TiO2/Eu-MCM纳米超分子材料的组装和光催化性能

利用有机相-水相界面共沉淀溶胶支持自组装方法制备粒径为15 nm、孔径为8 nm的分子筛Eu-MCM, 它拥有734 m²/g的比表面积和1.49 cm³/g的比孔容. 把TiO₂组装到Eu-MCM的孔道中, 组装成TiO₂/Eu-MCM纳米复合材料. XRD, RAMAN和选区电子衍射花样分析表明纳米复合材料中的TiO₂为锐钛型. TiO₂/Eu-MCM的发光表现为Eu^3＋离子的特征光谱, 激发峰分别为342 (⁵L₁₀), 358 (⁵L₉), 378 (⁵L₇), 390 (⁵L₆), 411 (⁵D₃), 462 (⁵D₂)和524 (⁵D₁) nm; 发射峰为579, 592, 613, 653和701 nm, 归属于⁵D₀→⁷F_J (J＝0, 1, 2, 3, 4)组态间的跃迁. 纳米复合材料的发光强度都要比Eu-MCM的发光强, 其中43%TiO₂/Eu-MCM的发光最强. 荧光和紫外漫反射结果表明客体TiO₂对主体分子筛存在能量传递效应. 在微弱的紫外灯光照射下, TiO₂/Eu-MCM纳米复合材料对苯酚的光催化氧化性能和其发光强度具有一定的相关性. 29%TiO₂/Eu-MCM的纳米复合材料拥有的比表面积、孔容和孔径分别为204 m²/g, 0.24 cm³/g和4.7 nm. 29%TiO₂/Eu- MCM对苯酚具有68%的最高光催化氧化产率和85%催化氧化选择性.     

Eu3+在Ba2TiSi2O8中的发光

The barium titano-silicate phosphors doped with Eu³⁺ were synthesized by high temperature solid state reaction. The structures of as-synthesized samples were characterized by powder XRD. The maximum peaks of emission spectra of Ba₂TiSi₂O₈ and Ba₂TiSi₂O₈∶Eu³⁺ were respectively located at 450 and 618 nm, coming from the transitions of charge-transfer bands of Ti⁴⁺-O^2- and forced electric-dipole transition ⁵D₀-⁷F₂ of Eu³⁺. The luminous mechanisms of Ba₂TiSi₂O₈ and Ba₂TiSi₂O₈∶Eu³⁺ were suggested. The effects of concentration of Eu³⁺ on the luminous performance of Ba₂TiSi₂O₈∶Eu³⁺ were also studied and the results showed that the optimum concentration of Eu³⁺ was 0.12 mol per mole of matrix.     

Energy transfer in solution of lanthanide complexes

The lanthanides with their well-defined energy levels provide an excellent basis to study different Ln(III)-specific energy transfer processes in a variety of chemical environments. The studies concerning intramolecular and intermolecular energy transfer processes with participation of Ln(III) ions and a variety of ligand groups in solution are reviewed. Phenomena of energy transfer from ligands to Ln(III) ions, resulting consequently in a great enhancement of the Ln(III) ion luminescence (ligand sensitized luminescence), as well as from Ln(III) to other species and between Ln(III) ions are presented.     

一种新的滤纸基质固体表面低温荧光(燐光)测定装置

对自行研制的铜制滤纸基质低温荧光（燐光）测定的样品支架，进行了滤纸基质固体表面低温荧光测定的可行性研究。与同类冷冻装置和室温装置比较，本装置用于滤纸基质固体表面低温荧光（燐光）测定具有以下优点；样品的分析周期大大地缩短，由45min缩短为5-6min；装置简单、便宜耐用；操作简便，简化了室温测定时的滤纸干燥程序，应用范围广，方法的重现性好，检样分析结果的相对标准偏差RSD%小于10%，荧光（燐光）分析灵敏度高，检出限低，线性范围宽。     

Theoretical and photoluminescence studies on the d10-s2 AuI-TlI interaction in extended unsupported chains

