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Yuzhu Liu Qiusha Zheng Yan Zhang Rongrong Zhang Yanmei Wang Dr. Bing Zhang Prof. 《Chemphyschem》2009,10(5):830-834
Velocity ion imaging (see figure) is used to analyze the photodissociation mechanism of 1‐C4H9I (left image) and 2‐C4H9I (right image) at 266 nm. For 2‐C4H9I, a new channel for formation of I and I* atoms is observed. It is attributed to the repulsive mode along the C? I stretch, coupled with some bending motions.
43.
TmF3 doped TeO2–ZnO–La2O3 (TZL) glasses and fibers have been prepared by the conventional melt-quenching and suction casting methods, respectively. 2 μm emission properties and energy transfer mechanisms of the TZL glasses and fibers have been analyzed and discussed. The oscillator strength, Judd–Ofelt parameters, radiative transition probability and radiative lifetime of Tm3+ have been calculated based on the absorption spectra and Judd–Ofelt theory. The maximum emission cross-section of Tm3+ is 6.9 × 10?21 cm2 near 2 μm. Emission spectra have been obtained from both TZL fibers and bulk glass when excited with a 794 nm pump. The results of 2 μm emission spectra indicate that the line width of Tm3+ measured in fibers is narrower than that in the bulk glass sample. The peak position of the emission spectra shifts to longer wavelength with increment of the fiber length. 相似文献
44.
本文研究了R3中一类四次可逆系统及其扰动系统的周期轨与极限环问题,利用Poincáre紧化理论讨论了相关平面系统的定性性质,证明了所考虑的系统存在无穷多对称周期轨的结论.然后借助一系列技巧性变换,并利用平均方法证明了R3中这类四次可逆系统的扰动系统在其某周期轨邻域至少存在两个具有不同稳定性的极限环的结论. 相似文献
45.
以L-苯丙氨酸(L-Phe)、L-色氨酸(L-Trp)和L-亮氨酸(L-Leu)3种常见的氨基酸为手性源,经过酯化、缩合等步骤制备3种手性功能单体AAc-L-Phe(AAc:丙烯酸)、AAc-L-Trp和AAc-L-Leu,其结构经过IR、1H NMR确证。 并将手性单体AAc-L-Phe与温敏材料N-异丙基丙烯酰胺(NIPAam)共聚,制备了手性共聚物P(NIPAam-co-AAc-L-Phe),结构经IR确证,示差扫描量热分析测试证明其具有温敏性。 这些手性功能单体有可能用于制备环境响应性手性高分子聚合物。 相似文献
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Dandan?Lian Bing?Shi Rongrong?Dai Xiaohua?JiaEmail author Xiangyang?WuEmail author 《Journal of nanoparticle research》2017,19(12):401
A kind of novel ZnSnO3/SnO2 hollow urchin nanostructure was synthesized by a facile, eco-friendly two-step liquid-phase process. The structure, morphology, and composition of samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption techniques. The results revealed that many tiny needle-like SnO2 nanowires with the average diameter of 5 nm uniformly grew on the surface of the ZnSnO3 hollow microspheres and the ZnSnO3/SnO2 hollow urchin nanostructures with different SnO2 content also were successfully prepared. In order to comprehend the evolution process of the ZnSnO3/SnO2 hollow urchin nanostructures, the possible growth mechanism of samples was illustrated via several experiments in different reaction conditions. Moreover, the gas-sensing performance of as-prepared samples was investigated. The results showed that ZnSnO3/SnO2 hollow urchin nanostructures with high response to various concentration levels of acetone enhanced selectivity, satisfying repeatability, and good long-term stability for acetone detection. Specially, the 10 wt% ZnSnO3/SnO2 hollow urchin nanostructure exhibited the best gas sensitivity (17.03 for 50 ppm acetone) may be a reliable biomarker for the diabetes patients, which could be ascribed to its large specific surface area, complete pore permeability, and increase of chemisorbed oxygen due to the doping of SnO2. 相似文献
48.
聚集诱导发光(AIE)材料吸引了许多光电器件和生物荧光技术领域的科学家的关注.对聚集诱导发光化合物构效关系的深入理解对于设计新材料至关重要.在本工作中,基于经典的AIE基元四苯基乙烯,设计并合成了一系列具有AIE性质,含不同电子给体/受体取代基的炔酮衍生物.对这一系列化合物的光物理性质进行了系统研究并分别探讨了取代基团对发光波长、发光效率和AIE性质的影响.它们的聚集态最大发射波长位于511~565 nm,在四氢呋喃/水混合溶液中的荧光量子产率可达31%.在末端苯环上的电子给体/受体取代基团会降低聚集态的发光效率,而引入硝基取代基则会在发射波长红移的同时,显著猝灭荧光.最为重要的是,这些化合物结构中的炔酮基元可以在一系列金属离子中选择性地与Pd2+配位,猝灭纳米聚集体的发光,并有望作为一个有效的Pd2+荧光传感器. 相似文献
49.
Mingzhi Zhang Rongrong Zhang Jiaqun Wang Xiang Yu Yaling Zhang Qingqing Wang Weihua Zhang 《中国化学》2016,34(12):1344-1352
Osthole is a natural coumarin derivative and has a broad scope of biological activities. Two series of novel fused osthole analogues were designed, and synthesized through a highly efficient microwave‐promoted synthetic protocol via the reaction of 4‐hydroxycoumarins and β‐ketoesters. The reaction conditions including solvent, catalyst, microwave power and irradiation time were also optimized. The pyrano[3,2‐c]chromene‐2,5‐diones and furo[3,2‐c]coumarins were obtained through two distinct intramolecular cyclization processes, and the proposed mechanism was also discussed. 相似文献
50.
Based on the ray acoustics approach, the trapping effects on a microsphere by an ideally spherically-focused ultrasound are discussed. The acoustical radiation force from a focused ultrasound beam on a spherical particle in a three-dimensional sound field is calculated considering the effect of the attenuation of the ultrasound beam both inside the particle and in the surrounding medium. The results show that as long as the particle is in the range of the ultrasound beam and as long as the appropriate parameters of the transducer are selected, the particle will be captured in the vicinity of the focus of the ultrasound beam. Also, the particle radius and different parameters of the transducer are analyzed for their affect on the radiation force. 相似文献