Esterification of acetic acid with N-butanol over the catalysts of surface hydrophobicity and lipophobicity

A series of silica-supported silicotungstic acid catalysts (H4SiW12O40, abbreviated as HSiW), modified with various loadings of Teflon (HSiW/SiO2-Teflon), were prepared by impregnation method. The surface properties of the catalysts were studied by means of XRD, BET, NH3-TPD and the Drop Shape Analyzer (DSA) measurements. Both the surface hydrophobicity and the surface lipophobicity of HSiW/SiO2-Teflon catalysts are enhanced by means of the addition of Teflon.

Direct electron transfer of horseradish peroxidase and its electrocatalysis based on carbon nanotube/thionine/gold composites

Horseradish peroxidase (HRP) was incorporated into multiwalled carbon nanotube/thionine/Au (MTAu) composite film by electrostatic interactions between positively charged HRP and negatively charged MTAu composite. The results of electrochemical impedance spectroscopy (EIS) confirmed adsorption of HRP on the surface of MTAu modified GC electrode.

Sintering-resistant hollow fibers of LaMgAl11O19 prepared by electrospinning

Lanthanum magnesium hexaaluminate (LMA) is very important ceramic material for catalytic combustion of natural gas. The sintering-resistant hollow fibers of LMA with diameters ranging from 1 to 3 mu m were fabricated from alcoholic solutions containing polyvinyl pyrrolidone (PVP) and aqueous solution of lanthanum, magnesium and aluminum nitrates. The interaction between PVP and nitrates were studied by X-ray diffraction and Fourier transmission-infrared spectroscopy. The forming mechanism of hollow fibers and the sintering ability of hollow LaMgAl11O19 fibers were discussed.

毛细管电泳电化学法对苯丙胺的检测

建立了毛细管电泳电化学法检测尿样中苯丙胺的方法。以直径33μm的碳纤维电极为工作电极,在最佳检测条件即检测电位1.30 V,15 kV下电动进样3 s,选择电泳分离高压为15 kV,电泳缓冲液为pH10.0的20 mmol/L的磷酸盐,实验发现,在1.0×10-8~1.0×10-5mol/L范围内,响应电流与苯丙胺浓度呈良好的线性关系,线性相关系数为0.998 4,检出限达3.3×10-9mol/L。对于浓度为1.0×10-5mol/L的苯丙胺,峰电流及迁移时间的RSD分别为2.4%和2.5%(n=7)。对于尿样中2.0×10-5mol/L的苯丙胺,回收率为75%。

基于电化学电容检测的新型钙离子传感器

通过金-硫共价键,将巯基十六羧酸以自组装的方式固定到金电极表面。再通过EDC、NHS的活化作用,对钙调蛋白的氨基与巯基十六羧酸暴露于自组装层外的羧基进行共价键和,从而将钙调蛋白固定到电极表面,制成一种新型的钙离子电容传感器。首先对传感器进行了等效电路分析,并分别考察了不同浓度电解质溶液对基底电容的影响,确定了进行实验所需的合适电解质浓度。用本实验室自行开发研制的电化学电容分析仪研究了该传感器对钙离子的响应能力,并进一步考察了其再生能力及稳定性。实验结果表明,在10-8~3×10-6mol/L的较宽范围内,钙离子浓度的对数值与总电容信号值之间呈线性关系,而且检出限可以达到10-9mol/L。制备好的传感器浸泡在0.02 mol/L,pH 7.0的磷酸缓冲溶液中在4℃冰箱中可以保存一个月而其对钙离子的响应能力未发现有显著的下降,说明其具有良好的稳定性。使用过的传感器用EDTA进行再生后基底电容的变化不超过0.3%,说明其具有良好的再生可...

