Showing papers by "Bing Yan published in 2008"

Mineralization of CI Reactive Yellow 145 in Aqueous Solution by Ultraviolet-Enhanced Ozonation

Abstract: We investigated the mineralization of CI Reactive Yellow 145 (RY145) in aqueous solution in a UV-enhanced ozonation (UV/O3) reactor. The effects of several operational parameters, including solution pH, initial dye concentration, ozone feed, and bulk temperature, on total organic carbon (TOC) removal were investigated. The experimental results illustrated that ozonation combined with UV radiation for removal of TOC was more efficient than ozonation alone or UV irradiation alone. At an initial pH of 8.0, bulk temperature of 30 °C, ozone feed of 4.8 g/h, and initial dye concentration of 500 mg/L, the TOC removal efficiency of RY145 reached ∼80% after 150 min under 175 W UV irradiation. Intermediates formed during RY145 mineralization were detected by gas chromatography coupled with mass spectrometry (GC/MS) and ion chromatography (IC). On the basis of our results, we propose a tentative degradation pathway.

Covalently bonded assembly and photoluminescent properties of rare earth/silica/poly(methyl methacrylate-co-maleic anhydride) hybrid materials

Abstract: Copolymer (MMA-co-MAL) of methyl methacrylate (MMA) and maleic anhydride (MAL) was prepared and grafted by 3-aminopropyltriethoxysilane (APES), which behaves as the structural precursor for functional bridge to assemble the covalently bonded systems through the coordination to rare earth ions (Eu 3+ , Tb 3+ ) with carboxylic groups of maleic anhydride. On the other hand, 1,10-phenanthroline (phen) is engaged in a second functional ligand to sensitize the luminescence of RE 3+ (rare earth ions) by intramolecular energy transfer process. Meanwhile, the cohydrolysis and copolycondensation processes happened between triethoxysilyl of modified copolymer (MMA-co-MAL-APES) and tetraethoxysilane (TEOS) with Si–O covalent bonds, resulting in the polymer-inorganic hybrids (phen-RE-MMA MMA-co-MAL-Si) exhibiting characteristic red or green emissions of Eu or Tb ions. Especially the luminescent quantum efficiencies of europium hybrid systems are estimated and discussed in detail.

Molecular assembly and photophysical properties of covalently bonded rare earth polymeric hybrid materials phen–RE–MSMA (MS)

Abstract: A new series of quaternary and ternary polymeric hybrid materials were assembled from 3-methacryloxypropyltrimethoxysilane (MS), methacrylic acid (MA), 1,10-phenanthroline (phen) and rare earth (Eu3+, Tb3+, and Dy3+) precursors. MS and MSMA (copolymer of MS and MA) behave as structural functional component to form the inorganic polymeric network or inorganic/organic polymeric host through the coordination to rare earth ions, while phen acts as the energy sensitizer for the luminescence of rare earth ions. Subsequently, six novel hybrid materials (phen–Eu(Tb, Dy)–MS, phen–Eu(Tb, Dy)–MSMA) were obtained, in which inorganic component is connected with polymer component through covalent bond. It was found that the introduction of organic polymer unit has influence on the microstructure and especially the luminescent properties of hybrid materials. The quantum efficiency of Eu hybrids was also studied. All these hybrids exhibit the characteristic luminescence of rare earth ions, which substantiates optimum energy match and effective intramolecular energy transfer between the triplet state energy of phen and emissive energy level of Eu3+, Tb3+ and Dy3+. It was worth pointing out that the quaternary hybrid materials (phen–Eu3+(Tb3+, Dy3+)–MSMA) with organic polymer unit (MA) present stronger luminescence intensities, longer lifetimes than those of ternary ones without MA (phen–Eu3+(Tb3+, Dy3+)–MS), suggesting the introduction of organic chain (MA) is beneficial for the photophysical property of hybrids.

Sol–gel synthesis and photoluminescence of RE3BO6: Eu3+/Tb3+ (RE = Y, Gd) microcrystalline phosphors from hybrid precursors

Abstract: Novel phosphors of Eu 3+ /Tb 3+ doped RE 3 BO 6 (RE = Y, Gd) have been prepared using an original modified in situ sol–gel synthesis route. Different optimized organic media were mixed with rare earth coordination polymers, and tri- n -butyl borate was added to assemble inorganic/organic multi-component hybrid precursors. After calcinations of the resulting precursors at 1000 °C, target phosphors were obtained. The microstructure and morphology information of the phosphors were investigated via the technique of X-ray powder diffraction (XRD) and scanning electronic microscopy, and it has been shown that these phosphors present symmetrical distribution and high packing density, whose grain sizes were around 200 nm. Analyzed by luminescent spectra, these phosphor particles show narrow lines of emissions respectively originating from their characteristic transitions, and the dominating emission peak is due to the hypersensitive transition. The RE 3 BO 6 : Eu 3+ /Tb 3+ (RE = Y, Gd) phosphors can be expected to gain more practical applications in commercial phosphors and other luminescent materials used in advanced devices.

