Synthesis,characterization and luminescent properties of europium complexes with 2,4,6‐tris‐(2‐pyridyl)‐s‐triazine as highly efficient sensitizers

Using 2,4,6‐tris‐(2‐pyridyl)‐s‐triazine (TPTZ) as a neutral ligand, and p‐hydroxybenzoic acid, terephthalic acid and nitrate as anion ligands, five novel europium complexes have been synthesized. These complexes were characterized using elemental analysis, rare earth coordination titrations, UV/vis absorption spectroscopy and infrared spectroscopy. Luminescence spectra, luminescence lifetime and quantum efficiency were investigated and the mechanism discussed in depth. The results show that the complexes have excellent emission intensities, long emission lifetimes and high quantum efficiencies. The superior luminescent properties of the complexes may be because the triplet energy level of the ligands matches well with the lowest excitation state energy level of Eu³⁺. Moreover, changing the ratio of the ligands and metal ions leads to different luminescent properties. Among the complexes, Eu₂(TPTZ)₂(C₈H₄O₄)(NO₃)₄(C₂H₅OH)·H₂O shows the strongest luminescence intensity, longest emission lifetime and highest quantum efficiency. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and characterization of novel europium β‐diketonate organic complexes for solid‐state lighting

Volatile Eu complexes, namely Eu(TTA)₃Phen, Eu_(x)Y_(1‐x)(TTA)₃ Phen; Eu_(x)Tb_(1‐x)(TTA)₃Phen; Eu, europium; Y, yttrium; Tb, Terbium; TTA, thenoyltrifluoroacetone; and Phen, 1,10 phenanthroline were synthesized by maintaining stichiometric ratio. Various characterization techniques such as X‐ray diffraction (XRD), photoluminescence (PL) and thermo gravimetric analysis/differential thermal analysis (TGA/DTA) were carried out for the synthesized complexes. Diffractograms of all the synthesized complexes showed well‐resolved peaks, which revealed that pure and doped organic Eu³⁺ complexes were crystalline in nature. Of all the synthesized complexes, Eu_0.5 Tb_0.5(TTA)₃Phen showed maximum peak intensity, while the angle of maximum peak intensity for all complexes was almost the same with slightly different d‐values. A prominent sharp red emission line was observed at 611 nm when excited with light at 370 nm. It was observed that the intensity of red emissions increased for doped europium complexes Eu_(x)Y_(1‐x)(TTA)₃Phen and Eu_(x)Tb_(1‐x)(TTA)₃ Phen, when compared with Eu complexes. Emission intensity increased in the following order: Eu(TTA)₃Phen > Eu_0.5 Tb_0.5(TTA)₃Phen > Eu_0.4 Tb_0.6(TTA)₃Phen > Eu_0.5Y_0.5(TTA)₃Phen > Eu_0.4Y_0.6(TTA)₃Phen, proving their potential application in organic light‐emitting diodes (OLEDs). TGA showed that Eu complexes doped in Y³⁺ and Tb³⁺ have better thermal stability than pure Eu complex. DTA analysis showed that the melting temperature of Eu(TTA)₃ Phen was lower than doped Eu complexes. These measurements infer that all complexes were highly stable and could be used as emissive materials for the fabrication of OLEDs. Copyright © 2012 John Wiley & Sons, Ltd.     

In Vitro Cytotoxic Activities,DNA‐, and BSA‐Binding Studies of a New Dinuclear Copper(II) Complex with N‐[3‐(Dimethylamino)propyl]‐N′‐(2‐carboxylatophenyl)‐ Oxamide as Ligand

