Enhancement of Europium Luminescence in Tetracycline–Europium Complexes in the Presence of Urea Hydrogen Peroxide

An increase in the europium emission band was observed, for the first time, with addition of urea hydrogen peroxide to the tetracycline–europium (Tc–Eu)solution. We have observed that the wavelength, the band width and the area of ⁵D₀→⁷F₂ europium transition change with the urea hydrogen peroxide concentration. We claim that the tetracycline–europium complexes can be used as probes of urea hydrogen peroxide concentration.     

Europium-sensitized Chemiluminescence of System Tetracycline–H<Subscript>2</Subscript>O<Subscript>2</Subscript>–Fe(II)/(III) and Its Application to the Determination of Tetracycline

Chemiluminescence (CL) of the reaction system tetracycline–H₂O₂–Fe(II)/(III)–Eu(III) was used for the determination of tetracycline hydrochloride in water, pharmaceutical preparations, and honey. The CL spectrum registered for this system shows emission bands typical of Eu(III) ions, with a maximum at λ ∼ 600 nm, corresponding to the electronic transitions of ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂. A strong chemiluminescence intensity characteristic of europium(III) ions in the system tetracycline–H₂O₂–Fe(II)/(III)–Eu(III), as contrasted to the emission of the system tetracycline–H₂O₂–Fe(II)/(III) without Eu(III), proves that the Eu(III) ion plays the role of a chemiluminescence sensitizer, accompanying tetracycline oxidation in the Fenton system (H₂O₂–Fe(II)/(III)). A linear dependence was observed for the integrated CL light intensity on the tetracycline concentration in the range of 2 × 10⁻⁷ to 3 × 10⁻⁵ mol l⁻¹ with the detection limit of 5 × 10⁻⁸ mol l⁻¹ in aqueous solution.     

The special features of the luminescence and light resistance of europium complexes and their mixtures with lanthanum complexes in polymethyl methacrylate

The kinetics of luminescence and transformation of short-lived products of the photolysis of europium and lanthanum complexes with thenoyltrifluoroacetone and 1,10-phenanthroline and their mixtures in polymethyl methacrylate films was studied by the nanosecond laser photolysis method with recording both light emission and absorption. Fast (535 and 585 nm, ⁵ D ₁ → ⁷ F ₀, ⁷ F ₃, decay time 0.7 μs) and slow (613 nm, ⁵ D ₀ → ⁷ F ₂, luminescence rise and decay times 0.7 μs and 0.5 ms, respectively) luminescence was studied. Induced absorption with a maximum at 600 nm and decay time ∼3 ms was observed; this absorption was assigned to triplet states of the deprotonated form of thenoyltrifluoroacetone. The dependences of luminescence intensity on the concentration of the components in a mixture of complexes were analyzed, and synergistic effects of luminescence strengthening were estimated. The kinetics of a decrease in luminescence intensity during photolysis was studied. Possible mechanisms of a decrease in the relative initial process rate and an increase in the quasi-stationary value of relative luminescence intensity as the concentration of complexes in the polymer increased were discussed.     

Luminescence of praseodymium (III) in solutions of mixed-ligand complexes with β-diketones

We have found that it is possible to enhance the luminescence of Pr(III) in solutions of complexes with β-diketones: acetylacetone derivatives containing fluoroalkyl substituents of different lengths and structures. We have established that in the presence of organic solvents, second (additional) ligands, and surfactants shielding the central ion from the quenching effect of the water molecules (OH oscillators), the intensity of luminescence for Pr(III) increases by a factor of 65, 38, and 45 respectively. In this case, cationic surfactants form ionic associates with Pr(III) β-diketonates, with incorporation of one more β-diketone molecule (ratio Pr:β-diketonate:surfactant = 1:4:1). As a result of suppression of intramolecular energy losses in solutions of Pr(III) β-diketonates, it is possible to observe its rather intense luminescence at 605 nm (the transition ¹D₂ → ³H₄), 612 nm (³P₀ → ³H₆), and 646 nm (³P₀ → 3F₂). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 746–750, November–December, 2006.     