Molecular construction and photophysics of luminescent covalently bonded hybrids by grafting the lanthanide ions into the silicon–oxygen networks and carbon chains

Abstract: Through the hydrogen transfer nucleophilic addition reaction between the hydroxyl groups of the glycol, the diglycol or the polyglycol and the isocyanate groups of 3-(triethoxysilyl)-propyl isocyanate (TEPIC), the hybrid precursor G–Si, DG–Si and PG–Si were obtained. And then G–Si, DG–Si or PG–Si has coordinated to the rare earth ions with the carbonyl groups to form the three kinds of hybrid materials through hydrolysis and copolycondensation with the tetraethoxysilane (TEOS) via sol–gel process. The data in NMR, FT-IR and ultraviolet absorption spectra indicate that the effective precursors have been obtained successfully. Moreover, seen from the fluorescent excitation and emission spectra, TG plots and electronic microscopy diagraphs, respectively, the obtained materials have the excellent fluorescent intensities, outstanding thermal stabilities and regular and homogenous trunk stripes microstructures. Ulteriorly, the X-ray diffraction patterns were obtained under the room temperature to describe the structure of the materials.

Covalently assembly and photophysical properties of novel lanthanide centered hybrid materials by functionalized thioacylureas bridge

Abstract: A novel molecular precursor (abbreviated as TAM-Si) derives from thioacetaminde (TAM) modified by 3-(triethoxysilyl)-propyl isocyanate (TEPIC) though the hydrogen transfer addition reaction. Then TAM-Si behaves as functional molecular bridge which coordinates to RE 3 (Eu 3+ , Tb 3+ ) as well as form Si O network with inorganic precursor (TEOS) after a sol–gel process (cohydrolysis and copolycondensation reaction), resulting in the covalently bonded hybrid materials (RE–TAM-Si). On the other hand, the hybrid material of TAM-Si without introduction of RE 3+ as well has been obtained. SEM pictures indicate that the TAM-Si show the sphere micromorphology with particle size of micrometer dimension while RE–TAM-Si hybrids present different nanometer particle, which suggests that lanthanide ions has influence on the microstructure of hybrid systems through its coordinated effect. The blue emission for TAM-Si hybrids and the narrow-width green and red emissions were achieved for Tb 3+ and Eu 3+ ions, respectively, indicating that the intramolecular energy transfer process take place from photoactive group to Tb 3+ and Eu 3+ ions in these hybrid microsphere systems. Especially the lifetime and quantum efficiency for europium hybrids have been determined.

Hybrid precursors synthesis and photoluminescence of rare earth ions : activated Sr3Y (PO4)3 phosphors

Abstract: Using rare earth coordination polymers with salicylic acid as precursors and composing with the polyvinyl alcohol (PVA) as dispersing media, Eu 3+ , Tb 3+ , Ce 3+ - activated Sr 3 Y(PO 4 ) 3 phosphors with different doping concentration and Sr 3 Y(PO 4 ) 3 : 3 mol % Pr 3+ were prepared via an modified wet chemical technology. The emission intensities of activators have been found to depend strongly on the doping concentration. The result is that the optimum concentration for Eu 3+ is 7 mol %, for Tb 3 is 9 mol % and for Ce 3+ is 3 mol %, respectively. Furthermore, the crystal field depression value D (Ln, A) of Sr 3 Y(PO 4 ) 3 have been calculated to be 16, 895 cm -1 when Ce 3+ was doped in Sr 3 Y(PO0 4 ) 3 .

Synthesis and Luminescence Properties of REAl3(BO3)4:Eu3+/Tb3+ (RE: Y, Gd) Phosphors from Sol—Gel Composition of Hybrid Precursors.

Abstract: Starting from rare earth nitrates and tri- n -butyl borate, Eu 3+ /Tb 3+ doped REAl 3 (BO 3 ) 4 (RE = Y, Gd) phosphors were synthesized by a modified sol–gel process derived from multi-component hybrid precursors. The microstructure and morphology of the phosphors were investigated by X-ray powder diffraction (XRD) and scanning electronic microscope; which indicates that these phosphors show good crystalline state and particle size of 100–200 nm order, specially presenting the novel cubic micro-rod patterns. The excitation spectra show a strong spectral band in narrow ultraviolet region of 200–300 nm, while there are still some apparent weak absorption in long-wavelengths region of 300–500 nm. The corresponding emission spectra indicate that these crystalline phosphors exhibit photoluminescence of the characteristic transitions of RE 3+ . The effects of doping concentration on emission intensities were examined, suggesting the quenching concentration of different activated ions in different phosphors. In addition, luminescence intensity presented by the same RE 3+ ion doped concentration among different systems was also compared.