Luminescence Spectroscopic Properties Research Articles

Effect of potassium or yttrium introduction in Yb3+-doped germano-gallate glasses on the structural, luminescence properties and fiber processing

Here we report on the effect of potassium or yttrium on the luminescence spectroscopic properties of Yb3+-doped germano-gallate glasses as well as the ability to shape them into optical fibers with the objective of using such glasses to produce near-infrared optical gain medium. Two ytterbium-doped germano-gallate glass systems, (100-x) (28Ga2O3 – 37GeO2 – 23BaO – 12K2O) – xYb2O3 (x = 0, 0.5 and 3 mol.%) and 29.6Ga2O3 – 39.1GeO2 – 24.3BaO – 7 (yY2O3 – zYb2O3) (y = 6.5, 4, 0 and z = 0.5, 3, 7 mol% respectively) have been prepared and the systematic investigation of their thermal, structural, optical and spectroscopic properties have been carried out. The increase in ytterbium oxide content leads to an increase of the glass transition temperature, crystallization temperature and the density of the glasses, as well as induces a red-shift of the cut-off wavelength. Raman spectroscopy analysis shows that both ytterbium oxide addition and potassium substitution by yttrium modify the 3D interconnected germano-gallate glass network. Lifetime diminishes with the increase of Yb3+ concentration but remains higher in the yttrium-containing glasses. We demonstrate that the production of crystal-free light guiding fibers via the preform-to-fiber approach becomes possible only in the yttrium-containing glass system. Cut-back optical attenuation measurements of the produced fibers show minimum losses of 3.3 dB/m at 1310 nm.

Synthesis of GdBO3:Eu3+ nanophosphors via acetylacetone assisted aqueous sol–gel route: Effect of some synthesis parameters

Abstract Nano-sized Eu3+ -doped GdBO3 vaterite type nanophosphors have been synthesized successfully via acetylacetone assisted aqueous sol–gel route. Systematic investigation of the influence of Eu3+ ion content and pH value of the suspension of precursors on structural, morphological and luminescence spectroscopic properties has been performed. X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, field emission-scanning electron microscopy (FE-SEM), Thermogravimetric and differential thermal gravimetry (TG/DTA), room temperature steady and time resolved photoluminescence (PL) spectroscopy techniques were employed to characterize the obtained powder samples. It has been found that the Eu3+ ion content and pH value precursors suspension have important effect on the structural, morphology and emission properties. The XRD analysis reveals that GdBO3: 10% mol Eu3+ synthesized at pH = 2 and pH = 10 exhibit the quasi-purest P63/mmc vaterite structure. The vibrational absorption of (BO3)3- group is assigned to the GdBO3 with calcite type or other vaterite structure namely triclinic and monoclinic. The morphologies of GdBO3 particles size increases with increasing of pH value. All sample present only the orange-red colors emission from 5D0 levels to the 7FJ levels (J = 0–3) of Eu3+ ion. Furthermore, it was found that 10% concentration of Eu3+ presents the quenching of emission in GdBO3. Also, it was that the emission intensity was affected by the pH value and sample with pH = 10 exhibits the highest emission intensity. The asymmetry ratio parameter R between red and orange emission intensities in function of Eu3+ content and pH value is determinate and discussed.

A high color purity red-emission phosphor based on Sm3+ and Eu3+ co-doped Ba3Bi(PO4)3

A series of red-emitting Sm3+/Eu3+ co-doped Ba3Bi(PO4)3 (BBP) phosphors were successfully synthesized through a high temperature solid-state reaction. Luminescence spectroscopic properties and decay kinetics of the samples were studied, revealing an energy transfer from Sm3+ to Eu3+ realized via electric dipole-dipole interaction in Sm3+/Eu3+ couple. The energy transfer efficiency was found to grow with the increase of Eu3+ content while no obvious concentration quenching of Eu3+ emission was detected up to the concentration of 25 %. The phosphor revealed a good thermal stability owing to relatively high activation energy of 0.21 eV deduced. Color coordinates and color purity of BBP:0.05Sm3+, 0.25Eu3+ phosphor were obtained to be (0.624, 0.374) and 88.9 %, respectively. The absorption of Eu3+ within the near ultraviolet spectral range was found to constantly enhance due to energy transfer from Sm3+. The results imply Sm3+/Eu3+ co-doped BBP has a great potential as a narrow-band red light-emitting phosphor applied in WLEDs.

Luminescence properties and host sensitization study of Ba3La(PO4)3:Ce3+ with (V)UV and X-ray excitation

We report on successful synthesis and comprehensive study of luminescence spectroscopic properties and decay kinetics of undoped and Ce3+-doped eulytite structure orthophosphate Ba3La(PO4)3 (BLP) upon excitation with UV-VUV and X-ray photons in a wide temperature range. An intrinsic emission located in the UV range is observed for undoped BLP upon both VUV and X-ray excitation. In turn, emission of Ce3+-doped BLP is represented by interconfigurational 5d-4f transitions arising from Ce3+ ions located in two crystallographic sites which demonstrate average decay time of 22 ns and 40 ns upon intracenter excitation. Pulse X-ray excitation results in appearance of slower (μs or longer) decay components and acceleration of the main 5d-4f emission decay component. Host sensitization of Ce3+ emission is well demonstrated by UV-VUV excitation spectra measurements both at liquid helium and at room temperature. Mechanisms influencing the efficiency and time scale of energy transfer from the host to Ce3+ dopant ions are analyzed and discussed while aiming to estimate the potentials of BLP:Ce3+ for scintillator and X-ray phosphor applications.

