Grubbs carbene complex-catalyzed cleavage of allyl vic-diols to aldehydes with a co-oxidant: application to the selective cleavage of huge marine molecules

An oxidative cleavage of allyl vic-diols to aldehydes catalyzed by a Grubbs carbene complex using a co-oxidant has been established for the first time, with good yields. The utility of this selective cleavage reaction was demonstrated through the use of two huge marine molecules, symbiodinolide and N-p-BrBz palytoxin.     

Analysis of photo-chemical degradation behaviour of polyethylene mulching film with pro-oxidants

It is generally accepted that polyolefins are bioinert. The last years, a new class of photodegradable polyethylene films with pro-oxidants has been developed, exhibiting optimised operational properties in terms of controlled UV and/or thermal ageing leading to an abrupt, predefined to some extent, rapid fragmentation into very small fragments. These photodegradable or fragmentable polyethylene films are promoted in the market for various commercial applications. In some cases, these materials are presented as, or are claimed to be, biodegradable materials. Such materials are already used in agriculture in the form of photodegradable mulching films which become fragmented into small remains after the end of their useful lifetime and are incorporated into the soil. However, it has not been verified yet beyond any doubt, that these remains do in fact biodegrade in natural soil, under what conditions, at which rate and what are their effects in agricultural production, the soil and the environment. An experimental investigation has been carried out focusing on the combined effects of critical factors on the controlled (predefined) photo-chemical degradation of photodegradable mulching LLDPE films with pro-oxidants and the behaviour of their remains in the soil. The analysis of the photo-chemical degradation behaviour presented in this paper was carried out through parallel experiments performed under real field and controlled laboratory conditions. The main factors investigated include materials, exposure time, temperature and UV radiation.     

Sulfur-Containing Vinyl Monomers. XV. Kinetic Study of Radical Polymerization of Vinyl Mercaptobenzothiazole and Its Copolymerization

A kinetic study of radical polymerization of vinyl mercaptobenzothiazole (VMBT) with α,α′-azobisisobutyonitrile (AIBN) at 60°C was carried out. The rate of polymerization (R_p) was found to be expressed by the rate equation: R_p = k[AIBN]^0.5 [VMBT]^1.0, indicating that the polymerization of this monomer proceeds via an ordinary radical mechanism. The apparent activation energy for overall polymerization was calculated to be 20.9 kcal/mole. Moreover, this monomer was copolymerized with methyl methacrylate, acrylonitrile, vinyl acetate, phenyl vinyl sulfide, maleic anhydride, and fumaronitrile at 60°C. From the results obtained, the copolymerization parameters were determined and discussed.     

The fate and behavior of glufosinate-enantiomers and their metabolites in open-field soil and weeds

In this study, a chiral method based on high performance liquid chromatography–Q-Exactive Orbitrap Mass Spectrometry was developed to determine glufosinate stereoisomers and three metabolites in weed. Fortified recoveries in weed and soil samples were from 78.6 to 94.3 %, with relative standard deviations of less than 9.8 % and fortified values ranging from 0.04 to 40 mg/kg for the glufosinate enantiomers and 0.08–8 mg/kg for three metabolites. When glufosinate was given at the peak of weed growth in three orchards, it was mostly distributed and degraded in the weeds, with little remaining in the soil. The two glufosinate enantiomers degraded rapidly in the weeds and soils, with half-lives ranging from 0.7 to 3.1 days. The degradation of glufosinate enantiomers in Guizhou and Hunan weeds was enantioselective, with l-glufosinate being preferentially degraded. In Hainan weed, the degradation rate of the two enantiomers was nearly the same. In open field soils, glufosinate enantiomers were almost non-enantioselective. 3-methylphosphinico-propionic acid (MPP) was the primary glufosinate metabolite in weeds and soils, accounting for up to 14 % of the parent. N-acetyl-glufosinate (NAG) was relatively low, with less than 1 % of the parent glufosinate metabolized into 2-methylphosphinico-acetic acid (MPA).     