Intramolecular Energy Transfer and Co-luminescence Effect in Rare Earth Ions (La, Y, Gd and Tb) Doped with Eu3+ β-diketone Complexes

In this paper, Eu³⁺ β-diketone Complexes with the two ligands 1-(2-naphthoyl)-3, 3, 3-trifluoroacetonate (TFNB) and 2’2-bipyridine (bpy) have been synthesized. Furthermore, we reported a systematical study of the co-fluorescence effect of Eu(TFNB)₃bpy doped with inert rare earth ions (La³⁺, Gd³⁺ and Y³⁺) and luminescence ion Tb³⁺. The co-luminescence effect can be found by studying the luminescence spectra of the doped complexes, which means that the existence of the other rare earth ions (La³⁺, Y³⁺, Gd³⁺ and Tb³⁺) can enhance the luminescence intensity of the central Eu³⁺, which may be due to the intramolecular energy transfer between rare earth ions and Eu³⁺. The efficient intramolecular energy transfer in all the complexes mainly occurs between the ligand TFNB and the central Eu³⁺. Full characterization and detail studies of luminescence properties of all these synthesized materials were investigated in relation to co-fluorescence effect between the central Eu³⁺ and other inert ions. Further investigation into the luminescence properties of all the complexes show that the characteristic luminescence of the corresponding Eu³⁺ through the intramolecular energy transfers from the ligand to the central Eu³⁺. Meantime, the differences in luminescence intensity of the ⁵D₀→⁷F₂ transition, in the ⁵D₀ lifetimes and in the ⁵D₀ luminescence quantum efficiency among all the synthesized materials confirm that the doped complex Eu_0.5Tb_0.5(TFNB)₃bpy exhibits higher ⁵D₀ luminescence quantum efficiency and longer lifetime than the pure Eu(TFNB)₃bpy complex and other materials.     

Thermally stimulated recombination processes and luminescence in Li<Subscript>6</Subscript>(Y,Gd,Eu)(BO<Subscript>3</Subscript>)<Subscript>3</Subscript> crystals

The thermally stimulated recombination processes and luminescence in crystals of the lithium borate family Li₆(Y,Gd,Eu)(BO₃)₃ have been investigated. The steady-state luminescence spectra under X-ray excitation (X-ray luminescence spectra), the temperature dependences of the X-ray luminescence intensity, and the glow curves for the Li₆Gd(BO₃)₃, Li₆Eu(BO₃)₃, Li₆Y_0.5Gd_0.5(BO₃)₃: Eu, and Li₆Gd(BO₃)₃: Eu compounds have been measured in the temperature range 90–500 K. In the X-ray luminescence spectra, the band at 312 nm corresponding to the ⁶ P _J → ⁸ S _7/2 transitions in the Gd³⁺ ion and the group of lines at 580–700 nm due to the ⁵ D ₀ → ⁷ F _J transitions (J = 0–4) in the Eu³⁺ ion are dominant. For undoped crystals, the X-ray luminescence intensity of these bands increases by a factor of 15 with a change in the temperature from 100 to 400 K. The possible mechanisms providing the observed temperature dependence of the intensity and their relation to the specific features of energy transfer of electronic excitations in these crystals have been discussed. It has been revealed that the glow curves for all the crystals under investigation exhibit the main complex peak with the maximum at a temperature of 110–160 K and a number of weaker peaks with the composition and structure dependent on the crystal type. The nature of shallow trapping centers responsible for the thermally stimulated luminescence in the range below room temperature and their relation to defects in the lithium cation sublattice have been analyzed.     

