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61.
62.
近年来,半导体量子点特别是InAs量子点的基本物理性质和潜在应用得到了广泛研究。许多研究者利用InAs量子点结构的改变以调制其光电特性。本文采用液滴外延法在GaAs(001)表面沉积了不同沉积量的In(3 ML、4 ML、5 ML),以研究In的成核机制和表面扩散。实验发现,随着In沉积量的增加,液滴尺寸(包括直径、高度)明显增大。不仅如此,在相同的衬底温度下,沉积量越大,液滴密度越大。利用经典成核理论,计算了GaAs(001)表面In液滴形成的临界厚度为0.57 ML,计算的结果与已报道的实验一致。从In原子在表面的迁移和扩散,以及衬底中Ga和液滴中的In之间的原子互混原理解释了In液滴形成和形貌演化的机理。实验中得到的In液滴临界厚度以及In液滴在GaAs(001)上成核机理,可以为制备InAs量子点提供实验指导。 相似文献
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64.
Decarboxylative CC cross-couplings of 2-aminopyrimidine-5-carboxylic acids under a Pd/Ag-based catalytic system opens a new platform for the introduction of diverse C5 substituents. The reaction methods proceeded efficiently with a wide range of the acids and the coupling partners of aryl iodides, alkenes, bromoalkynes, and azoles. Considering ready availability of 2-aminopyrimidine-5-carboxylic acid from the oxidative dehydrosulfurative CN cross-coupling of the 3,4-dihydropyrimidin-1H-2-thiones, this reaction method unambiguously pave a shortcut to densely substituted 2-aminopyrimidine derivatives with unprecedented diversity. 相似文献
65.
Yinghao Liu Xingxing Wang Dr. Junyan Li Dr. Qiang Zhang Zijian Niu Dr. Sen Wang Yanjing Gao Mingkun Gao Dr. Risheng Bai Dr. Yida Zhou Dr. Weibin Fan Prof. Osamu Terasaki Prof. Jun Xu Prof. Jihong Yu 《Angewandte Chemie (International ed. in English)》2023,62(49):e202312131
Creation of intrapenetrated mesopores with open highway from external surface into the interior of zeolite crystals are highly desirable that can significantly improve the molecular transport and active sites accessibility of microporous zeolites to afford enhanced catalytic properties. Here, different from traditional zeolite-seeded methods that generally produced isolated mesopores in zeolites, nanosized amorphous protozeolites with embryo structure of zeolites were used as seeds for the construction of single-crystalline hierarchical ZSM-5 zeolites with intrapenetrated mesopores (mesopore volume of 0.51 cm3 g−1) and highly complete framework. In this strategy, in contrast to the conventional synthesis, only a small amount of organic structure directing agents and a low crystallization temperature were adopted to promise the protozeolites as the dominant growth directing sites to induce crystallization. The protozeolite nanoseeds provided abundant nucleation sites for surrounding precursors to be crystallized, followed by oriented coalescence of crystallites resulting in the formation of intrapenetrated mesopores. The as-prepared hierarchical ZSM-5 zeolites exhibited ultra-long lifetime of 443.9 hours and a high propylene selectivity of 47.92 % at a WHSV of 2 h−1 in the methanol-to-propylene reaction. This work provides a facile protozeolite-seeded strategy for the synthesis of intrapenetrated hierarchical zeolites that are highly effective for catalytic applications. 相似文献
66.
Zhenguo Lv Guangzhe Yao Minglei Ge Yu Bai Mengxuan Wu Huizi Ouyang Jihong Feng Jun He 《Journal of separation science》2023,46(22):2300475
Physochlainae Radix (PR) is an essential herbal medicine that has been generally applied for treating cough and asthma. In this study, a comprehensive strategy for quality evaluation of PR from different origins was established by integrating qualitative identification, quantitative analysis, and chemometric methods. A total of 58 chemical components were identified by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS/MS), and a sensitive and rapid UHPLC-QqQ-MS/MS method was established for the simultaneous determination of 12 compounds. In addition, multivariate statistical analysis was applied for discriminant analysis to compare the differences among 30 batches of PR samples. The results showed that the 30 batches of PR collected from four provinces could be clustered into three categories, in which scoparone, protocatechuic acid, tropic acid, and scopolin were important components to distinguish the primary and non-primary producing areas, as well as superior and inferior products of PR. Chemometric results were consistent and validated each other, and systematically explained the intrinsic quality characteristics of PR. This study first demonstrated that LC-MS combined with multivariate statistical analysis, provided a comprehensive and effective means for quality evaluation of PR. 相似文献
67.