紫外光辐照下CH3NH3PbI3基钙钛矿太阳能电池失效机制

随着光伏产业的不断发展,有机无机杂化钙钛矿太阳能电池的研发成为科学与工业界广泛关注的焦点。到目前为止,其光电转换效率已经提高到了25.2%,成为替代硅基太阳能电池的核心方案之一。然而,钙钛矿太阳能电池的稳定性较差,容易受到环境中氧气、水分、温度甚至光照的影响,这严重制约了其大规模推广与应用。大量科学研究表明,如何避免紫外辐照下有机无机杂化钙钛矿太阳能电池的性能衰减,对于提高钙钛矿太阳能电池的光照稳定性至关重要。然而到目前为止,仍然没有系统的工作来对紫外辐照下钙钛矿太阳能电池性能以及微结构演化过程进行详细的表征与分析。本文中,我们利用聚焦离子束-扫描电子显微分析(FIB-SEM)以及球差校正透射电子显微分析(TEM)等技术,全面地研究了紫外辐照过程中有机无机杂化钙钛矿太阳能电池性能变化规律以及电池微结构演化特征。实验结果表明,紫外辐照过程中太阳能电池内部会形成0.5–0.6 V的内建电场,钙钛矿中的I^-离子在电场的驱动下向金属Au电极和空穴传输层2, 2’, 7, 7’-四[N, N-二(4-甲氧基苯基)氨基]-9, 9'-螺二芴(Spiro-OMeTAD)一侧迁移;随后,空穴传输层与金电极的界面处,碘离子与光生空穴一起与金电极发生反应,将金属态Au氧化成离子态Au⁺。而Au⁺离子则在内建电场的驱动下反向迁移穿过钙钛矿MAPbI₃层,直接被SnO₂和MAPbI₃界面处的电子还原形成金属Au纳米团簇。除此之外,紫外辐照过程中钙钛矿太阳能电池性能降低的同时,往往伴随着Spiro-OMeTAD与钙钛矿界面处物质迁移、钙钛矿薄膜内晶界展宽以及Au纳米颗粒周围MAPbI₃物相分解等现象。以上各种因素的协同作用,共同导致了紫外光照下有机无机杂化钙钛矿太阳能电池光电转换性能(PCE)、开路电压(V_oc)以及短路电流(J_sc)等性能参数的急剧下降。     

CuNPs as an activator of K2S2O8 for the decolorization of diazo dye in aqueous solution

Degradation of trypan blue (TB) by persulfate/CuNPs system was investigated as a function of TB concentration, persulfate concentration, CuNPs concentration, pH, and reaction temperature in aqueous solution. The rate of the decolorization and destruction of aromatic ring were studied spectrophotometrically. The dye mineralization was performed with potassium dichromate for the determination of chemical oxygen demand (COD) in solution. The blue color reaction mixture became red-chocolate, purple, light blue to dark blue as a function of time. The CuNPs acted as an activator of K₂S₂O₈ and generates various reactive oxygen and/or sulphur species. Decolorization of dye starts due to the cleavage of azo bond by the generated radical species. The role of sulfate radicals (SO₄^?-), and hydroxyl radicals (HO^?) were established by using different radical scavengers. Degradation and mineralization of dye follows first-order kinetics. These results can support the design of remediation processes and also assist in predict their fate in environment.     

Highly efficient photocatalytic degradation for antibiotics and mechanism insight for Bi2S3/g-C3N4 with fast interfacial charges transfer and excellent stability