A new dinuclear copper(II) complex bridged by N‐[3‐(dimethylamino)propyl]‐N′‐ (2‐carbo‐xylatophenyl)oxamide (H₃dmapob), and endcapped with 2,2′‐diamino‐4,4′‐bithiazole (dabt), namely [Cu₂(dmapob)(dabt)(CH₃OH)(pic)]·(DMF)_0.75·(CH₃OH)_0.25 has been synthesized and characterized by elemental analysis, molar conductivity measurement, infrared and electronic spectra studies, and single‐crystal X‐ray diffraction. In the crystal structure, both copper(II) ions have square–pyramidal coordination geometries. The Cu···Cu separation through the oxamido bridge is 5.176(9) Å. A two‐dimensional supramolecular framework is formed through hydrogen bonds and π–π stacking interactions. The reactivities toward herring sperm DNA and bovine serum albumin (BSA) show that the complex can interact with the DNA via intercalation mode and bind to the BSA responsible for quenching of tryptophan fluorescence by the static quenching mechanism. The in vitro anticancer activities suggest that the copper(II) complex is active against the selected tumor cell lines. The influence of different bridging ligands in dinuclear complexes on the DNA‐ and BSA‐binding properties as well as anticancer activities is preliminarily discussed.     

Luminescence enhancement of terbium(III) perchlorate by 2,2′‐dipyridyl on bis(benzylsulfinyl)methane complex and luminescence mechanism

A novel ternary complex, Tb₂L₄·L′·(ClO₄)₆·8H₂O, has been synthesized using bis(benzylsulfinyl)methane as the first ligand L and 2,2′‐dipyridyl as the second ligand L′. The ternary complex was characterized by element analysis, molar conductivity, coordination titration analysis, infrared, thermogravimetric‐differential scanning calorimetric and ultraviolet spectra. The results indicated that the composition of the complex was Tb₂L₄·L′·(ClO₄)₆·8H₂O (L = C₆H₅CH₂SOCH₂SOCH₂C₆H₅; L′ = Dipy). Fourier transform infrared results revealed that the perchlorate group was bonded with the Tb(III) ion by the oxygen atom, and the coordination was bidentate. The fluorescent spectra illustrated that the complex displayed characteristic fluorescence in the solid state. After the introduction of the second ligand, 2,2‐dipyridyl, the relative emission intensity and fluorescence lifetime of the ternary complex Tb₂L₄·L′·(ClO₄)₆·8H₂O were enhanced compared to the binary complex TbL_2.5(ClO₄)₃·3H₂O. This indicated that the presence of both organic ligand bis(benzylsulfinyl)methane and the second ligand 2,2‐dipyridyl could sensitize the fluorescence intensity of Tb(III) ion, and introduction of the 2,2‐dipyridyl group resulted in an enhancement of the fluorescence of the Tb(III) ternary rare earth complex. The strongest characteristic fluorescence emission intensity of the ternary complex was 9.36 times that of the binary complex. The phosphorescence spectra and fluorescence lifetime of the complex were also measured. Copyright © 2014 John Wiley & Sons, Ltd.     

Green‐light emission through energy transfer from Ce3+ to Tb3+ ions in the Li2SO4–Al2(SO4)3 system

An energy transfer process from Ce³⁺ to Tb³⁺ ions was successfully achieved in a Li₂SO₄–Al₂(SO₄)₃ mixed‐sulphate system. A wet‐chemical synthesis was employed to prepare the Li₂SO₄–Al₂(SO₄)₃ system by doping Ce³⁺ and Tb³⁺ ions individually as well as collectively. The phases were identified using X‐ray diffraction studies. The as‐prepared samples were characterized by FT‐IR and photoluminescence measurements. Green‐light emission was exhibited by Ce³⁺, Tb³⁺ co‐doped Li₂SO₄–Al₂(SO₄)₃ system, thus, indicating its potential as a material for display devices or in the lamp industry.     

