Structure, charge-transfer and luminescent properties bis(2-methyl-8-hydroxyquinoline) gallium chloride

Bis(2-methyl-8-hydroxyquinoline) Gallium Chloride (GaMq2Cl) has been synthesized and characterized by X-ray crystallography. It is known from X-ray diffraction data on single crystals that the crystals of GaMq2Cl were monoclinic, space group C2/c, a = 28.701 A, b = 9.5405 A, c = 15.1434 A, Z = 8. Its thermal stability, electron structures and structural stability were investigated by TG analysis and quantum chemical calculations. The complex was a thermally stable material, with decomposition temperature being 348 degrees C. The electron-transfer property of GaMq2Cl is of advantage over hole-transfer property. Under UV excitation at 365 nm, the complex emits blue fluorescence with the maximum emission peak at 471 nm. Finally, blue-green light-emitting devices using this complex as the emissive layer were also fabricated and investigated, with emission wavelength at 502 nm. The results promote GaMq2Cl as a good candidate for luminescent material.     

Synthesis and characterization of 5,7-dimethyl-8-hydroxyquinoline and 2-(2-pyridyl)benzimidazole complexes of zinc(II) for optoelectronic application

Bis(5,7-dimethyl-8-hydroxyquinolinato)zinc(II) (Me₂q)₂Zn and 5,7-dimethyl-8-hydroxyquinolinato(2-(2-pyridyl)benzimidazole) zinc(II) Me₂q(pbi)Zn have been synthesized and characterized by various techniques. These metal complexes have high thermal stability (>300 °C) and high glass transition temperatures (>150 °C). The vacuum deposited films of these materials show good film forming property and are suitable for opto-electronic applications. Multilayered organic electroluminescent (EL) devices have been fabricated having structure ITO/α-NPD/zinc complex/BCP/Alq₃/LiF/Al, which produce emission with chromaticity having Commission Internationale d’Eclairage (CIE) coordinates x = 0.506 and y = 0.484 for (Me₂q)₂Zn; x = 0.47 and y = 0.52 for (Me₂q)(pbi)Zn complex. The electroluminescence spectra show peak emission centered at 572 and 561 nm respectively for these materials.     

Supercritical hydrothermal synthesis of Cu2O(SeO3): Structural characterization, thermal, spectroscopic and magnetic studies

Cu₂O(SeO₃) has been synthesized in supercritical hydrothermal conditions, using an externally heated steel reactor with coupled hydraulic pump for the application of high pressure. The compound crystallizes in the P2₁3 cubic space group. The unit cell parameter is a = 9.930(1) Å with Z = 12. The crystal structure has been refined by the Rietveld method. The limit of thermal stability is, approximately, 490 °C. Above this temperature the compound decomposes to SeO₂(g) and CuO(s). The IR spectrum shows the characteristic bands of the (SeO₃)²⁻ oxoanion. In the diffuse reflectance spectrum two intense absorptions characteristic of the Cu(II) cations in five-coordination are observed. The ESR spectra are isotropic from room temperature to 5 K, with g = 2.11(2). The thermal evolution of the intensity and line width of the signals suggest a ferromagnetic transition in the 50-45 K range. Magnetic measurements, at low temperatures, confirm the existence of a ferromagnetic transition with a critical temperature of 55 K.     

Preparation, photoluminescence and thermal stability of sodium tris(pyridine dicarboxylato) europate(III) complex incorporated into silica matrix

Silica-based composite materials incorporated with sodium tris(pyridine dicarboxylato) europate(III), SiO₂ : Na₃Eu(DPA)₃, where H₂DPA is 2,6-pyridine dicarboxylic acid, were prepared by a sol-gel method. Photoluminescent properties of SiO₂ : Na₃Eu(DPA)₃ composite were studied after heat treatment between room temperature and 600 °C. The strong red emission of SiO₂ : Na₃Eu(DPA)₃ was intensified by heat-treatment under appropriate conditions. The thermal stability of Na₃Eu(DPA)₃·9H₂O and its silica-based composite was examined. The results demonstrate that SiO₂ : Na₃Eu(DPA)₃ composite material possesses very good thermal stability with intense visible fluorescence, and may be applied as a potential luminescent material.     

