SYNTHESIS AND CHARACTERIZATION OF POLY{4-[2-(tert-BUTYLDIMETHYLSILOXY)ETHYL]STYRENE} AND ITS HYDROLYSIS DERIVATIVE

The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene(TBDMES)was studied in methylcyclohexane(MeChx)/methylchloride(MeC1)(50/50 V/V)solvent mixture at-80℃.The initiator 1,1- diphenylethylene(DPE)capped 2-chloro-2,4,4-trimethylpentane(TMPCl)was formed in situ in conjunction with titanium tetrachloride(TiCl_4).The Lewis acidity of TiCl_4 was decreased by the addition of titanium(IV)isopropoxide(Ti(OiPr)_4)to accomplish living polymerization of TBDMES.Hydrolysis of poly(TBDMES)i...     

Catalysis of the coupling reaction of aryl chlorides with bis(pinacolato)diboron by tricyclohexylphosphine-cyclopalladated ferrocenylimine complexes

Tricyclohexylphosphine-cyclopalladated ferrocenylimine complexes were found to be very efficient catalysts for the one-pot borylation/Suzuki cross-coupling reactions of aryl chlorides with bis(pinacolato)diboron. Typically, using 0.5–1.0 mol% of catalyst in the presence of 3.0 equivalents of K₂CO₃ as base in dioxane at 100 °C provided the corresponding symmetrical biaryls in good to excellent yields.     

Chemical and mechanical stability of EPDM in a PEM fuel cell environment

Proton exchange membrane (PEM) fuel cell stack requires elastomeric gaskets in each cell to keep the reactant gases within their respective regions. Long-term durability of the fuel cell stacks depends heavily on the functionality of the elastomeric gasket material. Chemical and mechanical stability of the elastomeric material is of great concern to the overall performance of the fuel cell stacks. The degradation of a commercially available gasket material, ethylene-propylene-diene monomer (EPDM), was investigated in a simulated PEM fuel cell environment in this work. One solution and two temperatures, based on actual fuel cell operation, were used in this study. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the gasket material before and after exposure to the simulated PEM fuel cell environment over time. Atomic absorption spectrometry was used to identify the leachants in the soaking solution from the elastomeric material. Microindentation test and dynamic mechanical analysis (DMA) were conducted to assess the change of mechanical properties of the samples exposed to the environment. The atomic absorption spectrometer analysis shows that silicon and calcium were leached from the material into the soaking solution. The ATR-FTIR results indicate that the chemical changes were not apparent. The microindentation test and DMA results reveal that mechanical properties were not changed significantly.     

A new route for simple and rapid determination of hydrogen peroxide in RAW264.7 macrophages by microchip electrophoresis

A new method using MCE with LIF detection was developed for the determination of hydrogen peroxide (H₂O₂). Bis(p‐methylbenzenesulfonyl)dichlorofluorescein, a new fluorogenic reagent synthesized by our laboratory was employed as a labeling reagent, the derivatization reaction was performed in 0.10 M HEPES buffer (pH 7.4) for 30 min at 37°C. The detection of H₂O₂ was accomplished in 55 s, using a 40 mM HEPES buffer, 20% mannitol, pH 7.4, on a glass microchip. The RSDs of migration time and peak area were 1.8 and 3.7%, respectively. Method validation showed the linear response ranging from 0.50 to 50 μM with an LOD (S/N=3) of 0.20 μM (19.1 amol). The proposed method was applied to determine H₂O₂ in phorbol myristate acetate‐stimulated RAW264.7 macrophages, the concentration of H₂O₂ was found to be 1.86±0.05 μM; recoveries for macrophage samples were from 96.7 to 97.8%, within‐days and between‐days accuracies were 4.5% (n=5) and 6.8% (n=5), respectively.     

细乳液聚合制备载有CdTe的交联聚苯乙烯荧光微球

利用改进的正相细乳液聚合法, 对疏水的CdTe纳米晶进行包覆, 得到了纳米级的交联聚苯乙烯荧光微球. 研究发现, 较高的引发剂浓度和较高的交联度有利于抑制相分离的发生和荧光的保持. 进而将3-甲基丙烯酰氧基丙基三甲氧基硅烷作为共聚单体, 得到了表面硅羟基功能化的聚苯乙烯荧光微球, 改善了微球在水相中的分散性, 并将此类荧光功能微球成功用于细胞成像.     

Visible light photodegradation of dyes over mesoporous titania prepared by using chrome azurol S as template

Mesoporous TiO₂ with anatase crystalline structure (MTiO₂/CAS) has been synthesized by using chrome azurol S (CAS, 2″,6″-dichloro-3,3′-dimethyl-4′-hydroxy-3″-sulfofuchson-5,5′-dicarboxylic acid) as template. It was characterized by X-ray diffraction, nitrogen adsorption/desorption, diffuse reflectance UV–visible and FT-IR spectrometry, and transmission electron microscopy. It was found that MTiO₂/CAS had substantial photocatalytic activity in the degradation of methylthionine chloride, rhodamine B, gentian violet, safranin T, methyl violet, and fuchsine basic whereas Degussa P25 (P25) had negligible photodegradation yield (<6%) under visible light irradiation.     