Influence of rare earth elements (Y,Gd and Lu) on the luminescent properties of green phosphor ZnMoO4:Tb3+

(Zn,Ln_x)MoO₄:Tb³⁺ (Ln = Y³⁺, Gd³⁺ and Lu³⁺) were prepared using the co‐precipitation method. Phase impurity, morphology and composition were investigated by power X‐ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The experimental results show that crystal structure is not destroyed after doping an appropriate amount of Y³⁺, Gd³⁺ and Lu³⁺. EDS analysis reveals that Y, Gd and Lu have been successfully doped into ZnMoO₄. In addition, the morphology of the phosphors is notably improved, exhibiting homogeneous dispersion morphology and irregular shapes of particle size ~ 0.5–1 µm. The luminescent intensity of (Zn,Ln_x)MoO₄:Tb³⁺ (Ln = Y³⁺, Gd³⁺ and Lu³⁺) phosphor is obviously higher than that of ZnMoO₄:Tb³⁺ phosphor. The energy transfer process between trivalent rare earth ions indicates that the inert earth ions can act as an energy bridge from MoO₄^2‐ to Tb³⁺. Copyright © 2013 John Wiley & Sons, Ltd.     

Antioxidation and DNA‐Binding Properties of Binuclear Lanthanide(III) Complexes with a Schiff Base Ligand Derived from 8‐Hydroxyquinoline‐7‐carboxaldehyde and Benzoylhydrazine

8‐Hydroxyquinoline‐7‐carboxaldehyde (8‐HQ‐7‐CA), Schiff‐base ligand 8‐hydroxyquinoline‐7‐carboxaldehyde benzoylhydrazone, and binuclear complexes [LnL(NO₃)(H₂O)₂]₂ were prepared from the ligand and equivalent molar amounts of Ln(NO₃)?6 H₂O (Ln=La³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Dy³⁺, Ho³⁺, Er³⁺, Yb³⁺, resp.). Ligand acts as dibasic tetradentates, binding to Ln^III through the phenolate O‐atom, N‐atom of quinolinato unit, and C?N and ? O? C?N? groups of the benzoylhydrazine side chain. Dimerization of this monomeric unit occurs through the phenolate O‐atoms leading to a central four‐membered (LnO)₂ ring. Ligand and all of the Ln^III complexes can strongly bind to CT‐DNA through intercalation with the binding constants at 10⁵–10⁶ M ^?1. Moreover, ligand and all of the Ln^III complexes have strong abilities of scavenging effects for hydroxyl (HO^.) radicals. Both the antioxidation and DNA‐binding properties of Ln^III complexes are much better than that of ligand.     

Structures and luminescent sensors of mixed‐counterions based salen‐type lanthanide coordination polymers

Reactions of N,N′‐bis (salicylidene)‐1,2‐cyclohexanediamine (H₂L) with mixed lanthanide counterions of LnCl₃·6H₂O and Ln (NO₃)₃·6H₂O afford six H₂L lanthanide coordination polymers, e.g. {[Pr(H₂L)₂(NO₃)₂Cl]·2CH₂Cl₂}_n ( 1 ); {[Ln(H₂L)_1.5(NO₃)₃]₂·5CHCl₃·mCH₃OH}_n [Ln = Sm ( 2 ), Eu ( 3 ), Gd ( 4 ), Tb ( 5 ) and Yb ( 6 ); m = 1 ( 2 – 5 ); m = 0 ( 6 )]. X‐ray crystallographic analysis reveals that complex 1 exhibits three‐dimensional diamondoid topologic structure and complexes 2 – 6 are of two‐dimensional structure. Luminescent spectra show that complexes 1 and 6 have characteristic near‐infrared (NIR) emission of praseodymium (III) and ytterbium (III) ions and complexes 2 – 5 emit luminescence in the visible region. Complexes 3 and 6 reveal sensitive luminescence responses to formaldehyde.     

