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81.
Andrew M. Smith Richard F. Collins Rein V. Ulijn Ewan Blanch 《Journal of Raman spectroscopy : JRS》2009,40(9):1093-1095
Raman optical activity (ROA) is a relatively new technique used to determine the structure of chiral molecules and is proving useful in the study of biological molecules such as proteins and DNA/RNA. Here, for the first time, we demonstrate the applicability of ROA as a technique to study achiral groups in chiral environments, detecting the induced chirality of N‐(fluorenyl‐9‐methoxycarbonyl) (Fmoc) in a chiral self‐assembled structure of Fmoc‐dipeptides. This technique is therefore of interest to those studying self‐assembled systems that adopt a chiral structure. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
82.
凝胶-模板法制备高比表面积氧化镁 总被引:1,自引:0,他引:1
以四水乙酸镁为前驱体,以大米粉形成的凝胶为模板,采用新的凝胶-模板法制备了一系列的氧化镁材料,并用X射线衍射、扫描电镜、低温氮气吸附-脱附、X射线荧光分析、热重-差示扫描量热、CO2程序升温脱附和氨程序升温脱附等手段对样品进行了表征.该方法主要利用大米粉在水中加热形成凝胶来分散镁盐前驱体,再通氧焙烧去除模板从而获得多孔MgO材料.结果表明,制得的MgO具有高比表面积(可达206m2/g)和双介孔结构(孔径分别位于3.9和5~40nm附近).与直接焙烧四水乙酸镁制得的MgO相比,这类新型高比表面积MgO具有较多的强碱位和较少的酸性位,并在异丙醇催化分解反应中表现出更高的丙酮收率和选择性,有望成为一类优良的固体碱催化剂. 相似文献
83.
无机纳米晶的形貌调控及生长机理研究 总被引:6,自引:0,他引:6
形貌及尺寸规整可控的纳米晶体的合成是目前十分引人注目的纳米材料研究领域.制备合成中的形貌调控及其功能化是这些纳米材料能够得到应用的关键问题.研究者们希望在纳米晶的任一阶段均能实现控制并在期望的阶段停止,从而得到尺寸、形态、结构及组成确定的纳米晶体.本文综述了近年来无机纳米晶体的典型合成路径,深入探讨了纳米晶在成核、生长及熟化阶段的控制原理,研究了液相合成纳米材料过程中晶体结构与生长行为的相关性问题,并总结了几类具有代表性的低维、多维纳米晶体的形成规律和生长机理.探索纳米粒子的调控合成对于纳米材料的规模化生产及应用具有重要的理论价值和指导意义. 相似文献
84.
85.
用3-(甲基丙烯酰氧)丙基三甲氧基硅烷(MPS)、 氨丙基三乙氧硅烷(APTES)和正硅酸乙酯(TEOS)溶胀聚苯乙烯中空微球的壳层, 在壳层表面通过溶胶-凝胶过程, 使亲油和亲水基团通过自组装作用分别朝向聚苯乙烯基体和水相, 形成Janus结构. 用良溶剂N,N-二甲基甲酰胺(DMF)溶解除去聚苯乙烯, 得到二氧化硅基复合Janus纳米材料. 改变反应体系pH值和单体用量等可以调控Janus纳米材料微结构, 得到Janus中空球和纳米片. 相似文献
86.
In this paper, passively mode-locked erbium-doped fiber lasers based on saturable absorber (SA) have been theoretically studied. The energetics and pulse properties for different fiber laser cavity configurations have been investigated and the effects of each component (active fiber, passive fiber, and SA) in the laser cavity have been studied. This numerical study takes into account the temporal change in the saturable absorption (dq/dt).The presented simulations could be highly useful for understanding, optimizing, and improving passively mode-locked fiber lasers with SA. 相似文献
87.
An effective central insertion scheme (CIS) that allows to study the electronic structure of nanomaterials at the first principles
level is introduced. Taking advantage of advanced numerical methods, such as the implicitly restarted Arnoldi method (IRAM)
and spectral transformation, together with efficient parallelization technique, this scheme can provide accurate electronic
structures and properties of one-, two-, and three-dimensional nanomaterials with only a fraction of computational time required
for conventional quantum chemical calculations. Electronic structures of several nanostructures, such as single-walled carbon
nanotubes of sub-100 nm in length, silicon nanoclusters of sub-6.5 nm in diameter and metal doped silicon clusters, calculated
at hybrid density functional level are presented.
相似文献
88.
89.
Yifan Zhang Rui Cai Dashuang Wang Kailin Li Qing Sun Yuntao Xiao Hao Teng Xiaohan Huang Tao Sun Zhaohui Liu Kexin Yao Yuxin Zhang Pingan Yang 《Molecules (Basel, Switzerland)》2022,27(3)
The porous and biomimetic cobalt silicate@diatomite (Co2SiO4@diatomite) was successfully synthesized by a two-step method, including the hydrothermal method and calcination to improve the electromagnetic wave absorption property. Different hydrothermal times were well-tuned for Co2SiO4@diatomite composites with different loadings of Co2SiO4. Interestingly, the Co2SiO4@diatomite composites (6 h, 25 wt%) had a smaller minimum reflection loss. Moreover, the minimum reflection loss (RLmin) could reach −12.03 dB at 16.64 GHz and the matched absorber thickness was 10 mm, while the effective absorption bandwidth (EAB, RL ≤ −10 dB) could be 1.92 GHz. In principle, such findings indicate that Co2SiO4@diatomite nanocomposites could be a promising candidate for high-efficiency microwave absorption capability. 相似文献
90.
Nataliya N. Yazvinskaya Mikhail S. Lipkin Nikolay E. Galushkin Dmitriy N. Galushkin 《Molecules (Basel, Switzerland)》2022,27(3)
This paper has experimentally proved that hydrogen accumulates in large quantities in metal-ceramic and pocket electrodes of alkaline batteries during their operation. Hydrogen accumulates in the electrodes in an atomic form. After the release of hydrogen from the electrodes, a powerful exothermic reaction of atomic hydrogen recombination with a large energy release occurs. This exothermic reaction is the cause of thermal runaway in alkaline batteries. For the KSL-15 battery, the gravimetric capacity of sintered nickel matrix of the oxide-nickel electrode, as hydrogen storage, is 20.2 wt%, and cadmium electrode is 11.5 wt%. The stored energy density in the metal-ceramic matrix of the oxide-nickel electrode of the battery KSL-15 is 44 kJ/g, and in the cadmium electrode it is 25 kJ/g. The similar values for the KPL-14 battery are as follows. The gravimetric capacity of the active substance of the pocket oxide-nickel electrode, as a hydrogen storage, is 22 wt%, and the cadmium electrode is 16.9 wt%. The density of the stored energy in the active substance oxide-nickel electrode is 48 kJ/g, and in the active substance of the cadmium electrode it is 36.8 kJ/g. The obtained results of the accumulation of hydrogen energy in the electrodes by the electrochemical method are three times higher than any previously obtained results using the traditional thermochemical method. 相似文献