The luminescence of Eu2+ in mixed phase system

The dependence of the structure of the hosts on the M ion radius in MMgAl10O17 (M = Be, Mg, Ca, Sr, Ba, Pb, Eu, Mn, Fe, Co, Ni, Zn, Cd, Sn) system was studied and the luminescence of Eu2+ the mixed phase system was discussed. When M ion radius is less than 0.10 nm, the system MMgAl10O17 constructs by the mixed phases consisting of manegtoplumbite and spinel, alpha-alumina or spinel and alpha-alumina. In the mixed phase of manegtoplumbite and spinel and alpha-alumina, Eu2+ ion preferentially occupies lattice site of the cations in manegtoplumbite well matched with the radius and charge of Eu2+. There exists only d-->f transition emission of Eu2+ and no characteristic emission of Eu3+ occurs in those hosts. In the mixed phase of spinel and alpha-alumina, Eu2+ can enter the lattice site of Mg2+ ion or Al3+ ion and the d-->f and f-->f transition of Eu2+ can been observed respectively. Meanwhile, since the radius and charge of matrix lattice ions substituted by Eu2+ do not match with those of Eu2+, the valence state of Eu2+ is unstable. Eu2+ is partly changed into Eu3+ and the emission of Eu3+ is obviously observed even under the condition of reduction atmosphere. If reaction temperature is more than 1 150 degrees C, Al2O3 forms alpha-Al2O3 structure, the f-->f transition of Eu2+ appears. If reaction temperature is less than 1 150 degrees C, a mixed phase of alpha-Al2O3 and gamma-Al2O3 is formed, the f-->f transition of Eu2+ disappears and a new band emission from d-->f transition of Eu2+ occurs.

Vibrational spectrum and luminescence properties of CaAl2B2O7 : Eu3+

The vibrational spectrum of the CaAl2B2O7 was investigated. It was shown that the vibrations of the BO3 groups are present in the region of 1400 similar to 600 cm(-1), and the bands at 519 nm(-1) may originate from the AlO6 vibration. The luminescence properties of Eu3+ in CaAl2B2O7 were investigated. It was found that the Eu3+ ion in CaAl2B2O7 occupies two different sites. Investigation on the phonon sideband of Eu3+ indicates that BO3 groups are present in the:surroundings of Eu3+ ions.

Luminescence enhancement by blending PVK with blue PPV copolymer

The PL and EL properties of the polymer blends of PVK and blue PPV copolymer were studied. Considerable enhancement of both the photoluminescent and the electroluminescent intensity were observed by using the polymer blends as emission layer in the LED devices. The energy transfer process and the formation of exciplex in the polymer blends were also discussed.

Preparation and luminescence properties of the ternary europium complex incorporated into an inorganic polymer matrix by a sol-gel method

Ternary europium complexes with thenoyltrifluoroacetone (TTA) and phenanthroline (phen) were incorporated into SiO2/polymer matrix by a sol-gel method. The gels exhibit the characteristic emission bands of europium ion. In addition, Eu3+ presents a longer fluorescence lifetime in gel than in the corresponding pure complex powder. Concentration effects on the luminescence intensity were investigated. The reasons that are responsible for above results are also discussed in the context.

Valence stability and change of Eu(II)in oxides

Valence stability and change of Eu(II) in oxides have been studied by luminescence spect a. The results show that the valence stability and change of Eu(II)in oxides is closely related to the radius and electric charge of positive ions substituted by Eu(II) and crystal structure of the host such as Al2O3 which can form alpha-Al2O3 single phase and alpha-Al2O3 and gamma-Al2O3 mixed phases under different reaction temperatures. A, fairly good explanation is made by the proposed relation between energy coefficient and crystal structure for the first time to the observed experiment results. if the energy coefficients of substitution ions is more than that of Eu(II), the lattice substitution of Eu(II)for these ions is not occured generally and valence stare of Eu(II)is not stable and be easily changed into Eu(III). The lattice of gamma-Al2O3 can stablize the valence state of Eu(II)within certain coped concentration and in alpha-Al2O3 crystal lattice Eu(II)can be easily changed into Eu(III).