Energy transfer between Ce3+ → Gd3+ or Tb3+ in KNaSO4 microphosphor

KNaSO₄ microphosphor doped with Ce,Gd and Ce,Tb and prepared by a wet chemical method was studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) characterization. KNaSO₄ has a 5‐µm particle size detected by SEM. KNaSO₄:Ce³⁺,Tb³⁺ showed blue and green emission (at 494 nm, 557 nm, 590 nm) of Tb³⁺ due to ⁵D₄ → ⁷F_J (J = 4, 5, 6) transitions. KNaSO₄:Ce³⁺,Gd³⁺ showed luminescence in the ultraviolet (UV) light region at 314 nm for an excitation at 271 nm wavelength. It was observed that efficient energy transfer took place from Ce³⁺ → Gd³⁺ and Ce³⁺ → Tb³⁺ sublattices indicating that Ce³⁺ could effectively sensitize Gd³⁺ or Tb³⁺ (green emission). Ce³⁺ emission weakened and Gd³⁺ or Tb³⁺ enhanced the emission significantly in KNaSO₄. This paper discusses the development and understanding of photoluminescence and the effect of Tb³⁺ and Gd³⁺ on KNaSO₄:Ce³⁺. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and fluorescence properties of 1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazol derivatives and their terbium complexes

Eight novel 1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazol derivatives have been designed and synthesized, and their corresponding Tb³⁺ complexes were also prepared successfully. The fluorescence properties and fluorescence quantum yields of the target complexes were investigated, the results showed that the ligands were an efficient sensitizer for Tb³⁺ luminescence, and the target complexes exhibited characteristic fluorescence emissions of Tb³⁺ ion. The fluorescence intensity of the complex substituted by chlorine was stronger than that of other complexes. The substituents' nature has a great effect upon the electrochemical properties of the target complexes. The results showed that the introduction of the electron‐withdrawing groups tended to decrease the oxidation potential and highest occupied molecular orbital energy levels of the target Tb³⁺ complexes; however, introduction of the electron‐donating groups can increase the corresponding complexes' oxidation potential and highest occupied molecular orbital energy levels. Copyright © 2014 John Wiley & Sons, Ltd.     

Intense green‐, red‐emitting Tb3+, Tb3+/Bi3+‐doped and Sm3+, Sm3+/La3+‐doped Ca2Al2SiO7 phosphors

This paper focuses on an optical study of a Tb³⁺/Bi³⁺‐doped and Sm³⁺/La³⁺‐ doped Ca₂Al₂SiO₇ phosphor synthesized using combustion methods. Here, Ca₂Al₂SiO₇:Sm³⁺ showed a red emission band under visible light excitation but, when it co‐doped with La³⁺ ions, the emission intensity was further enhanced. Ca₂Al₂SiO₇:Tb³⁺ shows the characteristic green emission band under near‐ultraviolet light excitation wavelengths, co‐doping with Bi³⁺ ions produced enhanced photoluminescence intensity with better colour tunable properties. The phosphor exhibited better phase purity and crystallinity, confirmed by X‐ray diffraction. Binding energies of Ca(2p), Al(2p), Si(2p), O(1s) were studied using X‐ray photoelectron spectroscopy. The reported phosphor may be a promising visible light excited red phosphor for light‐emitting diodes and energy conversion devices.     

Fluorescence enhancement of europium (III) perchlorate by 1,10‐phenanthroline on the 1‐(naphthalen‐2‐yl)‐2‐(phenylsulthio)ethanone complex and luminescence mechanism

A novel ligand, 1‐(naphthalen‐2‐yl)‐2‐(phenylsulthio)ethanone was synthesized using a new method and its two europium (Eu) (III) complexes were synthesized. The compounds were characterized by elemental analysis, coordination titration analysis, molar conductivity, infrared, thermo gravimetric analyzer‐differential scanning calorimetry (TGA‐DSC), ¹H NMR and UV spectra. The composition was suggested as EuL₅ · (ClO₄)₃ · 2H₂O and EuL₄ · phen(ClO₄)₃ · 2H₂O (L = C₁₀H₇COCH₂SOC₆H₅). The fluorescence spectra showed that the Eu(III) displayed strong characteristic metal‐centered fluorescence in the solid state. The ternary rare earth complex showed stronger fluorescence intensity than the binary rare earth complex in such material. The strongest characteristic fluorescence emission intensity of the ternary system was 1.49 times as strong as that of the binary system. The phosphorescence spectra were also discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Thermoluminescence and photoluminescence studies on γ‐ray‐irradiated Ce3+,Tb3+‐doped potassium chloride single crystals

