聚4—氨基联苯溶液的性质

本文报导了聚4-氨基联苯的电化学合成,测定了它的ESR、IR及紫外可见光谱。聚合物在THF、DMF和DMSO中能全部溶解。界面移动法测得聚4-氨基联苯的DMF饱和溶液中正离子的迁移率为1.48×10~(-8)m~2·S~(-1)·V~(-1)。     

Singlewall carbon nanotubes covered with polystyrene nanoparticles by in‐situ miniemulsion polymerization

This work is to make carbon nanotubes dispersible in both water and organic solvents without oxidation and cutting nanotube threads. Polystyrene‐singlewall carbon nanotube (PS‐SWNT) composites were prepared with three different methods: miniemulsion polymerization, conventional emulsion polymerization, and mixing SWNT with PS latex. The two factors, crosslinking and surface coverage of PS are important factors for the mechanical and electrical properties, including dispersion states of SWNT in various solvents. The PS‐SWNT composite prepared via a conventional emulsion polymerization showed SWNT bundles entirely covered with PS, whereas the PS‐SWNT composite prepared via a miniemulsion polymerization showed SWNT partially covered with crosslinked PS nanoparticles. The method of mixing SWNTs with PS latex did not show the well dispersed state of carbon nanotubes because PS was not crosslinked and was dissolved in a solvent, and nanotubes separated from PS precipitated. So the PS nanoparticle‐SWNT composite had lower electrical resistance, and higher mechanical strength than the other composites made by the latter two methods. As the amount of SWNT increases, the bare surface area of SWNT increases and the electrical conductivity increases in the composite made by the miniemulsion polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 573–584, 2006     

Gold ultra-microelectrode arrays: application to the steady-state voltammetry of hydroxide ion in aqueous solution.

Gold ultra-microelectrode arrays are used to explore the electrochemical oxidation of hydroxide ions and are shown to be analytical useful. Two types of ultra-microelectrode arrays are used; the first consist of 256 individual electrodes of 5 microm in radius, 170 of which are electrochemically active in a cubic arrangement which are separated from their nearest neighbour by a distance of 100 microm. The second array compromises 2597 electrodes of 2.5 microm in radius and of which 1550 of which are electrochemically active in a hexagonal arrangement separated by the nearest neighbour by 55 microm. Well defined voltammetric waves are found with peak currents proportional to the concentration of hydroxide ions in the range 50 microM to 1 mM. Detection limits of 20 microM using the 170 ultra-microelectrode and 10 microM with the 1550 ultra-microelectrode array are shown to be possible but with a higher sensitivity of 4 mA M(-1) observed using the 1550 ultra-microelectrode array compared to 1.2 mA M(-1) with the 170 ultra-microelectrode array.     

On conservative approximation by linear polynomial operators an extension of the Bernstein's operator

In this work we study linear polynomial operators preserving some consecutive i-convexities and leaving invariant the polynomials up to a certain degree. First, we study the existence of an incom patibility between the conservation of certain i-convexities and the invariance of a space of polynomials. Interpolation properties are obtained and a theorem by Berens and DeVore about the Bernstein's operator is extended. Finally, from these results a generalized Bernstein's operator is obtained. This work was supported by Junta de Andalucia. Grupo de investigación: Matemática Aplicada. Código: 1107     

断续喷洒去溶电热雾化法在电感耦合等离子体原子发射光谱方法中的应用研究

本文所讨论的电热雾化法是采用继续喷洒去溶技术,使试样在石墨炉表面逐步积累的进样方法。文章简要介绍了实验条件的选择和控制以及石墨炉装置的结构,探讨了提高电热雾化法相对检测能力的途径。实验结果表明:谱线黑度值与试样积累时间的对数值之间具有较好的线性关系。     

Chiralcel OD-RH手性柱拆分卡维地洛对映体

采用Ch iralcelOD-RH(纤维素3,5-二甲基苯基氨基甲酸酯)手性固定相高效液相色谱法研究了乙腈-高氯酸钠缓冲盐体系对卡维地洛的手性拆分情况,讨论了流动相的各个因素(有机相的种类和比例、缓冲盐浓度、酸度等)对手性拆分的影响。在乙腈-高氯酸钠缓冲盐(pH 5.5,50 mmol/L)的体积比为35∶65的色谱条件下,卡维地洛对映体获得了基线分离。     

高介电常数TiO2纳米晶的表面态研究

将钛酸四丁酯和硬脂酸在熔融状态下混合均匀后置于冷水浴中,使其凝固成凝胶,通过控制烧结过程中氧气的含量,成功地制备出粒度均匀、介电性能好的纳米晶TiO2.通过采用X射线光电子能谱和表面光电压谱对纳米晶TiO2表面状态的分析发现,材料表面存在大量的氧空位缺陷,暴露在粒子表面上的主要是一些金属Ti4+.纳米材料的这种表面状态对其极化性质具有重要的影响,使其在接近静态条件下的低频介电常数远大于常规材料的介电常数.