Study on the energy transfer between UO22+ and Eu3+ in sol-gel derived titania matrix by luminescence spectroscopy

The TiO2 gel doped with UO22+ and Eu3+ has been prepared by a sol-gel method. The quenching of the UO22+ emission by Eu3+ and the energy transfer from the excited state of UO22+ to the ground state oh Eu3+ have been investigated. The energy transfer has been studied by the measurement of luminescence lifetime tau, calculations of energy transfer efficiency eta(ET) and energy transfer rate W-ET The experimental results indicated that the quenching is combined static and dynamic mechanism, but the static mechanism is dominant.

Synthesis, crystal structure and luminescence studies of a lanthanide coordination polymer with a new double betaine ligand

A novel europium(III) coordination polymer with a new double betaine derivative, {[Eu(L')(NO3)(H2O)(3)](NO3)(2). 3.5H(2)O}(n) (L-1 = 1,3-bis(pyridinio-4-carboxylato)-propane) has been synthesized and its structure determined. Its luminescence properties have also been studied. The title metal carboxylate coordination polymer contains centrosymmetric dimeric units in which each pair of metal ions is linked by a pair of syn-anti carboxylato-O,O' groups, and each pair of such dimeric units is bridged by the backbones of L-1 ligands to form infinite double chains in the b direction. These metal carboxylate chains are further cross-linked by hydrogen bonds among both coordinated and discrete nitrate anions, aqua ligands and lattice water molecules to form a three-dimensional network. Luminescent data show that the L-1 ligand is a good energy donor and the complex has a relatively long luminescent lifetime.

Preparation and luminescence properties of terbium-Sal complex in-situ synthesized in silica matrix by a two-step sol-gel process

In-situ synthesis of terbium complex with salicylic acid (Sal) in silica matrix was made by a two-step sol-gel process. The terbium complex with salicylic acid was formed in sol-gel derived silica gel, and confirmed by the luminescence excitation spectra and infrared(IR) spectra. As compared to the pure terbium complex powder, the silica gel containing terbium complex exhibits its characteristic emission and presents a longer fluorescence lifetime than that for the pure complex. The luminescence properties of the complex containing;silica gel were investigated and compared with that of both terbium doped the silica gel and thp pure complex powder. The reasons leading to the above results were also discussed.

Luminescence and its temperature effects on Sm2+ in alkaline earth borates

The luminescence of Sm2+ in alkaline earth berates (BaB8O13, SrB4O7 and SrB6O10) is reported. The temperature effects on luminescence and decay time of Sm2+ are studied. Due to the thermal population, D-5(1) --> F-7(J) transitions of Sm2+ in BaB8O13, SrB4O7 and SrB6O10 are observed at room temperature. The f-d broad emission transitions of Sm2+ in SrB4O7 and SrB6O10 are observed at high temperature whereas no f-d transition is observed in BaB8O13.

Luminescent properties of divalent samarium-doped strontium hexaborate

The valence change of samarium from trivalent to divalent in strontium hexaborate (SrB6O10) prepared in air is observed. The temperature dependence of the luminescence and vibronic transitions of Sm2+ are studied. The Sm2+ ions occupy three crystallographic sites. With increasing temperature, the D-5(0)-->F-7(0) transition line exhibits red shifts, and the half-width increases. At room temperature, due to the thermal population through the 4f(5)5d channel, the D-5(1)-->F-7(J) transitions are observed even though the vibrational energy is very close to the energy gap between the D-5(1) and D-5(0) levels in the host. A coupled phonon energy of about 108 cm(-1) is determined from the vibronic transitions of Sm2+ in the host.

Vibrational spectrum and luminescence properties of the system Al2O3-B2O3-Eu2O3

The system Al2O3-B2O3-Eu2O3, with Al/B ratio varying from 4.5 to 2 and Eu/(Al+B)=0.02, was synthesized by solid state reaction. The vibrational spectra of the system Al2O3-B2O3-Eu2O3 were investigated. It was found that no definite change in the regions of 1200 similar to 1000 cm(-1) due to the adsorption BO4 groups with decreasing Al/B ratio, indicating no Al3+ ion was substituted by Eu3+ ions and other changes revealed that there was an amorphous phase and Eu3+ ions may dope into the amorphous phase. The studies on the luminescent properties of the system Al2O3-B2O3 also show that Eu3+ ions dope into amorphous phase. The investigations on the phonon sideband of Eu3+ indicate that electron-phonon coupling strength decreases with Al/B ratio change from 3 to 2, leading to the non-radiative decay rate decreases and the Eu3+-emission intensity increase.

