Fluorescence enhancement and cofluorescence in complexes of terbium（Ⅲ） with trimellitic acid

The fluorescence of terbium (III) was enhanced by about three orders of magnitude in the presence of trimellitic acid (benzene-1, 2, 4-tricarboxylic acid (TLA)) in aqueous solution at pH 6. The fluorescence intensity could be greatly increased when the system of Tb³⁺-TLA was treated with La³⁺(or Gd³⁺) and TritonX-100. The addition of La³⁺(or Gd³⁺⁾ enhances the fluorescence of the system by about two orders of magnitude due to cofluorescence, and the TritonX-100 micellar medium plays an important role for stabilization of the system. Both the intermolecular energy transfer mode and intramolecular energy transfer mode are responsible for the mechanism of fluorescence enhancement. In the optimum conditions, the fluorescence intensity is a linear function of Tb³⁺ concentration in the range of 7.8 × 10⁻⁹-3.6 × 10⁻⁶ mol/L for the system Tb³⁺-La³⁺-TLA and 1.0 × 10⁻⁸-4.7 × 10⁻⁶ mol/L for the system Tb³⁺-Gd³⁺-TLA, and the limits of detection are 4.6 × 10⁻¹⁰ mol/L and 6.0 × 10⁻¹⁰ mol/L, respectively.     

Syntheses, characteristics, and fluorescence properties of complexes of europium with benzoic acid and its derivatives

The binary complexes of europium with benzoic acid and its derivatives (phthalic acid, m-phthalic acid,o-aminobenzoic acid, salicylic acid, and sulfosalicylic acid) were synthesized and their compositions were identified by elemental analyses. UV and IR of the complexes have been investigated. The UV spectra indicated that the complexes‘ ultraviolet absorption were mainly the ligands‘ absorption. The IR spectra showed that the IR spectra of complexes are different from those of free ligands. The fluorescence properties of them were investigated by using luminescence spectroscopy, the results showed that only three complexes appear as better luminescence, they were Eu-benzoic acid,Eu-m-phthalic acid and Eu-phthalic acid, while the others exhibited the ligands‘ wideband emission.     

Fluorescence and cofluorescence enhancement of Tb（Ⅲ） complexes with pyromellitic acid by M （M = Gd, La, Ca, and Sr ions）

Fluorescence and cofluorescence properties of Tb(Ⅲ) solid complexes were studied using pyromellific acid (PMA) as ligand and fluorescence inert ions as doping elements. The cofluorescence enhancement, a result of ligand sensi-tized fluorescence, was observed in Th(Ⅲ) solid complexes doped with fluorescent inert ions La(Ⅲ), Gd(Ⅲ), Ca(Ⅲ), and Sr(Ⅲ). The effect of the type and content of doping elements on fluorescence enhancement was studied, and optimum con-ditions were determined. The results show that Gd (La, Ca, Sr) has clear cofluorescence effect in solid complex Tb-M-PMA system, and in present work, rare earth complex fluorescent powder that emits bright green fluorescence at ultraviolet exci-tation was obtained, which had potential application as fluorescent anti-counterfeit ink,     

Syntheses and crystal structures of rare earth （Nd, Gd） 1-D chain complexes with N-p-tolylsulfonyl-β-alanine

1 Introduction The interaction of metal ions such as transition metal and rare earth metal with amino acids and peptide derivatives is of considerable interest as it often represents the role of metal ions in the en- zymes. Sulphonamides derived from amin…     

Synthesis, characterization, and biological activities of Pt（Ⅱ） and Pd（Ⅱ）complexes with 2′,3′,4′,5,7-pentahydroxy flavone

Pt(Ⅱ) and Pd(Ⅱ) complexes with 2′,3′,4′,5.7-pentahydroxy-flavone were synthesized and characterized by ele-mental analysis, molar conductance, IR, ′HNMR, TG-DTA, UV-Vis spectroscopic techniques, and fluorescence analysis.The scavenging effect on the superoxide radical (O2) and the inhibitory effect on lipid peroxides were also investigated. Both the ligand and the complexes exhibit scavenging effect on superoxide radicals, and the effect of the complexes is greater than that of the ligand. The Pt(Ⅱ) complex exhibits the strongest scavenging efficiency. Both Pt(Ⅱ) and Pd(Ⅱ) com-plexes have the inhibitory effect on lipid peroxides, and the effect of the complexes is greater than that of the ligand, but the Pt(Ⅱ) complex has a high effect of promoting lipid peroxides.     

