Charge carrier mobility and electroluminescence in a green-emitting alternating block copolymer with a methoxy Bi-substituted chromophore

We determine the mobility of positive and negative charge carriers in a soluble green-emitting alternating block copolymer with, a methoxy bi-subsbituted conjugated segment. The negative charge carrier mobility of 6 x 10(-11) cm(2)/V.s is directly determined using space-charge-limited current analytical expressions. Positive charge carrier transport is also space-charge-limited, with a mobility of I x 10(-8) cm(2)/V.s. The electron trap distribution is exponential, with a characteristic energy of similar to 0.12 eV. A hole trap with energy similar to 0.4 eV was observed. This copolymer is used as emissive material in organic light-emitting diodes that present brightness of similar to 900 cd/m(2) at 12.5 V.

The role of redox property of La2-x(Sr,Th)(x)CuO4 +/-lambda playing in the reaction of NO decomposition and NO reduction by CO

Two systems of mixed oxides, La2-xSrxCuO4 +/- lambda (0.0 less than or equal to x less than or equal to 1.0) and La(2-x)Tn(x)CuO(4 +/-) (lambda) (0.0 less than or equal to x less than or equal to 0.4), with K2NiF4 structure were prepared. The average valence of Cu ions and oxygen nonstoichiometry (lambda) were determined by means of chemical analysis. Meanwhile, the adsorption and activation of nitrogen monoxide (NO) and the mixture of NO + CO over the mixed oxide catalysts were studied by means of mass spectrometry temperature-programmed desorption (MS-TPD). The catalytic behaviors in the reactions of direct decomposition of NO and its reduction by CO were investigated, and were discussed in relation with average valence of Cu ions, A and the activation and adsorption of reactant molecules. It has been proposed that both reactions proceed by the redox mechanism, in which the oxygen vacancies and the lower-valent Cu ions play important roles in the individual step of the redox cycle. Oxygen vacancy is more significant for NO decomposition than for NO + CO reaction. For the NO + CO reaction, the stronger implication of the lower-valent Cu ions or oxygen vacancy depends on reaction temperature and the catalytic systems (Sr- or Th-substituted). (C) 2000 Elsevier Science B.V. All rights reserved.

Eu~(2+):MAl_2O_4(M=Ba~(2+),Sr~(2+))的发光与晶体化学键相关性的研究

本文应用复杂晶体化学键理论对Eu~(2+):MAl_2O_4(M=Ba~(2+),Sr~(2+))晶体的化学键参数进行了计算,讨论了晶体中Eu~(2+)的发光性与其所取代离子格位的化学键性质间的关系。

M_2B_5O_9Cl:Eu(M=Ca,Sr,Ba)的真空紫外光谱特性的研究

采用高温固相反应法合成了M_2B_5O_9Cl:Eu(M=Ca,Sr,Ba)中荧光体,测量了荧光体的真空紫外激发光谱,研究了M_2B_5O_9Cl:Eu(M=Ca,Sr,Ba)的真空紫外光谱特性,观察到基质吸收带位于120～200 nm区域,Eu~(2+)离子的5d能级劈裂随着M~(2+)的半径的增加而减小,同时也观察到基质与稀土离子之间存在的能量传递。

Hydrothermal synthesis and structure of [{Mo8V4O36(VO4)(VO)(2)}(n)](7n-) bi-capped alpha-Keggin fragments linked to a chain

The title compound, (H(2)en)(3)H3O {MO8V4O36 (VO4) (VO)(2)} . 4H(2)O, was hydrothermally synthesized and structurally characterized by means of IR, ESR spectrum and single crystal X-ray diffraction. It crystallized in a monoclinic system with space group P2(1)/c, a=1. 980 4(4) nm, b=2. 063 4(4) nm, c=1. 192 0(2) nm, (beta =94. 76(3)degrees and deep black colour. The compound contains V-centered bi-capped alpha -Keggin fragments {Mo8V7O42} that are linked together by edge-shared units (VO5)-O-N via V-O-V bonds, forming a chain.