Bi₂S₃/g-C₃N₄ (BSCN) samples with different mass ratios of CN to BS were prepared by a facile and practicable hydrothermal method with 2D g-C₃N₄ nanosheets (CN). The microscopic morphology and structure of pure CN, BS and BSCN were measured by multiple testing methods. Analysis results show that the BSCN was prepared successfully, and the Bi₂S₃ nanoparticles closely and uniformly adhered to the surface of CN with sheet-like structure. The introduction of Bi₂S₃ did not change the structure of the CN. The results of the ultraviolet–visible spectroscopic analysis, photoluminescence spectra and electrochemical performance indicated that BSCN showed superior visible-light response compared with CN, and the separation and transfer efficiency of photogenerated carriers was significantly improved. With the decrease of mass ratio of CN/BS, the photocatalytic activity of BSCN initially increased and then decreased for 20 ppm of Rhodamine B solution (RhB), and the Bi₂S₃/g-C₃N₄-B with a mass ratio of 8:1 for CN to BS showed optimal photocatalytic performance (98.98%). Furthermore, the Bi₂S₃/g-C₃N₄-B exhibited apparent degradation effects (1.021 x10^-2, 0.879 x10^-2 and 0.793 x10^-2 min^?1) to three kinds of antibiotics (tetracycline, ciprofloxacin, and oxytetracycline). The BSCN samples still maintained higher degradation efficiency after five cycles of degradation to tetracycline. The capture experiments and the electron spin resonance (ESR) spectra analysis indicated that the h⁺ and ·O₂^? played a major role, and ·OH played secondary role during the photocatalytic reaction.     

纳米白藜芦醇脂质体的物理化学稳定性研究

纳米载药脂质体的物理化学稳定性,是其实际应用中的关键问题。文章采用薄膜旋转蒸发法-超声法制备了白藜芦醇纳米脂质体（RES-Lip）,采用透射电子显微镜观察其微观形貌,并考察RES-Lip的物理化学稳定性。通过电导法测定了RES-Lip的相变温度（Tm）,及其在凝聚过程的凝聚速率常数（Kco）和表观活化能（Eco）;采用动态透析-紫外分光光度法,研究了温度和pH对RES-Lip降解的影响。结果表明,RES-Lip为球形囊泡结构,粒径小于100 nm;RES-Lip的相变温度为64℃;凝聚速率常数Kco随体系温度升高而升高;表观活化能Eco为86.056 kJ/mol;RES-Lip的降解符合一级动力学模型,降解的表观活化能Ea为59.3157 kJ/mol,降解过程是吸热、自发、熵增过程。本实验制备得到的RES-Lip在4℃、pH=7.40的条件下储存,稳定性较好。     

Degradation and recovery in poly(butylene adipate-co-terephthalate)/ thermoplastic starch blends

The economic and social impact of the increasing waste disposal problems of conventional plastic materials are well known and promoted the search for better recyclable and biodegradable polymers, blends and compounds. Fully biodegradable blends of poly(butylene adipate-co-terephthalate) (PBAT), a synthetic copolyester, and thermoplastic starch (TPS), a natural polysaccharide, are of technical and economic interest in the quest for eco-friendly polymeric materials to substitute conventional alternatives. One of less desirable characteristics of many new biodegradable materials is their relative thermal instability (degradation) under processing conditions.In the present work, PBAT/TPS blends with up to 30% TPS were processed at different temperatures in a laboratory internal mixer, with and without the incorporation of a chain extender additive (Joncryl). The rate of change of torque during the melt processing stage, adjusted to eliminate minor temperature variations, is a very sensitive indicator of variation of molar mass due to degradation and recovery. It was found that TPS content promotes thermal degradation in the PBAT/TPS blends at levels above those observed in neat components, in a strongly composition and temperature-dependent process. The addition of 1% of the chain extender additive partially reverts the process, especially during processing at high temperature.     

复杂条件下高分子材料老化规律、寿命预测与防治研究新进展

复杂条件下有机高分子材料的老化、寿命预测和防治研究对满足相关行业发展的迫切需求,实现节能减排、环境保护及可持续发展等战略目标具有重大意义。本文重点综述了近年来针对聚烯烃、工程塑料、橡胶、涂料等大宗高分子材料在我国复杂大气环境中的自然老化及人工模拟加速老化研究的新进展,对材料老化失效基本规律和分子机理、老化数据库的建立及老化分级图谱的绘制进行了介绍,探讨了户外自然环境和人工模拟环境下材料老化失效规律的对应关系、服役寿命理论的预测模型及失效防治延寿新方法,并对其中存在的问题及下一步发展方向进行了展望。