Synthesis and luminescence properties of novel 8‐hydroxyquinoline derivatives and their Eu(III) complexes

Six novel 8‐hydroxyquinoline derivatives were synthesized using 2‐methyl‐8‐hydroxyquinoline and para‐substituted phenol as the main starting materials, and were characterized by ¹H nuclear magnetic resonance (NMR), mass spectrometry (MS), ultraviolet (UV) light analysis and infra‐red (IR) light analysis. Their complexes with Eu(III) were also prepared and characterized by elemental analysis, molar conductivity, UV light analysis, IR light analysis, and thermogravimetric–differential thermal analysis (TG–DTA). The results showed that the ligand coordinated well with Eu(III) ions and had excellent thermal stability. The structure of the target complex was EuY^1–6(NO₃)₃.2H₂O. The luminescence properties of the target complexes were investigated, the results indicated that all target complexes had favorable luminescence properties and that the introduction of an electron‐donating group could enhance the luminescence intensity of the corresponding complexes, but the addition of an electron‐withdrawing group had the opposite effect. Among all the target complexes, the methoxy‐substituted complex (–OCH₃) had the highest fluorescence intensity and the nitro‐substituted complex (–NO₂) had the weakest fluorescence intensity. The results showed that 8‐hydroxyquinoline derivatives had good energy transfer efficiency for the Eu(III) ion. All the target complexes had a relatively high fluorescence quantum yield. The fluorescence quantum yield of the complex EuY³(NO₃)₃.2H₂O was highest among all target complexes and was up to 0.628. Because of excellent luminescence properties and thermal stabilities of the Eu(III) complexes, they could be used as promising candidate luminescent materials.     

Photoluminescence of Alq3‐ and Tb‐activated aluminium–tris(8‐hydroxyquinoline) complex for blue chip‐excited OLEDs

The tris(8‐hydroxyquinoline)–aluminium complex is the most important and widely studied as electron transporting and green light emitting material. Alq₃ and Tb_xAl_(1‐x)q₃ have been synthesized (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) and blended films of Alq₃ and Tb_xAl_(1‐x)q₃ with PMMA and PS at different percentage weight (wt%) concentrations (e.g., 0.1, 1, 5, 10, 25 and 50 wt%) have been prepared. The synthesized materials and their blended thin films have been characterized by a photoluminescence (PL) technique; the synthesis and PL characterization are reported in this paper. The synthesized metal complex shows bright emission of green light with blue light excitation (440 nm) and the prepared Tb_xAl_(1‐x)q₃ phosphor may be applicable in blue chip‐excited OLEDs for the newly developed wallpaper lighting technology. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of pressure‐assisted thermal annealing on the optical properties of ZnO thin films

ZnO thin films were prepared by the polymeric precursor method. The films were deposited on silicon substrates using the spin‐coating technique, and were annealed at 330 °C for 32 h under pressure‐assisted thermal annealing and under ambient pressure. Their structural and optical properties were characterized, and the phases formed were identified by X‐ray diffraction. No secondary phase was detected. The ZnO thin films were also characterized by field‐emission scanning electron microscopy, Fourier transform infrared spectroscopy, photoluminescence and ultraviolet emission intensity measurements. The effect of pressure on these thin films modifies the active defects that cause the recombination of deep level states located inside the band gap that emit yellow–green (575 nm) and orange (645 nm) photoluminescence. Copyright © 2012 John Wiley & Sons, Ltd.     

Spectrofluorimetric determination of aluminium using 2‐hydroxy‐1‐naphthylidene‐(8‐aminoquinoline)

A sensitive and selective spectrofluorimetric method has been developed for the rapid determination of aluminium. This method is based on the complex formation between aluminium and 2‐hydroxy‐1‐naphthylidene‐(8‐aminoquinoline) (HNAQ). The optimum conditions for the complex formation were a metal‐to‐ligand (M : L) stoichiometric ratio of 1:1, a pH of 5.5 and a 0.20 m acetate buffer. The fluorescence of the complex was monitored at an emission wavelength of 502 nm with excitation at 438 nm. Under these conditions, linear calibration curves were obtained in the ranges 0.05–1 and 1–5 ppm. The detection limit was 3.4 ppb for the former and 13.5 ppb for the latter. The maximum relative standard deviation of the method for an aluminium standard of 200 ppb was 1.5% (n = 5). This method was successfully applied for the determination of aluminium in drinking water, pharmaceutical antacid tablets and suspension samples. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of γ‐irradiation on thermal and thermoluminescence properties of polystyrene/europium (III) oxide composite film

