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Europium-doped LaF3 nanoparticles have been prepared by the ionic reaction in the ethanol at 60 degrees C. From the XRD pattern of nanoparticles and the emission spectra of Eu3+ ions, it has been concluded that the Eu3+ ions could easily substitute the La3+ sites and the solid solution La(1-x)Eu(x)F3 can be synthesized. Due to very low phonon energies of LaF3 matrix, the 5D1 emission of Eu3+ ions in La(1-x)Eu(x)F3 nanoparticles can be observed at room temperature when doping concentration of Eu3+ ions is lower than 30 mol%. The quenching process of 5D1 emission can be attributed to cross-relaxation. Since clusters of Eu3+ ions and resonance energy transfer only occurs within one particle due to the hindrance by the particle boundary, the concentration quenching resulted from resonance energy transfer between neighboring Eu3+ ions occurs at higher Eu3+ concentrations in the Eu3+ doped LaF3 nanoparticles.

The complex of Eu(TTA)3Dipy was in situ synthesized in vinyltriethoxysilane-derived sol–gel glass (organically modified silicate, ORMOSIL) during heat treatment to obtain homogeneous transparent monolith by using thenoyltrifluoroacetone (TTA) as ligand and 2,2′-dipyridyl (Dipy) as synergic agent. The ORMOSIL doped with the Eu(TTA)3Dipy complex exhibits enhanced red light emission (∼614 nm) under UV excitation. The steady-state PL spectra at various temperatures and time-resolved luminescence spectra of the Eu(TTA)3Dipy complex in situ synthesized in the ORMOSIL and the complex polycrystalline powder dissolved in ethanol solution were measured. The photophysical properties responsible for the electronic transitions and excitation energy migration of the complex in ORMOSIL were discussed in this paper by comparison to that in ethanol. [Copyright &y& Elsevier]

Abstract: The luminescence behavior of the dibenzoyl methane europium(III) complexes (Eu(DBM)3) in sol–gel derived host materials have been investigated. The steady-state excitation and emission spectra and the time-resolved spectra of the 1% EuCl3 and 3% DBM co-doped gel indicated an efficient ligand-to-metal energy transfer. The Eu(DBM)3 complexes in the gel showed longer 5D0 lifetimes in comparison with Eu(DBM)3·3H2O complexes. The luminescence intensity of the 1% EuCl3 and 3% DBM co-doped gel decreased continuously with increasing temperature and time of heat treatment, which indicated the gradual decomposition of the Eu(DBM)3 complexes in the gel during heat treatment. [Copyright &y& Elsevier]

The in situ synthesis processes and luminescence behaviors of the europium complexes of β-diketonates (i.e., acetylacetonate, trifluoroacetylacetonate and hexafluoracetylacetonate) in sol–gel-derived host materials have been investigated. The emission and excitation spectra of the EuCl3 and β-diketonates co-doped gels were different from those of a EuCl3 singly doped gel, indicating that the Eu3+ β-diketonates complexes are in situ synthesized in the EuCl3 and β-diketonates co-doped gels. The emission intensities of the EuCl3 and β-diketonates co-doped gels were much stronger than that of the EuCl3 singly doped gel. The luminescence decay curves from the 5D0 state in the EuCl3 and β-diketonates co-doped gels, which were obtained by monitoring the 5D0→7F2 emission line, were satisfactorily fitted by a single-exponential function. The luminescence lifetimes of the EuCl3 and β-diketonates co-doped gels significantly changed with the kind of β-diketonate. The luminescence behaviors of the EuCl3 and β-diketonates co-doped gels with heat-treatment temperature also changed with the kind of β-diketonate. [Copyright &y& Elsevier]

Luminescence behavior of Eu(TTFA)3 and TbSSA co-doped gel has been investigated. The excitation and emission spectra of the EuCl3 and thenoyltrifluoroacetone co-doped gel appeared to exhibit intramolecular energy transfer from the coordinated thenoyltrifluoroacetonate to the europium ions, and the luminescence behavior of sulphosalicylic acid and TbCl3 co-doped gel also indicated the synthesis of TbSSA in the gel. The luminescence behavior of x% Eu(TTFA)3 and (1–x)% TbSSA (x=0–1) co-doped gel changed significantly with the ratio of Eu(TTFA)3 and TbSSA. By adjusting the ratio of the Eu(TTFA)3 and TbSSA in the gel, the luminescence of different colors which resulted from the mixture of the emission bands of Eu3+ ions and Tb3+ ions can be observed. [Copyright &y& Elsevier]

The 2-pyridinecarboxylic acid europium(III) complexes (Eu(PA)3) could be dissolved by acetic acid (HAC). The relationship between absorbance and concentration of Eu(PA)3 complexes in HAC was linear. The Eu(PA)3 complexes have been in situ synthesized in the 1% EuCl3 and 3% 2-pyridinecarboxylic acid (PA) co-doped gels. The concentration of the Eu(PA)3 complexes which had been in situ synthesized in the gel was obtained by measuring absorption spectra of the HAC solution in which the Eu(PA)3 complexes in the gel had been extracted according to the relationship between the absorbance and the concentration of the Eu(PA)3 complexes in HAC. The dependence of the concentration of the Eu(PA)3 complexes which were in situ synthesized in the gel on the heat treatment time at 90 °C have been determined. [Copyright &y& Elsevier]