Hydrothermal synthesis and structure of a bi-capped Keggin polyoxoanion, [(As2AsMo8V4O40)-As-III-Mo-V-O-IV](5-)

The title compound, [NH3CH2CH2CH2NH2][NH3CH2CH2CH2NH3](2)[As-2(III) As-v Mo-8 V-4(IV) O-40] (.) 5H(2)O, was hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Crystal data: monoclinic, C2/c, a = 45.375(9) Angstrom, b = 11.774(2) Angstrom, c = 23.438(5) Angstrom, beta = 96.62(3)degrees. X-ray crystallographic study showed that the crystal structure was constructed by bi-capped alpha -Keggin fragments [(As2AsMo8V4O40)-As-III-Mo-v-O-IV](5-) polyoxoanion. (C) 2001 Elsevier Science B.V. All rights reserved.

Determination of the impurities elements in high-purity cadmium by inductively coupled plasma mass spectrometry

A method for the determination of impurity elements in high purity cadmium by inductively coupled plasma mass spectrometry was developed. The spectral interference arising from Cd was discussed and the magnitude of interference by the polyatomic ion of Cd was compared. The effect of the high concentration Cd on the analyte signal was studied. The results showed that Cd possessed both significant suppression effects on the light mass elements signal and enhancement effects on the heavy mass elements signal,and the effects can be corrected by the use of internal standard elements. In this paper, Y and Bi was employed for the light mass elements and the heavy mass elements,respectively. As, Be, Co, Cu, Ga, Ge, Mn, Mo, Pb, Ni, Sr, Au, Tl, Th, V and U in high purity cadmium were determined. Detection limits are 0.005-0.052 mu g L-1,and the recoveries of standard addition are 82%-108%.

Luminescence of unusual bismuth in barium berates BaB8O13 : Bi)

The luminescence of unusual divalent bismuth (Bi2+) in BaB8O13 is reported. The emission band with maximum peak at 592 nm corresponds to the P-2(3/2)-->P-2(1/2) transition of Bi2+ in the matrix and the excitation spectrum with two bands peaked at 470 and 580 nm respectively corresponds to two split crystal-field levels of P-2(3/2) state. The small Stokes shift (similar to 350 cm(-1)) reflects the rigid structure of the host for the Bi2+ ions.

Evaluation of bond covalency and bond valence in Sr-doped perovskite-type compounds

Formulas for decomposing of complex crystals to a sum of binary crystals are described and applied to the study of bond covalency in La1-xSrxFeO3 (0.0 less than or equal to x less than or equal to 0.9) and Ca1-xSrxMnO3 (0.0 less than or equal to x less than or equal to 0.5). The bond valence is treated by bond-valence sums scheme. The results indicate that, for both compounds, with the increasing doping level, the bond covalency and bond valence show the same trend, namely, larger bond covalency corresponds to higher bond valence. For La1-xSrxFeO3, with the increase of doping level, the bond covalency of La-O, Ca-O decreases in the orthorhombic (0.0 less than or equal to x less than or equal to 0.2) and rhombohedral (0.4 less than or equal to x less than or equal to 0.7) systems, then increases slightly for the cubic (0.8 less than or equal to x less than or equal to 0.9) system, but that of Fe-O increases for all crystal systems. A sharp decrease in bond covalency was observed where the crystal changes from orthorhombic to rhombohedral, while a smooth trend was seen for the rhombohedral-to-cubic transition. On the other hand, for orthorhombic Ca1-xSrxMnO3, the bond covalency of Ca-O, Sr-O, and Mn-O (4-coordinate site) decreases with the increasing doping level, that of Mn-O (2-coordinate site) increases.