Low-temperature investigation of electronic excitations in wide-gap materials doped with RE3+ or Cr3+ ions

The processes of photon multiplication in insulators have been considered. The luminescence of Tb³⁺ ions (⁵ D ₃ → ⁷ F _J , ⁵ D ₄ → ⁷ F _J transitions) upon intracenter excitation, the optical excitation of oxyanions, or the formation of separated electrons and holes has been studied for CaSO₄ doped with Tb³⁺ and Na⁺ ions at 6–9 K. An increase in Tb³⁺ concentration from 0.2 to 4 at % and transition from single Tb³⁺-Na⁺ states to centers that contain two or three terbium ions leads to the redistribution of the luminescence intensities in favor of the ⁵ D ₄ → ⁷ F _J transitions and increase in their efficiency due to the possibility of the cooperative ⁵ D ₃ → ⁵ D ₄ and ⁷ F ₆ → ⁷ F _J transitions and the 4f ⁷5d ¹ → ⁵ D ₃ and ⁷ F ₆ → ⁵ D ₄ transitions in the two- and three-terbium centers. Based on the example of MgO single crystals with highly mobile excitons, holes, and electrons, the migration of free excitons and holes toward Cr³⁺ ions in the crystal bulk and their exit from the bulk to the surface have been revealed at 9 K. Surface losses limit the luminescence quantum yield of MgO:Cr³⁺, CaSO₄:Tb³⁺, and many other materials.     

Temperature sensing behavior of Eu<Superscript>3+</Superscript> doped tellurite and calibo glasses

The effect of temperature on the luminescence intensity of the two bands due to ⁵ D ₁→⁷ F ₁ and ⁵ D ₀→⁷ F ₁ transitions in Eu³⁺ on excitation with the 476.5 nm line from an Ar⁺ laser has been studied in tellurite and calibo glasses. It is interesting to note that the peak intensity of the ⁵ D ₁→⁷ F ₁ transition increases with increasing temperature where as that of the ⁵ D ₀→⁷ F ₁ transition decreases. The ratio of the intensities of the two bands have been used to estimate the temperature. PACS 42.70 Ce     

Luminescence and recombination processes in bulky Li6Gd x Y1 − x (BO3)3:Eu crystals

The luminescence and recombination processes in crystals of lithium borates Li₆Gd _x Y_{1 − x} (BO₃)₃:Eu have been investigated. The steady-state X-ray luminescence (XRL) spectra, the temperature dependences of the XRL intensity, and the thermally stimulated luminescence (TSL) spectra have been measured for the Li₆Gd(BO₃)₃, Li₆Eu(BO₃)₃, Li₆Y_0.5Gd_0.5(BO₃)₃:Eu, and Li₆Gd(BO₃)₃:Eu compounds in the temperature range of 90–500 K. It is established that the band at 312 nm, which is due to the ⁶ P _J → ⁸ S _7/2 transitions in Gd³⁺ ions and the group of lines at 580–700 nm, which are due to the ⁵ D ₀ → ⁷ F _J (J = 0 … 4) transitions in Eu³⁺ ions dominate in the XRL spectra. The XRL intensity in these bands increases several times with a change in temperature from 100 to 400 K for undoped crystals. The likely mechanisms of the observed temperature dependence of the XRL intensity and their relationship with the features of electronic-excitation energy transfer in these crystals are discussed. The spectra of all crystals under study exhibit a dominant composite TSL peak with a maximum at 110–160 K and a series of weaker peaks, the composition and structure of which depend on the crystal type. The nature of the shallow traps, which are responsible for the TSL at temperatures below room, and their relationship with the defects of lithium cation sublattice are discussed.     

Ultraviolet and visible upconversion luminescence of Tm(0.1)Yb(5):FOV oxyfluoride nanophase vitroceramics