Single crystals of KCl doped with Ce³⁺,Tb³⁺ were grown using the Bridgeman–Stockbarger technique. Thermoluminescence (TL), optical absorption, photoluminescence (PL), photo‐stimulated luminescence (PSL), and thermal‐stimulated luminescence (TSL) properties were studied after γ‐ray irradiation at room temperature. The glow curve of the γ‐ray‐irradiated crystal exhibits three peaks at 420, 470 and 525 K. F‐Light bleaching (560 nm) leads to a drastic change in the TL glow curve. The optical absorption measurements indicate that F‐ and V‐centres are formed in the crystal during γ‐ray irradiation. It was attempted to incorporate a broad band of cerium activator into the narrow band of terbium in the KCl host without a reduction in the emission intensity. Cerium co‐doped KCl:Tb crystals showed broad band emission due to the d–f transition of cerium and a reduction in the intensity of the emission peak due to ⁵D₃–⁷F_j (j = 3, 4) transition of terbium, when excited at 330 nm. These results support that energy transfer occurs from cerium to terbium in the KCl host. Co‐doping Ce³⁺ ions greatly intensified the excitation peak at 339 nm for the emission at 400 nm of Tb³⁺. The emission due to Tb³⁺ ions was confirmed by PSL and TSL spectra. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of UV‐emitting Gd3+‐doped LiCaBO3 phosphor

Incorporating the Gd³⁺ rare earth ion in the LiCaBO₃ host lattice resulted in narrow‐band UV‐B emission peaking at 315 nm, with excitation at 274 nm. The LiCaBO₃:Gd³⁺ phosphor was synthesized via the solid‐state diffusion method. The structural, morphological and luminescence properties of this phosphor were characterized by X‐ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. Electron paramagnetic resonance (EPR) characterization of the as‐prepared phosphors is also reported here. XRD studies confirmed the crystal formation and phase purity of the prepared phosphors. A series of different dopant concentrations was synthesized and the concentration‐quenching effect was studied. Critical energy transfer distance between activator ions was determined and the mechanism governing the concentration quenching is also reported in this paper. Copyright © 2015 John Wiley & Sons, Ltd.     

Enhanced green emissions of Er3+/Yb3+ co‐doped Gd2(MoO4)3 by co‐excited up‐conversion processes

Improving the emission from rare earth ions doped materials is of great importance to broaden their application in bio‐imaging, photovoltaics and temperature sensing. The green emissions of Gd₂(MoO₄)₃:Er³⁺/Yb³⁺ powder upon co‐excitation with 980 and 808 nm lasers were investigated in this paper. Distinct enhancement of green emissions was observed compared with single laser excitation. Based on the energy level structure of Er³⁺, the enhancement mechanism was discussed. Moreover, the result of temperature‐dependent enhancement revealed that the enhancement factor reached its maximum (2.5) as the sample heated to 120°C, which is due to the competition of two major thermal effects acting in the co‐excited up‐conversion processes. In addition, the same enhancement of green emissions was also observed in Gd₂(MoO₄)₃:Er³⁺ powder and NaYF₄:Er³⁺/Yb³⁺ powder.     