Synthesis and photoluminescence of Eu（DBM）3phen/APTES-SBA- 15 with morphology of pearl-like chains

Novel ordered mesoporous Eu（DBM）3phergAPTES-SBA-15 （EAS） composites with reasonable photoluminescence property and interesting morphology of bundles of pearl-like chains were synthesized. The characteristics of the mesostructure and the optical properties of the prepared samples were investigated by means of XRD, FTIR, SEM, TEM, N2 adsorption-desorption and PL spectroscopy. The results indicate that the as-made EAS composites have long-distance ordered mesoporous structure. Compared with the Eu（DBM）3phen complex, it is found that the EAS composites perform a considerable photoluminescence with good color purity. It is proposed that the anchored amin~ from the APTES and quantum size effect of the Eu（DBM）3phen complex have great effect on the photoluminescence of the EAS composites.     

Synthesis and luminescence properties of rare earth ternary complexes consisting of Tb（Ⅲ）, β-diketones and 1,10-phenanthroline （phen）

In order to study the luminescent properties of ternary rare earth complexes with β-diketone ligand, three new β-diketone ligands, 1-phenyl-3-(p-phenylethynylphenyl)-1,3-propanedione(HPPP), 1-(2-thienyl)-3-(p-phenylethynylphenyl)-1,3-propanedione (HTPP) and 1-(2-furyl)-3-(p-phenylethynylphenyl)-1,3-propanedione (HFPP), were synthesized by Sonogashira coupling reaction and Claisen condensa- tion. Three new ternary rare earth complexes, TbL3phen (L = PPP, TPP, or FPP), were synthesized by the reaction of rare earth chloride TbCl3,1,10-phenanthroline (phen) with HPPP, HTPP, or HFPP respectively, in alcohol solution. The compositions were characterized by means of elemental analysis, chemical analysis, and IR spectra. Luminescent properties of the three new complexes have been studied. The results show that the ternary Tb(III) complexes only emit the weak fluorescence of the Tb(III) ion, which reveals the triplet state energy of the ligands does not match well with the excited state vibrating energy of Tb3 ion.     

Processing, microstructure, and properties of laser remelted Al2O3/Y3Al5O12（YAG） eutectic in situ composite

Laser remelting and rapid solidification were performed in preparing the high-performance Al2O3/Y3Al5O12（YAG） eutectic in situ composite. The microstructure characteristic and solidification behavior were studied using scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS）, X-ray diffractometry（XRD） and simultaneous thermal analysis（STA）. The hardness and fracture toughness were obtained using an indentation technique. The results show that the laser remelted Al2O3/YAG composite has a homogeneous eutectic microstructure without microcrack and pore. The component phases of Al2O3 and YAG are three-dimensionally and continuously reticular connected, and finely coupled without grain boundaries, colonies and amorphous phases between interfaces. The eutectic interspacing is greatly refined with increasing the scanning rate and average is only l μm. The synthetically thermal analysis indicates that the eutectic temperature of Al2O3-YAG is 1 824 ℃, well matching the phase diagram of Al2O3-Y2O3 system. The maximum hardness reaches 19.5 GPa and the room fracture toughness is 3.6 MPa.m^1/2.     

