Electrospinning preparation and photoluminescence properties of erbium complex doped composite fibers

In this paper, an Er(III) complex of Er(DBM)3IPD, where DBM=1,3-diphenyl-propane-1,3-dione and IPD=4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-N,N-diphenylaniline, is synthesized and doped into poly(vinylpyrrolidone) submicron fibers through electrospinning technique. The crystal structure and morphology are investigated in detail. The composite fibers exhibit smooth and uniform morphology on the substrate, with an average diameter of ～1.4 μm. Photophysical data suggest that DBM ligand sensitizes Er(III) center efficiently and provides an optimal condition for radiative decay, and low temperature can enhance the emission intensity by suppressing the quenching effect. It is found that the photostability of Er(III) complex doped composite fibers is largely improved compared with that of pure complex.     

Growth of piezoelectric water-free GeO2 and SiO2-substituted GeO2 single-crystals

Using the slow-cooling method in selected fluxes, we have grown spontaneously nucleated single-crystals of pure GeO(2) and SiO(2)-substituted GeO(2) materials with the α-quartz structure. These piezoelectric materials were obtained in millimeter size as well-faceted, visually colorless, and transparent crystals. Cubic-like or hexagonal prism-like morphology was identified depending on the chemical composition of the single-crystals and on the nature of the flux. Both the silicon substitution rate and the homogeneity of its distribution were estimated by Energy Dispersive X-ray spectroscopy. The cell parameters of the flux-grown GeO(2) and Ge(1-x)Si(x)O(2) (0.038 ≤ x ≤ 0.089) solid-solution were deduced from their X-ray powder diffraction pattern. As expected, the cell volumes decrease as the silicon content substitution increases. A room temperature Infrared spectroscopy study confirms the absence of hydroxyl groups in the as-grown crystals. Unlike what was observed for hydrothermally grown GeO(2) crystals, these flux-grown oxide materials did not present any phase transition before melting as pointed out by a Differential Scanning Calorimetry study. Neither a α-quartz/β-quartz transition as encountered in SiO(2) near 573 °C nor a α-quartz to rutile transformation were detected for these GeO(2) and Ge(1-x)Si(x)O(2) single-crystals.     

Synthesis, characterization, and photoluminescence property of LaCO3OH microspheres

Novel LaCO3OH microspheres with the hexagonal phase were synthesized by a hydrothermal method using La(NO3)(3).6H2O and urea CO(NH2)2 as the starting materials. Various experimental parameters were examined, such as the reaction temperature, the reaction time, and the molar ratios of the starting reagents. The as-synthesized products were characterized by powder X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence (PL). The PL result showed one broad emission band centered at 438 nm (lambdaex=365 nm) of the pure LaCO3OH microspheres. In addition, a possible formation mechanism of LaCO3OH microspheres and the PL property of pure LaCO3OH microspheres were discussed.     

Fabrication of 3D rotor-like ZnO nanostructure from 1D ZnO nanorods and their morphology dependent photoluminescence property

A facile and eco-friendly sonochemical route to fabricate well-defined dentritic (rotor-like) ZnO nanostructures from 1D ZnO nanorods without alloying elements, templates and surfactants has been reported. Phase and structural analysis has been carried out by X-ray diffraction (XRD) and Fourier Transform Infra-Red (FTIR) spectroscopy, showed the formation of hexagonal wurtzite structure of ZnO. Scanning electron microscopic (SEM) study showed the formation of rotor-like ZnO nanostructure having a central core which is surrounded by side branches nanocones. Transmission electron microscopic (TEM) study showed that these nanocones grow along [0001] direction on the six {01–10} planes of central core ZnO nanorods. A plausible formation mechanism of rotor-like ZnO nanostructures was studied by SEM which indicates that the size and morphology of side branches can be controlled by adjusting the concentration of OH^? ions and time duration of growth. The photoluminescence (PL) spectrum of the synthesized rotor-like ZnO nanostructures exhibited a weak ultraviolet emission at 400 nm and a strong green emission at 532 nm recorded at room temperature. The influence of morphology on the origin of green emission was discussed in detail. The results suggested a positive relationship among polar plane, oxygen vacancy and green emission.     