The reactions of solutions of TlPF(6) and OPPh(3) in tetrahydrofuran or acetone with NBu(4)[AuR(2)] (R=C(6)Cl(5), C(6)F(5)) gave the new complexes [Au(C(6)Cl(5))(2)](2)[Tl(OPPh(3))][Tl(OPPh(3))(L)] (L=THF (1), acetone (2)) and the previously reported [Tl(OPPh(3))(2)][Au(C(6)F(5))(2)] (3). The crystal structures of complexes 1 and 2 display extended unsupported chains with short intermolecular interactions between alternating gold(I) and thallium(I) centres. Moreover, the Tl(I) centres show two different types of geometrical environments, such as pseudotetrahedral and distorted trigonal-bipyramidal, due to the presence of solvent molecules that act as ligands in the solid-state structure. Quasirelativistic and nonrelativistic ab initio calculations were performed to study the nature of the intermetallic Au(I)-Tl(I) interactions and are consistent with the presence of a high ionic contribution (80 %) and dispersion-type (van der Waals) interaction with a charge-transfer contribution (20 %) when relativistic effects are taken into account. All complexes are luminescent in the solid state at room temperature and at 77 K. Complexes 1 and 2 show site-selective excitation, probably due to the different environments around the Tl(I) centres. The DFT and time-dependent (TD)-DFT calculations are in agreement with the experimental excitation spectra for all complexes and confirm the site-selective excitation behaviour as a function of the Tl(I) geometrical environment.     

Oxygen Atom Adsorption and Diffusion on Pd Low-index Surfaces and （311） Stepped Surface

Introduction Atom adsorption on transition metal surfaces has attracted special attention as a base for understanding the fundamental processes of oxidative catalysis. Particularly interesting is the adsorption and diffusion of oxygen on well-defined metal surfaces. An oxygen covered palladium surface, for example, plays a central role in several important reactions such as oxidation of carbon monoxide and ammonia. In particular, the (100), (111), (110) surfaces and the interactions with oxyge…     

Luminescence Properties of Terbium-, Cerium-, or Europium-Doped α-Sialon Materials

New interesting luminescent α-sialon (M_(m/val+)^val+ Si_12-(m+n) Al_(m+n)OnN_(16−n)) (M=Ca, Y) materials doped with Ce, Tb, or Eu have been prepared and their luminescence properties studied. These show that Tb and Ce are in the 3+ and Eu in the 2+ state. Low-energy 4f↔5d transitions are observed as compared to the luminescence of these ions doped in oxidic host-lattices. This is partially explained by the nitrogen-rich coordination of the rare-earth ion and partially by the narrow size of the lattice site. The latter gives rise to a strong crystal-field splitting of the 5d band and a rather large Stokes shift for Ce³⁺ and Eu²⁺ (6500-7500 and 7000-8000 cm⁻¹, respectively). For (Y,Tb)-α-sialon the Tb³⁺ 4f→5d excitation band (∼260 nm) is in the low-energy host-lattice absorption band (?290 nm), giving rise to a strong absorption for 254-nm excitation, but a low quantum efficiency. The latter is due to photoionization processes or selective excitation of Tb³⁺ at the defect-rich surface, resulting in radiationless transitions. Ce- and Eu-doped Ca-α-sialon show bright long-wavelength luminescence (maxima at 515-540 and 560-580 nm for Ce and Eu, respectively) with a high quantum efficiency and high absorption for 365- and 254-nm excitation. The Eu²⁺ emission intensity and absorption increases for increasing m, which is explained by the Eu²⁺ richer α-sialon composition. The position of the Eu^2α emission does not shift with changing composition of the host-lattice (m, n values), indicating that the local coordination of the Eu²⁺ ion is hardly dependent on the matrix composition.     