Heterobinuclear Zn‐Ln (Ln = La,Nd, Eu,Gd, Tb,Er and Yb) complexes based on asymmetric Schiff‐base ligand: synthesis,characterization and photophysical properties

With a novel asymmetric Schiff‐base zinc complex ZnL (H₂L = N‐(3‐methoxysalicylidene)‐N′‐(5‐bromo‐3‐methoxysalicylidene)phenylene‐1,2‐diamine), obtained from phenylene‐1,2‐diamine, 3‐methoxysalicylaldehyde and 5‐bromo‐3‐methoxysalicylaldehyde, as the precursor, a series of heterobinuclear Zn‐Ln complexes [ZnLnL(NO₃)₃(CH₃CN)] (Ln = La, 1; Ln = Nd, 2; Ln = Eu, 3; Ln = Gd, 4; Ln = Tb, 5; Ln = Er, 6; Ln = Yb, 7) were synthesized by the further reaction with Ln(NO₃)₃·6H₂O, and characterized by Fourier transform‐infrared, fast atom bombardment mass spectroscopy and elemental analysis. Photophysical studies of these complexes show that the strong and characteristic near‐infrared luminescence of Nd³⁺, Yb³⁺and Er³⁺ with emissive lifetimes in the microsecond range has been sensitized from the excited state of the asymmetric Schiff‐base ligand due to effective intramolecular energy transfer; the other complexes do not show characteristic emission due to the energy gap between the chromophore and lanthanide ions. Copyright © 2012 John Wiley & Sons, Ltd.     

Emission analysis of Tb3+‐and Sm3+‐ion‐doped (Li2O/Na2O/K2O) and (Li2O + Na2O/Li2O + K2O/K2O + Na2O)‐modified borosilicate glasses

Four series of borosilicate glasses modified by alkali oxides and doped with Tb³⁺ and Sm³⁺ ions were prepared using the conventional melt quenching technique, with the chemical composition 74.5B₂O₃ + 10SiO₂ + 5MgO + R + 0.5(Tb₂O₃/Sm₂O₃) [where R = 10(Li₂O /Na₂O/K₂O) for series A and C, and R = 5(Li₂O + Na₂O/Li₂O + K₂O/K₂O + Na₂O) for series B and D]. The X‐ray diffraction (XRD) patterns of all the prepared glasses indicate their amorphous nature. The spectroscopic properties of the prepared glasses were studied by optical absorption analysis, photoluminescence excitation (PLE) and photoluminescence (PL) analysis. A green emission corresponding to the ⁵D₄ → ⁷F₅ (543 nm) transition of the Tb³⁺ ions was registered under excitation at 379 nm for series A and B glasses. The emission spectra of the Sm³⁺ ions with the series C and D glasses showed strong reddish‐orange emission at 600 nm (⁴G_5/2 →⁶H_7/2) with an excitation wavelength λ_exci = 404 nm (⁶H_5/2→⁴F_7/2). Furthermore, the change in the luminescence intensity with the addition of an alkali oxide and combinations of these alkali oxides to borosilicate glasses doped with Tb³⁺ and Sm³⁺ ions was studied to optimize the potential alkali‐oxide‐modified borosilicate glass.     

Synthesis and photoluminescence characteristics of (Y,Gd)BO3:RE (RE = Eu3+, Ce3+, Dy3+ and Tb3+) phosphors for blue chip and near‐UV white LEDs

A series of Eu³⁺‐, Ce³⁺‐, Dy³⁺‐ and Tb³⁺‐doped (Y,Gd)BO₃ phosphors was synthesized by a solid‐state diffusion method. X‐Ray diffraction confirmed their hexagonal structure and the scanning electron microscopy results showed crystalline particles. The excitation spectra revealed that (Y,Gd)BO₃ phosphors doped with Eu³⁺, Ce³⁺ , Dy³⁺ and Tb³⁺ are effectively excited with near UV‐light of 395 nm/blue light, 364, 351 and 314 nm, respectively. Photoluminescence spectra of Eu³⁺‐, Ce³⁺‐ and Tb³⁺/Dy³⁺‐doped phosphor showed intense emission of reddish orange, blue and white light, respectively. The phosphor Y_0.60Gd_0.38BO₃:Ce_0.02 showed CIE 1931 color coordinates of (0.158, 0.031) and better color purity compared with commercially available blue BAM:Eu²⁺ phosphor. The phosphor (Y,Gd)BO₃ doped with Eu³⁺, Dy³⁺ and Tb³⁺ showed CIE 1931 color coordinates of (0.667, 0.332), (0.251, 0.299) and (0.333, 0.391) respectively. Significant photoluminescence characteristics of the prepared phosphors indicate that they might serve as potential candidates for blue chip and near‐UV white light‐emitting diode applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Luminescence and energy‐transfer properties of color‐tunable Ca2Mg0.25Al1.5Si1.25O7:Ce3+/Eu2+/Tb3+ phosphors for ultraviolet light‐emitting diodes