In the present study, polystyrene:europium (III) oxide polymer films at a ratio of 95:5 wt% were prepared using a solution casting technique. These polymeric films were irradiated with 5, 25 and 50 kGy γ‐radiation doses and their thermoluminescence (TL) and thermal properties were studied as a function of radiation dose. Analysis of Fourier transform infrared spectra revealed different modes of vibration and polymer–filler interaction. Reduction of vibrational modes with radiation dose was observed. The TL glow curve intensity was observed to increase with increasing radiation dose and to become broader in the 378 K and 444 K regions. Detrapping of electrons implied by the glow curve was caused by thermally induced macromolecular motion, concurrent with β‐relaxation in polystyrene. The TL glow curve parameters were computed using a glow curve deconvolution method. Differential scanning calorimetry analysis indicated that the glass transition temperature (T_g) increased with increase in dose, suggesting crosslinking of the polymer chain. Scanning electron microscopy analysis evidenced the change in surface morphology due to γ‐irradiation.     

Chemiluminescence method for the determination of piroxicam by the enhancement of the tris‐(4,7‐diphenyl‐1,10‐phenanthrolinedisulphonic acid) ruthenium(II) (RuBPS)–cerium(IV) system and its application

A simple, rapid chemiluminescence (CL) method was described for the determination of piroxicam, a commonly used analgesic agent drug. A strong CL signal was detected when cerium(IV) sulphate was injected into tris‐(4,7‐diphenyl‐1,10‐phenanthrolinedisulphonic acid) ruthenium(II) (RuBPS)–piroxicam solution. The CL signal was proportional to the concentration of piroxicam in the range 2.8 × 10^–8–1.2 × 10^–5 mol/L. The detection limit was 2 × 10^–8 mol/L and the relative standard deviation (RSD) was 3.7% (c = 7.0 × 10^–7 mol/L piroxicam; n = 11). The proposed method was applied to the determination of piroxicam in pharmaceutical preparations in capsules, spiked serum and urine samples with satisfactory results. Copyright © 2008 John Wiley & Sons, Ltd.     

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.     

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.     

Synthesis,crystal structure and fluorescence properties of terbium complexes with phenoxyacetic acid and 2,4,6‐tris‐(2‐pyridyl)‐s–triazine

Two complexes of Tb³⁺, Gd³⁺/Tb³⁺ and one heteronuclear crystal Gd³⁺/Tb³⁺ with phenoxyacetic acid (HPOA) and 2,4,6‐tris‐(2‐pyridyl)‐s–triazine (TPTZ) have been synthesized. Elemental analysis, rare earth coordination titration, inductively coupled plasma atomic emission spectrometry (ICP‐AES) and thermogravimetric analysis‐differential scanning calorimetry (TG‐DSC) analysis show that the two complexes are Tb₂(POA)₆(TPTZ)₂·6H₂O and TbGd(POA)₆(TPTZ)₂·6H₂O, respectively. The crystal structure of TbGd(POA)₆(TPTZ)₂·2CH₃OH was determined using single‐crystal X‐ray diffraction. The monocrystal belongs to the triclinic system with the P‐1 space group. In particular, each metal ion is coordinately bonded to three nitrogen atoms of one TPTZ and seven oxygen atoms of three phenoxyacetic ions. Furthermore, there exist two coordinate forms between C₆H₅OCH₂COO^– and the metal ions in the crystal. One is a chelating bidentate, the other is chelating and bridge coordinating. Fluorescence determination shows that the two complexes possess strong fluorescence emissions. Furthermore, the fluorescence intensity of the Gd³⁺/Tb³⁺ complex is much stronger than that of the undoped complex, which may result from a decrease in the concentration quench of Tb³⁺ ions, and intramolecular energy transfer from the ligands coordinated with Gd³⁺ ions to Tb³⁺ ions. Copyright © 2015 John Wiley & Sons, Ltd.     