D.C. conduction phenomenon and spectrum of a novel bis(7-formyl-8-hydroxyquinoline) zinc complex

A novel bis(7-formyl-8-hydroxyquinoline)zinc complex was prepared from 7-formyl-8-hydroxyquinoline. This compound was characterized on the basis of elemental analysis, i.r., ¹H nuclear magnetic resonance, magnetic moment and conductivity measurements. The compound was a non-conductor in dimethylformamide. A tentative structure for this compound is suggested. The electrical conductivity at various temperatures for an annealing time of 1 h has been measured. The activation energy of this compound is found to be 0.68 eV. Conduction parameters including the Schottky coefficient (_s), Schottky electrode barrier (_s), jump distance (d) and dielectric constant () have been determined. The aim of this study is also to understand the mechanism of conduction of this zinc(II) complex.     

Fabrication and electrogenerated chemiluminescence properties of uniform octahedral 8-hydroxyquinoline zinc (Znq2)

Well-defined octahedral Znq₂ has been synthesized via a facile solvothermal route. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images show that the as-prepared product has an octahedral structure with an edge length of 2 μm. The reaction parameters, such as solvent, reaction time and temperature, play an important part in the morphology of the final product. A possible formation mechanism for octahedral Znq₂ is proposed. The as-prepared octahedral Znq₂ exhibits excellent electrogenerated chemiluminescence (ECL) behaviour.     

Equilibrium, thermodynamic and kinetic studies for the biosorption of aqueous lead(II), cadmium(II) and nickel(II) ions on Spirulina platensis

The biosorption of lead(II), cadmium(II) and nickel(II) ions from aqueous solution by Spirulina platensis was studied as a function of time, concentration, temperature, repetitive reactivity, and ionic competition. The kinetic results obeyed well the pseudo second-order model. Freundlich, Dubinin Radushkevich and Temkin isotherm models were applied in describing the equilibrium partition of the ions. Freundlich isotherm was applied to describe the design of a single-stage batch sorption system. According to the thermodynamic parameters such as DeltaG degrees, DeltaH degrees and DeltaS degrees calculated, the sorption process was endothermic and largely driven towards the products. Sorption activities in a three metal ion system were studied which indicated that there is a relative selectivity of the biosorbent towards Pb2+ ions. The measurements of the repetitive reusability of S. platensis indicated a large capacity towards the three metal ions.     

Facile combustion synthesis and photoluminescence properties of Ce3+ doped Sr2La8(SiO4)6O2 phosphors

The Sr₂La₈(SiO₄)₆O₂:Ce³⁺ powder phosphor with apatite structure has been successfully synthesized via a facile route of sol-combustion technique. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) spectroscopy were used to characterize the as-prepared samples. Sr₂La₈(SiO₄)₆O₂:Ce³⁺ phosphor was composed of particles with average sizes range about 300 nm. The phosphor exhibited an absorption ranging from 220 to 390 nm in ultraviolet range and a broad blue-violet emission band peaked at 403 nm with a CIE coordinates of (0.167, 0.028). The concentration quenching mechanism was also determined to be dipole–dipole interaction.     

Luminol chemiluminescence in unbuffered solutions with a cobalt(II)-ethanolamine complex immobilized on resin as catalyst and its application to analysis.

Using a heterogeneous catalyst, Co(II)-ethanolamine complex sorbed on Dowex-50W resin, the chemiluminescence (CL) of luminol in unbuffered or weakly acidic solution was studied in the presence of H2O2. The maximum luminol CL wavelength at pH 5.7 was 448 nm, 23 nm longer than that in a basic solution (pH 10.5). Three different ligands, mono-, di-, and triethanolamine, and six transition metal ions, Co(II), Cu(II), Ni(II), Mn-(II), Fe(II), and Fe(III) were compared by CL measurements. The CL intensity decreased in the order mono- > di- > triethanolamine and Co(II) > Cu(II) > Ni(II) > Fe-(III) > Mn(II) > Fe(II). This heterogeneous CL system was developed as H2O2 and glucose flow-through sensors. Detection limits (S/N = 3) of H2O2 and glucose using Dowex-50W-X4-Co(II)-monoethanolamine as catalyst are 1 x 10(-7) M and 1 x 10(-6) M, respectively. On the basis of the studies of the CL, fluorescence, UV-vis and ESCA spectra and the effect of dissolved oxygen in luminol solution, a mechanism for CL emission in unbuffered solution was considered as the formation of a superoxide radical ion during the decomposition of H2O2 catalyzed by the Co(II)-ethanolamine immobilized resin. Then the superoxide radical ion acted on luminol and the CL was emitted. The applications of the proposed method to determine H2O2 in rainwater without any special pretreatment and glucose in human urine and orange juice samples give satisfactory results.     

