optical thermometry in 10˜300 K range through manipulating the energy transfer from WO66− to Ho3+. A comprehensive five-level rate-equation model is developed to establish the relation between lifetime ratios and temperature. It is found that the lifetime ratios of 540 nm (Ho3+) and 471 nm (WO66−) emissions are dependent on the phonon energy of Y2WO6 host and temperature. The values of sensor sensitivity reach the maximum 2.1% K−1 at 211 K in 30%Ho3+ doped Y2WO6, which is higher than the maximum of the reported phosphors at low temperature. It overcomes the shortcoming of unobvious thermal population of thermally coupled levels in low temperature range through traditional Boltzmann distributing method.

We present an optical pressure sensor KMgF3:Eu2+ suitable for experiments in diamond anvil cell (DAC), which we have calibrated against the ruby reference sensor at pressures ranging from atmospheric up to 30 GPa (300 kbar), at room temperature. The emission spectra of KMgF3:Eu2+ consist of one prominent emission line related to the 6P7/2 → 8S7/2 electronic transition (zero phonon line) accompanied by weak phonon sidebands. The energy of emission at atmospheric pressure was determined to be 27846 ± 7 cm−1. The edge of the excitation spectrum lies at wavelength around 325 nm (30800 cm−1) making it suitable to excite with He-Cd laser (325 nm). The sensor exhibits linear pressure shift of rate equal to −0.815 ± 0.007 cm−1/kbar at pressures up to 300 kbar. The pressure shift of the emission is totally reversible and the pressure sensor is suitable for multi cycle pressure experiments. The sensor's exceptional feature is that excitation and emission spectra lie in near UV, which makes it very convenient to use in high pressure optical measurements in visible and IR region with no interference from the sensor's luminescence.

An analytic absorption function was derived to investigate the dynamics of photoisomerization in a poly(methyl methacrylate) thin film doped with disperse orange 3 (DO3). The temporal absorption measured using the pump-probe method was well-behaved, following an analytic function with a single exponential term. The isomerization and thermal-relaxation rates were evaluated by curve-fitting. The analytic absorption function was validated by measuring the thermal-relaxation rates with the pump separately on and off. Using this function, an analytic method for determining the photoisomerization parameters was demonstrated: for DO3 in poly(methyl methacrylate), the photoisomerization quantum yields for trans-cis and cis-trans processes were determined to be ϕ TC = 0.12 ± 0.01 and ϕ CT = 0.77 ± 0.06 , respectively. The absorption cross section for the cis isomer was measured to be σ C = ( 0.92 ± 0.03 ) × 10 − 16 cm 2 . This analytic method can thus be used to characterize the dynamics of photoisomerization in dye doped thin films.

The novel luminescent polymer-rare earth complexes, denoted as (PFSi-IPDI)-Tb(Ⅲ)-Phen, have been successfully synthesized and can be made into flexible films. Amino-modified fluorine silicone oil-isophorone diisocyanate (PFSi-IPDI) was used as the host macromolecular ligand, and 1, 10-Phenanthroline (Phen) as the secondary small-molecular co-ligand. The luminescent lanthanide complexes were characterized by fourier transform infrared (FITR), scanning electron microscope (SEM), thermogravimetric analysis (TGA). The luminescent properties were investigated through photoluminescence excitation (PLE) and emission (PL) spectroscopy. FTIR analysis verifies the successful preparation and integration of PFSi-IPDI to Tb3+. The comparatively uniform morphological structure can be observed in the images of SEM. The polymer-rare earth complexes display the typical luminescence emission peaks under the excitation wavelength of 330 nm. From the decay curve, the short lifetime (about 0.89 ms) is observed for (PFSi-IPDI)-Tb(Ⅲ)-Phen (0.6 mol/L). Moreover, these luminescent polymer-rare earth complexes possess superior thermal stability (T5 > 195 °C). All the interesting results suggest the potential application of the luminescent polymer-rare earth complexes in green-emitting luminescent materials under high temperature.