Luminescence characteristics of europium and terbium complexes with 1,10-phenanthroline in-situ synthesized in a silica matrix by a two-step sol-gel process

In-situ synthesis of europium and terbium complexes with 1,10-phenanthroline (phen) in silica matrix by a two-step sol-gel process has been proposed. The formation of europium and terbium complexes with phen in sol-gel derived silica gel were confirmed by the luminescence excitation spectra. The silica gels that contain in-situ synthesized europium and terbium complex exhibit the characteristic emission bands of the rare earth ions. Furthermore. the rare earth ions present longer fluorescence lifetimes than the comparable pure complex powder and the complexes dissolved in ethanol solutions. The luminescence properties of the silica gels codoped with europium (or terbium) and phen were also investigated with respect to the gels doped with europium (or terbium). (C) 1999 Elsevier Science B.V. All rights reserved.

Classification of valence changes of trivalent rare earth ions in alkaline earth borates using artificial neural networks

The investigations of classification on the valence changes from RE3+ to RE2+ (RE = Eu, Sm, Yb, Tm) in host compounds of alkaline earth berate were performed using artificial neural networks (ANNs). For comparison, the common methods of pattern recognition, such as SIMCA, KNN, Fisher discriminant analysis and stepwise discriminant analysis were adopted. A learning set consisting of 24 host compounds and a test set consisting of 12 host compounds were characterized by eight crystal structure parameters. These parameters were reduced from 8 to 4 by leaps and bounds algorithm. The recognition rates from 87.5 to 95.8% and prediction capabilities from 75.0 to 91.7% were obtained. The results provided by ANN method were better than that achieved by the other four methods. (C) 1999 Elsevier Science B.V. All rights reserved.

Stability and luminescence properties of Tb (III) complexes with adrenaline

Stability and luminescence properties of Tb (III) complexes with adrenaline have been studied. The Tb (III) complexes with adrenaline are quite stable. The fluorescence spectra of the Tb (III) complexes with adrenaline show the characteristic fluorescence bands of Tb (III) ions which are attributed to energy transfer from ligands to Tb (III) ions.

Structural characterization and luminescence studies of new lanthanide(III) complexes with nicotinic and isonicotinic acid N-oxides

Four new polymeric lanthanide(III) complexes of nicotinic acid N-oxide and isonicotinic acid N-oxide have been synthesized and structurally determined. In the isomorphous compounds [(Ln(L-1)(3) (H2O)(2))(n)]. 4nH(2)O(HL1 = nicotinic acid N-oxide; Ln = Eu, 1; Ln = Er, 2) the lanthanide(III) ions form infinite double chains along the b direction through the coordination of bridging carboxylate and N-oxide groups. The chains are cross-linked through hydrogen bonds between aqua ligands and uncoordinated N-oxide groups and between aqua ligands and lattice water molecules, to form a three-dimensional network. [(Eu(L-2)(2)-(H2O)(4))(n)](NO3)(n). nH(2)O (HL2 = isonicotinic acid N-oxide, 3) has a polymeric structure in which the europium (III) ions are connected into infinite chains by pairs of syn-syn carboxylate groups. Adjacent chains are interlinked by hydrogen bonds between aqua ligands and N-oxide groups to form a layer parallel to the (100) plane, and such layers are connected by hydrogen bonds between nitrate anions and aqua ligands, and between oxide groups and lattice water molecules, into a three-dimensional network. In [(Er-2(L-2)(4)(H2O)(10))](NO3)(2). H2O, 4, dinuclear units are inter-linked into a three-dimensional network through hydrogen bonding between aqua ligands and N-oxide groups of both bidentate bridging and unidentate L-2 ligands. Factors affecting the formation of coordination chains and dinuclear units are discussed. Luminescence properties of 1 and 3 have also been studied. (C) 1998 Elsevier Science Ltd. All rights reserved.