The ultraviolet upconversion luminescence of Tm³⁺ ions sensitized by Yb³⁺ ions in oxyfluoride nanophase vitroceramics when excited by a 975 nm diode laser was studied. An ultraviolet upconversion luminescence line positioned at 363.6 nm was found. It was attributed to the fluorescence transition of ¹D₂→³H₆ of Tm³⁺ ion. Several visible upconversion luminescence lines at 450.7 nm, (477.0 nm, 462.5 nm), 648.5 nm, (680.5 nm, 699.5 nm) and (777.2 nm, 800.7 nm) were also found, which result respectively from the fluorescence transitions of ¹D₂→³F₄, ¹G₄→³H₆, ¹G₄→³F₄, ³F₃→³H₆ and ³H₄→³H₆ of Tm³⁺ ion. The careful measurement and analysis of the variation of upconversion luminescence intensity F as a function of the 975 nm pumping laser power P prove that the upconversion luminescence of ¹D₂ state is partly a five-photon upconversion luminescence, and the upconversion luminescence of ¹G₄ state and ³H₄ state are respectively the three-photon and two-photon upconversion luminescence. The theoretical analysis suggested that the upconversion mechanism of the 363.6 nm ¹D₂→³H₆ upconversion luminescence is partly the cross energy transfer of {³H₄(Tm³⁺), ³F₄(Tm³⁺), ¹G₄(Tm³⁺)→¹D₂(Tm³⁺)} and {¹G₄(Tm³⁺)→³F₄(Tm³⁺), ³H₄(Tm³⁺)→¹D₂(Tm³⁺)} between Tm³⁺ ions. In addition, the upconversion luminescence of ¹G₄ and ³H₄ state results respectively from the sequential energy transfer {²F_5/2(Yb³⁺)→²F_7/2(Yb³⁺), ³H₄(Tm³⁺)→¹G₄(Tm³⁺)} and {²F_5/2(Yb³⁺) →²F_7/2(Yb³⁺), ³F₄(Tm³⁺)→³F₂(Tm³⁺)} from Yb³⁺ ions to Tm³⁺ ions. Supported by the National Natural Science Foundation of China (Grant No. 10674019)     

Synthesis and Fluorescence Properties of Lanthanide (III) Perchlorate Complexes with Naphthyl-Naphthalinesulphonylpropyl Sulfoxide

A ligand with double sulfinyl groups, naphthyl-naphthalinesulphonylpropyl sulfoxide(dinaphthyl disulfoxide, L), was synthesized by a new method and its several lanthanide (III) complexes were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis, IR, TG-DTA, ¹HNMR and UV spectra. The composition of these complexes, were RE₂(ClO₄)₆·(L)₅·nH₂O (RE = La, Nd, Eu, Tb, Yb, n = 2 ∼ 6, L = C₁₀H₇SOC₃H₆SOC₁₀H₇). The fluorescent spectra illustrated that the Eu (III) complex had an excellent luminescence. It was supposed that the ligand was benefited for transferring the energy from ligand to the excitation state energy level (⁵D₀) of Eu (III). The Tb (III) complex displayed weak luminescence, which attributed to low energy transferring efficiency between the average triplet state energy level of ligand and the excited state (⁵D₄) of Tb (III). So the Eu (III) complex displayed a good antenna effect for luminescence. The phosphorescence spectra and the relationship between fluorescence lifetime and fluorescence intensity were also discussed.     

Study of frequency upconversion in Yb<Superscript>3+</Superscript>/Eu<Superscript>3+</Superscript> by cooperative energy transfer in oxyfluoroborate glass matrix

Oxyfluoroborate glass co-doped with Eu and Yb ions has been prepared and characterized for its optical properties through photoluminescence, absorption and lifetime measurements. An intense red upconversion is observed from the ⁵D₀ level of Eu³⁺ ions through energy transfer from Yb³⁺ to Eu³⁺ ion when excited with 980 nm. The Judd–Ofelt parameters have been evaluated to estimate the local site symmetry around the Eu³⁺ ions. These parameters have been used to derive radiative properties such as transition probabilities, branching ratios, radiative lifetimes and stimulated emission cross-sections for the ⁵D₀–⁷F_J transitions. Decay of excitation of the ⁵D₀ level has been measured by monitoring the ⁵D₀→⁷F₂ transition (613 nm) at room temperature. Quantum efficiency for this transition is found to be 73%. We also monitored the effect of temperature on the fluorescence emission of Eu³⁺. PACS 42.70.Ce; 42.70.Hj     

Temperature-dependent nepheloxetic shift of the 5 D 0→7 F 0 luminescence line of a Eu3+ ion in a superionic Na5Y(:Eu)Si4O12 single crystal