Homogeneous transparent monolithic samples doped with Eu(TTA)3(TPPO)2 chelate have been prepared by using the in situ synthesis technique. The time-resolved spectra of Eu(TTA)3(TPPO)2 chelate dispersed in both vinyltriethoxysilane-derived sol–gel glass and ethanol solution were measured at room temperature. The possible mechanisms responsible for the electronic transitions and excitation energy migration of the chelate in the sol–gel glass were discussed. The decay curves of the 5D0 level of the europium ions in Eu(TTA)3(TPPO)2 chelate in above two matrices were also obtained in the temperature range from 13 to 300 K and the temperature dependence of the lifetime of the 5D0 level was studied. [Copyright &y& Elsevier]

Abstract: The phonon sideband spectra (PSB) and emission spectra of Eu3+ in transparent SiO2–PbF2 glass and glass ceramics containing β-PbF2 nanocrystals were investigated. The local vibration around Eu3+ ion in glass and glass ceramics was obtained by analyzing the phonon sideband associated with the Eu3+:5D2→7F0, and the Judd–Ofelt parameters were calculated from emission spectra. According to PSB, phonon energy around Eu3+ ion in glass ceramics was much lower than that in glass. The J–O parameters and emission spectra indicated that the Eu3+ ions had entered into crystalline environment of the β-PbF2 nanocrystals. [Copyright &y& Elsevier]

Abstract: Europium-doped LaF3 nanoparticles have been prepared by the ionic reaction in the ethanol at 60°C. From the XRD pattern of nanoparticles and the emission spectra of Eu3+ ions, it has been concluded that the Eu3+ ions could easily substitute the La3+ sites and the solid solution La1−x Eu x F3 can be synthesized. Due to very low phonon energies of LaF3 matrix, the 5D1 emission of Eu3+ ions in La1−x Eu x F3 nanoparticles can be observed at room temperature when doping concentration of Eu3+ ions is lower than 30mol%. The quenching process of 5D1 emission can be attributed to cross-relaxation. Since clusters of Eu3+ ions and resonance energy transfer only occurs within one particle due to the hindrance by the particle boundary, the concentration quenching resulted from resonance energy transfer between neighboring Eu3+ ions occurs at higher Eu3+ concentrations in the Eu3+ doped LaF3 nanoparticles. [Copyright &y& Elsevier]

The in situ synthesis processes and luminescence behaviors of the 2-pyridinecarboxylic acid europium (PA:Eu3+) complexes in sol–gel derived host materials have been investigated. The Raman scattering spectrum of the 1 mol% EuCl3 and 3 mol% PA co-doped gel was similar to that of the PA:Eu3+ complex powders that were synthesized in ethanol, which indicated that the PA:Eu3+ complexes have been in situ synthesized in the 1 mol% EuCl3 and 3 mol% PA co-doped gel. The excitation and the emission spectra of the 1 mol% EuCl3 and 3 mol% PA co-doped gels, which were similar to that of the PA:Eu3+ complex powders, also indicated an efficient ligand-to-metal energy transfer which belonged to the complexes. The decay curve of the 1 mol% EuCl3 and 3 mol% PA co-doped gel can be fitted to a double-exponential function. After the gel was heated at 90 °C for 12 h, the decay curve can be fitted to a single-exponential function due to vaporization of the most residual water in the gel. The dependence of luminescence intensity and the decay time of x% EuCl3 and 3x% PA co-doped gels that were heated at 90 °C for 12 h on various concentrations of the EuCl3 and PA were also investigated. The luminescence intensity and the decay time reached a maximum for 1 mol% EuCl3 and 3 mol% PA co-doped gel that were heated at 90 °C for 12 h. [Copyright &y& Elsevier]

The luminescence behavior of the europium (Eu) complexes with hexafluoracetylacetonate (HFA:Eu3+ complexes) in the ORMOSIL matrices has been investigated. The steady-state excitation and emission spectra of the 1 mol.% EuCl3 and the 3 mol.% hexafluoracetylacetonate (HFA) co-doped gel were similar to that of the HFA:Eu3+ complexes powders which were synthesized in ethanol solution, which indicated that the HFA:Eu3+ complexes have been synthesized in the 1 mol.% EuCl3 and the 3 mol.% HFA co-doped gel. The time-resolved spectra of the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gel exhibited the ligand-to-metal energy transfer process, which also confirmed the synthesis of the HFA:Eu3+ complexes in the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gel. The decay curves of the luminescence 5D0 state obtained by monitoring the 5D0→7F2 emission line for the HFA:Eu3+ complexes powders and for the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gel could both be fitted to a single-exponential fitting function. The temperature of heat treatment has significant influence on the luminescence behavior of the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gel. The luminescence intensities of the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gel reached a maximum at approximately 110 °C and decreased gradually with increasing temperature. However, the 5D0 excited-state lifetimes of the Eu3+ ions in the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gels increased gradually with increasing temperature. [Copyright &y& Elsevier]

The luminescence of Eu2+ in alkaline earth aluminates of the type SrO·Al2O3 has been studied. In SrO·Al2O3:Eu2+ phosphor, green Eu2+ luminescence is observed from Eu2+ on the two different strontium sites present in the lattice. Their concentration quenching processes of the two inequivalent Eu2+ ions are investigated, respectively, and the corresponding concentration quenching mechanism is verified as dipole-dipole interaction. The value of the critical transfer distance is calculated. [Copyright &y& Elsevier]