Synthesis and supramolecular properties of molecular clips with anthracene sidewalls

Novel molecular clips with anthracene sidewalls (1 a-c) were synthesized; they form stable host-guest complexes with a variety of electron-deficient aromatic and quinoid molecules. According to single-crystal structure analyses of clip 1 c and 1,2,4,5-tetracyanobenzene (TCNB) complex 14@1 b, the clips' anthracene sidewalls have to be compressed substantially during the complex formation to provide attractive pi-pi interactions between the aromatic guest molecule and the two anthracene sidewalls in the complex. The compression and expansion of aromatic sidewalls are calculated by molecular mechanics to be low-energy processes, so the energy required for compression of the anthracene sidewalls during complex formation is apparently overcompensated by the gain in energy resulting from the attractive pi-pi interactions. The finding that complexes of the clips 1 a-c are more stable than those of the corresponding clips 2 a-c can be explained in terms of the larger van der Waals contact surfaces of the anthracene sidewalls in 1 a-c (relative to the naphthalene sidewalls in 2 a-c). Color changes resulting from charge-transfer (CT) bands are observed in complex formation by 1 a-c: from colorless to red or purple with TCNB (14), and from yellow to green with 2,4,7-trinitro-9-fluorenone TNF (17). Independently, the host 1 b and guest 14 fluoresce from their respective excited singlet states, whilst in the complex 14@1 b the charge-transfer state quenches the higher-energy singlet states of the two components, and as a result luminescence is only observed from this new CT state. To the best of our knowledge, complex 14@1 b is the first example of CT luminescence from a host-guest complex. The binding constant determined for the formation of the TCNB complex 14@1 b from a UV/Vis titration experiment (Ka = 12 400 m(-1)) agrees well with the value (K(a) = 12 800 m(-1)) obtained by 1H NMR titration.     

Main‐chain viologen polymers with organic counterions exhibiting thermotropic liquid‐crystalline and fluorescent properties*

A series of viologen polymers with bromide, tosylate, and triflimide as counterions were prepared by either the Menshutkin reaction or metathesis reaction in a common organic solvent. Their polyelectrolyte behavior in methanol was determined by solution viscosity measurements, and their chemical structures were determined by Fourier transform infrared and Fourier transform NMR spectroscopy. They were characterized for their thermotropic liquid‐crystalline properties with a number of experimental techniques. Each of the viologen polymers with organic counterions had a low melting transition or fusion temperature above which it formed either a high‐order smectic phase or a low‐order smectic phase. Each of them also exhibited a smectic‐to‐isotropic transition. The ranges of the liquid‐crystalline phase were 80–88 °C for viologen polymers with tosylate as a counterion and 120–146 °C for viologen polymers with triflimide as a counterion. They had excellent thermal stability. The ranges of thermal stability were 288–329 °C for viologen polymers with tosylate as a counterion and 343–350 °C for viologen polymers with triflimide as a counterion. The fluorescence property for all of the viologen polymers in either aqueous or methanol solution was also included in this study. For example, the viologen polymer containing the 4,4′‐bipyridinium and p‐xylyl units along the backbone of the polymer chain with triflimide as a counterion had an absorption spectrum (λ_max = 265 nm), an excitation spectrum (λ_ex values = 357, 443, and 454 with monitoring at 533 nm), and an emission spectrum (λ_em = 536 nm with excitation at 430 and 450 nm) in methanol. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 659–674, 2002; DOI 10.1002/pola.10134     

聚氯乙烯结构缺陷和热不稳定性之间关系的研究 2.各种结构缺陷含量和热脱氯化氢速率之间的关系

本工作采用溴加成法、酚解法、FTIR法及臭氧裂解法分别测定了五种不饱和蒸气压下聚合的PVC样品(u-PVC)和五种商品PVC样品(s-PVC)的总双键、总不稳定氯、孤立双键和内部双键的含量.通过研究结构缺陷和PVC的平均分子量及脱HCl速率的相互关系,揭示了不饱和总双键值,总不稳定氯和孤立双键含量彼此的相关性是建立在它们分别与1/M_n的相关性基础之上,从而得出了这三种定量值测得的主要都是端基烯丙基氯结构.根据三者对脱HCl速率的良好线性相关性,首次提出了端基烯丙基氯结构在HCl催化作用下异构化成内部烯丙基氯从而成为脱HCl速率主要原因的机理.