Yafei Guo Yushun Zhang Jiuling Li Fen Zhao Yang Liu Min Su Yubo Jiang Yuqi Liu Jihong Zhang Bo Yang Rui Yang 《中国化学》2016,34(4):425-431
An inclusion complex of podophyllotoxin (PPT) with γ‐cyclodextrin (γ‐CD) was prepared. The behavior, characterization, and water solubility of the inclusion complex were carefully investigated via fluorescence spectroscopy, thermogravimetry, differential scanning calorimetry, X‐ray diffraction analysis, and 1H and 2D nuclear magnetic resonance spectroscopy. Furthermore, antitumor activity to human cancer lines and toxicity in mice were studied. Results showed that the inclusion complex formed in a 1:1 ratio with a considerable apparent stability constant Ks (4245.5 L·mol?1). Water solubility was considerably improved. In addition, the anticancer activity of the inclusion complex was better than that of cis‐platinum (DDP, positive control). Most importantly, the toxicity of podophyllotoxin inclusion complex reduced and became more safety to mice which will be great valuable to research its applications as a kind of antitumor drug to human in the further. 相似文献
68.
Trace determination of organophosphate esters in environmental water samples with an ionogel‐based nanoconfined ionic liquid fiber coating for solid‐phase microextraction with gas chromatography and flame photometric detection 下载免费PDF全文
Long Pang Rong Pang Liming Ge Liqing Zheng Jihong Zhao Hongzhong Zhang 《Journal of separation science》2016,39(22):4415-4421
Organophosphate esters, widely used as flame retardants and plasticizers, are regarded as a class of emerging pollutants. In this work, a novel approach was developed for the fabrication of a solid‐phase microextraction fiber by using hybrid silica‐based materials with immobilized ionic liquids with sol–gel technology, and the prepared solid‐phase microextraction fiber was then coupled with gas chromatography and flame photometric detection for the analysis of six organophosphate esters. The high loading of 1‐hexadecyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide was confined within the hybrid network. The developed solid‐phase microextraction fiber possesses a coating thickness of ~35 μm with good thermal stability and long lifetime. The parameters affecting the extraction efficiency such as extraction time, temperature, pH, and ionic strength of the sample solution were optimized. Under the optimized conditions, the limits of detection were in the range of 0.04?0.95 μg L?1, and the precision of the method assessed with repeatability and reproducibility of (RSD%) ?13 and ?29%, respectively. The proposed method was successfully applied to determine the six organophosphate esters in three real water samples, with recoveries in the range of 64.8?125.4% at two different spiking concentration levels. As a result, the proposed method demonstrated its potential for application in trace determination of organophosphate esters in actual water samples. 相似文献
69.
Shao Li Di Zhang Min Wang Saige Ma Jihong Liu Yufen Zhao Yong Ye 《Journal of fluorescence》2016,26(3):769-774
A novel FRET-based probe LS3 was designed and synthesized. As expected, it exhibited high selectivity and sensitivity for detecting Cu2+ over other commonly coexistent metal ions. The detection limit was measured to be 0.0423 μM for Cu2+, which can meet the selective requirements for practical application. In addition, the newly synthesized compound 3a/b have potential value of further synthesizing more analogous FRET-based probes. 相似文献
70.
Three new chloride-rich zincophosphates including two zero-dimensional (0D) clusters [dl-Co(en)3]2[Zn4(H2PO4)2(HPO4)2Cl8] (denoted ZnPO-CJ33) and [d-Co(en)3]2[Zn4(H2PO4)2(HPO4)2Cl8] (denoted ZnPO-CJ34), and one-dimensional (1D) zincophosphate chain [dl-Co(en)3][Zn2(H2PO4)(HPO4)2Cl2] (denoted ZnPO-CJ35) have been solvothermally prepared. ZnPO-CJ33 and ZnPO-CJ34 possess the same cluster structure as the macroanionic [Zn4H6P4O16Cl8]6- unit formed by alternation of ZnOCl3/ZnO3Cl and HPO4/H2PO4 tetrahedra but differ in the countercations. The racemic [dl-Co(en)3]3+ cations are located among the clusters of ZnPO-CJ33, whereas chiral [d-Co(en)3]3+ cations are located among the clusters of ZnPO-CJ34. ZnPO-CJ34 templated by the optically pure chiral [d-Co(en)3]3+ cations is the first chiral monomeric zincophosphate. ZnPO-CJ35 templated by the racemic [dl-Co(en)3]3+ cations possesses a 1D infinite chain structure formed by the alternation of ZnO3Cl and HPO4/H2PO4 tetrahedra. The 1D chain structure of ZnPO-CJ35 can also be viewed as generated from the condensation of 0D clusters of ZnPO-CJ33, with the terminal Cl ions replaced by HPO4 groups. Experimentally, the structural transformation from ZnPO-CJ33 to ZnPO-CJ35 has been investigated. 相似文献