Photoluminescent properties of di(8-hydroxyquinolato) zinc impregnated in nanoporous glass

Photoluminescent properties of a metal-organic complex, di(8-hydroxyquinolato) zinc, impregnated in nanoporous glass were investigated. In comparison with those in the normal organic fluorescent material, the emission band of the impregnated organic phosphor became wider. Blueshift (14 nm) was observed due to π*→n emission transition. The excitation band of the embedded organic phosphor had a larger blueshift and was divided into several sub-bands. The intensity in the short wavelength end of the embedded organic fluorescent material became much stronger.     

Enhanced Brightness of Eu^3＋ Complex in Organinc Electroluminescent Devices by Using Another Rare—Earth Ion

Rare-earth ions Tb^3 and La^3 were used as a bridge to improve the energy transfer from the polymer to an Eu complex.The material Tb(La)0.5Eu0.5(BSA)3 phen was synthesized and used as the emission layer in the device:ITO/PVK:Tb(La)0.5Eu0.5(BSA)3phen/Alq/Al.The two device were compared in detail and it was found that the device using La0.5Eu0.5(BSA)3phen as the emission material had better monochromatic characteristics with the maximal brightness of 102 ca/m^2 and the colour coordinates x=0.55 and y=0.36.     

Synthesis and Structural Characterizations of Ternary Iron(Ⅱ) Mixed Ligand Complex: Low Cost Materialsas a Precursor for Preparation of Nanometric Fe_2O_3 Oxide

The reaction of the ligands, ethylenediaminetetraacetic acid terasodium salt (Na₄EDTA) and N-N heterocyclic diamines like2,2’-bipyridine (bipy) with iron(Ⅱ) sulfate with 1∶2∶2 stoichiometric ratios form the mononuclear ternary complex of formulae, [Fe₂(EDTA)(bipy)₂] at pH~7. The FTIR and Raman laser spectra of the iron(Ⅱ) complex show that 2,2’-bipyridine is present asa bidentate ligand and the ethylenediaminetetraacetic acid terasodium salt as monodentate carboxylate anion. The electronic spectra and magnetic moments data suggest the six coordination number. It has two iron(Ⅱ) centers in octahedral environments, which are interlinked by carboxylato-O atoms of ethylenediaminetetraacetate and by nitrogen atoms of the two 2,2-bipyridine ligands in a chelating mode. Thermal analysis study show thatiron(Ⅱ) complex containing EDTA and 2,2’-bipyridine on its thermalde composition form the corresponding Fe₂O₃ oxide in nano size at the temperature range ~475 ℃. The iron(Ⅱ) complex was performed as a convenient low cost precursor for the preparation of Fe₂O₃ nanoparticles by the the thermal decomposition method. The iron(Ⅲ) oxide composition has been discussedusing FTIR, X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX).     

锰(Ⅱ)-胡椒碱-溴化十六烷基三甲基胺三元体系的荧光特性及应用

The fluorescence characteristics of the complex of piperine with cation in micellar system were studied. At the same time, the influence of experimental condition on the fluorescence intensity was also studied. The experiments indicated that piperine had very low fluorescence signal itself. But in pH 8.77 Na₂HPO₄-NaH₂PO₄ buffer solution, both Mn(Ⅱ) and cationic surfactant cetyltrimethylammonium bromide can enhance the fluorescence intensity and stability of piperine. Based on this, a sensitive method has been developed for the quantitative determination of piperine in Mn(Ⅱ)-piperine-cetyltrimethylammonium bromide ternary system. Under the optimum conditions, there is a linear relationship between the enhancement of fluorescence intensity and the concentration of Mn(Ⅱ). The optimal conditions are as follows: the concentration of Mn(Ⅱ) is 2.5×10-4 mol·L-1 and the concentration of cetyltrimethylammonium bromide is 5×10-4 mol·L-1. The fluorescence intensity was determined by a 1 cm quartz cell with the excitation wavelength of 352 nm and the emission wavelength of 452 nm. The linear range of concentration of piperine was 2.02-10.1 μg·mL-1 with the relative coefficient of 0.998 5 and the detection limit of 0.060 2 μg·mL-1. The relative standard deviation (RSD) was 1.10%. The proposed method has been successfully applied to the quantitative determination of piperine in the Mongolian medicine Piper longum L, and the recovery was within the range of 97.6%-102.0%. The results were very satisfactory.     