The phosphors of Na 2 Ca 2-2 x Eu 2 x Si 3 O 9 ( x = 0, 0.03, 0.05, 0.07, 0.09) were first synthesized by sol-gel method. The crystal phase formations of the phosphors were detected by X-ray powder diffraction (XRD) measurements and the structure refinement. The photoluminescence spectra, the concentration quenching, the luminescence decay curves and the luminescence color chromaticity were measured, respectively. The excitation spectra indicate that the phosphors can be effectively excited by near UV-LED chips. Two kinds of Eu 2+ sites centered at 545 nm and 505 nm were discussed by analyzing the spectra, concentration-dependent luminescence intensity and lifetimes. This is a potential tool for monitoring the bioactivity of 45S5 glass-ceramics in situ.

A green-emitting Tb(III) complex based on siloxane-modified pressure sensitive adhesives (SPSA-Tb(III)) was successfully synthesized by emulsion polymerization. Siloxane-modified pressure sensitive adhesives (SPSA) were used as host materials. The structural coordination, photoluminescence excitation (PLE) and luminescence (PL) spectra, and thermal characterization of this luminescent polymer were investigated. The result from the FT-IR spectra reveals that SPSA have successfully coordinated with the Tb(III) ions. The luminescent analysis indicates that SPSA-Tb(III) displays Tb(III) typical emission peaks at 489, 545, 583, and 622 nm under the excitation of 369 nm. When monitored at 545 nm, strong and sharp excitation bands appear from 300 to 500 nm. And SPSA-Tb(III) has short lifetime (0.25 ms). Meanwhile, SPSA-Tb(III) exhibits high thermal stability (T d = 402 °C) owing to the high bond dissociation energy of Si O bonds. All the results suggest that it is expected to be used as a superior green-emitting material under high temperature.

Tb(III), Eu(III) and Tb(III)/Eu(III) activated silicone fluorinated acrylate (SFA) have been successfully synthesized using the method of semi-continuous emulsion polymerization. The copolymers are characterized by flourier transform infrared (FT-IR), thermal gravity analysis (TGA), photoluminescence excitation (PLE) and emission (PL) spectroscopy. The copolymer containing Tb(III) and Eu(III) ions display green and red luminescent colors under UV light excitation, respectively. The TGA curves show the thermal decomposition temperatures of the copolymers are up to about 300 °C. The PL spectra show a strong green emission at 546 nm ( 5 D 4 → 7 F 5 ) of Tb(III) complexed copolymers, and show a prominent red emission at 615 nm ( 5 D 0 → 7 F 2 ) of Eu(III) complexed copolymers. Different concentrations of Eu(III) and Tb(III) ions are introduced into the copolymer and the energy transfer from Tb(III) to Eu(III) ions in the copolymer was found. Thus, based on the results it can be suggested that SFA:Eu(III), SFA:Tb(III) and SFA:Tb(III)/Eu(III) can be used potentially as luminescent materials.

Eu 2+ -doped borate fluoride BaAlBO 3 F 2 was synthesized by the conventional high temperature solid state reaction. The crystal phase formations were confirmed by X-ray powder diffraction (XRD) measurements and the structure refinement. The photoluminescence (PL) excitation and emission spectra, and the decay curves were investigated. Eu 2+ -doped BaAlBO 3 F 2 phosphor can be efficiently excited by near-UV light and presents narrow blue luminescence band centered at 450 nm. The maximum absolute quantum efficiency (QE) of BaAlBO 3 F 2 :0.05Eu 2+ phosphor was measured to be 76% excited at 398 nm light at 300 K. The thermal stability of the blue luminescence was evaluated by the luminescence decays as a function of temperature. The phosphor shows an excellent thermal stability with high thermal activation-energy on temperature quenching effects because of the rigid crystal lattices.

