keV 质子辐照对Kapton/Al光学性能的影响

 采用空间综合辐照设备对Kapton/Al薄膜进行了质子辐照地面模拟试验，选取质子能量90 keV,辐照通量5.0×10¹¹ cm¹²·s^-1。通过辐照前后光谱反射系数的变化考察了实验样品的光学性能退化特征。借助于反射光谱和紫外-可见吸收光谱和傅里叶转换红外光谱分析技术分析了辐照后Kapton/Al光学性能的退化机理。研究结果表明：辐照过程中样品表面发生了复杂的化学反应，随着辐照剂量的增加光能隙逐渐减小，Kapton吸收曲线的末端边缘发生红移并且在可见光区吸收强度增加。     

Proton radiation tolerance of nanocrystal memories

We report on proton radiation tolerance of Si-nanocrystal (Si-NCs) MOS structures aiming at non-volatile memory applications. Si-NCs were formed by low-energy (1 keV) ion-beam-synthesis within a 9 nm thick SiO₂ layer. A 2-D layer of Si-NCs with 3 nm mean diameter and 10¹² cm⁻² surface density was successfully achieved. After fabrication of Al capacitors, samples with and without Si-NCs were 1.5 and 6.5 MeV proton were irradiated at doses ranging from 1 Mrad (SiO₂) to 120 Mrad (SiO₂). Significant irradiation-dose-dependent shifts are detected in the C–V curves of the NC-MOS cells and programmed cells are found to undergo bit flip. Despite the above, the attainable memory windows after write/erase operations remain unchanged. Retention time characteristics at room temperature for the write and erase states of irradiated and non-irradiated samples reveal that even after an irradiation dose as high as 120 Mrad (SiO₂) the devices still exhibit long time charge storage behavior. We observe that the erase state flat-band voltage decay rate does not depend on the irradiation-dose while the opposite happens for the write state flat-band voltage decay rate which is found to be directly dependent on D_it values giving insight to the physics of the discharging mechanisms.     

Hydrogenase enzymes: Recent structural studies and active site models

Recent developments in active site structure determination of the three types of hydrogenase enzymes are described. Aspects of recent studies using model complexes relevant to the structure and function of the enzymes are reviewed.     

Preparation and properties of covalently cross-linked sulfonated copolyimide membranes containing benzimidazole groups

A series of sulfonated copolyimides containing benzimidazole groups (SPIs) were synthesized by random copolymerization of 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 2-(4-aminophenyl)-5-aminobenzimidazole (APABI), 4,4′-diaminodiphenyl ether-2,2′-disulfonic acid (ODADS) and 9,9-bis(4-aminophenyl)fluorene (BAPF) in m-cresol in the presence of benzoic acid and triethylamine at 180 °C for 20 h. Membranes with good mechanical properties were prepared by solution cast method. Proton exchange treatment resulted in ionic cross-linking and the membranes were further covalently cross-linked by treating them in polyphosphoric acid (PPA) at 180 °C for 6 h. The covalently cross-linked membranes displayed slightly lower ion exchange capacities (IECs) and proton conductivities than the corresponding covalently uncross-linked ones because small part of the sulfonic acid groups had been consumed during the cross-linking process. Fenton’s test (3% H₂O₂ + 3 ppm FeSO₄, 80 °C) revealed that benzimidazole groups played an important role in the radical oxidative stability of the membranes, while the cooperative effect of benzimidazole groups and covalent cross-linking led to much more significant enhancements in the radical oxidative stability of the membranes than each alone. The membrane 4 (ODADS/APABI/BAPF = 2/1/1, by mol), for example, after covalent cross-linking could maintain membrane form within 8 h measurement, which was much longer than that (3 h) before covalent cross-linking under the same conditions. The membrane 5 (ODADS/BAPF = 3/1, by mol) without benzimidazole groups, however, after covalent cross-linking started to break into pieces after 85 min measurement, which was only slightly longer than that (60 min) before cross-linking under the same conditions.     

Synthesis of proton conductive inorganic–organic hybrid membranes through copolymerization of dimethylethoxyvinylsilane with vinylphosphonic acid

Proton conductive inorganic–organic hybrid membranes were synthesized from dimethylethoxyvinylsilane (DMEVS), vinylphosphonic acid (VPA) and 3-glycidoxypropyltrimethoxysilane (GPTMS) through copolymerization followed by sol–gel process. The ratio of phosphorus to silicon in the copolymer almost corresponded to the charged molar ratio of VPA to DMEVS when the ratio of VPA to DMEVS was below 1/2. Self-standing, homogeneous, highly transparent membranes were synthesized from DMEVS–VPA copolymer and GPTMS via sol–gel condensation. Differential thermal analysis-thermogravimetry analyses indicated that these membranes were thermally stable up to 200 °C. The results of Fourier transform infrared and ¹³C NMR revealed that phosphonic acid groups of VPA were chemically bound to organosiloxane network. The copolymerization and condensation of (DMEVS–VPA)/GPTMS were confirmed by ³¹P and ²⁹Si NMR spectra. The proton conductivity of the hybrid membranes increased with phosphonic acid content. The membrane of (DMEVS–VPA)/GPTMS showed a remarkable conductivity of 6.3 × 10⁻² S cm⁻¹ at 130 °C and 100% relative humidity.     

