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Imaging the doping elements is critical for understanding the photocatalytic activity of doped TiO2 thin film. But it is still a challenge to characterize the interactions between the dopants and the TiO2 lattice at the atomic level. Here, we use high angle annular dark-field/annular bright-field scanning transmission electron microscope (HAADF/ABF-STEM) combined with electron energy loss spectroscopy (EELS) to directly image the individual Cr atoms doped in anatase TiO2(001) thin film from [100] direction. The Cr dopants, which are clearly imaged through the atomic-resolution EELS mappings while can not be seen by HADDF/ABF-STEM, occupy both the substitutional sites of Ti atoms and the interstitial sites of TiO2 matrix. Most of them preferentially locate at the substitutional sites of Ti atoms. These results provide the direct evidence for the doping structure of Cr-doped A-TiO2 thin film at the atomic level and also prove the EELS mapping is an excellent technique for characterizing the doped materials. 相似文献
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化学发光能够对火焰结构和燃烧过程进行良好的表征,但利用化学发光对湍流火焰进行测量的研究相对较少。为了更深入地研究和发展湍流燃烧理论,设计了伴燃射流燃烧器,通过ICCD相机和相应滤波片获取了OH^*和CH^*的化学发光图像,对甲烷/空气层流和湍流预混火焰的化学发光特性进行了研究,并利用分布高度、峰值位置、强反应区占比、峰值等参数对不同速度和当量比时的OH^*和CH^*进行表征。结果表明,层流时OH^*和CH^*的分布明显不同,而湍流的混合作用导致二者的分布范围趋向一致。随着当量比增大,不同速度下OH^*和CH^*的分布高度都呈单调递增趋势,但湍流的增长趋势要相对平缓;峰值位置的变化趋势与分布高度几乎一致,间接表明OH^*和CH^*的主导生成反应不变。强反应区占比在层流和湍流状态下的表现完全相反:从贫燃到富燃,层流中由大于0.1降低到0.05以下,而湍流中则由0.05上升到0.1以上,表明湍流对贫燃时的燃烧反应起抑制作用,在富燃时反而起促进作用。另外, OH^*和CH^*的峰值变化可以对火焰的流动状态进行判断,且CH^*尤为明显:随当量比增加,如果峰值先升后降,则可以认为火焰为层流状态;如果峰值单调递增,则是湍流状态。以速度和当量比为自变量,以OH^*和CH^*的峰值比为因变量,提出了不同速度条件下利用化学发光对当量比进行定量表征的统一关系式,解决了不同速度时需要分别进行拟合的问题,对后续的化学发光燃烧诊断研究具有重要意义。 相似文献
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以溴化1-(2,3,4,6-四-O-乙酰基-β-D-吡喃葡萄糖基)-3-丁基咪唑盐(化合物1)、吡啶和醋酸钯为原料,快速合成了空气稳定的1-(2,3,4,6-四-O-乙酰基-β-D-吡喃葡萄糖基)-3-丁基-咪唑-2-亚基]-溴化钯(II)-吡啶(配合物2).配合物2的结构中存在乙酰基-β-D-吡喃葡萄糖基,糖环上有多个手性碳,其核磁共振氢谱(1H NMR)和碳谱(13C NMR)较复杂,不易归属.本文通过元素分析对配合物2的组成进行表征,运用1D和2D NMR技术(包括1H NMR、13C NMR、DEPT135、DEPT90、DEPT45、COSY、1H-13C HSQC、1H-13C HMBC)对配合物2的1H和13C NMR信号进行全归属.研究发现,在乙酰基-β-D-吡喃葡萄糖基的稠环上多个弱配位的氧和乙酰基氧原子上孤电子对的作用下,配合物2的氮杂环卡宾-钯(II)-吡啶金属键形成对稠环上碳氢化学环境的影响比对丁基的影响更为明显. 相似文献
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Imaging the doping elements is critical for understanding the photocatalytic activity of doped TiO2 thin film. But it is still a challenge to characterize the interactions between the dopants and the TiO2 lattice at the atomic level. Here, we use high angle annular dark-field/annular bright-field scanning transmission electron microscope (HAADF/ABF-STEM) combined with electron energy loss spectroscopy (EELS) to directly image the individual Cr atoms doped in anatase TiO2(001) thin film from [100] direction. The Cr dopants, which are clearly imaged through the atomic-resolution EELS mappings while can not be seen by HADDF/ABF-STEM, occupy both the substitutional sites of Ti atoms and the interstitial sites of TiO2 matrix. Most of them preferentially locate at the substitutional sites of Ti atoms. These results provide the direct evidence for the doping structure of Cr-doped A-TiO2 thin film at the atomic level and also prove the EELS mapping is an excellent technique for characterizing the doped materials. 相似文献
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Hyehwang Kim Dr. Zheng-wang Qu Prof. Dr. Stefan Grimme Nahil Al-Zuhaika Prof. Dr. Douglas W. Stephan 《Angewandte Chemie (International ed. in English)》2023,62(43):e202312587
The phosphino-phosphonium cations of the form [R3PPR′2]+ are labile and provide access to the constituent Lewis acidic and Lewis basic fragments. This permits frustrated Lewis pair-type addition reactions to alkynes, affording unprecedented phosphino-phosphination reactions and giving cations of the form [cis-R3PCHC(R′′)PR′2]+. This reactivity is further adapted to prepare several examples of a rare class of dissymmetric cis-olefin-linked bidentate phosphines. 相似文献
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