溶剂热合成片状介孔CeO2及光致发光性能

本文以乙二醇为溶剂,Ce(NO3)3·6H2O为铈源,尿素为沉淀剂,采用了溶剂热法一步合成了二维片状结构的介孔CeO2,同时讨论了不同反应时间对晶型的影响。通过SEM、TEM、XRD、EDS和N2吸附-脱附等检测手段进行了表征,结果表明所合成CeO2是由大量较规整的片状结构单元组成,在片状结构上分布着均匀有序的介孔,产物具有立方萤石型结构,并考察了相应的光致发光性能。     

Low-temperature growth and photoluminescence property of ZnS nanoribbons

At a low temperature of 450 degrees C, ZnS nanoribbons have been synthesized on Si and KCl substrates by a simple chemical vapor deposition (CVD) method with a two-temperature-zone furnace. Zinc and sulfur powders are used as sources in the different temperature zones. X-ray diffraction (XRD), selected area electron diffraction (SEAD), and transmission electron microscopy (TEM) analysis show that the ZnS nanoribbons are the wurtzite structure, and there are two types-single-crystal and bicrystal nanoribbons. Photoluminescence (PL) spectrum shows that the spectrum mainly includes two parts: a purple emission band centering at about 390 nm and a blue emission band centering at about 445 nm with a weak green shoulder around 510 nm.     

The near-infrared broadband emission from bismuth-doped GeO2-WO3 and GeO2-BaO glasses

Glasses with the composition of (99.5-chi)GeO2-chiWO(3)-0.5Bi2O3 (chi=3, 6, 9 mol%) and (99.5-psi)GeO2-psiBaO-0.5Bi2O3 (psi=3, 6, 9 mol%) were prepared. Their thermal, emission and absorption measurements were carried out. The near-infrared super broadband emission of the prepared samples peak around 1.3 microm was discovered. The results indicated, in GeO2-WO3-Bi2O3 glasses, increasing amount of WO3 brought about the broadening of FWHM, prolonging of lifetime and enhancing of thermal stabilities. While in GeO2-BaO-Bi2O3 glasses, concomitant with the increasing amount of BaO were the broadened FWHM as well as the prolonged lifetime. Red-shift tendency of absorption edges was discovered in both two groups of glasses indicating the Bi5+ ions might take responsibility for the broadband emission.     

Melt spinning of syndiotactic 1, 2-polybutadiene for preparation of carbon fibers

The thermal crosslinking and loss of vinyl unsaturation of syndiotactic 1, 2-polybutadiene(_s-PB) at 180–230°C were prevented by stabilizers with 3, 5-di-t-butyl-4-hydroxybenzyloxy group. The _s-PB samples (mp 140–198°C and MW 20,000–70,000) that contained the stabilizers could be melt-spun at a temperature below 220°C into 1-denier fibers to be used for the preparation of carbon fibers. The _s-PB fibers with higher mp and/or higher MW could be obtained by the addition of a high boiling solvent such as tetralin. The relationship between the molecular structures of _s-PB and the properties of resulting _s-PB fibers, including the degree of molecular orientation measured by birefringence and x-ray diffraction, is presented. Spun fibers showed small swellings here and there along the fiber axis, which would have resulted from the inhomogeneity of the melt of _s-PB spun at a temperature slightly above the melting point. The gelation was unlikely to occur.     

Self-assembly behavior and photoluminescence property of bispyrenyl-POSS nanoparticle hybrid

Two flexible ether bonds were designed to connect two pyrene rings on a polyhedral oligomeric silsesquioxane (BPy-POSS) to enrich the fraction of "intrinsic intramolecular pyrene-dimer" on the surface of crystal isobutyl-POSS (iBu-POSS) thin-films. Compared to the monomer emission of 1-pyrenemethanol (Py-OH), the emission spectra of BPy-POSS in dichloromethane show the large proportion of intramolecular and intermolecular excimers due to the formation of pyrenyl dimers or aggregates via the easy rotation of two adjacent ether bonds and the π-π interaction of pyrene rings, respectively. By blending inert iBu-POSS, the fluorescent dimers or aggregates of 5 wt.% and 20 wt.% BPy-POSS are distributed on the surface of iBu-POSS crystal fractal pattern as shown by confocal photoluminescence microscopy. Upon exposure to the vapors of nitrobenzene, the 5 wt.% BPy-POSS blend shows the similar quenching efficiency as 100 wt.% BPy-POSS blends, indicating the better excimer dispersion for vapor permeability of blend thin-films.     