VUV spectroscopic properties and 4fn-15d level positions of trivalent lanthanide ions doped into Na3Y(BO3)2

Luminescence spectroscopic properties of lanthanide ions (Ce3+, Pr3+, Gd3+, Tb3+, and Dy3+) doped into Na3Y(BO3)2 were investigated upon UV-VUV excitation with synchrotron radiation. The positions of 4fn–15d state of Ce3+, Pr3+, Tb3+ and Dy3+ in host matrix Na3Y(BO3)2 were deduced according to the excitation spectra. Crystal-field depression D(A), an important parameter to predict the positions of the lowest 4fn–15d levels, was established on the basis of the 5d levels of Ce3+ in Na3Y(BO3)2. Then, the average value of D(A) was obtained and further verified for 4fn–15d configurations of Pr3+, Tb3+ and Dy3+ in Na3Y(BO3)2. Finally, the lowest 4fn–15d levels of the other trivalent lanthanide ions in Na3Y(BO3)2 were predicted. The spectroscopic information on 4fn–15d levels of lanthanide ions in Na3Y(BO3)2 may provide new insights useful for designing of new efficient scintillators and WLED phosphors.

Site occupancy and luminescence of Ce3+ ions in whitlockite-related strontium lutetium phosphate

Ce3+-doped Sr9Lu(PO4)7 polycrystalline material has been synthesized using a solid state reaction at high temperature. Luminescence spectroscopic properties and emission decay kinetics have been studied upon UV-VUV excitation. Emission from Ce3+ ions located in two types of crystallographic sites has been identified in low-temperature spectra. Ce3+ ions have been shown to prefer occupying Sr2+ sites rather than Lu3+ sites. The temperature-dependent decay curves of Ce3+ 5d→4f emission demonstrate an excellent luminescence thermal stability.

3,4,3-LI(1,2-HOPO): In vitro formation of highly stable lanthanide complexes translates into efficacious in vivo europium decorporation

The spermine-based hydroxypyridonate octadentate chelator 3,4,3-LI(1,2-HOPO) was investigated for its ability to act as an antenna that sensitizes the emission of Sm(III), Eu(III), and Tb(III) in the Visible range (Φ(tot) = 0.2-7%) and the emission of Pr(III), Nd(III), Sm(III), and Yb(III) in the Near Infra-Red range, with decay times varying from 1.78 μs to 805 μs at room temperature. The particular luminescence spectroscopic properties of these lanthanide complexes formed with 3,4,3-LI(1,2-HOPO) were used to characterize their respective solution thermodynamic stabilities as well as those of the corresponding La(III), Gd(III), Dy(III), Ho(III), Er(III), Tm(III), and Lu(III) complexes. The remarkably high affinity of 3,4,3-LI(1,2-HOPO) for lanthanide metal ions and the resulting high complex stabilities (pM values ranging from 17.2 for La(III) to 23.1 for Yb(III)) constitute a necessary but not sufficient criterion to consider this octadentate ligand an optimal candidate for in vivo metal decorporation. The in vivo lanthanide complex stability and decorporation capacity of the ligand were assessed, using the radioactive isotope (152)Eu as a tracer in a rodent model, which provided a direct comparison with the in vitro thermodynamic results and demonstrated the great potential of 3,4,3-LI(1,2-HOPO) as a therapeutic metal chelating agent.

Application of molecular dynamics techniques and luminescent probes to the study of glass structure: the SiO 2–GeO 2 case

In this paper, we report on the results obtained from molecular dynamic simulation of a Eu 3+-doped germanosilicate glass. This simulation provides further information on the structure. In particular it reveals a homogeneous distribution of SiO 4 and GeO 4 units, a decrease of defects compared to SiO 2 and GeO 2 glasses, and a trend to clustering of the doping ions. Using the modified crystal-field theory, the luminescence spectroscopic properties have been computed and comparison with experimental data has allowed a correlation of the spectral features with two main types of local environment depending on the coordination number and on the medium-range arrangement around the doping ions.

Theoretical approach to the problem of finding effective luminophors in the isocarbostyril series

It has been established that the main reason for the low fluorescence quantum yield of unsubstituted isocarbostyril (I) is the thermally activated intersystem crossing Sππ ⇝ Tnπ. The positions in the molecule at which the introduction of substituents should cause the greatest bathochromic displacement of the absorption spectra have been determined on the basis of data from quantum-chemical calculations. Lowering of the S1 level results in a decrease in the probability of intersystem crossing and, as a consequence, in an increase in the quantum yield. A number of derivatives of I have been synthesized, and their luminescence-spectroscopic properties have been investigated. The causes of the instability of 4-hydroxy- and 4-NH2-isocarbostyrils have been discussed.

ChemInform Abstract: Synthesis and Luminescence Spectroscopic Properties of Dibenzo(b,i)phenoxazine and Some of Its Derivatives.

AbstractThermal cyclization of the aminonaphthol (I) with the dihydroxynaph‐thalene (II) gives the dibenzophenoxazine (III) which is transformed into the derivatives (V) ‐ (VII) by common methods.

ChemInform Abstract: Synthesis and Luminescence Spectroscopic Properties of Benzo(f)quinoline Derivatives with Fused Alicycle.

AbstractDas Azomethin (II) reagiert mit den cyclischen Ketonen (I) über die Zwischenstufen (III) oder (V) zu den Benzochinolinen (IV).