Luminescence of unusual bismuth in barium berates BaB8O13 : Bi)

The luminescence of unusual divalent bismuth (Bi2+) in BaB8O13 is reported. The emission band with maximum peak at 592 nm corresponds to the P-2(3/2)-->P-2(1/2) transition of Bi2+ in the matrix and the excitation spectrum with two bands peaked at 470 and 580 nm respectively corresponds to two split crystal-field levels of P-2(3/2) state. The small Stokes shift (similar to 350 cm(-1)) reflects the rigid structure of the host for the Bi2+ ions.

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.

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.

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.

Luminescence properties of rare-earth (Eu3+ and Tb3+) complexes with paraaminobenzoic acid and 1,10-phenanthroline incorporated into a silica matrix by sol-gel method

Ternary complexes of europium and terbium with paraaminobenzoic acid and 1,10-phenanthroline (Eu(p-ABA)(3). phen . 2H(2)O and Tb(p-ABA)(3). phen . 2H(2)O, where p-HABA = paraaminobenzoic acid and phen = 1,10-phenanthroline) were introduced into a silica matrix by sol-gel method. The luminescence behavior of the complexes in silica gels was studied in comparison with the. corresponding solid-state complexes by means of emission, excitation spectra, and Lifetimes. Within the range of effective dopant concentrations, the luminescence intensities of rare-earth complexes in silica gel increase with the increasing of their dopant concentration. The lifetimes of rare-earth ions (Eu3+ and-Tb3+) in silica gel doped with europium and terbium complexes become longer than those in pure complexes. Very small amounts of rare-earth complexes doped in silica gel matrix can exhibit excellent luminescence properties, (C) 1998 Elsevier Science Ltd.

The reduction of Eu3+ in SrB6O10 prepared in air and the luminescence of SrB6O10 : Eu

The reduction of Eu3+ to Eu2+ in SrB6O10 prepared in air by a high-temperature solid state reaction was studied. The luminescent properties of Eu2+ in this matrix show f-d broad band emission peaking at about 386 and 432 nm at room temperature. A charge compensation mechanism is proposed as a possible explanation. The luminescence of Eu3+ with f-f transitions was studied in this sample and reflected that the Eu3+ ion occupied a site with non-centro-symmetry. The ESR spectrum was used to detect the existence of Eu2+ in the samples. (C) 1998 Elsevier Science S.A.

Synthesis, luminescence, energy transfer and Langmuir-Blodgett films of amphiphilic complexes of rare earths with monooctadecyl phthalate

Three new amphiphilic rare earth complexes with only two organic long chains Ln (MOP)(2)Cl (MOP=monooctadecyl phthalate, Ln=Eu, Tb, Gd) were synthesized and characterized by elemental analysis. The complexes (Eu, Tb) showed good luminescence property with long fluorescence lifetime, whereas the intensity and lifetime of Tb complex are greater than those of Eu complex, By measuring the triplet energy levels of ligand based on energy transfer mechanism, above phenomena have been well explained. The Langmuir films of the complexes on the air/water interface were also studied and the results show that all of them have good film-forming property.

Studies on plant calmodulin and its interaction with antagonist W-7 by Ln(3+) luminescence probes

Plant calmodulin (CaM) has been extracted from cauliflower, and the purified CaM has been identified with the activation of NAD kinase (NADK) and the inhibition effect of CaM antagonist W-7. CaM's intrinsic fluorescence and Tb3+ fluorescence showed that there was one tyrosine residue and four metal-binding sites in cauliflower CaM. Based on Forster-type nonradiative energy theory, the distances of Tyr --> site III, IV have been determined, and these are 1.23 nm (Tyr --> site III ) and 1.18 nm(Tyr --> site IV). The Eu3+ and Tb3+ fluorescence probes showed that the combination of CaM with W-7 resulted in significant change on CaM's conformation, but did not affect coordination environment of metal-binding sites.

Relationship between luminescence and matrices in the system Al2O3-B2O3-Ce2O3

The system Al2O3-B2O3-Ce2O3, with Al/B ratio varying from 4.5 to 2 and Ce/(Al + B) = 0.02, has been prepared at the temperature from 1 200 to 1 400 degrees C. Relationship between luminescence and matrices in the system Al2O3-B2O3-Ce2O3 was investigated. It was found that some changes of the matrices occurred with Al/B ratio varying from 4.5 to 2. These results lead to a great change in luminescence properties, indicating variation of Ce-surroundings of crystal field. With the decrease of the ratio from 3 to 2, the excitation and emission peaks shift to shorter wavelengths. it was also found that a new type of rare earth luminescent materials was obtained with appropriate Al/B ratio.

Luminescence properties of the rare earth (Eu3+ and Tb3+) complexes with 1,10-phenanthroline incorporated in silica matrix by a sol-gel method

Europium and terbium complexes with 1,10-phenanthroline were introduced into silica gel by the sol-gel method. The luminescence behavior of the complexes in silica gels was studied compared with the corresponding solid state complexes by means of emission, excitation spectra and lifetimes. (C) 1998 Published by Elsevier Science S.A. All rights reserved.