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61.
62.
The a-SiNx:H with a large bandgap of 3.8 eV was utilized to decorate ZnO nanowires. The UV emission from the a-SiNx:H-decorated ZnO nanowires are greatly enhanced compared with the undecorated ZnO nanowire. The deep-level defect emission has been completely suppressed even though the sample was annealed at temperatures up to 400 °C. The incorporation of H and N is suggested to passivate the defect states at the nanowire surface and thus result in the flat-band effect near ZnO surface as well as reduction of the nonradiative recombination probability. 相似文献
63.
为了在光栅制作中对光栅掩模占宽比及槽深加以控制,结合光刻胶在显影过程中的非线性特性,建立了光栅掩模槽形演化的数学模型,由此分析和模拟曝光量、条纹对比度对光栅槽形的影响。结果表明:在显影条件确定时,光栅掩模占宽比随光刻胶曝光量的增大而减小,条纹对比度减小,则不仅使光栅占宽比减小,同时也是使光栅槽深减小的主要原因,这样做的前提是预先通过实验和计算确定出一个曝光量上限Ec。该方法能够反映光栅掩模形状的演化规律,为全息光栅参数预测和工艺控制提供依据。 相似文献
64.
Xiaojun Zeng Wenhao Yan Samson B. Zacate Aijie Cai Yufei Wang Dongqi Yang Kundi Yang Wei Liu 《Angewandte Chemie (International ed. in English)》2020,59(38):16398-16403
The difluoromethyl group (CF2H) is considered to be a lipophilic and metabolically stable bioisostere of an amino (NH2) group. Therefore, methods that can rapidly convert an NH2 group into a CF2H group would be of great value to medicinal chemistry. We report herein an efficient Cu‐catalyzed approach for the conversion of alkyl pyridinium salts, which can be readily synthesized from the corresponding alkyl amines, to their alkyl difluoromethane analogues. This method tolerates a broad range of functional groups and can be applied to the late‐stage modification of complex amino‐containing pharmaceuticals. 相似文献
65.
A facile and efficient one-pot synthesis of 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones was developed. The reaction of ethyl 3-(2-hydroxyphenyl)-3-oxopropanoates and 2,5-dimethoxy-2,5-dihydrofuran were performed in presence of K10 Montmorillonite Clay heterogeneous catalyst under the solvent-free condition at 80?°C for 1?h, and followed by further converted to 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones via refluxing in the alkaline EtOH solution for 0.5?h. The demonstrate method not only avoided the usage of any expensive transition-metals, but also eliminated the tedious intermediate purification. Moreover, due to the wide functional group tolerance, it could be applied to various substrates and gave product in good to excellent yields. 相似文献
66.
67.
在优良抗风湿药物萘普生的重要中间体6-甲氧基-2-乙酰素的合成中存在溶剂硝基苯的毒性及所带来的污染。而改用二氯乙烷作溶剂,只加少量硝基苯即可。为配合合成工艺的优化,用气相色谱(GC)、气相色谱-质谱(GC/MS)对反应产物、副产物及多个杂质进行了定性分析研究,并在5%OV-101ChromosorbWAWDMCS柱上完成了产物的内标定量分析。从而减少了副反应和高沸点杂质的生成,最终生产出了95%以上含量的6-甲氧基-2-乙酰萘产品,收率达到60%。 相似文献
68.
(R)-α-alkyl-2-furfurylamines (7), ranging from 5–67%d.e., are obtained by asymmetric alkylation of d-camphor ketimine (3). Using 1,3-diiodopropane and dibromoxylene as alkylating reagents, diimine derivatives (6f) and (6g) are formed. However, 1,2-dibromoethane gives coupling product (6h). 相似文献
69.
We report an experimental investigation on the Doppler-free saturated absorption spectroscopy of buffer-gas-cooled Barium monofluoride (BaF) molecules in a 4 K cryogenic cell. The obtained spectra with a resolution of 19 MHz, much smaller than previously observed in absorption spectroscopy, clearly resolve the hyperfine transitions. Moreover, we use these high-resolution spectra to fit the hyperfine splittings of excited A(v = 0) state and find the hyperfine splitting of the laser-cooling-relevant A2Π1/2(v = 0, J = 1/2,+) state is about 18 MHz, much higher than the previous theoretically predicted value. This provides important missing information for laser cooling of BaF molecules. 相似文献
70.
Shikun Jia Dong Xing Dan Zhang Wenhao Hu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(48):13314-13317
Asymmetric functionalization of aromatic C H bonds of N,N‐disubstituted anilines with diazo compounds and imines is reported for the efficient construction of α,α‐diaryl benzylic quaternary stereocenters in good yields with high diastereoselectivities and excellent enantioselectivities. This RhII/chiral phosphoric acid cocatalyzed transformation is proposed to proceed through a metal‐carbene‐induced zwitterionic intermediate which undergoes electrophilic trapping. To the best of our knowledge, this is the first asymmetric example of metal carbene‐induced intermolecular functionalization of aryl C H bonds. 相似文献