Dependence of charge trapping of fluorescent and phosphorescent dopants in organic light-emitting diodes on the dye species and current density

This paper utilizes multilayer organic light-emitting diodes with a thin layer of dye molecules to study the mechanism of charge trapping under different electric regimes. It demonstrates that the carrier trapping was independent of the current density in devices using fluorescent material as the emitting molecule while this process was exactly opposite when phosphorescent material was used. The triplet--triplet annihilation and dissociation of excitons into free charge carriers was considered to contribute to the decrease in phosphorescent emission under high electric fields. Moreover, the fluorescent dye molecule with a lower energy gap and ionized potential than the host emitter was observed to facilitate the carrier trapping mechanism, and it would produce photon emission.     

Detecting the intrinsic Baldwin Effect of the optical FeII complex in Luminous Seyfert 1 Galaxy Fairall 9

We analyze the optical spectra of Fairall 9,a luminous Seyfert 1 galaxy.They are obtained from the AGN Watch program that has monitored this object for 9 months.The flux and variation of the optical FeII complex is measured using multi-component profile modeling with FeⅡ templates.A convincing intrinsic Baldwin Effect(BEff) of optical FeⅡ emission blends in Fairall 9 is discovered for the first time.The variation of FeⅡ/Hβ(RFe) in Fairall 9 is obtained.We also detect a marginal anti-correla tion between RFe...     

Fabrication of Semiconductor Polymer Membranes Combined with a Colored Charge Transfer Complexes Used in the Manufacture of Solar Cells as a Source of Alternative Energy

The main task of this article was to prepared of new pigment model in situ solar cells accordance to charge-transfer complexes of rhodamine C (RhC) donor as dye laser gain media with iodine (σ-acceptor) and chloranilic acid, CLA (π-acceptor). The synthesis stoichiometry of these complexes were of 1∶2 (donor∶acceptor) with general formulas [(RhC)]I·I₃ and [(RhC)(CLA)₂]. The discussed data of elemental analysis, conductivity measurements, FT-IR, UV-Vis spectroscopy and photometric titration data visualized the stoichiometry, formula and complexity of the complexes. The physicochemical and spectroscopic analyses obtained suggested that the electron transfer occurred through nitrogen atom in a tertiary amine -N(C₂H₅)₂ of RhC donor with acceptor. The synthesized solid complexes were under go to thermogravimetric analyses to investigate their thermal stability and decomposition steps. The molar conductance measurements revealed that RhC complexes have an electrolytic statement. The thermal stability of rhodamine C complexes was enhanced in comparable with RhC itself. The polymer membranes of poly-methyl methacrylate) (PMMA) combined with the RhC charge(transfer complexes in chloroform solvent have been prepared and characterized by (infrared & electronic) spectroscopy and scanning electron microscopy (SEM) morphological examination. The photo-stability properties of the RhC complexes have been investigated.     

Optical spectra and local structure of Eu3+ ions doped in Nb2O5-La2O3-B2O3-BaO glasses

The xNb2O5-(15-x)La2O3-40B2O3-45BaO (x = 5, 7.5, 12.5 mol%) glasses doped with Eu3+ ions in 1mol% are fabricated by the melting method. The Fourier transform infrared (FTIR) spectra, phonon sideband spectra, emission and excitation spectra of the glasses are measured. The crystal field parameter and coordination number of Eu3+ ions in the glasses are obtained according to the splitting of their 5D0 - 7F1levels. The intensity parameters Ω2 and Ω4 of Eu3+ ions for optical transition are calculated from their emission spectra in terms of reduced matrix U(t) (λ= 2,4,6) character for optical transitions. The results indicate that the intensity parameters Ω2 and Ω4 increase with the increase of Nb2O5 content, suggesting that the symmetry becomes lower, the band of Eu and O atoms becomes stronger and the covalence increases with the increase of Nb2O5 content.     