Photoluminescence profiles and fast/slow annealing effects of Eu(III)/Tb(III)‐codoped silica phosphor materials

A silica (SiO₂) nanoparticle matrix was codoped with luminescent Eu(III) and Tb(III) ions using a modified Stöber method. The effects of fast and slow thermal annealing on photoluminescence profile imaging were examined. Slow annealing treatment suppressed more quenching sites than fast thermal annealing to further increase the photoluminescence signals. The photoluminescence signals observed between 450 and 720 nm were assigned to the ⁵D₀ → ⁷F_J (J = 0,1,2,3,4) of Eu(III) and the ⁵D₄ → ⁷F_J (J = 6,5,4,3) transitions of Tb(III). Photoluminescence was largely sensitized by indirect excitation and was much stronger than that generated by direct excitation. The Eu(III) and Tb(III) ions were doped at lower symmetry sites in the silica matrix. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of 5‐(4′‐carboxyphenyl)‐10,15,20‐tris‐(4 pyridyl)‐porphyrin and its peptidyl phosphonate derivatives

The synthesis and characterization of three new 4‐pyridyl porphyrin‐peptidyl‐phosphonate compounds, containing a diphenyl 3‐pyridylmethyl‐phosphonate moiety, is described in this article. Nitrogen atoms in the pyridine rings of the obtained compounds were alkylated using methyl iodide, to give additional three, water soluble derivatives of these peptidyl‐porphyrin conjugates. All the synthesized compounds could serve as potential photosensitizers for the photodynamic therapy (PDT) method of tumor therapy and displayed activity as inhibitors of aminopeptidase N. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.     

Posttranslational oxidative modification of (R)‐2‐(2,4‐dichlorophenoxy)propionate/α‐ketoglutarate‐dependent dioxygenases (RdpA) leads to improved degradation of 2,4‐dichlorophenoxyacetate (2,4‐D)

Microbial activities and the versatility gained through adaptation to xenobiotic compounds are the main biological forces to counteract environmental pollution. The current results present a new adaptive mechanism that is mediated through posttranslational modifications. Strains of Delftia acidovorans incapable of growing autochthonously on 2,4‐dichlorophenoxyacetate (2,4‐D) were cultivated in a chemostat on 2,4‐D in the presence of (R)‐2‐(2,4‐dichlorophenoxy)propionate. Long‐term cultivation led to enhanced 2,4‐D degradation, as demonstrated by improved values of the Michaelis–Menten constant K_m for 2,4‐D and the catalytic efficiency k_cat/K_m of the initial degradative key enzyme (R)‐2‐(2,4‐dichlorophenoxy)propionate/α‐ketoglutarate‐dependent dioxygenases (RdpA). Analyses of the rdpA gene did not reveal any mutations, indicating a nongenetic mechanism of adaptation. 2‐DE of enzyme preparations, however, showed a series of RdpA forms varying in their pI. During adaptation increased numbers of RdpA variants were observed. Subsequent immunoassays of the RdpA variants showed a specific reaction with 2,4‐dinitrophenylhydrazine (DNPH), characteristic of carbonylation modifications. Together these results indicate that posttranslational carbonylation modified the substrate specificity of RdpA. A model was implemented explaining the segregation of clones with improved degradative activity within the chemostat. The process described is capable of quickly responding to environmental conditions by reversibly adapting the degradative potential to various phenoxyalkanoate herbicides.     

Green synthesis of enantiopure (S)‐1‐(benzofuran‐2‐yl)ethanol by whole‐cell biocatalyst

Optically active aromatic alcohols are valuable chiral building blocks of many natural products and chiral drugs. Lactobacillus paracasei BD87E6, which was isolated from a cereal‐based fermented beverage, was shown as a biocatalyst for the bioreduction of 1‐(benzofuran‐2‐yl) ethanone to (S)‐1‐(benzofuran‐2‐yl) ethanol with highly stereoselectivity. The bioreduction conditions were optimized using L. paracasei BD87E6 to obtain high enantiomeric excess (ee) and conversion. After optimization of the bioreduction conditions, it was shown that the bioreduction of 1‐(benzofuran‐2‐yl)ethanone was performed in mild reaction conditions. The asymmetric bioreduction of the 1‐(benzofuran‐2‐yl)ethanone had reached 92% yield with ee of higher than 99.9% at 6.73 g of substrate. Our study gave the first example for enantiopure production of (S)‐1‐(benzofuran‐2‐yl)ethanol by a biological green method. This process is also scalable and has potential in application. In this study, a basic and novel whole‐cell mediated biocatalytic method was performed for the enantiopure production of (S)‐1‐(benzofuran‐2‐yl)ethanol in the aqueous medium, which empowered the synthesis of a precious chiral intermediary process to be converted into a sophisticated molecule for drug production.     

