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631.
632.
高速大容量光纤光栅解调仪的研究 总被引:4,自引:0,他引:4
采用半导体光放大器和可调谐法布里-珀罗滤波器,以环路结构组成高速扫描激光器,结合光耦合器、光环路器和光电二极管等,形成4通道大容量高速光纤光栅解调仪。系统采用2kHz的类三角波调制信号,驱动法布里-珀罗滤波器在50nm的光谱范围内进行快速扫描。通过引入光纤梳状滤波器和单峰滤波器组成的参考通路,消除法布里-珀罗滤波器的非线性效应和扫描波长漂移问题,使得解调仪具有很好的稳定性和线性度。高速光纤光栅解调仪的稳定性为2pm,分辨率为1pm,线性度为0.99957,测量精度为5pm,解调频率为2kHz。 相似文献
633.
634.
利用分子梳技术和动态光散射研究了三氯六氨络合钴和DNA分子之间的相互作用. 从荧光显微镜中可直接观察到经YOYO-1染色后?-DNA分子的平均伸直长度比未染色的DNA分子增长约30%. 这是由于荧光染料YOYO-1分子插入双链DNA的碱基对中从而使DNA分子的长度增加. 另外研究了染色后的DNA-[Co(NH3)6]3+混合物的伸直长度随三氯六氨络合钴浓度的变化关系,实验结果表明当钴离子浓度从0增加到3 μmol/L,其混合物的伸直长度由原来的20.9 μm减小到5.9 μm. 利用动态光散射技术证实了这个结果,发现在相同的实验条件下加入钴离子前后DNA-Co(NH3)6]3+混合物的流体力学半径从203.8 nm减小到39.26 nm. 相似文献
635.
Stefan van Rootselaar Evert Peterse Dr. Daniel Blanco-Ania Prof. Dr. Floris P. J. T. Rutjes 《European journal of organic chemistry》2023,26(22):e202300053
Piperidine alkaloids are members of the alkaloid family that is characterized by the presence of a six-membered nitrogen-containing heterocycle. Piperidine alkaloids are found mainly in plants and often exhibit interesting biological and pharmacological activities. Despite the accumulation of these natural products in plants, relatively low quantities of alkaloids are produced in absolute terms and thus synthesis of alkaloids and derivatives thereof remains relevant to identify targets for drug discovery. Throughout the years, researchers have come up with a myriad of methods to synthesize piperidine derivatives. This review describes methods that employ stereoselective Mannich reactions to create the core of piperidine alkaloids. Asymmetric induction in the Mannich reaction has been achieved by a range of methods that have been divided into three conceptual approaches: (1) chiral pool-based (internal asymmetric induction), (2) chiral auxiliary-based (relayed asymmetric induction) and (3) asymmetric catalysis-based (external asymmetric induction). Of each approach, we describe the reaction mechanism and rationalize the stereochemical outcome of the Mannich products. 相似文献
636.
Abhijeet Singh Jagmeet Singh Prof. Dr. Mahendra Nath 《European journal of organic chemistry》2023,26(4):e202201319
A facile synthetic strategy for the synthesis of a new series of β,β’-fused 2-arylpyrimido[4,5-b]porphyrins has been developed by using condensation cyclization reaction with ammonia. 2-Aroylamino-3-formylporphyrins were synthesized from 2-aroylaminoporphyrins under Vilsmeier–Haack reaction conditions, which were then efficiently converted to the corresponding 2-arylpyrimido[4,5-b]-5,10,15,20-tetrakis(4-chlorophenyl)-porphyrins via a condensation cyclization reaction. The nickel(II), copper(II), free-base and zinc(II) analogues of 2-arylpyrimido[4,5-b]porphyrins were successfully synthesized in 65–72 % yields and structurally characterized on the basis of spectral data analysis. On photophysical evaluation, 2-arylpyrimido[4,5-b]porphyrins demonstrated a 12–19 nm bathochromic shift in their electronic absorption spectra and up to 10 nm red shift in their emission spectra as compared to the simple meso-(tetrakis(4-chlorophenyl))porphyrins due to the extended π-conjugation. 相似文献
637.
Hongyuan Fu Ming Zhang Dr. Youdi Zhang Qingyuan Wang Zheng'ao Xu Dr. Qiuju Zhou Zhengkai Li Yang Bai Prof. Yongfang Li Prof. Zhi-Guo Zhang 《Angewandte Chemie (International ed. in English)》2023,62(35):e202306303
The operational stability of polymer solar cells is a critical concern with respect to the thermodynamic relaxation of acceptor-donor-acceptor (A-D-A) or A-DA'D-A structured small-molecule acceptors (SMAs) within their blends with polymer donors. Giant molecule acceptors (GMAs) bearing SMAs as subunits offer a solution to this issue, while their classical synthesis via the Stille coupling suffers from low reaction efficiency and difficulty in obtaining mono-brominated SMA, rendering the approach impractical for their large-scale and low-cost preparation. In this study, we present a simple and cost-effective solution to this challenge through Lewis acid-catalyzed Knoevenagel condensation with boron trifluoride etherate (BF3 ⋅ OEt2) as catalyst. We demonstrated that the coupling of the monoaldehyde-terminated A-D-CHO unit and the methylene-based A-link-A (or its silyl enol ether counterpart) substrates can be quantitatively achieved within 30 minutes in the presence of acetic anhydride, affording a variety of GMAs connected via the flexible and conjugated linkers. The photophysical properties was fully studied, yielding a high device efficiency of over 18 %. Our findings offer a promising alternative for the modular synthesis of GMAs with high yields, easier work up, and the widespread application of such methodology will undoubtedly accelerate the progress of stable polymer solar cells. 相似文献