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111.
Nanomaterials with helical morphologies have attracted much attention owing to their potential applications as nanosprings, chirality sensors and in chiral optics. Single‐handed helical Ta2O5 nanotubes prepared through a supramolecular templating approach are described. The handedness is controlled by that of the organic self‐assemblies of chiral low‐molecular‐weight gelators (LMWGs). The chiral LMWGs self‐assemble into single‐handed twisted nanoribbons through H‐bonding, hydrophobic association, and π‐π stacking. The Ta2O5 nanotubes are formed by the adsorption and polycondensation of Ta2O5 oligomers on the surfaces and edges of the twisted organic nanoribbons followed by removal of the template. The optical activity of the nanotubes is proposed to originate from the chiral defects on the inner surfaces of the tubular structures. Single‐handed twisted LiTaO3 nanotubes can also be prepared using Ta2O5 nanotubes. 相似文献
112.
Effect of chain structure on the glass transition temperature and viscoelastic property of cis‐1,4‐polybutadiene via molecular simulation 下载免费PDF全文
Yangyang Gao Youping Wu Jun Liu Liqun Zhang 《Journal of Polymer Science.Polymer Physics》2017,55(13):1005-1016
In this work, by adopting the united atom model of cis‐1,4‐poly(butadiene) (PB), we systemically investigate the effect of the chain structure on the glass transition temperature (Tg) and the viscoelastic property of PB system. First, we analyze the atom translational mobility, bond reorientation dynamics, torsional dynamics, conformational transition rate, and dynamic heterogeneity of the PB chains with different chain structures in detail by determining the corresponding Tg. In addition, our results clearly indicate that with the decrease of the amount of the free end atoms of PB via the end‐linking method, the mobility of the PB chains quickly decreases. As a result, the Tg of the PB chains gradually increases. Depending on the chain structure and the calculation method, the Tg of the PB chains varies from 154 to 240 K. In addition, the temperature dependence of the dynamic properties has different Arrhenius behaviors above and below Tg. The calculated activation energy varies from 7.37 to 16.37 KJ/mol for different chain structures above Tg, which can be compared with those for other polymers. In addition, through the end‐linking approach the strong interaction between the PB chains improves the storage modulus G′ and the loss modulus . Meanwhile, the immobility of the free end atoms effectively reduces the friction loss of the chains under the shear field, which is reflected by the low loss factor . In summary, this work can further help to understand the effect of the chain structure on the dynamic properties of the PB chains. Meanwhile, it provides an effective approach to reduce the energy loss during the dynamic periodic deformation, which can cut the fuel consumption via the end‐linking method. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1005–1016 相似文献
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用硝酸-高氯酸的混合酸对车前草、泽泻、乌元参、茯苓4种药材进行处理,用火焰原子吸收光谱法测定其中Ca、Mg、Fe、Zn、Mn、Co 6种微量元素。样品加标回收率在96.0%—103.5%之间,相对标准偏差(RSD)小于3.2%,该方法测量简便、准确,结果可靠。 相似文献
114.
介绍了能量色散X荧光分析方法在含水Fe样品测量中的应用.用ANTG -2000型海底X荧光探测系统对含Fe为10%~60%的Fe样进行测量,建立水分对Fe元素特征K α射线影响的校正模型.结果表明,通过该模型校正,对含饱和水情况下Fe样品的分析相对误差小于4%,具有良好的分析效果. 相似文献
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基于反式 1,4-聚异戊二烯(TPI)的形状记忆性能, 以聚氨酯海绵为基底, 包覆TPI制备出了一种具有疏水超亲油特性的三维多孔形状记忆海绵. 由于这种海绵具有良好的形状记忆特性, 可以通过反复按压/恢复过程, 实现对海绵孔径在微米尺寸(约875 μm)与纳米尺寸(约450 nm)间可逆调控. 利用材料特殊的浸润特征及其可控的孔尺寸, 进一步研究了其在油-水分离中的应用. 研究结果表明, 微米尺寸大孔径海绵有利于对不相溶油-水混合物进行快速高效分离, 而纳米尺寸小孔径海绵则有利于对乳液混合物进行分离, 实现了同一材料同时满足不相溶油-水混合物及乳液体系的分离要求. 相似文献
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Two ferrates, K2FeO4 and BaFeO4, had been prepared and characterized by XRD, IR and SEM. The electrochemical tests of the samples were carried out in the voltage range of 0.8~2.0 V and current density of 0.5~3.0 mA·cm-2. The results indicated that performance of Zn-BaFeO4 battery was superior to that of Zn-MnO2 and Zn-K2FeO4 batteries. Nanometer SrTiO3 prepared by Sol-gel methode with different ratio was added to the BaFeO4 cathode in order to improve the discharge performance. The discharge capacity of the BaFeO4 cathode was increased from 224 mAh·g-1 to 246 mAh·g-1 by addition of 5% nanometer SrTiO3. The reason of enhancing BaFeO4 electrochemical performance was discussed. 相似文献
120.
Selective Photooxidation of a Mustard‐Gas Simulant Catalyzed by a Porphyrinic Metal–Organic Framework 下载免费PDF全文
Dr. Yangyang Liu Dr. Ashlee J. Howarth Prof. Joseph T. Hupp Prof. Omar K. Farha 《Angewandte Chemie (International ed. in English)》2015,54(31):9001-9005
The photooxidation of a mustard‐gas simulant, 2‐chloroethyl ethyl sulfide (CEES), is studied using a porphyrin‐based metal–organic framework (MOF) catalyst. At room temperature and neutral pH value, singlet oxygen is generated by PCN‐222/MOF‐545 using an inexpensive and commercially available light‐emitting diode. The singlet oxygen produced by PCN‐222/MOF‐545 selectively oxidizes CEES to the comparatively nontoxic product 2‐chloroethyl ethyl sulfoxide (CEESO) without formation of the highly toxic sulfone product. In comparison to current methods, which utilize hydrogen peroxide as an oxidizing agent, this is a more realistic, convenient, and effective method for mustard‐gas detoxification. 相似文献