Synthesis and luminescence of Eu3+‐doped in triple phosphate Ca8MgBi(PO4)7 with whitlockite structure

Triple whitlockite‐type structure‐based red phosphors Ca₈MgBi_1?x(PO₄)₇:xEu³⁺ (x = 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80 and 1.00) were synthesized by a conventional solid‐state reaction route and characterized by their X‐ray crystal structures. The X‐ray diffraction (XRD) patterns, Fourier transform infrared spectra, morphologies, photoluminescence spectra, UV/Vis reflectance spectra, decay times and the International Commission on Illumination (CIE) chromaticity coordinates of Ca₈MgBi_1?x(PO₄)₇:xEu³⁺ were analyzed. Eu‐doped Ca₈MgBi(PO₄)₇ phosphors exhibited strong red luminescence with peaks at 616 nm due to the ⁵D₀ → ⁷ F₂ electric dipole transition of Eu³⁺ ions after excitation at 396 nm. The UV/Vis spectra indicated that the band gap of Ca₈MgBi_0.30(PO₄)₇:0.70Eu³⁺ is larger than that of Ca₈MgBi(PO₄)₇. The phosphor developed in this study has great potential as a red‐light‐emitting phosphor for UV light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Photoluminescence imaging of europium (III)‐doped γ‐Al2O3 nanofiber structures

Aluminium oxide (Al₂O₃) has widely been used for catalysts, insulators, and composite materials for diverse applications. Herein, we demonstrated if γ‐Al₂O₃ was useful as a luminescence support material for europium (Eu) (III) activator ion. The hydrothermal method and post‐thermal treatment at 800°C were employed to synthesize Eu(III)‐doped γ‐Al₂O₃ nanofibre structures. Luminescence characteristics of Eu(III) ions in Al₂O₃ matrix were fully understood by taking 2D and 3D‐photoluminescence imaging profiles. Various sharp emissions between 580 to 720 nm were assigned to the ⁵D₀→⁷F_J (J = 0, 1, 2, 3, 4) transitions of Eu(III) activators. On the basis of X‐ray diffraction crystallography, Auger elemental mapping and the asymmetry ratio, Eu(III) ions were found to be well doped into the γ‐Al₂O₃ matrix at a low (1 mol%) doping level. A broad emission at 460 nm was substantially increased upon higher (2 mol%) Eu(III) doping due to defect creation. The first 3D photoluminescence imaging profiles highlight detailed understanding of emission characteristics of Eu(III) ions in Al oxide‐based phosphor materials and their potential applications.     

Physiological Importance of Poly‐(R)‐3‐hydroxybutyrates

Poly‐(R)‐3‐hydroxybutyrates (PHB), linear polymers of (R)‐3‐hydroxybutyrate, are components of all biological cells in which short polymers (<200 monomer residues) are covalently attached to certain proteins and/or noncovalently associated with polyphosphates – inorganic polyphosphate (polyP), RNA, and DNA. The low concentrations, lack of unusual atoms or functional groups, and flexible backbones of this complexed PHB, referred to as cPHB, make them invisible to many analytical procedures; whereas other physical properties – water‐insolubility, high intrinsic viscosity, temperature sensitivity, multiple bonding interactions with other molecules – make them requisite participants in vital physiological processes as well as contributors to the development of certain diseases.     

Synthesis and properties of a new red luminescence europium complex containing a 2‐(benzimidazol‐2‐yl)‐8‐octyloxyquinoline as the second ligand

A new Eu(III) complex, Eu(III)(DBM)₃BIOQ, has been synthesized with dibenzoylmethane (DBM) as the first ligand and 2‐(benzimidazol‐2‐yl)‐8‐octyloxyquinoline (BIOQ) as the second ligand. The stability of the complex was analysed by DSC–TG. The results show that the Eu(III) complex has a relatively high thermal stability with a melting point of 235 °C and a decomposition temperature (onset) of 252 °C. The fluorescence properties of the compound were also investigated. The fluorescence results reveal that the as‐prepared complex shows the characteristic maximum emission spectra of Eu(III) at 611 nm (λ_ex = 350 nm). In addition, the photoluminescence spectrum of the complex in the solid state exhibits a single and symmetrical emission band at 611 nm, with a full width at half‐maximum of 4.7 nm, showing high colour purity. This finding indicates the possibility for the development of brighter red luminescent materials. Copyright © 2011 John Wiley & Sons, Ltd.