Unusual route for preparation of manganese(II), cobalt(II), zinc(II) and cadmium(II) carbonate compounds: synthesis and spectroscopic characterizations

The manganese(II) carbonate, MnCO₃·H₂O, cobalt(II) carbonate, CoCO₃·4H₂O, zinc(II) carbonate, ZnCO₃ and cadmium(II) carbonate, CdCO₃, respectively, were synthesis by a new simple unusual route during the reaction of aqueous solutions of MnX₂, CoX₂, ZnX₂ and CdX₂, where (X = Br⁻ and ClO₄⁻) with urea at high temperature within ∼ 90°C for 6 h. The infrared spectra of the reaction products clearly indicate the absence of the bands of urea, but show the characteristic bands of ionic carbonate, CO₃²⁻. A general mechanism describing the preparation of manganese(II), cobalt(II), zinc(II) and cadmium(II) carbonate compounds are discussed.     

Enhanced photoluminescence response of Er-Si nanoparticle codoped Al2O3 films by controlled synthesis in the nanoscale and thermal processing

Nanostructured Er³⁺-Si nanoparticles (NPs) codoped Al₂O₃ films were synthesized by a one step laser based deposition process which allows to form the Si NPs in situ at room temperature, and to control their size and separation with the Er ions in the nanoscale. Two different thermal annealing treatments are studied in order to optimize the photoluminescence (PL) emission: rapid thermal annealing (RTA) at 900 °C during 2 min, and conventional furnace step annealing at different temperatures up to 750 °C for 1 h. After RTA process the films show an important enhancement on the photoluminescence lifetime values which is related to a reduction of the non-radiative decay channels. Nevertheless, the Si NPs to Er ions energy transfer is strongly reduced. In contrast after conventional furnace annealing up to 700 °C, although there is only a moderate increase of the photoluminescence lifetime values, the excitation of Er ions through Si NPs is still active and as a consequence a large enhancement of the photoluminescence intensity with respect to the Er-only doped film is achieved. These different behaviours are most likely related to structural and chemical changes in the Er environment upon the different annealing processes.     

Ba2(Y,Sc)NbO6:Bi3+ solid solution nanocrystals: synthesis,photoluminescence properties,and white LEDs application

Journal of Materials Science: Materials in Electronics - In the recent years, luminescent phosphor materials have contributed much to reduce the serious environmental problems such as environmental...     

2-[(8-羟基喹啉)-2-基]-5-(2-噻吩基)[60]富勒烯吡咯烷的合成、光学及电化学性能

通过1,3-偶极环加成反应合成出2-[(8-羟基喹啉)-2-基]-5-(2-噻吩基)[60]富勒烯吡咯烷,利用UV-Vis、FT-IR、RAMAN、MALDI-TOF MS、1 HNMR、13C NMR等手段对产物的结构进行了表征,并研究了产物的光学及电化学性能。结果表明,相对于C60来说,该产物的紫外吸收波长及荧光发射波长均发生红移,各对氧化还原峰的半峰电位发生明显的负移,更有利于应用于光电转化领域。     

The structural characterization and its influence on photoluminescence of lithium tetra-(8-hydroxy-quinolinato) Boron

Lithium tetra-(8-hydroxy-quinolinato) boron (LiBq₄) is one kind of blue light-emitting material with good performances. In this paper, LiBq₄ sample was synthesized and purified. The purity is up to 97.6%. In order to investigate the influence of LiBq₄ structure on its optical characteristics, especially on the shift of photoluminescence (PL) central wavelength, compared with that of tris-(8-hydroquinoline) aluminum (Alq₃), a joint experiment based on a combination of X-ray diffraction (XRD) spectrum, infrared absorption (IRA) spectrum, hydrogen nuclear magnetic resonance (HNMR) spectrum, absorption and photoluminescence spectra of LiBq₄ was performed. IRA and HNMR spectra generally make certain the molecular structure, and illuminate the interaction among the atoms in LiBq₄. Absorption and photoluminescence spectra qualitatively suggest the basic optical characteristic of LiBq₄ and that the emitted light results from 8-hydroxyquinoline rings. By comparing LiBq₄ with Alq₃, the conclusion that besides B−N covalent bond, B−O is another important factor which heavily influence on the PL peak can be drawn. Furthermore, the influence of LiBq₄‘s special coupling manner on PL peak is demonstrated too.     