Structure and luminescent properties of YAG : Eu, Bi synthesized by sol-gel method

(Y1-xEux)(3)Al5O12 and (Y1-x-yEuxBiy)(3)Al5O12 were prepared by so-gel method. Their structures of the luminophor are similar to that of YAG, which is recorded on the ASTM card and belongs to a cubic system. The luminescent properties show that the reaction temperature of the current sol-gel method is in the range of 400-500 degrees C, which is lower than that of the conventional solid state reaction. The luminophors have the strongest emission intensity when the values of x and y are 0.06 and 0.013, respectively.

LiMAlF_6(M=Ca,Sr)基质中Ce~3+、Eu~3+、Tb~3+的光谱研究

合成了Ce3+、Eu3+、Tb3+激活的LiMAlF6(M=Ca,Sr)磷光体，研究了它们的光谱特性．观察到稀土离子在LiCaAlF6和LiSrAlF6中的光谱十分相似．这与它们所处的晶场环境相同有关．发现Ce3+在此基质中有较弱的330nm发射，这一Ce3+的发光中心可用于作为材料质量的评价.

甲烷与二氧化碳重整制取合成气反应的研究ⅢSr(La)NiAl11O19积炭动力学

用热重（ＴＧＡ）方法，研究了ＬａＮｉＡｌ１１Ｏ１９和ＳｒＮｉＡｌ１１Ｏ１９催化剂上甲烷与二氧化碳重整反应的积炭动力学．实验结果表明，甲烷裂解是ＣＨ４＋ＣＯ２反应中主要的积炭反应；甲烷与二氧化碳重整反应的积炭速率随反应温度升高而增大，但其衰减速度也较快；ＣＨ４＋ＣＯ２反应的积炭速率相对甲烷分压的反应级数是１，相对二氧化碳分压的反应级数是－０．５；在ＳｒＮｉＡｌ１１Ｏ１９中掺入Ｌａ３＋离子，提高了催化剂上甲烷裂解反应的活化能，降低了ＣＯ２消炭反应的活化能，从而提高了催化剂的抗积炭能力.

YAG∶Eu~(3+)、Bi~(3+)的溶胶-凝胶法合成及其结构和发光性能

溶胶－凝胶法以其各组分混合均匀性好、反应温度低、节省能源等诸多优点而引起了人们极大兴趣［１，２］．近年来，利用该法研制玻璃和陶瓷等无机材料的报道越来越多［３，４］．但研制稀土固体发光材料的报道则较少．钇铝石榴石Ｙ３Ａｌ５Ｏ１２（ＹＡＧ）是一种很好的基…

La_(2-x)(Sr,Th)_xCuO_(4±λ)系催化剂的表征及对CO+NO反应催化性能的研究

合成了x值不同的La2 -xSrxCuO4±λ( 0 .0≤x≤ 0 .1 )和La2 -xThxCuO4±λ( 0 .0≤x≤ 0 .4)两系列K2 NiF4型复合氧化物催化剂 ,用XRD和IR研究了催化剂的晶体结构 .利用化学分析和XPS等方法测定了该系列含Cu氧化物中Cu离子的平均价态、非化学计量氧 (λ)和催化剂的表面和体相组成 .通过控制B位Cu离子的价态和氧化物的非化学计量氧在一定范围内有规律的变化 ,考察对NO +CO反应的催化性能 ;利用MS TPD法研究了该系列氧化物对NO和CO +NO等小分子的吸附和活化性能 ,在此基础上探讨了含Cu的A2 BO4型复合氧化物对NO +CO反应中的催化作用本质 .发现在低温反应条件下 ,NO分子的活化是控制步骤 ,催化剂的活性与低价离子及其含量有关 .在较高反应温度下 ,NO的吸附为控制步骤 ,催化活性与氧空位有关

混合导电型陶瓷透氧膜材料的化学稳定性

考察了Sr-Co -Fe -O系列和Bi-Sr-Fe -O系列混合导电型无机透氧膜材料在氧分压小于 1.0 13Pa的气氛中 ,在 850℃和 950℃高温下加热 2 4～ 10 0h前后结构的变化。发现Bi -Sr -Fe-O系列透氧膜材料具有良好的化学稳定型 ,可以用于还原气氛下的催化反应。