EPR studies on H-abstractions/spin-trapping reactions of new 'magic blue' reagents with alcohols

The H-abstractions/spin-trapping reactions with primary, secondary and tertiary alcohols of new 'magic blue' reagents, namely, the blue F113 (CClF₂CCl₂F) solution containing bis{perfluoro[1-(2-fluorosulfonyl)ethoxy]ethyl} nitroxide (2) and perfluoro[1-nitroso-1-(2-fluorosulfonyl)ethoxy]ethane (3) both generated in the reaction of perfluoro[2-(2-fluorosulfonyl)ethoxy]propionyl peroxide (1) with sodium nitrite in F113 at room temperature, were studied by EPR. Based on the interpretation of the EPR spectra of the spin adducts, nitroxides, the region-selectivity of H-abstraction has been disclosed and the possible mechanistic paths of H-abstraction have also been discussed. EPR of H-abstraction by using 'magic blue' reagents can also be used for producing various hydroxyalkyl radicals from common alcohols.     

土壤腐殖质各组分红外光谱研究

土壤腐殖质是土壤中所特有的一类特殊的高分子化合物,具有重要的肥力和环境调节功能。其中胡敏素的提取和纯化很困难,从而限制了对其性质和结构的研究。为揭示胡敏素的结构性质,本研究按Pallo分组,将胡敏酸(HA)分为焦磷酸钠提取的胡敏酸(HAP)、氢氧化钠提取的胡敏酸(HAS);富里酸(FA)分为焦磷酸钠提取的富里酸(FAP)和氢氧化钠提取的富里酸(FAS);胡敏素(HM)分为铁结合胡敏素(HMi)、粘粒结合胡敏素(HMc)和不溶性胡敏素(HMr)三个组分,采用红外光谱法对黑土、草甸土以及黑土底土加入大量玉米秸秆培养后腐殖质各组分的结构特征进行研究。腐殖质各组分按Pallo法分组。结果表明:铁结合胡敏素(HMi)、粘粒结合胡敏素(HMc)与胡敏酸(HA)、富里酸(FA)具有相似的光谱特征,但存在明显差异。黑土、草甸土中HMi和HMc的脂族性强于HA和FA;HMi与HMc相比,HMi具有较高的脂族性。黑土中氢氧化钠提取的胡敏酸(HAS)的脂族性强于焦磷酸钠提取的胡敏酸(HAP);NaOH提取的富里酸(FAS)的脂族性强于Na4P2O7提取的富里酸(FAP)。草甸土中HAP的脂族结构较多,而HAS脂族结构相对较少。在培养土中,新形成的FA脂族性强于HA、HMi和HMc组分。新形成的HMc脂族性强于HMi和HMc的脂族性强于HAP,而弱于HAS。     

多层栅介质层有机薄膜晶体管的存储与光响应特性

在真空室内一次性制备了具有多层栅介质层结构的有机薄膜晶体管(OTFTs).结果表明,制备的OTFTs具有电控开关、存储和光敏多重功能特性.分析认为,存储特性归功于器件的结构,采用了分离的CaF2纳米粒子岛作为电荷俘获中心.在光照环境下,观察到了两种不同类型的光响应特性.快速的光响应来自于有源层吸收了能量大于带隙的光子所...     

光纤模式混合器在差分吸收光谱系统中的应用研究

差分吸收光谱技术(DOAS)已经发展为监测对流层痕量气体的重要技术，一般采用光电倍增管(PMT)作为探测器.由于光电二极管阵列(PDA)在多道探测及像元灵敏性方面的优势，采用PDA代替扫描探测装置将能改善系统剩余噪声，提高系统性能.但实际应用中由于使用收发一体Cassegrain望远镜造成灯谱与大气谱结构不统一，在消除PDA像元间差异的过程中给系统带来误差，从而导致剩余噪声的标准偏差达到1.4×10^-3.根据光纤扰模原理在系统中加入自制光纤模式混合器很好的解决了上述难题，在实际应用中起到良好的作用，系统剩余噪声的标准偏差为3.4×10^-4. 关键词： 差分吸收光谱 扰模 模式混合器 剩余噪声     

蒸镀法制备全有机并五苯薄膜场效应晶体管

以全蒸镀方法在真空室内一次性制备了正装结构的全有机并五苯薄膜场效应晶体管。正装结构全蒸镀法有利于简化工艺制备程序,缩小器件尺寸,提高集成度。制备的绝缘层厚度仅为50nm的全有机薄膜场效应晶体管,器件的工作电压降至10V,相同电压下饱和输出电流有了明显提高。筛选适当的有机绝缘材料,改善全有机薄膜场效应晶体管有源层/绝缘层的界面性能,使阈值电压几乎降至0V,场效应迁移率提高了3倍多,输出饱和电流也有了明显的提高。     

OX2(X=F，Cl，Br，I，At)中的离域π63键

本文在理论层面上研究了OX₂(X=F,Cl,Br,I,At)分子的电子结构,结果表明其中存在离域π⁶₃键,氧原子采取sp²杂化方式,与价层电子对互斥理论预测的结果不符. 提出了离域稳定化能衡量形成离域π⁶₃键对能量降低的贡献,证实离域π⁶₃键对分子结构起到了额外的稳定作用. 这些现象可以总结为一种配位效应.     

Beam dynamics studies on BEPC-Ⅱstorage rings at the commissioning stage

During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider(BEPC Ⅱ),which started on Nov.12,2006 and Oct.24,2007,respectively,we got the luminosity one tenth of its design value,provided beams to synchrotron radiation users for about 4 months,and studied beam dynamics as well.In this paper,some beam dynamics studies on the storage rings and their preliminary results are given.     

Research Progress of Lithium Plating on Graphite Anode in Lithium‐Ion Batteries

Lithium plating on graphite anode is triggered by harsh conditions of fast charge and low temperature, which significantly accelerates SOH (state of health) degradation and may cause safety issues of lithium ion batteries (LIBs). This paper has reviewed recent research progress of lithium plating on graphite anode. Firstly, we summarize the forming mechanisms of Li plating with corresponding influence factors, the detecting methods and hazard of Li plating. Then, approaches to suppress Li plating are discussed, including anode surface modification, electrolyte composition optimization and development of optimal charge strategies. Finally, we conclude and propose the remaining challenges and prospects in terms of mechanism research, detecting approaches, and suppressing methods of Li plating. This review highlights the development of Li plating research and plays a guiding rule of further study on Li plating in LIBs.     

Theoretical analysis of magnetic sensor output voltage

The output voltage is an important parameter to determine the stress state in magnetic stress measurement, the relationship between the output voltage and the difference in the principal stresses was investigated by a comprehensive application of magnetic circuit theory, magnetization theory, stress analysis as well as the law of electromagnetic induction, and a corresponding quantitative equation was derived. It is drawn that the output voltage is proportional to the difference in the principal stresses, and related to the angle between the principal stress and the direction of the sensor. This investigation provides a theoretical basis for the principle stresses measurement by output voltage.