A decrease in the wavelength of the ⁵ D ₀→⁷ F ₀ luminescence line of a Eu³⁺ ion in a single crystal of the superionic conductor Na₅Y(:Eu)Si₄O₁₂ is observed as a consequence of raising the temperature. The effect is interpreted as the result of a change in the distribution of mobile Na⁺ cations in the second coordination sphere of the luminescing rare-earth ion. Fiz. Tverd. Tela (St. Petersburg) 39, 1997–2000 (November 1997)     

A Mechanism of the influence of Gd(III) and other Ln(III) ions on sensitized luminescence of Eu(III) and Tb(III) ions in aqueous and ethanol solutions: The role of hydroxyl bridges

We studied sensitization of Eu(III) and Tb(III) ions by molecules of 1,10-phenanthroline and 2,2-bipyridil in D₂O and d ₆-ethanol and the influence of Nd(III), Pr(III), Sm(III), Gd(III), and Ho(III) ions on the luminescence intensity I _lum and lifetime τ_lum of Eu(III) and Tb(III) in solutions. The stability constants of complexes of Eu(III) and Gd(III) with 2,2′-bipyridil are measured by spectrophotometric and luminescence methods. It is shown that luminescence of Eu(III) is quenched by Gd(III) ions at the ion concentration equal to 10^?2–10^?1 M, which is caused by competing between these ions for a sensitizer. At the concentration of Ln(III) ions equal to 10^?6?10^?3 M, the sensitized luminescence of Eu(III) and Tb(III) was quenched and τ_lum decreased in the presence of Nd(III) ions, whereas in the presence of Gd(III) the luminescence intensity increased. It is proved that a bridge that connects the two ions upon energy transfer is formed by hydroxyl groups. The intensity of luminescence of Eu(III) and Tb(III) in aqueous solutions and its lifetime decreased in the presence of hydroxyl groups, while upon addition of Gd(III) to these solutions these quantities were restored. We also found that the addition of Gd(III) to deoxygenated ethanol solutions of 2,2′-bipyridil and Eu(III) slows down photochemical and thermal reactions between bipyridil and Eu(III), resulting in the increase in the luminescence intensity of Eu(III).     

Luminescence quenching of lanthanides in complexes with β-diketones containing different fluorinated radicals

It is shown that luminescence quenching of lanthanide (Ln) ions by water molecules (OH-oscillators) entering the first coordination sphere of a complex decreases as the chain of the fluorinated radical lengthens from CF₃ to C₆F₁₃. The amounts of water molecules in binary and different-ligand Eu complexes with some fluoro derivatives of acetyl acetone are determined. It is established that, unlike OH-oscillators, the elimination of hydrogen oscillations at the central carbon atom by β-diketone deuteration provides the same increase (1.1–1.2 fold) in luminescence intensity in all the investigated Eu complex compounds. A. V. Bogatskii Physicotechnical Institute, National Academy of Sciences of Ukraine, 86, Lyustdorfskaya Read, Odessa, 270080, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 217–220, March–April, 1997.     

Eu3+-based optical centers with a high efficiency of the 5D0 → 7F4 transition in alumina gel films

A record peak luminescence intensity of the ⁵ D ₀ → ⁷ F ₄ transition in Eu³⁺ ions and broadening of their UV excitation band are obtained by doping of Eu-containing alumina gel films with bismuth oxyfluoride and subsequent thermal treatment at T ≥ 700°C. The results obtained are explained by the formation of complex Eu—Bi centers with C _3V symmetry in the Al₂O₃ structure, efficient migration of excitations from EuAlO₃ crystallites to these centers, and the sensitization of the luminescence of the rare-earth activator by Bi³⁺ ions. __________ Translated from Optika i Spektroskopiya, Vol. 98, No. 2, 2005, pp. 224–228. Original Russian Text Copyright ? 2005 by Malashkevich, Shevchenko, Bokshits, Kornienko, Pershukevich.     