Microstructure and Wear Resistance Evolution of HVOFSprayed WC-（W,Cr）2C-Ni Coating with Post Heat Treatment In Air Atmosphere

WC-(W,Cr)2C-Ni coating was prepared on 1Cr18Ni9Ti stainless steel and C-276 Ni-base Hastelloy by high velocity oxy-fuel(HVOF)spraying.The effect of post heat treatment in air atmosphere on the microstructure,phase composition,microhardness,fracture toughness,and wear resistance of HVOF-sprayed WC-(W,Cr)2C-Ni coating was investigated.The microstructure and phase composition of the coatings were analyzed by means of field emission scanning electron microscopy(FESEM)and X-ray diffraction(XRD).The microhardness and fracture toughness of the coatings were measured using a microhardness tester and a Vickers hardness tester.Moreover,dry friction and wear behavior of the coatings sliding against Si3N4 ball was investigated using an oscillating friction and wear tester;and the worn surfaces of the coatings were analyzed by means of scanning electron microscopy(SEM).It was found that heat treatment within 500-800°C resulted in crystallization of amorphous phase in as-sprayed coating,generating nanoscale new phases such as NiWO4,CrWO4 and Cr2WO6.Besides,heat treatment led to increase of the microhardness of as-sprayed coating,and the highest microhardness was obtained after heat treatment at 800°C.The fracture toughness and wear resistance of the as-sprayed coating increased with increasing heat treatment temperature up to 700°C but tended to decrease with further elevating temperature.In other words,the mechanical properties and wear resistance of the as-sprayed coatings were worsened owing to excessive growth of oxidation grains and depletion of ductile Ni binder after heat treatment above 700°C.Thus it was suggested that as-sprayed ceramic composite coating should be post heat treated in air at a moderate temperature of 700°C so as to achieve the optimized mechanical properties and wear resistance.     

Fluorescence enhancement and cofluorescence in complexes of terbium(III) with trimellitic acid

1. Introduction Rare earth elements have an important function inlife process. The fluorescence enhancement of lan-thanides in aqueous solutions has therefore becomean area of active study in trace-level estimation oflanthanides using spectrofluorimetry [1]. Its possiblemechanism and application as fluorescence probesin biological systems have also attracted attention inrecent years [2]. Generally, fluorescence enhance-ment can be achieved through ligand sensitization.Various ligands have bee…     

Fluorescence enhancement and cofluorescence in complexes of terbium(Ⅲ) with trimellitic acid

The fluorescence of terbium (Ⅲ) was enhanced by about three orders of magnitude in the presence of trimellitic acid (benzene-l, 2, 4-tricarboxylic acid (TLA)) in aqueous solution at pH 6. The fluorescence intensity could be greatly increased when the system of Tb3+-TLA was treated with La3+ (or Gd3+) and TritonX- 100. The addition of La3+ (or Gd3+) enhances the fluorescence of the system by about two orders of magnitude due to cofluorescence, and the TritonX-100 micellar medium plays an important role for stabilization of the system. Both the intermolecular energy transfer mode and intramolecular energy transfer mode are responsible for the mechanism of fluorescence enhancement. In the optimum conditions, the fluorescence intensity is a linear function of Tb3+ concentration in the range of 7.8 × 10-9-3.6 × 10-6 mol/L for the system Tb3+-La3+-TLA and 1.0 × 10-8-4.7 × 10-6 mol/L for the system Tb3+-Gd3+-TLA, and the limits of detection are 4.6 ×10-10 mol/L and 6.0 × 10-10 mol/L, respectively.     

Fluorescence and cofluorescence enhancement of Tb(Ⅲ) complexes with pyromellitic acid by M (M =Gd,La,Ca,and Sr ions)

Fluorescence and cofluorescence properties of Tb(Ⅲ) solid complexes were studied using pyromellitic acid (PMA) as ligand and fluorescence inert ions as doping elements. The cofluorescence enhancement, a result of ligand sensitized fluorescence, was observed in Tb(Ⅲ) solid complexes doped with fluorescent inert ions La(Ⅲ), Gd(Ⅲ), Ca(Ⅲ), and Sr(Ⅲ). The effect of the type and content of doping elements on fluorescence enhancement was studied, and optimum conditions were determined. The results show that Gd (La, Ca, Sr) has clear cofluorescence effect in solid complex Tb-M-PMA system, and in present work, rare earth complex fluorescent powder that emits bright green fluorescence at ultraviolet excitation was obtained, which had potential application as fluorescent anti-counterfeit ink.     