Two polymeric metal complexes based on polycarbazole containing complexes of 8-hydroxyquinoline with Zn(II) and Ni(II) in the backbone: Synthesis,characterization and photovoltaic applications

Two novel polymeric metal complexes PZn(Q)₂–C and PNi(Q)₂–C based on polycarbazole containing complexes of 8-hydroxyquinoline with Zn(II) and Ni(II) were synthesized and applied in dye-sensitized solar cells (DSSCs) as photosensitizers. They possess moderate thermal stability and good open-circuit voltages, and the power conversion efficiency of them reached to 1.11% and 0.45%, respectively, under simulated AM 1.5 G solar irradiation (100 mW cm⁻²), which shows a new strategy to design photosensitizers for DSSCs.     

Structural,thermal, spectroscopic and magnetic studies of the (C2N2H10)0.5[FexV1−x(HPO3)2] (x = 0.26, 0.52, 0.74) solid solution

The (C₂N₂H₁₀)_0.5[Fe_xV_1−x(HPO₃)₂] (x = 0.26, 0.52 0.74) compounds have been obtained by mild solvothermal conditions in the form of micro-crystalline powder with brown color. The crystal structures were refined by X-ray powder diffraction data using the Rietveld method. The compounds crystallize in the monoclinic system, space group P2/c with the unit-cell parameters, a = 9.262(5) Å, b = 8.823(5) Å, c = 9.714(6) Å, β = 120.84(3)°; a = 9.245(1) Å, b = 8.823(1) Å, c = 9.698(1)Å, β = 120.80(1)° and, a = 9.254(4)Å, b = 8.822(4)Å, c = 9.702(4)Å, β = 120.73(3)° for (C₂N₂H₁₀)_0.5[Fe_0.26V_0.74 (HPO₃)₂] (1), (C₂N₂H₁₀)_0.5[Fe_0.52V_0.48(HPO₃)₂] (2), and (C₂N₂H₁₀)_0.5[Fe_0.74V_0.26(HPO₃)₂] (3). The compounds show an open crystalline structure with three-dimensional character, whose formula for the anionic inorganic skeleton is [M(HPO₃)₂]²⁻. The inorganic framework is formed by [MO₆] octahedra inter-connected by phosphite groups. The structure of the compounds exhibits channels extended along the [1 0 0] and [0 0 1] directions and the ethylendiammonium cations are located inside these channels, linked through hydrogen bonds and ionic interactions. The infrared spectra show the bands corresponding to the stretching (P–H) vibration of the phosphite group and the band corresponding to the deformation mode of the ethylendiammonium cation, δ(NH₃⁺). The thermal and thermodiffractometric behavior show that the compounds are stable up to approximately 300 °C, at higher temperatures the decomposition of the crystal structure by calcination of the organic cation starts. The diffuse reflectance spectra show bands of the V³⁺ ion (d²), and a band of the Fe³⁺ ion (d⁵), in a slightly distorted octahedral symmetry. The values of the Dq and Racah parameters (B and C) have been calculated for the V(III) cation. Magnetic measurements were performed on a powdered sample from 5 to 300 K at magnetic fields 1000, 500 and 100 G, in the ZFC and FC modes. At the magnetic field of 1000 G antiferromagnetic interactions were observed, but at 100 G have been detected higher values of the χ_m in the FC mode than those observed in the ZFC one, indicating the existence of a dominant ferromagnetic component at low temperature. The magnetization measurements show hystheresis loops at 5 K, with values of the remanent magnetization and coercive field of 1.91 emu/mol and 23 Gauss for (1), 25 emu/mol and 300 Gauss for (2), and 3 emu/mol and 50 Gauss for the compound (3).     

温敏型聚合物PNIPAAM的合成及应用研究进展

聚N-异丙基丙烯酰胺(简称PNIPAAM)是一类研究广泛的温敏型功能高分子水凝胶.从制备方法、应用及其改性这三个方面综述了近年来对PNIPAAm的研究进展,并提出今后的发展方向.