Substituent Effects on Phosphate-Catalyzed Proton Exchange in Amides

The kinetics of phosphate-catalyzed proton exchange have been measured with NMR lineshape analysis for a series of amides, ureas, and carbamates. A hypothetical energy profile for transition structures of concerted phosphate catalysis ?_c and of stepwise phosphate catalysis ?₁, ?₂ is used for discussion of the substituent effects. The concerted mechanism of phosphate catalysis operates only for amides RCONHCH₃ for which the electron-donating ability of the substituent R is comparable with, or better than, that of the methyl group. We conclude that concerted phosphate catalysis is inoperative in proteins or polypeptides.     

Reaction of 2-trifluoroacetyl-1,8-Bis(dimethylamino)naphthalene with strong organic bases: Deprotonation of 1-NMe2 group resulting in the formation of Benzo[g]indole derivatives versus nucleophilic addition to CO group

A novel approach to pyrrole ring closure in 2-trifluoroacetyl- and 2-ethoxycarbonyl-1,8-bis(dimethylamino)naphthalenes via treatment with 2-lithium-1,8-bis(dimethylamino)naphthalene producing the corresponding benzo[g]indole derivatives, was examined with different alkyl- and aryllithium compounds as well as with LDA. It was found that the highest yields of benzo[g]indoles (up to 70%) are obtained with aryllithium reagents when they contain NMe₂ group in ortho-position to the carbanionic centre. In all other cases the formation of acyclic alcohol arising from ordinary intermolecular addition of the carbanion to the CO group strongly prevails. The dramatic facilitation of deprotonation of the N-Me group in substrate followed by pyrrolic cyclization in the case of 2-lithium-N,N-dimethylanilines was explained through a specific structure of the reaction transition state.     

基于质子转移反应-飞行时间质谱快速鉴别不同产地闽北水仙茶

采用质子转移反应-飞行时间质谱仪(PTR-TOF-MS), 构建了3个产地(武夷山、建阳、建瓯)113个闽北水仙茶样品香气的化学指纹图谱, 对所得的闽北水仙茶香气指纹图谱进行主成分分析(PCA), 获得了不同产地闽北水仙茶样品的质谱信息特征, 然后采用软独立建模分类法(SIMCA)、K最邻近结点算法(KNN)、偏最小二乘判别分析法(PLS-DA)对闽北水仙茶的质谱信息进行了模式识别.结果表明, PTR-TOF-MS结合分类识别模式能有效区分不同产地的闽北水仙茶.PCA 提取了3个主成分, 累计贡献率为84.66%;3个识别模型的校正集判别正确率分别为89.38%、100.00%和100.00%, 预测集的判别正确率分别为83.18%、 96.46%和95.57%.基于此成功建立了不同产地的闽北水仙茶识别模型.本方法无需样品预处理、分析速度快、灵敏度高、对茶叶无损伤, 为茶叶产地溯源提供了新方法.     

质子交换膜燃料电池零下冷启动研究

在零下启动过程中,质子交换膜燃料电池阴极中氧气还原反应生成的水会在催化剂层内部结冰,因而阻碍氧气传输,覆盖催化剂层反应活性位点,降低电化学活性面积,影响燃料电池发电性能,甚至会导致零下启动失败;同时,结冰/融化循环还会破坏膜电极结构,影响燃料电池寿命。因此,质子交换膜燃料电池零下启动技术的研究对促进燃料电池汽车的推广应用有重要意义。本文针对质子交换膜燃料电池的零下启动过程,从实验研究、机理解释、模型分析及策略开发等角度对文献内容进行了梳理,并对涉及质子交换膜燃料电池零下启动过程的专利技术进行了总结。     

聚苯基喹噁啉的研究与应用进展

聚苯基喹噁啉(PPQ)是一类重要的热塑性芳杂环聚合物材料。苯基取代喹噁啉环赋予了PPQ优良的耐热稳定性、耐水解性以及在有机溶剂中良好的溶解性。本文综述了近年来国内外在PPQ材料基础研究与应用领域内的最新进展情况,从四酮单体的合成、PPQ的合成以及在高技术领域中的应用等角度进行了阐述。着重介绍了PPQ在集成电路层间介质材料、先进显示用电子传输材料以及燃料电池质子交换膜材料中的应用,最后结合作者的研究工作对PPQ材料在未来高技术领域中的应用前景进行了展望。