Er^3＋／Yb^3＋：Sr3Y2（BO3）4晶体的光谱和激光性质

采用提拉法生长了双掺Yb3+和Er3+离子浓度分别为18.63%和0.87%(原子分数)的Sr3Y2(BO3)4晶体.利用测量的偏振吸收谱结合Judd-Ofeh理论,拟合得到了该晶体中Er3+离子的偏振和有效J-O参数.测量了Er3+离子4I13/2能级和Yb3+离子2F5/2能级的荧光衰减曲线,并计算了4I13/2能级的荧光量子效率和Yb3+到Er3+的能量传递效率.利用Fuchtbauer-Ladenberg公式计算了Er3+离子4I13/2→4I15/2跃迁的偏振受激发射截面.在平-凹谐振腔中,利用97nm波长光纤耦合准连续半导体激光端面泵浦1.12mm厚的该晶体,当输出镜透过率为1.5%时,获得了最大输出功率为1.3 w和斜率效率为20%的1560 nm附近的激光输出.结果表明,Er3+/Yb3+:Sr3+Y2+(BO3)4晶体是一种优良的1.5～1.6 μm波段激光的增益介质.     

MnOx/Al2O3/Ce0.45Zr0.45M0.10Oy （M = Mn, Y, La） catalysts used for ethanol catalytic combustion

MnOx/Al2O3/Ce0.45Zr0.45M0.10Oy (M = Mn,Y,La) catalysts were prepared by impregnation method and characterized by BET,TPR and XRD analyses.The catalytic activities toward ethanol combustion were investigated in a microreactor.The results demonstrated that the catalytic activity of MnOx/Al2O3/Ce0.50Zr0.50O2 monolithic catalyst could be improved by doping Mn,Y and La into Ce0.50Zr0.50O2.When doping Y into Ce0.50Zr0.50O2,the catalyst MnOx/Al2O3/Ce0.45Zr0.45Y0.10O1.95 showed the highest activity.The 100% conversion temperature of ethanol was 230 ℃.Furthermore,once the conversion of ethanol started,the complete conversion was quickly achieved.The doping of Mn,Y and La led to better activity for ethanol combustion and lower temperature reduction peaks in TPR profiles.The doping of Mn resulted in enhanced oxygen storage capacity (OSC),larger area of the reduction peaks,and excellent reactivity,and the doping of Y resulted in the lowest reduction temperature and the best activity.     

Catalytic methanol decomposition to carbon monoxide and hydrogen over Pd/CeO2-ZrO2-La2O3 with different Ce/Zr molar ratios

The catalytic behaviors of Pd (1.4 wt%) catalysts supported on CeO2-ZrO2-La2O3 mixed oxides with different Ce/Zr molar ratios were investigated for methanol decomposition. Nitrogen adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD) and Pd dispersion analysis were used for their characterization. Pd/Ce0.76Zr0.18 La0.06 O1.97 catalyst showed the highest BET surface area, best Pd dispersion capability and strongest metal-support interaction. Moreover, XPS showed that there was lattice defect oxygen or mobile oxygen. According to the result of O 1s measurements the lattice defect oxygen or mobile oxygen helped to maintain Pd in a partly oxidized state and increased the activity for methanol decomposition. The Pd/Ce0.76Zr0.18La0.06O1.97 catalyst exhibited the best activity. A 100% conversion of methanol was achieved at around 260℃, which was about 20-40 ℃ lower than other catalysts     

Synthesis of magnetic nickel spinel ferrite nanospheres by a reverse emulsion-assisted hydrothermal process

Nickel ferrite nanospheres were successfully synthesized by a reverse emulsion-assisted hydrothermal method. The reverse emulsion was composed of water, cetyltrimethyl ammonium bromide, polyoxyethylene(10)nonyl phenyl ether, iso-amyl alcohol and hexane. During the hydrothermal process, β-FeO(OH) and Ni_0.75Fe_0.25(CO₃)_0.125(OH)₂·0.38H₂O (INCHH) nanorods formed first and then transformed into nickel spinel ferrite nanospheres. The phase transformation mechanism is proposed based on the results of X-ray powder diffraction, transmission electron microscopy and energy-dispersive X-ray spectroscopy, etc. Nickel ferrite may form at the end of the INCHH nanorods or from the solution accompanied by the dissolution of β-FeO(OH) and INCHH nanorods. The X-ray photoelectron spectroscopy analysis shows that a few Fe³⁺ ions have been reduced to Fe²⁺ ions during the formation of nickel ferrite. The maximum magnetization of the nickel ferrite nanospheres obtained after hydrothermal reaction for 30 h is 55.01 emu/g, which is close to that of bulk NiFe₂O₄.