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991.
用气相输运平衡技术成功地制备出了近化学计量组分的Er∶LiNbO3晶体,系统 地研究了该 晶体的吸收边移动、可见—红外透射谱、荧光光谱的物理特性.与同成分Er∶LiNbO3 sub>晶体 相比, 近化学计量组分Er∶LiNbO3晶体的吸收边出现了“蓝移”;OH- sup>吸收带明显减弱 ;在可见—近红外波段呈现出更高的透过率;同时Er3+离子的发光强度也明显 提高. 这些结果表明近化学组分的Er∶LiNbO关键词:
近化学组分掺铒铌酸锂晶体
- 吸收带')" href="#">OH-吸收带
透射谱
荧光光谱 相似文献
992.
993.
妊娠与五种元素的关系 总被引:7,自引:0,他引:7
测定了2692例孕妇各孕周分娩期血清,884例新生儿脐血清中的铜,锌,铁,钙,镁,并比较了正常与异常妊娠孕妇血清中的五种元素,为防治妊高症,胎膜早破提供理论依据,并探讨了脐血清与母血清微量元素的相关性。 相似文献
994.
995.
Chang-An Geng Xue-Mei Zhang Zhi-Yong Jiang Jun Zhou Ji-Jun Chen 《Tetrahedron letters》2010,51(18):2483-1825
Swerilactones E (1), F (2), and G (3), three unusual lactones with a phenyl group, were isolated from the traditional Chinese herb of Swertia mileensis. Their structures were determined based on extensive spectroscopic analysis and X-ray single crystal crystallography. Our anti-HBV assay on the Hep G 2.2.15 cell line in vitro showed that compounds 1 and 2 exhibited significant inhibitory activities against the secretion of HBsAg with IC50 of 0.22 and 0.70 mM and HBeAg with IC50 of 0.52 and >6.78 mM, respectively. 相似文献
996.
Xuejuan Cao Huai Liu Junnan Wei Xing Tang Xianhai Zeng Yong Sun Tingzhou Lei Geng Zhao Lu Lin 《催化学报》2019,40(2):192-203
The production of γ-valerolactone (GVL) from lignocellulosic biomass has become a focus of research owing to its potential applications in fuels and chemicals. In this study, (n)CuOx-CaCO3 (where n is the molar ratio of Cu to Ca) compounds were prepared for the first time and shown to function as efficient bifunctional catalysts for the conversion of biomass-derived methyl levulinate (ML) into GVL, using methanol as the in-situ hydrogen source. Among the catalysts with varied Cu/Ca molar ratios, (3/2)CuOx-CaCO3 provided the highest GVL yield of 95.6% from ML. The incorporation of CaCO3 with CuO resulted in the formation of Cu+ species in a CuOx-CaCO3 catalyst, which greatly facilitated the hydrogenation of ML. Notably, CuOx-CaCO3 also displayed excellent catalytic performance in the methanolysis products of cellulose, even in the presence of humins. Therefore, a facile two-step strategy for the production of GVL from cellulose could be developed over this robust and inexpensive catalyst, through the integration of cellulose methanolysis catalyzed by sulfuric acid, methanol reforming, and ML hydrogenation in methanol medium. 相似文献
997.
Zhang X Qu Y Bu L Tian H Zhang J Wang L Geng Y Wang F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(21):6238-6248
A series of monodisperse oligo(9,9-di-n-octylfluorene-co-bithiophene)s (OFbTs) with molecular lengths of up to 19.5 nm and molecular weights up to 7025 g mol(-1) has been synthesized by a divergent/convergent approach involving Stille coupling reactions. Stille coupling is quite efficient in preparing this class of oligomers, and even the molecule with nine fluorene units and eight bithiophene units (F9Th16) can be synthesized in a yield as high as 70 %. Because of easy functionalization of the thiophene ring at its alpha position, no additional protecting group allowing activation for further reaction is necessary. However, the synthetic routes must be optimized to eliminate contamination of the targeting compounds with the homocoupling product of the organotin reagents. Synthesis of the longest oligomer F13Th24 in a relative large quantity is limited by its low yield due to the pronounced ligand-exchange side reactions of the starting materials and reaction intermediates. All oligomers longer than F4Th6 are nematic mesomorphs and exhibit enhanced glass transition temperature and clearing point with increasing molecular length, as revealed by differential scanning calorimetry and polarizing optical microscopy. Absorption and photoluminescence (PL) measurements reveal that OFbTs are well-conjugated systems with an effective conjugation length longer than the length of F13Th24. 相似文献
998.
999.
1000.
Yiqi Luo Zhengdong Liu Geng Wu Guanzhong Wang Tingting Chao Hai Li Juqing Liu Xun Hong 《中国化学快报》2019,30(5):1093-1096
The activity and stability of Cu nanostructures strongly depend on their sizes, morphology and structures.Here we report the preparation of two-dimensional(2 D) Cu@Cu-BTC core-shell nanosheets(NSs). The thickness of the Cu NSs could be tuned to sub-10 nm through a mild etching process, in which the Cu-BTC in situ grow along with the oxidation on the surface of the Cu NSs. This unique strategy can also be extended to synthesize one-dimensional(1 D) Cu@Cu-BTC nanowires(NWs). Furthermore, the obtained Cu@Cu-BTC NSs could be applied as an effective material to the memory device with the write-onceread-many times(WORM) behavior and the high I_(ON)/I (OFF) ratio(2.7 × 10~3). 相似文献