Synthesis, surface morphology, and photoluminescence properties of anatase iron-doped titanium dioxide nano-crystalline films

Iron (Fe)-doped (0 to 4%) TiO(2) nano-crystalline (nc) films with the grain size of about 25 nm have been deposited on n-type Si (100) substrates by a facile nonhydrolytic sol-gel processing. X-ray diffraction measurements prove that the films are polycrystalline and present the pure anatase phase. X-ray photoelectron spectroscopy spectra indicate that the chemical valent state of Fe element is +3 and the Fe(3+) ions replace the Ti(4+) sites. The Fe dopant effects on the surface morphology, microstructure, and dielectric functions of the nc-Fe/TiO(2) films have been studied by atomic force microscope, ultraviolet Raman scattering and spectroscopic ellipsometry. With increasing Fe composition, the intensity of Raman-active mode B(1g) increases, while that of the A(1g) phonon mode decreases. The dielectric functions have been uniquely extracted by fitting ellipsometric spectra with the Adachi's dielectric function model and a four-phase layered model. It is found that the real part of dielectric functions in the transparent region and the optical band gap slightly decrease with the Fe composition due to the introduction of acceptor level Fe t(2g). Finally, the composition and temperature dependence of the surface and lattice defects in the Fe/TiO(2) films have been investigated by photoluminescence spectra in detail. At room temperature, the emission intensities decrease with increasing Fe compositions since the Fe incorporation could prolong the radiative lifetime and/or shorten the non-radiative lifetime. By analyzing the low temperature photoluminescence spectra, the intensities and positions of five emission peaks and shoulder structure can be unambiguously assigned. The phenomena could be reasonably explained by the physical mechanisms such as oxygen vacancies, localized excitons, self-trapped excitons, and indirect transitions, which are strongly related to the electronic band structure perturbed by the Fe doping.     

Verfeinerung der Kristallstruktur des Natriummetagermanats,Na2GeO3

Zusammenfassung Die Kristallstruktur des Natriummetagermanats, Na₂GeO₃, wurde mit dreidimensionalen Daten bis zu einemR-Wert von 4.4% verfeinert. Daraus ergab sich für die Metagermanatkette ein mittlerer Ge–O-Abstand von 1.836 Å für das Brückensauerstoffatom und von 1.713 Å für das terminale Sauerstoffatom. Der mittlere Na–O-Abstand beträgt 2.39 Å (KZ=5).

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Refinement of the crystal structure of sodium metagermanate, Na₂GeO₃

The crystal structure of sodium metagermanate, Na₂GeO₃, has been refined by three-dimensional data resulting anR-value of 4.4%. The mean Ge–O distances in the metagermanate chain were found to be 1.836 Å for the bridging oxygen atom and 1.713 Å for the terminal oxygen atom. An average value of 2.39 Å was calculated for the Na–O distance (c.n.=5).

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Mit 1 Abbildung     

Never-dried bacterial cellulose/fibrin composites: preparation,morphology and mechanical properties

BC/fibrin composites having fibrin/BC weight percent ratios ranging from 2/98 to 64/36 were produced by immersing never-dried-BC into varying compositions of fibrin/ionic liquid/DMSO solutions and for increasing time periods. The composite compositions were predicted from an FTIR/Beer’s law calibration method based on calibration samples which exhibited an RMSEP of 2.5 weight percent. Observations of the composite surface with atomic force microscopy and of the internal pore structure with scanning electron microscopy showed that increasing immersion times resulted into smoother surface composites and allowed further infiltration of fibrin into the microporous structure of BC. Tensile strength and cyclic creep tests demonstrated that the composition had significant impact on the ultimate tensile stress and cyclic creep strain level of BC/fibrin composites. It is proposed that these composites have potential for artificial blood vessel applications.     

Hydrothermal Synthesis and Luminescent Properties of Flowerlike Zn2GeO4 and Mn2+-Doped Zn2GeO4 Hierarchical Architectures

Three-dimensional(3D) flowerlike hierarchical Zn₂GeO₄ and Mn²⁺-doped Zn₂GeO₄ microstructures have been prepared by a facile hydrothermal approach. X-Ray diffraction(XRD), field emission scanning electron microscopy(FESEM), transmission electron microscopy(TEM) and photoluminescence(PL) spectrometry were employed to characterize the samples. Such flowerlike hierarchical Zn₂GeO₄ microstructures with an average diameter of 3―4 μm were found to be constructed by abundant single crystalline nanorods of about 90 nm in diameter. The luminescent properties of Zn₂GeO₄:xMn phosphors with different contents of Mn²⁺ as an activator were investigated. The Mn²⁺-doped samples showed green luminescence corresponding to the d-d transition of Mn²⁺ under the irradiation of UV light. The red shift(from 531 nm to 538 nm) in λ_em with increasing Mn²⁺ content was observed in the luminescent spectra, which should be attributed to a weak crystal field because of the substitution of Zn²⁺ by Mn²⁺ at a distorted tetrahedral lattice site.     

