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  • Author or Editor: Xu Zhang x
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Abstract

Titanium dioxide (TiO2), polythiophene and polythiophene/TiO2 were prepared by sol–gel and solid-state reaction methods. Water-free iron(III) chloride (FeCl3) was used as an oxidant. The phase composition, morphology and the spectral properties of the products were characterized by XRD, TEM, UV–Vis and FT-IR techniques. The photocatalytic activity of the products was evaluated by the degradation of methyl orange under sunlight irradiation. TEM results showed that the polythiophene/TiO2 composite particles were well dispersed, rod-like shaped with 20 × 80 nm dimensions. UV–Vis analysis indicated that the absorption edge of polythiophene/TiO2 was 605 nm. Compared with the unmodified TiO2 and bare polythiophene, polythiophene/TiO2 exhibited largely enhanced activity for the photocatalytic degradation of methyl orange under sunlight irradiation. A degradation efficiency of methyl orange of 85.6% could be obtained within 120 min. The sensitization mechanism of polythiophene for the TiO2 photocatalyst is discussed briefly.

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Authors: Fan Lan, Xiang Wang, Xianglan Xu, Rongbin Zhang and Ning Zhang

Abstract

SnO2 catalysts were prepared with the precipitation method by varying the pH and SnCl4 concentration. For comparison, another two SnO2 samples were also synthesized with sol–gel and combustion methods. All of the catalysts were characterized by N2-BET, XRD and H2-TPR. It was found that the CO oxidation activity of the precipitation samples increases with an increase in pH, while the CH4 oxidation activity seems unchanged. The change of the SnCl4 concentration has little influence on the activity for both CO and CH4 oxidation. The sol–gel sample has relatively higher CO but similar CH4 oxidation activity, due to its higher surface area and finer particle sizes. On the contrary, the combustion sample displays the lowest activity for both reactions, due to its extra low surface area and inert oxygen species.

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Abstract  

A cellulose xanthate supported palladium(0) complex was synthesized using a simple method and characterized by XPS, TG/DTA etc. The complex has good thermal stability from room temperature to 250 °C and it was found to be an efficient catalyst for the Heck reaction of acrylic acid or styrene with aryl iodide at low temperature under atmospheric pressure, and the substituted trans-cinnamic acid or 1, 2-stilbene was obtained with high yield at 90 °C. The reaction duration is about 8 h. The cellulose xanthate supported palladium(0) complex could be separated from the reaction mixture easily and reused for several cycles. The yield of the product was up to 55.3% when the catalyst was run for 10 times. The active center in the complex is Pd metal.

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Changes in microbial population, pH, sugar, organic acid, anthocyanins, total soluble phenolics, and anti-glucosidase contents were measured during fermentation of mulberry juice at 30 °C by probiotic Leuconostoc mesenteroides showing rapid growth after an approximately 1-day lag phase and reaching a maximum of 8.6 log CFU ml−1 after 4 d. During the rapid growth phase, the main mulberry juice sugars, glucose and fructose, were largely consumed, and the acidic metabolites, lactic acid and acetic acid, were produced accordingly. A slow decrease in the concentration of the main organic acid, citric acid, was also observed during fermentation. After 4 d fermentation, anthocyanin content showed a 44.4% reduction, but the total amount of soluble phenolics and α-glucosidase inhibitory activity showed no significant changes (P>0.05). This suggests that L. mesenteroides fermentation of mulberry juice is a good strategy to enhance its probiotic value and to decrease the sugar content without changing the anti-glucosidase activity, which is required to reduce postprandial rise in blood glucose.

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Authors: Guangsong Sun, Hui Xu, Huaming Li, Huoming Shu, Chengtang Liu and Qi Zhang

Abstract  

Gd2O3/Ag3VO4 photocatalysts are synthesized through the impregnation method and characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectra (DRS). It is shown that Gd3+ is dispersed on the surface of Ag3VO4 in the form of Gd2O3. The DRS analysis indicates that the ability of visible-light absorption of Gd2O3/Ag3VO4 catalysts is enhanced greatly. The photocatalytic activities of the samples are evaluated by degradation of Rhodamine B dye under UV and visible-light irradiation, respectively. The experimental results show that the role of Gd2O3 content has a significant impact on the photocatalytic activities of the samples. The mechanism of enhanced photocatalytic activity after the Gd introduction is discussed.

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Abstract

Asymmetric electro-epoxidation of olefins had been achieved with sodium hypochlorite (NaClO) as an oxidant, which was generated by electrolysis in two-phase systems of aqueous sodium chloride (NaCl) and ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4)). The electrolysis conditions by different current densities (0.8, 0.9, 1.0, 1.1 and 1.3 mA/cm2) and pH values (8, 9, 10, 11, 12 and 13) were optimized and 1.1 mA/cm2 and pH 11 were selected. The proposed reaction mechanism is also discussed. The performance of new catalytic systems in four kinds of reaction media in the presence or absence of ammonium acetate (NH4OAc) as a cocatalyst was investigated systematically. Compared to the chemical epoxidation systems, the enantiomeric excess (ee) values and yields for the epoxidation of styrene, α-methylstyrene and indene were acceptable in the electrocatalytic epoxidation systems.

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