A series of Ca₂Mg_0.25Al_1.5Si_1.25O₇:Ce³⁺/Eu²⁺/Tb³⁺ phosphors was been prepared via a conventional high temperature solid‐state reaction and their luminescence properties were studied. The emission spectra of Ca₂Mg_0.25Al_1.5Si_1.25O₇:Ce³⁺,Eu²⁺ and Ca₂Mg_0.25Al_1.5Si_1.25O₇:Ce³⁺,Tb³⁺ phosphors show not only a band due to Ce³⁺ ions (409 nm) but also as a band due to Eu²⁺ (520 nm) and Tb³⁺ (542 nm) ions. More importantly, the effective energy transfer from Ce³⁺ to Eu²⁺ and Tb³⁺ ions was confirmed and investigated by emission/excitation spectra and luminescent decay behaviors. Furthermore, the energy level scheme and energy transfer mechanism were investigated and were demonstrated to be of resonant type via dipole–dipole (Ce³⁺ to Eu²⁺) and dipole–quadrupole (Ce³⁺ to Tb³⁺) reactions, respectively. Under excitation at 350 nm, the emitting color could be changed from blue to green by adjusting the relative doping concentration of Ce³⁺ and Eu²⁺ ions as well as Ce³⁺ and Tb³⁺ ions. The above results indicate that Ca₂Mg_0.25Al_1.5Si_1.25O₇:Ce³⁺,Eu²⁺/Tb³⁺ are promising single‐phase blue‐to‐green phosphors for application in phosphor conversion white‐light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

A new quaternary photoluminescence enhancement system of Eu−N‐(o‐vanillin)‐1,8‐diaminonaphthalene−1,10‐phenanthroline−Zn and its application in determining trace amounts of europium and zinc

A new sensitive quaternary photoluminescence enhancement system has been successfully developed to determine trace amounts of Eu³⁺ and Zn²⁺. The photoluminescence intensity of Eu ? N‐(o‐vanilin)‐1,8‐diaminonaphthalene systems was greatly increased by the addition of specific concentrations of 1, 10‐phenanthroline and Zn²⁺. The excitation and emission wavelengths were 274 and 617 nm, respectively. Under optimal system conditions, the photoluminescence intensity showed a linear response toward Eu³⁺ in the range of 5.0 × 10^–6 ~ 2.0 × 10^–5 M with a limit of detection (= 2.2 × 10^–9 M) and the photoluminescence intensity of the system decreased linearly by increasing the Zn²⁺ concentration in the range of 5.0 × 10^–8 ~ 1.0 × 10^–6 M with a limit of detection (= 8.8 × 10^–11 M). This system was successfully applied for the determination of trace amounts of Eu³⁺ in a high purity La₂O₃ matrix and in the synthetic rare earth oxide mixture, and of Zn²⁺ in a high purity Mg(NO₃)₂ · 6H₂O matrix and in synthetic coexisting ionic matrixes. The energy transfer mechanism, photoluminescence enhancement of the system and interference of other lanthanide ions and common coexisting ions were also studied in detail. Copyright © 2013 John Wiley & Sons, Ltd.