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91.
研究了二价金属离子在温和条件下(低于100℃,暴露于空气中)从水滑石M2+/Fe2+/Fe3+-LDHs(M=Co,Ni,Mn,Zn)转化成尖晶石铁氧体的过程中所起的作用。结果表明,该转化过程不仅与晶化温度有关,还与M2+在元素周期表中所处的位置有关。当这些二价金属离子处于同一周期并且相邻较近时,M2+的半径越大,水滑石微晶向尖晶石铁氧体的转化就越容易。此外,Fe2+在转化过程中起着至关重要的作用,如果没有Fe2+的参与,在此条件下的转化将无法进行。 相似文献
92.
《Angewandte Chemie (International ed. in English)》2017,56(1):409-412
Heteroaromatic sulfoxides are a frequent structural motif in natural products, drugs, catalysts, and materials. We report a metal‐free visible‐light‐accelerated synthesis of heteroaromatic sulfoxides from sulfinamides and peroxodisulfate. The reaction proceeds at room temperature with blue‐light irradiation and allows the C−H sulfinylation of electron‐rich heteroarenes, such as pyrroles and indoles. An electrophilic aromatic substitution mechanism is proposed based on the substrate scope, substitution selectivity, and competition experiments with different nucleophiles. 相似文献
93.
Dr. Werner Fudickar Prof. Dr. Torsten Linker 《Angewandte Chemie (International ed. in English)》2018,57(39):12971-12975
The generation of reactive singlet oxygen under mild conditions is of current interest in chemistry, biology, and medicine. We were able to release oxygen from dipyridylanthracene endoperoxides (EPOs) by using a simple chemical trigger at low temperature. Protonation and methylation of such EPOs strongly accelerated these reactions. Furthermore, the methyl pyridinium derivatives are water soluble and therefore serve as oxygen carriers in aqueous media. Methylation of the EPO of the ortho isomer affords the parent form directly without increasing the temperature under very mild conditions. This exceptional behavior is ascribed to the close contact between the nitrogen atom and the peroxo group. Singlet oxygen is released upon this reaction, and can be used to oxygenate an acceptor such as tetramethylethylene in the dark with no heating. Thus, a new chemical source of singlet oxygen has been found, which is triggered by a simple stimulus. 相似文献
94.
The use of dimedone in green chemistry has been described for the synthesis of selective heterocyclic motifs which are both pharmacologically and industrially important. The objective of this review is to summarize some of the selected recent advances of dimedone in the synthesis of organic compounds utilizing green chemistry procedures. 相似文献
95.
印迹聚合物合成条件对聚合物性能的影响是分子印迹技术中的一项重要研究内容。以左旋麻黄碱为印迹分子,甲基丙烯酸为功能单体,使用不同的交联剂和致孔剂合成了印迹聚合物,并对所得到的印迹聚合物的比表面积、孔结构和结合特性进行了评价。研究结果说明合成的印迹聚合物对印迹分子具有很好的亲和能力及选择性。致孔剂可以影响聚合物比表面积的大小及单体组成。氯仿是甲基丙烯酸-乙二醇二甲基丙烯酸酯和甲基丙烯酸-季戊四醇三丙烯酸酯聚合链的良溶剂,导致了比表面积及孔容较小的聚合物结构;而以乙腈为致孔剂得到的聚合物有较大的比表面积。共聚物中羧基含量的测定结果也说明,在预聚溶液中单体浓度相同的条件下,以不同的致孔剂进行合成得到的聚合物中甲基丙烯酸的比例不同。聚合物的比表面积及单体浓度的差别都可能导致聚合物的结合容量不同。 相似文献
96.