A 3D porous zinc MOF constructed from a flexible tripodal ligand: Synthesis, structure, and photoluminescence property

A new metal-organic framework, [Zn₅(trencba)₂(OH)₂Cl₂·4H₂O] (1) [H₃trencba=N,N,N′,N′,N′′,N′′-tris[(4-carboxylate-2-yl)methyl]-tris(2-aminoethyl)amine], constructed from a flexible tripodal ligand based on C₃ symmetric tris(2-aminoethyl)amine, has been synthesized hydrothermally and characterized by elemental analysis, IR, TG, XRD and single-crystal X-ray diffraction analysis. Compound 1 contains an unprecedented linear penta-nuclear zinc cluster fragment. Each ligand links four penta-nuclear fragments, and every fragment links eight ligands to generate a three-dimensional non-interpenetrated porous framework. The uncoordinated water molecules were observed trapped in the void pores. Compound 1 represents the first example of (6,8)-connected 3D bi-nodal framework based on a single kind of organic ligand. The photoluminescence measurements showed that complex 1 exhibits relatively stronger blue emissions at room temperature than that of the ligand.     

Hierarchical tuning of 1-D macro morphology by changing the composition of a binary hydrogel and its influence on the photoluminescence property

1-D morphological tuning in the riboflavine(R)-melamine(M) hydrogel system (from helical fiber to rod-like to tubular morphology) with an interesting photoluminescence property by changing the composition of the RM components.     

TiO_2/Si复合材料的制备及其性能研究

为了提高单晶硅表面的光学利用效率,本文采用水热法在其表面生长一层平均棒长为900±50 nm,直径为100±20 nm的金红石相Ti O2纳米棒阵列。通过积分球反射光谱对这种Ti O2/Si复合材料进行抗反射性能表征,发现这种复合材料具有较好的抗反射性能;通过测量Ti O2/Si复合材料的光电流性能,发现其具有高效的光电转化效率,可有效提高太阳光的利用率;通过探讨Ti O2/Si复合材料对亚甲基蓝的降解,发现其在光催化降解染料效率方面具有显著的提高效果。     

The preparation, properties and application of carbon fibers for SPME

The conditions of preparation of new types of carbon fibers for solid phase micro extraction (SPME) prepared by methylene chloride pyrolysis (at 600 °C) on the quartz fiber (100 μm) as well as by supporting synthetic active carbon (prepared especially for this purposes) supported in a special epoxide-acrylic polymer is described. The properties of such carbon fibers for SPME were defined by determination of the partition coefficient of the tested substances (i.e., benzene, toluene, xylenes, trichloromethane and tetrachloromethane) and by the microscopic investigations with the application of the optical and scanning electron microscope.

The obtained carbon SPME fibers were applied to the analysis of some volatile organic compounds from its aqueous matrix. During chromatographic GC test, at the investigated SPME carbon fibers, we obtained different but mostly high partition coefficients for the determined compounds (Kfs from 120 for trichloromethane up to 11,500 for tetrachloromethane).

Owing to the high partition coefficients of the studied substances obtained on carbon fibers, it was possible to do the analysis of organic substances occurring in trace amounts in different matrices. In this paper, we present the analysis of BTX contents in the petrol analyzed with the application carbonized with CH₂Cl₂ SPME fiber (C1NM) and a headspace over the petrol sample (concentration of each BTX g/dm³).     

多功能含铕共聚物的制备及光致发光性质研究

合成含咔唑基团、含1,3,4-噁二唑基团、含稀土铕配合物的3类可聚合的单体,其结构用红外光谱、质谱、元素分析、核磁共振表征.通过自由基共聚方法制备了多功能合一的含铕共聚物,用元素分析、凝胶液相色谱、TGA、DSC和紫外光谱确认结构并表征性质;用荧光光谱研究它们的光致发光性质,讨论了不同状态、不同噁二唑基团取代基对发光机理的影响.     

Amorphous fluorescent organic emitters for efficient solution-processed pure red electroluminescence: synthesis, purification, morphology, solid-state photoluminescence, and device characterizations

New soluble and intrinsic amorphous red emitters 1 and 2 were obtained by Suzuki coupling. Due to the close molecular polarities, separation of target products from monocoupling impurities presents a challenge. The results showed highly pure 2 would be a potentially valuable fluorophore for solution-processed pure red electroluminescence in terms of visual sensitivity with respect to 1.