The concentration quenching and crystallographic sites of Eu²⁺ in Ca₂BO₃Cl

A yellow phosphor, Ca2BO3 Cl:Eu2+ , is prepared by the high-temperature solid-state method. Under the condition of excitation sources ranging from ultraviolet to visible light, efficient yellow emission can be observed. The emission spectrum shows an asymmetrical single intensive band centred at 573 nm, which corresponds to the 4f 6 5d 1 →4f 7 transition of Eu2+ . Eu2+ ions occupy two types of Ca2+ sites in the Ca2BO3 Cl lattice and form two corresponding emission centres, respectively, which lead to the asymmetrical emission of Eu2+ in Ca2 BO 3 Cl. The emission intensity of Eu2+ in Ca2BO3 Cl is influenced by the Eu2+ doping concentration. Concentration quenching is discovered, and its mechanism is verified to be a dipole–dipole interaction. The value of the critical transfer distance is calculated to be 2.166 nm, which is in good agreement with the 2.120 nm value derived from the experimental data.     

Pressure dependence of the thermal stability in LiMn2O4

Structural stability in terms of the decomposition temperature in LiMn₂O₄ was systematically investigated by a series of high-temperature and high-pressure experiments.LiMn₂O₄ was found to have structural stability up to 5 GPa at room temperature.Under ambient pressure,the compound decomposed at 1300℃.The decomposition temperature decreased with increasing pressure,yielding more complex decomposed products.Below the decomposition temperature,the crystal structure of LiMn₂O₄ varied with pressure.The presented results in this study offer new insights into the thermal and pressure stability of LiMn₂O₄ materials as a cathode for lithium-ion batteries that can operate under extreme conditions.Therefore,these findings may serve as a useful guide for future work for improving lithium-ion batteries.     

Optical spectra and local structure of Eu~(3+) ions doped in Nb_2O_5-La_2O_3-B_2O_3-BaO glasses

The xNb2O5-(15-x)La2O3-40B2O3-45BaO (x = 5, 7,5, 12.5 mol%) glasses doped with Eu3 mol% are fabricated by the melting method. The Fourier transform infrared (FTIR) spectra, phonon sideband spectra, emission and excitation spectra of the glasses are measured. The crystal field parameter and coordination number of Eu3 ions in the glasses are obtained according to the splitting of their 5D0 - 7F1 levels. The intensity parametersΩ2 andΩ4 of Eu3 ions for optical transition are calculated from their emission spectra in terms of reduced matrix U(t) (λ= 2, 4, 6) character for optical transitions. The results indicate that the intensity parametersΩ2 andΩ4 increase with the increase of Nb2O5 content, suggesting that the symmetry becomes lower, the band of Eu and O atoms becomes stronger and the covalence increases with the increase of Nb2O5 content.     

White emission from Tm3+/Tb3+/Eu3+ co-doped fluoride zirconate under ultraviolet excitation

We synthesize Tm3+/Tb3+/Eu3+triply-doped ZrF4–BaF2–LaF3–AlF3–NaF(ZBLAN) transparent glass by using a melt-quenching method. Under excitation of 365 nm, the white emission with Commission internationale deL’Eclairage(CIE) coordinates of(0.33, 0.33) is achieved at the Eu3+concentration of 1.1 mol%. The mechanisms for white emission and the energy transfer process of Tb3+→ Eu3+are discussed in terms of the photoluminescence, photoluminescence excitation spectra, and the light emission decay curves. The nature for the Tb3+→ Eu3+energy transfer is described with the aid of an energy level diagram.     

Luminescence properties of ZnS：Cu, Eu semiconductor nanocrystals synthesized by a hydrothermal process

ZnS:Cu, Eu nanocrystals with an average diameter of ～ 80 nm are synthesized using a hydrothermal approach at 200 C. The photoluminescence (PL) properties of the ZnS:Cu, Eu nanocrystals before and after annealing, as well as the doping form of Eu, are studied. The as-synthesized samples are characterized by X-ray diffraction, scanning electron microscopy, inductively coupled plasma-atomic emission spectrometry, and the excitation and emission spectra (PL). The results show that both Cu and Eu are indeed incorporated into the ZnS matrix. Compared with the PL spectrum of the Cu mono-doped sample, the PL emission intensity of the Cu and Eu-codoped sample increases and a peak appears at 516 nm, indicating that Eu 3+ ions, which act as an impurity compensator and activator, are incorporated into the ZnS matrix, forming a donor level. Compared with the unannealed sample, the annealed one has an increased PL emission intensity and the peak position has a blue shift of 56 nm from 516 nm to 460 nm, which means that Eu 3+ ions reduce to Eu 2+ ions, thereby leading to the appearance of Eu 2+ characteristic emission and generating effective host-to-Eu 2+ energy transfer. The results indicate the potential applications of ZnS:Cu, Eu nanoparticles in optoelectronic devices.     

