Er3+掺杂氟化物1550nm上转换发光材料的水热合成及发光性能

采用水热法合成了Er3+掺杂的1 550 nm氟化物上转换发光超细粉.与传统高温固相法样品相比,水热法合成的样品颗粒细小,与光电探测及成像器件耦合匹配应用时,更有利于提高器件的空间分辨率.探讨了Er3+掺杂四元氟化物1 550 nm上转换发光的物理机制,研究了Er3+掺杂浓度、反应温度及反应时间对产物上转换发光性能的影...     

氨基官能化聚乳酸电纺纤维的制备、 表征和应用

通过聚乳酸(PLA)和氨基丙基三乙氧基硅烷(KH550)混合进行静电纺丝制备氨基官能化聚乳酸纳米纤维. 采用滴定法测定了纤维表面氨基含量, 证明当KH550的添加量为3%~13%(质量分数)时, 有19%~26%的氨基出现在纤维的表面. 利用场发射扫描电子显微镜、 差示扫描量热(DSC)仪、 接触角测试仪和电子拉伸机对纤维形貌、 PLA的玻璃化转变温度和熔点以及纤维膜的亲水性和力学性能进行了表征. 结果表明, KH550的加入可以在电纺纤维表面引入氨基, 同时使纤维直径变细, 使PLA的玻璃化转变温度上升, 熔点下降, 电纺纤维膜的亲水性略有增加, 力学性能有所下降. 通过吸附将金纳米粒子负载到氨基官能化聚乳酸电纺纤维膜上, 得到负载型催化剂, 对硼氢化钠还原对硝基苯酚的反应具有良好的催化活性和重复使用性.     

近红外染料Yb(P4)(CoP) 掺杂 PS/SiO2复合纳米荧光标记物的制备及其性能

利用苯乙烯与3-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)化学反应合成共聚前驱物, 再采用凝胶-溶胶法,与四乙氧基硅烷在一定的条件下共同水解与缩合,合成了近红外染料 合镱(Ⅲ)掺杂的聚苯乙烯/二氧化硅复合纳米粒子。这种制备染料掺杂复合纳米粒子的方法既克服了传统物理包埋方法染料容易泄漏的问题,又不受到化学键合方法对近红外染料分子性质的限制。用扫描电子显微镜表征该复合纳米粒子呈球形,大小均匀,直径约100 nm。所制得的纳米粒子荧光性质稳定,受外界环境的影响小,具潜在生物亲和性,是一种新型的近红外荧光标记物。     

单磁场驱动的Tb1-xDyxFe2-y/Pb(Zr,Ti)O3三层膜磁电效应

研究了Tb_1-xDy_xFe_2－y (TDF)与锆钛酸铅(PZT)三层膜样品的制备和在单一直流磁场驱动下的磁电(ME)效应. 在该系列三层膜样品中测量到了巨大的ME耦合效应. 所得实验结果与同种样品在两磁场驱动下的ME效应完全不同. 这可能预示了某些新的物理内容. 该技术可简化ME效应在某些实际应用中的复杂度. 关键词： 1-xDy_xFe_2－y')" href="#">Tb_1-xDy_xFe_2－y PZT 单磁场 ME效应     

Investigation the positive moments on the M－T curve of YBCO films measured by using zero-field cooling

The superconducting transition of a YBCO film was measured by a MPMS-5 superconducting quantum interference device magnetometer, using a zero-field cooling process. The experimental results have shown that there are positive magnetic moment and positive peak on the M－T curve. We have proven that these anomalous behaviours are due to measurement error, but not phase transition. We have proposed a simple formula to explain and to calculate quantitatively these anomalous behaviours. It was found that, provided dH>0.59H_p (dH is the inhomogeneous field of the remnant field, H_p is the fully penetrated field of the measured sample), the experimental results will be positive, not negative. If dH≥2H_p, the experimental results will be symmetrical to their real negative values. From the M－T curve, which has positive moment and positive peak below T_c (superconducting transition temperature), we found a new possible method to obtain H_p of the measured sample.     

Bound states of the Klein－Gordon and Dirac equations for potential V0tanh2(r/d)

The exact bound state wavefunctions and energy equations of Klein－Gordon and Dirac equations are given with equal scalar and vector potential s(r)=v(r)=V(r)/2=V_0tanh^2(r/d). The relation between the energy equation and that of relativistic harmonic is discussed.     

Thermodynamic properties of the solvent extraction of ion pairs of metal chelate cations with some anions

Thermodynamic quantities were determined for the extraction of ion pairs of tris(1,10-phenanthroline)iron(II) and tris(2,2'-bipyridine)iron(II) chelate cations with halide, pseudohalide and polythionate anions from aqueous phase into nitrobenzene. Ion pairs with larger anions have more negative enthalpy changes with higher extractability. No clear trend was observed for the entropy changes. Linear relationships were observed between the free energy changes and the reciprocal radii of monovalent counter anions.     

Circular dichroism of some cyclopropane ring containing 1,3-cyclo-5,10-seco-steroidal ketones

Circular dichroism of the rearranged keto steroids 3 and 4, containing a condensed three and nine-membered ring system, shows that the conformation of the nine-membered ring is the same in solution as in the crystal; reduction of the kto group does not change this situation. CD also indicates that epimerization at C(5) in the pair $\text{7}\text{8}$ and the pair $\text{11}\text{12}$ leaves the cyclononanone ring conformation unchanged.     

Synthesis,structure and reactions of seco-steroids containing a medium-sized ring—IX : Reactions of Δ1(10)-unsaturated 5-oxo-5,10-seco-steroids with hydroxylamine and n-methylhydroxylamine

When treated with hydroxylamine or N-methylhydroxylamine, in the presence of proton donor catalysts, trans-Δ¹⁽¹⁰⁾-unsaturated 5-oxo-5,10-seco-steroids, such as 3 (but not the corresponding diastereomeric cis-compounds), are converted stereospecifically and in good yield to isoxazolidine derivatives (e.g. 4 and 13), resulting from transannular 1,3-dipolar addition of the intermediately formed oximes and nitrones to the trans-double bond in the cyclodecene ring moiety of the seco-steroid system. Reactions are described and physical evidence is presented which establish the constitution and configuration of the isoxazolidine-containing cycloaddition products, and the mechanistic and steric course of this transannular ring closure process is discussed.     

A convenient synthesis of 1α- and 1β-hydroxycholesterol

An efficient procedure for the preparation of 1α-hydroxycholesterol 3-acetate 4 is described, which starts from cholesterol and involves as key steps transannular cyclization of the ten-membered ring ontaining (E)-3β-acetoxy-5,10-seco-1(10)-cholesten-5-one 1 to the oxetane derivative 1α,5-epoxy-5α-cholestan-3β-ol acetate 3, and opening of the four-membered ether ring in the latter compound. 1β-Hydroxycholesterol diacetate 9 was obtained by oxidation of 4 to the 1-oxo derivative 8, followed by metal hydride reduction and acetylation.