SiO2–GeO2 Soot Preform as a Core for Eu2O3 Nanocoating: Synthesis and Photophysical Study

Nowadays solid state chemists have the possibility of work with low temperature strategies to obtain solid state materials with appropriate physical and chemical properties for useful technological applications. Photonic core shell materials having a core and shell domains composed by a variety of compounds have been synthesized by different methods. In this work we used silica-germania soot prepared by vapor-phase axial deposition as a core where a nanoshell of Eu₂O₃ was deposited. A new sol-gel like method was used to obtain the Eu₂O₃ nanoshell coating the SiO₂–GeO₂ particles, which was prepared by the polymeric precursor method. The photophysical properties of Eu³⁺ were used to obtain information about the rare earth surrounding in the SiO₂–GeO₂@Eu₂O₃ material during the sintering process. The sintering process was followed by the luminescence spectra of Eu³⁺ and all the samples present the characteristic emission related to the ⁵D₀→⁷F _J (J = 0, 1, 2, 3 and 4). The ratios of the ⁵D₀→⁷F₂/⁵D₀→⁷F₁ emission intensity for the SiO₂–GeO₂@Eu₂O₃ systems were calculated and it was observed an increase in its values, indicating a low symmetry around the Eu³⁺ as the temperature increases.     

Preparation of Y2O3:Eu thin films by excimer-laser-assisted metal organic deposition

Europium-doped yttrium oxide (Y₂O₃:Eu) thin films were successfully deposited on quartz and ITO/glass substrates by excimer-laser-assisted metal organic deposition (ELAMOD) at low temperatures. The effects of laser wavelength and thermal temperature on the films’ crystallinity and photoluminescence properties were investigated. Films irradiated by an ArF laser at 80 mJ/cm² and 400–500°C were highly crystallized compared with those prepared by thermal MOD. In contrast, when the film was irradiated by a KrF laser at 500°C, no crystalline Y₂O₃:Eu was formed. The Y₂O₃:Eu film irradiated by the ArF laser at 80 mJ/cm² and 500°C showed typical PL spectra of Eu³⁺ ions with cubic symmetry and a ⁵D₀→⁷F₂ transition at ∼612 nm. The PL intensity at 612 nm was much higher for the film prepared with ELAMOD than for that prepared by the thermal-assisted process, and the photoemission intensity of the film prepared with ELAMOD strongly depended on the substrate material.     

Surface-enhanced luminescence from Eu 3+ complex nearby Ag colloids

The effect of colloidal dispersion of silver on the luminescent properties of Eu (III) complex with pyridine-3,5-dicarboxylic acid (PyDC) was investigated. The luminescence from Förster type europium complex was enhanced several times with the presence of Ag colloid and the enhancement factor showed Ag concentration dependence. The observed enhancement effect was discussed in view of surface-enhancement effect and optical absorption due to surface plasmon resonance, both arising from excitation of surface plasmon polariton. The coordination structure around Eu (III) ion was also affected with the presence of Ag colloid, which induced the change in the intensity ratio between two emission bands of ⁵ D ₀ ⁷ F ₁ and ⁵ D ₀ ⁷ F ₂ transitions of Eu (III) ion.     

Intramolecular energy transfer in mesogenic europium (III) adduct

The absorption and emission spectra of a liquid-crystalline melt prepared on the basis of a synthesized mesogenic europium (III) adduct are studied in the temperature range from 77 to 348 K. The main channels and rate constants of intramolecular energy transfer from ligands to Eu (III) ions are determined from the absorption and luminescence spectra and luminescence kinetics of the sample under study. It is shown that the liquid-crystalline melt of the europium (III) adduct has a high photostability and an intense luminescence in the temperature range from 77 to 300 K, which allows one to consider it as a promising material for optoelectronic devices. Above room temperature, the relaxation time of the ⁵ D ₀ level of Eu (III) ions sharply shortens. An analysis of the kinetics of the luminescence corresponding to the ⁵ D ₀ → ⁷ F ₂ transition shows that the relaxation of the ⁵ D ₀ level in the temperature range from 300 to 348 K occurs through a charge-transfer state.