Rapid estimation of global sugars by UV photodegradation and UV spectrophotometry

The UV/UV method developed for the measurement of specific wastewater pollution parameters (ammonium, Kjeldahl nitrogen, total phosphorus) is adapted to the determination of sugars in fruit juices and soft drinks. The procedure is based on the UV spectrophotometric detection of by-products of UV photodegradation of carbohydrates. Time of analysis is greatly reduced by using specific pH conditions and diluted samples.     

可光固化超支化聚硅氧基硅烷的合成与表征

自20世纪80年代末期Kim和Webster首次采用AB2型单体合成超支化聚合物以来，超支化聚合物以其新颖的结构、独特的性能和广泛的应用前景受到了科学界和工业界的广泛关注．其中超支化有机硅聚合物，尤其是硅氧基聚合物，由于具有良好的高低温稳定性、耐腐蚀性、耐候性等，以及硅氯、硅氢等末端基团易于功能化改性的特点，使其在功能性涂层材料、催化剂以及液晶材料等领域具有重要的应用价值．到目前为止，有关超支化聚硅氧基硅烷的研究主要集中在AB2型单体（x≥2，A和B分别为硅氢基团和乙烯基、烯丙基等不饱和基团）的制备以及硅氢加成产物的功能化改性方面．     

Thermoanalytical and spectroscopic studies of the synthesis of suppokted palladium catalyst in A H2/PdCl2/SiO2 parent system

A 5 wt% Pd/SiO₂ catalyst was synthesized by heating PdCl₂-impregnated SiO₂ in H₂ at 300°C for 2 h. It was found that the metal particle dispersion is improved when the reduction step is preceded by calcination at 300°C for 2h. Thermogravimetry of the impregnated support in air, N₂ and H₂ atmospheres was used to monitor the interactions occurring during the various preparative steps (i.e. drying, calcination and reduction) of the catalyst. The solid prduct of each preparative step was characterized by X-ray diffractometry and UV/Vis diffuse reflectance spectroscopy. The results indicate that following the drying step (at 110°C in air) the palladium occurs in two detectable forms: PdCl₂ particles and Si?O?Pdⁿ⁺ surface species. The calcination appears to transform the PdCl₂ particles into the latter surface species. The H₂-reduction eventually converts the surface species into finely-dispersed Pd° metal particles (average size=8–14 nm). No other reduction products, such as Pd_ySi_x, were detected.     

金纳米粒子的阳光光化学合成和晶种媒介生长

在柠檬酸盐-HAuCl4溶液体系中, 于高原太阳紫外线辐射下光化学合成了分散良好、尺寸分布窄的胶体金纳米粒子. 研究了溶液的酸度和太阳辐射条件对Au(Ⅲ)离子光化学还原反应速率和形成金纳米粒子尺寸的影响; 采用晶种媒介生长技术, 通过改变Au(0)/Au(Ⅲ)比合成了平均直径为4.9~9.7 nm的球形金粒子. 根据紫外-可见吸收光谱和透射电子显微镜的表征和分析, 讨论了光化学反应中自由基反应、金纳米粒子成核和生长机理.     

C60哌嗪加成物的结构及光谱研究

用ＩＮＤＯ系列方法研究了Ｃ６０的哌嗪衍生物Ｃ６０Ｎ２（Ｃ２Ｈ４）２的结构。结果表明［６，６］，异构体具有Ｃ２ｖ对称性［６，５］，异构体具有Ｃｓ对称性，前者能量较低。以优化构型为基础，计算两种加成产物的ＵＶ谱，结果表明，［６，６］异构体的特征吸收与实验值相符，同时对［６，５］异构体的ＵＶ谱进行理论预测，对电子跃迁进行了理论指认，并分析了光谱红移的原因。     

Photodegradation of toluic acid isomers by UV/TiO2

This work elucidates the photodegradation of toluic acid isomers by UV/TiO₂. Effects of the toluic acid isomers, pH and form of TiO₂ on photodegradation are identified. The rate of photodegradation of toluic acid isomers in UV/TiO₂ obey the sequence p > o > m. Additionally, the reaction rates under acidic conditions exceed those under neutral and alkaline conditions.     

Synthesis and electrochromic properties of a new family of methacrylate polymers containing pendant oligothiophenes

A new family of methacrylate polymers containing pendant terthiophene, quaterthiophene, quinquethiophene, and sexithiophene was synthesized by the radical polymerization of the corresponding methacrylate monomers, and the electrochemical and electrochromic properties were investigated. The anodic oxidation of these polymers in the presence of tetra‐n‐butylammonium perchlorate as a supporting electrolyte produced radical‐cation salts of pendant oligothiophenes with ClO as a dopant. The electrochemically oxidized polymers had partially crosslinked structures resulting from the coupling reaction of pendant oligothiophene radical cations, the extent of crosslinking significantly decreasing with the increasing conjugation length of the pendant oligothiophenes. Comparative spectroelectrochemical studies of the monomers in solution and the polymers as solid films showed that π‐dimer formation of oligothiophene radical cations took place more readily for the polymer films than for the monomers in solution. This new family of methacrylate polymers containing pendant oligothiophenes constitutes a new class of potential electrochromic materials, undergoing reversible, clear color changes on electrochemical oxidation and reduction. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2471–2484, 2003     

In situ ESR and UV/vis spectroelectrochemical study of eosin Y upon reduction with and without Zn(II) ions.

The electroreduction of eosin Y on a platinum electrode in deaerated slightly acidic aqueous 0.1 mol L(-1) potassium chloride medium is followed in situ by electron spin resonance (ESR) spectroscopy and UV/Vis spectroscopy. The electrochemical formation of a semiquinone radical is proved by both the appearance of an absorbing band at 408 nm, and a strong ESR signal observed during a negative-going scan. The system is also studied in the presence of Zn(II) ions due to its importance for understanding the growth mechanism of nanostructured ZnO/Eosin Y hybrid films by electrodeposition; under such conditions the ESR and UV/Vis response of the semiquinone radical is not observed. Zinc (II) ions form a complex with the dye, which is reduced by a fast two-electron process.     

Separation and determination of neuraminic acids in nanogram quantities by liquid chromatography — A comparative study with different amino phases

Summary Neuraminic acid derivatives were separated easily by liquid chromatography on amino phases and using acetonitrile/15 mM phosphate buffer, pH 5.2 as mobile phase. Detection at 200 nm allowed determination of substances in the nanomole range. All solvent systems were used isocratically at room temperature. The separation did not depend on ion-exchange but on a partition mechanism, the solutes being separated according to their polarity. Thus, it was possible to optimize the resolution by varying the stationary phase and the composition of the eluent.Part of this work has been presented at the 15th International Symposium on Chromatography, Nürnberg, October 1–5, 1984.     

不饱和酸酐—吩噻嗪电荷转移络合物结构的探讨

用ＩＲ和ＵＶ两种方法首次研究了吩噻嗪与７个酸酐形成的电荷转移络合物，测定了它们的组成和溶剂效应，并推测出酸酐与吩噻嗪形成电荷转移络合物时相互作用的方式（结构）。