Electrospun cerium nitrate/polymer composite fibres: synthesis, characterization and fibre-division model

Cerium (Ⅲ) nitrate/poly(vinylpyrrolidone) (Ce(NO3)3/PVP) composite fibres have been prepared by electrospinning. After calcining the composite fibres in air at 500℃,CeO2 nanowires were obtained. The characterizations of the as-spun composite fibres and resultant nanowires have been carried out by a scanning electron microscope (SEM),an infrared spectrometer,an x-ray diffractometer and a fluorescence spectrophotometer. Interestingly,some unusual ribbon-like or twin fibres were observed besides the common fibres with circular or elliptic cross sections. We developed a fibre-division model resulting from Coulomb repulsion and solvent vaporization to interpret the formation of the ribbons or twin fibres,which has been confirmed by the SEM studies. Our results also indicate that the formation of the ribbons or twin fibres is less dependent on operation voltage and work distance.     

β-榄香烯含S, Se糖苷衍生物的设计合成

以β-榄香烯(1)为先导化合物, 经由其13位氯代物(2), 依据生物电子等排原理将具有相似共价半径的杂原子S和Se分别引入到β-榄香烯的骨架中, 得到一对相应的类似物3和6; 进而通过多种方法与系列糖供体对接, 立体选择性地合成了相应的乙酰化1,2-反式糖苷类衍生物11a~11c和12a~12c, 经水解脱去保护基团, 得到目标产物β-榄香烯含S糖苷13a~13c及其类似物β-榄香烯含Se糖苷14a~14c. 目标化合物的结构经IR, 1H NMR, 13C NMR, 77Se NMR, HRMS等方法确证.     

Dielectric properties of electrospun titanium compound/polymer composite nanofibres

Poly(vinylpyrrolidone)/tetrabutyl titanate (PVP/ [CH3(CH2)3O]4Ti) composite nanofibres are prepared by elec- trospinning. After calcining parts of composite nanofibres in air at 700 C, petal-like TiO2 nanostructures are obtained. The characterizations of composite nanofibres and TiO2 nanostructures are carried out by a scanning electron micro- scope, an x-ray diffractometer, and an infrared spectrometer. Electrospun nanofibres are pressed into pellets under different pressures in order to explore their dielectric properties. It is found that the dielectric constants decrease with frequency increasing. The dielectric constant of the composite nanofibre pellet increases whereas its dielectric loss tangent decreases due to the doped titanium ions compared with those of pure PVP nanofibre pellets. In addition, it is observed that the dielectric constant of the composite nanofibre pellet decreases with the increase of the pressure applied in pelletization.     

系列β-榄香烯糖苷衍生物的合成

以β-榄香烯为先导化合物, 经其13-位氯代物2合成乙酸酯3, 随后水解得β-榄香烯-13-醇(4), 进而通过两种糖苷化方法与系列代表性单糖及双糖对接, 得到相应的β-榄香烯糖苷衍生物9a～9e. 所有糖苷化反应均立体选择性地生成β-构型糖苷. 目标产物的结构经IR, 1H NMR, 13C NMR, HRMS等光谱确证.     

Electrical resistance response of polyaniline films to water, ethanol, and nitric acid solution

<正>This paper reports on electrical resistance vs.aging time for the response of polyanihne films under exposure to water,ethanol and nitric acid(HNO_3) solution.Camphor sulfonic acid-doped polyanihne films were prepared by a "doping-dedoping-redoping" method,the morphology and microstructures of the films were characterized by a scanning electron microscope and an x-ray diffractometer,the electrical resistance was measured by a four-probe method.It was found that a lower amount of water molecules infiltrating the film can decrease the film's resistance possibly due to an enhancement of charge carrier transfer between polyanihne chains,whereas excessive water molecules can swell inter-chain distances and result in a quick increase of resistance.The resistance of the film under exposure to ethanol increases and becomes much larger than the original value.However,HNO3 solution can decrease the film's resistance sharply possibly owing to doping effect of protonic acid.These results can help to understand the conduction mechanism in polyaniline films,and also indicate that the films have potential application in chemical sensors.     

两种β-榄香烯烃基硒醚类化合物的合成、表征

将硒用N2·H2O还原为Se2 2-后与卤代烃反应得到对称二硒醚,然后将其用NaBH4还原,再与13-氯-β-榄香烯作用,得到两种β-榄香烯烃基硒醚.用1H NMR,13C NMR,IR以及HRMS等手段对产物结构进行了表征.     

β-榄香烯烃基硒醚的一锅法合成

常温下将硒用N2H4&#8226;H2O还原后与卤代烃反应得到对称二硒醚, 不经分离直接用NaBH4还原, 再与13-氯-β-榄香烯作用得到β-榄香烯烃基硒醚. 此一锅法操作简便、条件温和、反应快速而且产率较高, 是合成不对称硒醚的一种简便实用的方法. 对化合物g的初步生物活性实验表明其具有显著的抗氧化作用.     

Electrospun fluorescein/polymer composite nanofibers and their photoluminescent properties

Fluorescein/polyvinyl pyrrolidone (PVP) composite nanofibers with different fluorescein loadings (with a weight concentration of 0-5.0%) are fabricated via electrospinning. Morphologies, structures and photoluminescent (PL) properties of these straight, helical or wavelike fibers are characterized by scanning electron microscopy (SEM), fluorescence microscopy and a spectrophotometer. It is found that the maximum emission of the as-spun fluorescein/PVP fibers occurs at 510 nm. The PL intensity of the composite fiber increases with fluorescein concentration, then fluorescence quenching appears when the concentration reaches 1.67%. The mechanism of fluorescence quenching of fluorescein is discussed. In addition, the composite fibers exhibit a much stronger PL intensity than fluorescein/PVP bulk film owing to larger specific surface area, which makes them promising materials for biomedical applications such as probes and sensors.