Electron microscopy and light scattering study of organometallic inverse micellar systems

Colloidal dispersions in hydrocarbons of lead and calcium salts of isooctanoic acids are studied by means of Transmission Electron Microscopy and Light Scattering. The complementary results obtained, using each technique, allow us to investigate the structure of the mineral core, the size and the morphology of the colloidal particles. Special attention is paid to the aggregation properties of the metal salts particles as a function of the dilution and solvent.     

Synthesis and electrophoretic deposition of high-dielectric-constant SrTiO3 nanoparticles

We have investigated on the synthesis of SrTiO₃ nanoparticles whose bulk exhibits dielectric constant of 300, and their colloidal dispersion. As a result, we successfully synthesized SrTiO₃ nanoparticles with an average diameter of 134–485 nm measured by a scanning electron microscopic observation. The SrTiO₃ nanoparticles with a negative charge (ζ = −25 to −31 mV) can be dispersed as colloidal nanoparticles in water, and the average diameter in the dispersion were 138–356 nm measured by a dynamic light scattering technique. The colloidal dispersion of SrTiO₃ nanoparticles is promising for fabrication of low-voltage organic field-effect transistors (FETs) by a wet-processing fabrication. We have also successfully prepared SrTiO₃ films with a thickness of 1–10 μm on n-doped silicon substrates by an electrophoretic deposition technique. The SrTiO₃ films on the silicon substrates are likely used as dielectric gate insulator to low-voltage organic FETs after a sintering treatment.     

单分散PS/SiO_2纳米复合微球的制备与表征

采用一种简单和低成本的方法制备单分散SiO2包覆聚苯乙烯(PS)(PS/SiO2)核-壳型纳米复合微球.首先在聚乙烯吡咯烷酮(PVP)存在下制备了PS纳米微球,然后在NH4OH/乙醇溶液中通过溶胶-凝胶过程在PS微球表面包覆SiO2.PS纳米微球的制备在水介质中进行,无需使用共单体,使用的是常用的过硫酸钾自由基引发剂;包覆处理前不用进行溶剂交换或离心处理.研究了PVP,NH4OH和原硅酸乙酯(TEOS)的用量对PS/SiO2纳米复合微球尺寸和形态的影响.随着PVP用量增加,PS微球变小,因此得到较小的PS/SiO2纳米复合微球;NH4OH用量对SiO2包覆层的厚度没有影响,但对SiO2包覆层的表面形态有影响,随着NH4OH用量增加包覆层表面变得粗糙;随着TEOS溶液用量增加,生成的SiO2增加,其包覆层的厚度增加.     

Electrochemical Properties of a Boron‐Doped Diamond Electrode Modified with Gold/Polyelectrolyte Hollow Spheres

Oppositely charged polyelectrolyte (poly(allyamine hydrochloride) (PAH) and poly(sodium 4‐styrene‐sulfonate) (PSS)), and negatively charged gold nanoparticles (Au) were assembled alternately on polystyrene (PS) spheres via layer‐by‐layer technique, and the different PAH/(PSS/PAH)_n/(Au/PAH)_m/Au composite hollow spheres were derived by dissolving PS core. These hollow spheres were used to modify boron‐doped diamond (BDD) electrodes for electrochemical sensors. The cyclic voltammetric results for dopamine (DA) detection demonstrated that hollow‐sphere‐modified BDD exhibited better electrocatalytic activity than did bare BDD. Influence of the wall thickness and composition of hollow spheres on electrochemical properties were investigated. The results showed that the oxidative peak potential of DA and the peak current varied with different PSS/PAH and Au/PAH layers. The optimized wall structure of hollows spheres was PAH/(PSS/PAH)₇/(Au/PAH)₅/Au.     

Cloning and Expression of Chitinase A from Serratia Marcescens for Large‐Scale Preparation of N,N‐Diacetyl Chitobiose

The gene of Serratia marcescens chitinase A (chiA) was cloned by PCR. The complete gene was constructed into a pRSET vector and expressed in Escherichia coli. The recombinant enzyme was purified to > 90% homogeneity by hydrophobic interaction chromatography followed by ion‐exchange separation. Measured with an electrospray‐ionization mass spectrometer, the molecular mass of the protein was 58,607 Da, consistent with a theoretical calculation of the deduced protein without the signal peptide. The recombinant enzyme was characterized and tested for the preparation of chitobiose. In general, the recombinant Chtinase A exhibited an exo‐type catalytic activity toward colloidal chitin and released both N‐acetylglucosamine and N,N‐diacetyl chitobiose as products. After extensive testing, we produced N,N‐diacetyl chitobiose as the predominant product when the enzymatic reaction was performed in sodium acetate buffer at pH 5.5; under such conditions, an enzymatic process is established for the production of the disaccharide on a 100‐g scale.     

Approximate expression for the electrophoretic mobility of a spherical colloidal particle covered with an ion-penetrable uncharged polymer Layer

An approximate analytic expression is derived for the electrophoretic mobility of a charged spherical colloidal particle covered with an ion-penetrable uncharged polymer layer in an electrolyte solution by taking into account the relaxation effects. This expression is applicable for all values of zeta potentials at large a(aca. 30), where is the Debye–Huckel parameter and a is the radius of the particle core. A simple expression for the ratio of the electrophoretic mobility of a polymer-coated particle to that of a bare particle without a polymer layer is also given.     

低温催化法制备石墨化碳空心球

石墨化碳空心球因具有密度小、稳定性好和可填充中空结构等特点,受到了研究者的广泛关注。本文结合国内外的研究进展,综述了近年来发展起来的采用过渡金属如铁、钴、镍等为催化剂,低温(<1 000℃)催化法合成石墨化碳空心球的最新研究进展。介绍了低温催化法提高碳空心球石墨化程度的机理,说明了石墨化碳空心球的表征方法,展望了石墨化碳空心球的应用前景。最后指出了相关研究中有待解决的问题。     

聚苯乙烯/二氧化锰复合微球的合成与表征

本文利用聚苯乙烯微球为模板水热合成了聚苯乙烯/二氧化锰有机无机复合微球.复合微球核层为聚苯乙烯微球,壳层是由大量的二氧化锰纳米棒紧密堆积形成的.利用扫描电子显微镜及透射电子显微镜表征可以看出产物含有大量的复合微球,对于可能的反应机理进行了讨论.     

酞菁与TiO2微粒间的光诱导电子转移相互作用

带有负电荷取代基的四磺化酞菁化合物与TiO2超微粒在溶液中通过静电相互吸引,能够形成基态复合物。通过吸收光谱和荧光光谱,计算了磺化酞菁与TiO2在溶液中的表现缔合平衡常数K.与相应的烷氧基取代酞菁化合物作比较,并通过单光子技术测定染料荧光寿命。结合荧光光谱,证明了磺化酞菁与TiO2在溶液中的缔合作用,有利于激发态酞菁染料向半导体TiO2的导带注入电子,从而发生分子间的电子转移反应,将磺化酞菁吸附在TiO2纳晶薄膜电极上,进行光电性能测试。结果表明,染料敏化TiO2纳晶薄膜电极光电响应的大小与染料在电极表面吸附的强弱有关。