β-Dicalcium silicate (β-Ca2SiO4) doped with Eu3+ was synthesized by sol–gel method. The luminescence intensity of the mineralization products formed during the hydroxyapatite (Ca10(PO4)6(OH)2, HA) conversion of Eu3+-doped β-Ca2SiO4, in 0.25 M K2HPO4 solution, were detected using luminescence spectroscopy. The results indicated that the luminescence intensity of Eu3+ ion gradually depressed with prolonged mineralization time, and it could hardly be detected with the complete transformation from β-Ca2SiO4:Eu3+ to hydroxyapatite. The change of Eu3+ ionic concentrations in the mineralization products and the final solutions after conversion reaction, were further examined using energy-dispersive X-ray and inductively-coupled plasma mass spectrometry, respectively. This suggested that the process of mineralization can be monitored with the luminescence intensity of Eu3+ ions in the mineralization products. The current study will open up a new and simple in vivo avenue for in situ monitoring hydroxyapatite conversion with a fiber luminescence spectrometer.

The white-light-emitting Na3Gd(PO4)2:Dy3+:Tm3+ phosphors were prepared by high temperature solid-state reaction technique. X-ray diffraction, luminescence excitation, emission, and decay measurements were performed. Upon Gd3+ 8S7/2 → 6IJ (275 nm) excitation, the phosphors emit intense blue and yellow luminescence originating from the Dy3+ 4F9/2 → 6H15/2 and Dy3+ 4F9/2 → 6H13/2 transitions together with the Gd3+ 6P7/2 → 8S7/2 transition at 313 nm. The excitation of Tm3+ ions by 352 nm radiation results also in efficient yellow and blue luminescence. The luminescence enhancement of Dy3+ in the presence of Tm3+ is discussed. The energy transfer process of the Tm3+–Dy3+ system is also explored. This study includes the color perception analysis of synthesized phosphors. The pure white-light is observed with Na3Gd(PO4)2:1%Dy3+:1%Tm3+ and is a promising material for white-lighting applications.

Red-emitting Mn4+-doped A2CaWO6 (A = Ca, Sr, Ba) phosphors have been synthesized by solid-state reaction. The crystallinities and structural properties were examined by X-ray diffraction (XRD). The luminescence properties were studied by luminescence excitation, emission spectra and decay curves. All the synthesized materials emit red light peaking around 680 nm which can be assigned to the 2Eg → 4A2g spin-forbidden transition of Mn4+ ions under the excitation of ultraviolet to blue light. The critical quenching concentrations of Mn4+ in A2CaWO6 (A = Ca, Sr, Ba) system are evaluated. The temperature dependent emission spectra and decay curves (10–520 K) were introduced to evaluate the thermal stability. Surprisingly, the proposed three kinds of red phosphors show quite different thermal behavior, which can be ascribed to the different crystal structure environment of Mn4+ ions in A2CaWO6 (A = Ca, Sr, Ba) system.

Ca2MgSi2O7:Eu2+ fibers were successfully fabricated by a sol–gel assisted electrospinning and subsequently calcination procedure. The phase formation, morphology and the luminescent properties of the fibers were determined. Two strong Eu2+ emission centers were observed in the emission spectrum, which were ascribed to two types of cation sites existing in the Ca2MgSi2O7 lattice, respectively. The Ca2MgSi2O7:Eu2+ fibers reveal bright green-emitting under the excitation of near UV and blue lights. Compared with the powder sample, the luminescent fibers had average grain sizes less than 1 μm and could be synthesized at a relatively lower temperature. The green luminescence in the luminescent fibers was also greatly enhanced. The intensity of the major peak at 539 nm was stronger and had longer average decay time than that at 466 nm. The Ca2MgSi2O7:Eu2+ fibers are expected to be used for optical detectors, bio-labeling and full-color display devices.