Surface-appropriate lipophobicity - Application in isobutene oligomerization over Teflon-modified silica-supported 12-silicotungstic acid

A series of silica-supported 12-silicotungstic acid catalysts (H4SiW12O40, abbreviated as HSiW), modified with various loadings of Teflon (HSiW/SiO2-Teflon), were prepared by an impregnation method. The surface properties of the catalysts were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), BET, infrared (IR) spectroscopy, NH3-TPD and the Drop Shape Analysis (DSA). SEM results combined with energy-dispersive X-ray (EDX) measurements of HSiW/SiO2-Teflon revealed that F-compound (Teflon) is effectively coated on the catalyst surface. The contact angles for water and oil of 50 wt% HSiW/SiO2 and HSiW/SiO2-Teflon indicate that HSiW/SiO2-Teflon catalyst enhances not only the surface hydrophobicity but also the surface lipophobicity by means of the addition of Teflon. Silica-supported 12-silicotungstic acid modified with Teflon exhibits higher C-8(=) selectivity and longer lifetime than that of silica-supported 12-silicotungstic acid in isobutene oligomerization. Thus, surface-appropriate lipophobicity of catalysts may be effective for decreasing the interaction between coke precursors and the catalyst surface and for removing deposited coke more easily.

Fabrication and photoluminescence properties of core-shell structured spherical SiO2@Gd2Ti2O7 : Eu3+ phosphors

A sol-gel technique was used to prepare Gd2Ti2O7:Eu3+-coated submicron silica spheres (SiO2@Gd2Ti2O7:Eu3+). The resulted SiO2@Gd2Ti2O7:Eu3+ core-shell particles were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive x-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra, as well as kinetic decays. The XRD results demonstrate that the Gd2Ti2O7:Eu3+ layers begin to crystallize on the SiO2 spheres after annealing at 800 degrees C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size similar to 620 nm), non-agglomeration, and smooth surface. The thickness of the Gd2Ti2O7:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (60 nm for four deposition cycles). Under the irradiation of 310 nm ultraviolet, the SiO2@GdTi2O7:Eu3+ samples show strong emission of Eu3+.

4,7-(氯磺酸基苯基)-1,10-菲啰啉-2,9-二羧酸-铕标记甲胎蛋白抗体

在合成BCPDA基础上 ,对甲胎蛋白抗体与BCPDA连接及与铕离子螯合条件进行了研究。BCPDA与甲胎蛋白抗体反应后 ,分离纯化最佳淋洗液为pH9.1的0.1mol/L碳酸盐缓冲溶液 ,BCPDA用量为甲胎蛋白抗体量 (mol)的120～160倍;反应时间为30min。讨论了Eu3+ BCPDA AFP抗体螯合物的荧光光谱 ,最佳温育时间为60min,体系pH值为7.8的Tris HCl溶液。当Eu3+ 浓度为10-6mol/L时,BCPDA的检出限为4.3×10-11mol/L。

VUV and Eu-L-3 edge XANES spectra of europium-doped strontium tetraborate prepared in air

VUV-UV and Eu-L-3 edge XANES spectra were measured for europium-doped strontium tetraborate prepared by solid state reaction at high temperature in air. The VUV-UV spectra show that the host absorption band of (SrBO7)-O-4 appears below 170 nm. The charge transfer band of Eu3+ doped in SrB4O7 is peaked at 272 nm. The 4f-5d transitions of Eu2+ consist of a band peaked at 310 nm with a shoulder at 280 nm and also include the bands peaked at 238 (weak) and 203 (strong) nm. The result of XANES spectrum at Eu-L3 edge of the synthesized sample indicates that Eu3+ and Eu2+ coexist in SrB4O7:Eu prepared in air, which is consistent with the results of the VUV-UV spectra.

Study of color centers and trace oxygen in KMgF3 : Eu single crystal

Using the Bridgeman-Stockbarger method, the KMgF3:EU2+ single crystal was grown. The color centers in unirradiated KMgF3:Eu crystal were studied. By thermal annealing, we confirmed the 422-nm emission resulted from color centers and oxygen centers, and we proved the energy transfer from EU2+ to color centers. From spectra, the relative oxygen content in crystal was calculated, and the relationships of oxygen displacing fluorine were studied.