Improved Blue-Green Electrophosphorescence from a Tuning Iridium Complex with Benzyl Group in Polymer Light-Emitting Devices

Electroluminescence performances from a tuning biscyclometlated iridium complex with benzyl group are demonstrated in double-layered polymer light-emitting devices （PLEDs） using a blend of poly（9,9-dioctylfluorene） and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole as a host matrix. Blue-green electrophosphorescent emission with a peak at 521 nm and a shoulder at 492nm was observed. The highest luminance efficiency of 4.8cd/A at current density of 0. 56 mA/cm^2 and a maximum luminance of 1944 cd/m^2 at 217.6 mA/cm^2 were achieved in the devices at the dopant concentration of 8%. The luminous performance of the devices becomes better with increasing dopant concentrations from 1% to 8%. This implies that the concentration quenching of this iridium complex with benzyl group can be efficiently inhibited in the devices.     

Intensities and spectral features of the ~4I_(13/2)-~4I_(15/2) potential laser transition of Er~(3+) centers in CaF_2-CeF_3 disordered crystal

A CaF_2-CeF_3 disordered crystal containing 1.06% of Er~(3+) ions was grown by the temperature gradient technique.Optical absorption and emission spectra recorded at room temperature and at 10 K, luminescence decay curve recorded at room temperature, and extended x-ray-absorption fine structure spectra were analyzed with an intention to assess the laser potential related to the ~4I_(13/2)→~4I_(15/2) transition of Er~(3+). In addition, the thermal diffusivity of the crystal was measured at room temperature. The analysis of room-temperature spectra revealed that the ~4I_(13/2) emission is long-lived with a radiative lifetime value of 5.5 ms, peak emission cross section of 0.73 × 10~(-20) cm~2, and large spectral width pointing at the tunability of the emission wavelength in the region stretching from approximately 1480 nm to 1630 nm. The energies of the crystal field components for the ground and excited multiplets determined from low-temperature absorption and emission spectra made it possible to predict successfully the spectral position and shape of the room-temperature ~4I_(13/2)→~4I_(15/2) emission band. Based on the correlation of the optical spectra and dynamics of the luminescence decay, it was concluded that in contrast to Yb~(3+) ions in heavily doped CaF_2 erbium ions in the CaF_2-CeF_3 crystal reside in numerous sites with dissimilar relaxation rates.     

A novel yellow phosphor for white light emitting diodes

This paper reports that a novel yellow phosphor, LiSrBO₃:Eusup>2+, was synthesized by the solid-state reaction. The excitation and emission spectra indicate that this phosphor can be effectively excited by ultraviolet (360 and 400~nm) and blue (425 and 460~nm) light, and exhibits a satisfactory yellow performance (565~nm). The role of concentration of Eusup>2+ on the emission intensity in LiSrBO₃ is studied, and it is found that the critical concentration is 3 mol\%, and the concentration self-quenching mechanism is the dipole--dipole interaction according to the Dexter theory. White light emitting diodes were generated by using an InGaN chip (460~nm or 400~nm) with LiSrBO₃:Eusup>2+ phosphor, the CIE chromaticity is (x=0.341, y=0.321) and (x=0.324, y=0.318), respectively. Therefore, LiSrBO₃:Eusup>2+ is a promising yellow phosphor for white light emitting diodes.     

Preparation and optical properties of poly(vinylidene difluoride)/(Y0.97Eu0.03)2O3 rare-earth nanocomposite

In this letter, poly(vinylidene difluoride) (PVDF)/(Y0.97Eu0.03)2O3 rare-earth nanocomposites were prepared by a simple co-precipitation method, and their morphology, structure, and optical properties were investigated. The scanning electron microscope (SEM) images showed that the (Y0.97Eu0.03)2O3 rare-earth nanoparticles formed 50 nm - 2μm aggregates in PVDF matrices. X-ray diffraction (XRD) curves indicated the incorporation and structure preserving of (Y0.97Eu0.03)2O3 nanoparticles in PVDF matrices. Photoluminescence (PL) spectra of the nanocomposite showed a characteristic red light emission at 612 nm, which was attributed to the intrinsic emission of (Y0.97Eu0.03)2O3 nanoparticles. Optical band gap (Eg) of the nanocomposite exhibited a decreasing trend with the increase of (Y0.97Eu0.03)2O3 content in PVDF matrices within the experimental dosage range.     

