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991.
Fushan Wen Jiesheng Chen Jin Hyeok Kim Jinghua Niu 《Journal of solid state chemistry》2004,177(9):3114-3118
Sb3+-doped Sr3(PO4)2 crystals has been synthesized using phosphoric acid, strontium hydroxide and antimony powder as the raw materials through a hydrothermal reaction method. The crystallinity and the microstructure were investigated using X-ray diffraction and scanning electron microscopy. The photoluminescent property was investigated using luminescent spectrometer. Phase pure Sr3(PO4)2 crystal was obtained and it has a shape of hexagonal rod. It showed the emission and excitation peaks at 396, 250, and 215 nm, respectively, indicating that the emission is attributed to 3P1-1S0 transition and the excitation is attributed to 1S0-3P1 and 1S0-1P1 transition. It was also observed that the intensity of photoluminescence is thermally stable up to 673 K. 相似文献
992.
Yue-qi Mo Jian Huang Jia-xin Jiang Xian-yu Deng Yu-hua Niu Yong Cao Institute of Optoelectronic Materials & Devices Colleg of Material Science Engineering South China University of Technology Guangzhou China 《高分子科学》2002,(5):461-465
It was found that traces of water in the reaction medium would result in a great increase of gel and a decrease ofmolecular weight of the poly(2-methoxy, 5-(2'-ethylhexyloxy)-1, 4-phenylene vinylene) during the polymerization, whichultimately led to inferior film qualities and device properties. The device (ITO/PEDOT/MEH-PPV/Ba/Al) with MEH-PPVprepared under dry conditions has an external quantum efficiency of above 2.0%. 相似文献
993.
近年来,Ni-Al基金属间化合物的研究特别活跃,是一类潜在高温结构材料。作者曾研究了铁基合金熔盐腐蚀的阻抗特征,提出了阻抗模型及图谱解析方法。本文研究Ni-Al系金属间化合物熔盐热腐蚀的阻抗特征。 材料为Ni_3Al和NiAl(Fe)金属间化合物。X-衍射分析证明是此结构。Ni_3Al成分为(at%):Al 21.2,B 0.1,Zr 0.3,Ni余量;NiAl(Fe)成分为(at%):Al 19.68,Fe 15.03,Mo 2.0,Hf 0.27, 相似文献
994.
用pH电位法测定了生理条件(37℃,I=0.15mol/L)和25℃,I=0.10mol/L时甘氨酰L-亮氨酸的质子化常数及其稀土配合物稳定常数。结果表明稀土可与该配体形成1:1配合物,并且配合物稳定性呈现明显“四分组效应”。讨论了钇的位置以及肽键对配合物稳定性的影响。 相似文献
995.
Xuemei Zhou 《物理化学学报》1985,37(6):2008064-0
Titania (TiO2) has been among the most widely investigated and used metal oxides over the past years, as it has various functional applications. Extensive research into TiO2 and industrial interest in this material have been triggered by its high abundance, excellent corrosion resistance, and low cost. To improve the activity of TiO2 in heterogeneous catalytic reactions, noble metals are used to accelerate the reactions. However, in the case of nanoparticles supported on TiO2, the active sites are usually limited to the peripheral sites of the noble metal particles or at the interface between the particle and the support. Thus, highly dispersed single metal atoms are desired for the effective utilization of precious noble metals. The study of oxide-supported isolated atoms, the so-called single-atom catalysts (SACs), was pioneered by Zhang's group. The high dispersion of precious noble metals results helps reduce the cost associated with catalyst preparation. Because of the presence of active centers as single atoms, the deactivation of metal atoms during the reaction, e.g., by coking for large agglomerates, is retarded. The unique coordination environment of the noble metal center provides special sites for the reaction, consequently increasing the selectivity of the reaction, including the enantioselectivity and stereoselectivity. Hence, supported SACs can bridge homogenous and heterogeneous reactions in solution as they provide selective reaction sites and are recyclable. Moreover, owing to the high site homogeneity of the isolated metal atoms, SACs are ideal models for establishing the structure-activity relationships. The present review provides an overview of recent works on the synthesis, characterization, and photocatalytic applications of SACs (Pt1, Pd1, Ir1, Rh1, Cu1, Ru1) supported on TiO2. The preparation of single atoms on TiO2 includes the creation of surface defective sites, surface modification, stabilization by high-temperature shockwave treatment, and metal-ligand self-assembly. Conventional characterization methods are categorized as microscopic imaging and spectroscopic methods, such as aberration-corrected scanning transmission electron microscopy (STEM), scanning tunneling microscopy (STM), extended X-ray absorption fine structure analysis (EXAFS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). We attempted to address the critical factors that lead to the stabilization of single-metal atoms on TiO2, and elucidate the mechanism underlying the photocatalytic hydrogen evolution and CO2 reduction. Although many fascinating applications of TiO2-supported SACs in photocatalysis could only be addressed superficially and in a referencing manner, we hope to provide interested readers with guidelines based on the wide literature, and more specifically, to provide a comprehensive overview of TiO2-supported SACs. 相似文献
996.
The 5'-amino-5'-phosphono derivatives of cytidine, cytosine arabinoside (ara-C), and uridine have been prepared via the corresponding nucleoside aldehydes. Phosphite addition to imines derived from the nucleoside aldehydes and p-methoxybenzylamine was efficient, and use of this amine allowed cleavage of the products to the parent amino phosphonic acids. The phosphite additions proved to be diastereoselective, with the cytidine and uridine derivatives favoring the 5'S stereochemistry and the ara-C derivative favoring the 5'R isomer. The stereochemistry of one cytidine derivative was established by single-crystal diffraction analysis, and detailed comparisons of the (13)C NMR data allowed assignments of the other amino phosphonates. 相似文献
997.
A microcalorimetric technique was used to investigate the influence of Zn^2 on the growth metabolism of Bacillus thuringiensis .LKB-2277 Bioactivity Monitor was employed to obtain the power-time curves,from which the maximum peak-heat output power(Pmax) in the log phase,the growth rate constants(k), the inhibitory ratios(I) ,the generational time(tG) and the total heat effect (Qtotal) in 23 h for the growth metabolism of Bacillus thuringiensis at 28℃ can be evaluated,The results indicate that the concentration of Zn^2 affects its growth obviously,Low concentration (0-50μg/mL) of Zn^2 promotes the growth of Bacillus thuringiensis while high concentration (50-500μg/mL) of Zn^2 inhibits its growth .When the concentration reached up to 600μg/mL,it can not grow at all. 相似文献
998.
随着我国乳制品人均消费量的逐年增长,乳制品进口贸易量也与日俱增,因此对进口乳制品的质量控制具有重要意义。调查发现,进口超高温瞬时灭菌(UHT)奶(俗称常温奶)的糠氨酸含量显著高于国产UHT奶,存在加热过度、添加复原乳的问题。虽然目前无法对进口乳制品企业进行源头和加工工艺的监管,但可在乳制品热处理工艺控制领域中采用监测乳品中某种反映工艺条件的标志物来控制乳品的质量,其中糠氨酸就是乳制品加工过程中反映工艺条件的标志物。该文简述了目前国内外对乳制品加工过程中9种标志物的研究概况,以期能为完善我国乳制品加工过程中的监管制度提供理论依据,保障消费者权益。 相似文献
999.
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