Aromatic poly(ester imide)s and poly(amide imide)s having 1,1 '-binaphthyl-2,2 '-diyls in the main chain

Full Paper: Two new 1,1'-binaphthyl-2,2'-diyl-based dianhydrides, i.e., 2,2'-bis(3,4-dicarboxybenzamido)-1,1'-binaphthyl dianhydride (BNDADA) and 2,2'-bis(3,4-dicarboxybenzoyloxy)-1,1'-binaphthyl dianhydride (BNDEDA), were synthesized and polymerized with various aromatic diamines to afford polyimides through the traditional two-step method. The polyimides with inherent viscosities ranging from 0.27 to 0.70 dl . g(-1) showed excellent solubilities in polar solvents such as DMAc, DMSO and NMP etc., except of the poly(ester imide) prepared from BNDEDA and benzidine. Poly(ester imide)s based on BNDEDA can also be readily dissolved in weakly polar solvents such as THF, CH2Cl2 and CHCl3. The glass transition temperatures of these polyimides are in the range of 210-310 degrees C; the 5% weight loss temperatures are in the range of 390-465 degrees C in nitrogen and 384-447 degrees c in air. These polymers from light yellow, tough films that were transparent above 365 nm. The effects of different flexible units attached in the 2- and 2'-positions, i.e., amide, ester and ether, on the properties of the polyimides obtained are discussed.

Study on a series of main-chain liquid-crystalline ionomers containing sulfonate groups

A series of main-chain Liquid-crystalline ionomers containing sulfonate groups pendant on the polymer backbone were synthesized by an interfacial condensation reaction of 4,4'-dihydroxy-alpha,alpha'-dimethyl benzalazine, a mesogenic monomer, with brilliant yellow (BY), a sulfonate-containing monomer, and a 1/9 mixture of terephthaloyl and sebacoyl dichloride. The structures of the polymers were characterized by LR and UV spectroscopies. DSC and thermogravimetric analysis were used to measure the thermal properties of those polymers, and the mesogenic properties were characterized by a polarized optical microscope, DSC, and wide-angle X-ray diffraction. The ionomers were thermally stable to about 310 degreesC. They were thermotropic liquid-crystalline polymers (LCPs) with high mesomorphic-phase transition temperatures and exhibited broad nematic mesogenic regions of 160-170 degreesC, and they were lyotropic LCPs with willowy leaf-shaped textures in sulfuric acid. However, the thermotropic liquid-crystalline properties were somewhat weakened because the concentration of BY was more than 8%. The inherent viscosity in N-methyl-2-pyrrolidone suggested that intramolecular associations of sulfonate groups occurred at low concentration, and intermolecular associations predominated at higher concentration. (C) 2001 John Wiley & Sons, Inc.

茂金属及非茂金属催化剂引发丁二烯聚合

综述了茂金属与非茂金属催化剂引发丁二烯聚合的研究进展。茂钒催化剂在丁二烯聚合中有较高的催化活性，聚合物顺－ 1,4－结构摩尔分数约为 80％， 1,2－结构摩尔分数约为 20％。

Nonradiative energy transfer study on the interface of compatibilized linear low density polyethylene/poly(methyl methacrylate) blends

Blends of chromophore-labeled LLDPE and chromophore-labeled PMMA compatibilized by block copolymer of hydrogenated polybutadiene and methyl methacrylate (PHB-b-PMMA) were studied by nonradiative energy transfer (NRET) technique. The ratio of fluorescence intensity of the donor at 336 nm and the acceptor at 408 nm (I-D/I-A) decreased with an increase in block copolymer content. At about 8 wt.-% block copolymer content I-D/I-A reached a minimum value, indicating the interdiffusion of LLDPE chains and PMMA chains in the interface is strongest. The influence of temperature on the interdiffusion of polymer chains in the interface was also examined. Samples quenched in liquid nitrogen from 140 degrees C showed lower energy transfer efficiencies than those annealed from 150 degrees C to room temperature.