First-principles study on with nitrogen and anatase TiO2 codoped praseodymium

<正>The crystal structures,electronic structures and optical properties of nitrogen or/and praseodymium doped anatase TiO₂ were calculated by first principles with the plane-wave ultrasoft pseudopotential method based on density functional theory.Highly efficient visible-light-induced nitrogen or/and praseodymium doped anatase TiO₂ nanocrystal photocatalyst were synthesized by a microwave chemical method.The calculated results show that the photocatalytic activity of TiO₂ can be enhanced by N doping or Pr doping,and can be further enhanced by N+Pr codoping.The band gap change of the codoping TiO₂ is more obvious than that of the single ion doping,which results in the red shift of the optical absorption edges.The results are of great significance for the understanding and further development of visible-light response high activity modified TiO₂ photocatalyst.The photocatalytic activity of the samples for methyl blue degradation was investigated under the irradiation of fluorescent light.The experimental results show that the codoping TiO₂ photocatalytic activity is obviously higher than that of the single ion doping.The experimental results accord with the calculated results.     

The luminescence enhancement of Eu^3＋ ion and SnO2 nanocrystal co-doped sol-gel SiO2 films

SnO₂ nanocrystal and rare-earth Eu～（3+） ion co-doped SiO₂ thin films are prepared by sol-gel and spin coating methods.The formation of tetragonal rutile structure SnO₂ nanocrystals with a uniform distribution is confirmed by X-ray diffraction and transmission electron microscopy.Fourier transform infrared spectroscopy is used to investigate the densities of the hydroxyl groups,and it is found that the emission intensity from the 5 D 0 7 F 2 transitions of the Eu～（3+） ions is enhanced by two orders of magnitude due to energy transfer from the oxygen-vacancy-related defects of the SnO₂ nanocrystals to nearby Eu～（3+） ions.The influences of the amounts of Sn and the post-annealing temperatures are systematically evaluated to further understand the mechanism of energy transfer.The luminescence intensity ratio of Eu～（3+） ions from electric dipole transition and magnetic dipole transition indicate the different probable locations of Eu～（3+） ions in the sol-gel thin film,which are further discussed based on temperature-dependent photoluminescence measurements.     

Analysis of asymmetry of the Dαemission spectra under the Zeeman effect in boundary region for D-D experiment on EAST tokamak

In 2015 campaign,deuterium atomic emission spectra(D_α)under the Zeeman effect in boundary region had been measured by a high resolution optical spectroscopic multichannel analysis(OSMA)system based on passive spectroscopy during the deuterium plasma discharge on EAST tokamak,and part of the works about the Zeeman effect on D_αspectra had already been done.However,the asymmetric phenomena of D_αemission spectra under the Zeeman effect were observed in process of analyzing the spectral data.To understand the asymmetric phenomena and acquire the useful local plasma information,an algorithm was proposed and used to analyze the asymmetry of the emission spectra under the Zeeman effect with all polarization components(πand±σ).In the algorithm,the neutral atoms were considered to follow the Maxwell distribution on EAST,and I+σ=I-σwas considered and set.Because of the line-averaged spectra along the viewing chord,the emission spectra were considered from two different regions:low-field side(LFS)and high-field side(HFS).Each spectral line was classified into three energy categories(the cold,warm,and hot)based on different atomic production processes in boundary recycling.The viewing angleθ(between the magnetic field B and the viewing chord),magnetic field B at two spectral emission positions(HFS and LFS)and the Doppler shift of all three energy categories of each spectral line were all considered in the algorithm.The effect of instrument function was also included here.The information of the boundary plasma were acquired,the reason for the asymmetric phenomena was discussed,and the boundary recycling during the discharge were studied in the paper.Based on fitting a statistical data of acquired fitting results,an important conclusion was acquired that the ratio of the spectral line intensity in HFS and LFS was proportional to the square of that of the corresponding magnetic field.