Triticonazole enantiomers: Separation by supercritical fluid chromatography and the effect of the chromatographic conditions 下载免费PDF全文
Jianfeng He Jun Fan Yilun Yan Xiaodong Chen Tai Wang Yaomou Zhang Weiguang Zhang 《Journal of separation science》2016,39(21):4251-4257
Enantiomeric pairs of triticonazole have been successfully separated by supercritical fluid chromatography coupled with a tris(3,5‐dimethylphenylcarbamoyl) cellulose‐coated chiral stationary phase in this work. The effects of co‐solvent, dissolution solvent, flow rate, backpressure, and column temperature have been studied in detail with respect to retention, selectivity, and resolution of triticonazole. As indicated, the co‐solvents mostly affected the retention factors and resolution, due to the different molecular structure and polarity. In addition, the dissolution solvents, namely, chloromethanes and alcohols, have been also important for enantioseparation because of the different interaction with stationary phase. Higher flow rate and backpressure led to faster elution of the triticonazole molecules, and the change of column temperature showed slight effect on the resolution of triticonazole racemate. Moreover, a comparative separation experiment between supercritical fluid chromatography and high performance liquid chromatography revealed that chiral supercritical fluid chromatography gave the 3.5 times value of Rs/tR2 than high performance liquid chromatography, which demonstrated that supercritical fluid chromatography had much higher separation efficiency. 相似文献
97.
应用非晶的Ti-Al薄膜为导电阻挡层,采用射频磁控溅射法和溶胶-凝胶法在Si衬底上制备了La_(0.5)Sr_(0.5)CoO_3/Pb(Zr_(0.4),Ti_(0.6))O_3/La_(0.5)Sr_(0.5)CoO_3/Ti-Al/Si (LSCO/PZT/LSCO/Ti-Al/Si)异质结,研究了550 ℃常规退火(CTA)和快速退火(RTA)工艺对LSCO/PZT/LSCO/Ti-Al/Si结构和性能的影响.实验发现非晶Ti-Al薄膜在经过不同退火工艺后仍具有非晶结构,快速退火6 min的样品具有较好的物理性能.在418 kV/cm的外加电场下,LSCO/PZT/LSCO电容器的剩余极化强度和矫顽电场强度分别为22 μC/cm~2和83 kV/cm.LSCO/PZT/LSCO电容器的漏电行为不依赖于退火工艺,当电场强度低于46.7 kV/cm时为欧姆导电,高于46.7 kV/cm时为肖特基导电机制. 相似文献
98.
An inflatable cuff wrapped around the upper arm is widely used in noninvasive blood pressure measurement. However, the mechanical interaction between cuff and arm tissues, a factor that potentially affects the accuracy of noninvasive blood pressure measurement, remains rarely addressed. In the present study, finite element (FE) mod-els were constructed to quantify intra-arm stresses generated by cuff compression, aiming to provide some theoretical evi-dence for identifying factors of importance for blood pressure measurement or explaining clinical observations. Obtained results showed that the simulated tissue stresses were highly sensitive to the distribution of cuff pressure on the arm sur-face and the contact condition between muscle and bone. In contrast, the magnitude of cuff pressure and small variations in elastic properties of arm soft tissues had little influence on the efficiency of pressure transmission in arm tissues. In par-ticular, it was found that a thickened subcutaneous fat layer in obese subjects significantly reduced the effective pres-sure transmitted to the brachial artery, which may explain why blood pressure overestimation occurs more frequently in obese subjects in noninvasive blood pressure measurement. 相似文献
99.
在酸性条件下合成氧化亚铜纳米立方体(英) 总被引:7,自引:0,他引:7
在微酸性(pH:4~6)的水热体系中130 ℃反应18 h合成了氧化亚铜纳米粒子,粒径约为100 nm,呈立方体外形。乙二胺和十六烷基胺在反应体系中充当缓冲试剂,调节反应液的pH值并控制体系中游离Cu2+的浓度,使得Cu2+不会被迅速还原成单质铜。所合成的纳米立方体的能带宽度约为2.51 eV,比氧化亚铜体材料和氧化亚铜纳米线蓝移了0.51 eV和0.17 eV,它有利于把太阳光谱中能量高的可见光转化成其他形式的能量。 相似文献
100.
合成了一系列以两个亚甲基为联接基的杂双子咪唑表面活性剂([Cm-2-Cnim]Br2, m, n=8, 10, 12, 14, 16; m≠n). 用氢谱和质谱对其结构进行了表征. 探索了物料比、反应温度和时间对反应产率的影响. 对合成的杂双子咪唑表面活性剂的表面活性进行了研究,讨论了分子结构的不对称程度对表面活性的影响. 相似文献