Sr2Mg(BO3)2:Ce3+,Li+ and Sr2Mg(BO3)2:Ce3+,Li+,Mn2+ phosphors have been synthesized by conventional solid state reaction technology at 900 °C for 12 h in reducing atmosphere. The phase purity, photoluminescence (PL) properties, thermal stability, energy transfer and luminescent decay curves have been investigated. Sr2Mg(BO3)2:Ce3+,Li+,Mn2+ phosphors show blue and deep-red 1 emission bands. The deep-red emission band is attributed to the energy transfer from Ce3+ to Mn2+. The fluorescence lifetimes of Ce3+ in co-doped sample are shorter than that in single doped one, which confirms that the energy transfer takes place. The phosphors have weak thermal quenching. The luminescence properties of Sr2Mg(BO3)2:Ce3+,Li+,Mn2+ make the phosphor a new bicolor emitting material.

Paper presents luminescence spectra and time resolved spectra of KMgF 3 :Eu 2+ system obtained at different temperatures and pressures, under excitation with 325 nm. At temperatures between 200 K and 292 K the spectra consist of sharp line peaked at 27,830 cm −1 related to 6 P 7/2 → 8 S 7/2 transition in Eu 2+ accompanied by the phonon sideband. Under pressure the red spectral shift with the rate equal to −0.6 cm −1 /kbar is observed. Luminescence decay is single-exponential with the lifetime equal to 5.2 ms independent of pressure and temperature. The emission spectra obtained at temperatures lower than 125 K consist of 5 sharp lines peaked at 27,590 cm −1 , and 27,670 cm −1 , 27,722 cm −1 , 27,766 cm −1 and 27,809 cm −1 , that relative intensity depends on temperature. Pressure shift of these lines was found to be equal to −0.6 cm −1 /kbar; the same as 6 P 7/2 → 8 S 7/2 transition in Eu 2+ , whereas their lifetime is shorter and is equal to 0.7 ms at 100 K. These new lines disappear at temperature greater than 200 K. We tentatively related them to the luminescence of Eu 2+ –F center (fluorine vacancy with electron) complex.

Eu2+-doped KMgPO4 was prepared by high temperature solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurement. Photoluminescence excitation spectrum measurements show that the phosphor can be efficiently excited by near UV light from 230 to 400 nm and presents a dominant luminescence band centered at 470 nm due to the 4f65d1→4f7 transition of Eu2+ ions at room temperature. The influence of temperature on the luminescence and decay times were investigated. There are two distinct Eu2+ sites in KMgPO4 lattices, which present different luminescence and lifetimes. The assignments of the Eu2+ sites were discussed on the base of the luminescence properties and the structure of KMgPO4 crystal. The unusual increase of the decay time of the 4f65d emission in KMgPO4 from 10 K to room temperature was reported.

For the purpose of improvement of the conversion efficiency of solar cells by applying the effect of the wavelength conversion of a rare earth (RE) ion, photoluminescence (PL) and photoluminescence excitation (PLE) spectra of the Sm-doped KMgF3 crystal were investigated. It was found that all the PLE spectra below 500 nm were effective to convert to PL spectra above 540 nm and that the solar cell possessed high spectral response. When a thin disc crystal of KMgF3:Sm was placed on the top of CdS/CdTe solar cell as a precursor for wavelength conversion, both the maximum output power and the conversion efficiency increased by 5% as compared with the case of a pure KMgF3 crystal. The present results are compared with the experimental results of wavelength conversion solar cells performed until now, and some features are discussed.

Luminescence properties of Eu 3+ ions (0.1,1.0 and 6.0 mol%) in K 2 YF 5 crystals are investigated by the site-selective laser-excitation spectroscopy. The excitation spectrum of the 5 Do emission exhibits two strong 7 F o → 5 D o excitation lines together with four weaker lines. Six different emission spectra are obtained under the excitation at each excitation line indicating that there existed at least six different sites for Eu 3+ . The relative intensity of the excitation lines is dependent on the Eu 3+ concentrations. The 5 D o emissions of Eu 3+ show two types of decay behavior with lifetimes of 0.5 and 5.0 ms at 15 K. It is suggested that the fast and slow decays correspond to isolated and paired Eu 3+ ions in K 2 YF 5 . The results are discussed in relation with one dimensional chain structure of the K 2 YF 5 lattice.