Spectroscopic studies of the Eu(III) and Gd(III) tris(3-aminopyridine-2-carboxylic acid) complexes

The synthesis and spectroscopic studies of the complexes of Eu(III) and Gd(III) with 3-aminopyridine-2-carboxylic acid (3-NH₂pic) are described. An experimental and theoretical analysis of the intensities of the ⁵D₀→⁷F_0,1,2,4 transitions of the Eu(III) ion is presented. An approximate structure for the Eu(III) complex is assumed and the theoretical calculations are based on a model, previously described, which takes into account the forced electric dipole and dynamic coupling mechanisms.     

Photoelectric properties of thin Eu3+-doped TiO2 films sensitized by cis-RuL2(SCN)2·2H2O

Thin nanocrystalline TiO2 films doped by europium ions (Eu3+) were obtained by the sol-gel method. The photoelectric properties of Eu3+-doped TiO2 film electrode sensitized by cis-RuL2(SCN)2·2H2O(L=cis-2,2'-bipyridine-4,4'-dicarboxlic acid) ruthenium complex were studied. The thin filmswere characterized by X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy. Effect of doping Eu3+ on microscopic structure and photoelectrical properties were discussed. The result shows that doping europium ions makes specific surface area of these films larger, which contributes toimproving the photoelectric properties. It is found that an optimal compositiondoped with 0.2 mol.% Eu3+ exhibits the highest photoelectric properties. I sc is 0.37 mA·cm-2 , which is 0.17mA·cm-2 bigger than that of un-doped films;Voc is 405 mV, which is 50 mV bigger than thatof un-doped films.     

Thermal stability and luminescence properties of 1,10-phenanthroline-tris （m-methylbenzoate） europium （or terbium） complexes in SiO2 gel

Silica gel luminophors containing 1, l O-phenanthroline-tris(m-methylbenzoate) europium (or terbium) complexes were prepared by sol-gel method. The thermal decomposition, excitation and emission spectra for the gel phosphors were measured and compared with that of solid complex powders. The thermal stability of the complexes was enhanced in SiO2 host matrix and the luminescence intensity remained unchanged.     

Thermal decomposition products of heteronuclear Cu---Re complexes, CuRE(dhbaen)(NO3)·nH2O (RE---La, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb, and Lu)

To facilitate the preparation of finer and more homogeneous CuREO_x and to achieve a lowering of the formation temperature, heteronuclear CuRE(1:1) complexes, CuRE(dhbaen)(NO₃)·nH₂O were synthesized as precursor. As it was expected for RE=La through Gd, only a mixture of CuO and CuRE₂O₄ was formed even when the complex decomposed at 800 °C since the Cu/RE ratio is 1. For RE=Y and Tb through Lu, Cu₂RE₂O₅ was formed by way of CuO and RE₂O₃. The structure of the decomposed product is controlled by the coordination number and ionic size of RE ion. The minimum radius ratio for eightfold coordination of RE³⁺ ion suggests that preparation of homogeneous Cu:RE(1:1) oxide with Cu₂Ho₂O₅ type structure is difficult for RE=La through Gd.     

Spectral properties of Eu(III) complexes with heteropolyanions immobilised in xerogel matrices

Eu³⁺ complexes with two heteropolymetalates (HPMs) were entrapped in various xerogel matrices by the sol-gel process. The spectral behaviour of these complexes in the rigid xerogel was studied by means of absorption and emission spectra. The luminescence emission experiments prove that photoexcitation of the HPM lattices (tungstate and molybdate) induced the energy transfer from the oxygen-to-metal charge transfer {O→M (= W, Mo)} triplet states to Eu³⁺ (⁷F_0,1,2→⁵D_0,1). Among the studied matrices with the Eu(III) complexes the best results, i.e. highest relative intensity and longest lifetime, were observed for methylated silicate (SiO₂-polydimethylsiloxane) and silica. In both the cases intensity of the emission could be improved by drying at elevated temperature. The studied materials consisting of complexes Eu³⁺ with the HPMs exhibit in practice stable emission intensity during UV irradiation.