Growth of monodisperse nanospheres of MnFe_2O_4 with enhanced magnetic and optical properties

Highly dispersive nanospheres of MnFe204 are prepared by template free hydrothermal method. The nanospheres have 47.3-nm average diameter, narrow size distribution, and good crystallinity with average crystallite size about 22 nm. The reaction temperature strongly affects the morphology, and high temperature is found to be responsible for growth of uniform nanospheres. Raman spectroscopy reveals high purity of prepared nanospheres. High saturation magnetization （78.3 emu/g）, low coercivity （45 Oe, 10e = 79.5775 A.cm-1）, low remanence （5.32 emu/g）, and high anisotropy constant 2.84 × 10^4 J/m3 （10 times larger than bulk） are observed at room temperatures. The nearly snperparamagnetic behavior is ~ spin due to comparable size of nanospheres with superparamagnetic critical thameter Dcr spm The high value of Keff may be due to coupling between the pinned moment in the amorphous shell and the magnetic moment in the core of the nanospheres. The nanospheres show prominent optical absorption in the visible region, and the indirect band gap is estimated to be 0.98 eV from the transmission spectrum. The prepared Mn ferrite has potential applications in biomedicine and photocatalysis.     

西北旱田黄土对Pb(Ⅱ)和氯吡硫磷复合污染的共吸附机制研究

通过静态批次实验研究旱田黄土对Pb(Ⅱ)和氯吡硫磷的共吸附行为,使用SEM,FTIR,XRD和理论分析揭示共吸附机制。实验结果发现:黄土对Pb(Ⅱ)和氯吡硫磷的共吸附符合Langmuir等温线方程,经计算得出的理论吸附容量qm分别为12.5和0.64mg.g-1,准二级动力学方程能更好地描述反应行为。吸附反应后,黄土表面形貌变化很小,FTIR图谱中的某些波峰红移、消失或强度减弱,综合XRD图谱及理论分析,认为:旱田黄土对Pb(Ⅱ)的吸附为表面配位络合和范德华力的作用,以化学吸附为主;而氯吡硫磷的去除涉及到黄土有机质对氯吡硫磷大分子的截留作用,以及氢键、范德华力的作用,以物理吸附为主,兼有化学吸附的贡献。旱田黄土有机质对Pb(Ⅱ)和氯吡硫磷的吸附有重要贡献。     

ICP-AES测定铜合金中的铜及10种杂质元素

建立了ICP-AES同时测定铜合金中铜及杂质元素磷、硅、锰、铁、镍、钴、锌、铅、铝、锡11种元素的分析方法,通过对样品溶解方法、元素分析谱线的选择和仪器分析参数进行试验比较,确定了实验条件,并对铜合金标准样品进行了精密度和回收率实验.结果表明,相对标准偏差小于3.0％,回收率在90％-110％之间.该方法快速简便,准确度高,可以满足日常检验的分析要求.     

芬布芬-铜（Ⅱ）-牛血清白蛋白相互作用的光谱法研究

模拟生理条件下,应用荧光光谱法研究了芬布芬对牛血清白蛋白,铜（Ⅱ）对牛血清白蛋白以及铜（Ⅱ）对芬布芬和牛血清白蛋白荧光光谱特性的影响.实验表明：铜（Ⅱ）和芬布芬均可使牛血清白蛋白的荧光强度发生静态猝灭,并且在铜（Ⅱ）存在下,芬布芬对牛血清白蛋白的荧光猝灭作用显著增强.根据荧光猝灭双倒数图计算芬布芬和牛血清白蛋白的结合常数为8.44×104,结合位点数为0.97.荧光猝灭双倒数图计算的结果表明,芬布芬和牛血清白蛋白之间的结合常数和结合位点数均随铜（Ⅱ）浓度的增大而增大.很据三者结合反应的研究,进一步探讨了芬布芬、铜（Ⅱ）在生物体内与蛋白质相互作用的机理.     

Strong reaction channels at barrier energies in the system 6Li + 208Pb

Large cross-section reaction channels were measured in the systems ⁶Li( ⁷Li) + ²⁰⁸Pb with high statistical accuracy at 5(3) energies around the Coulomb barrier from 29 to 39 MeV. These channels were assigned (mainly) to the breakup of ⁶Li, very loosely bound, into α + d and to the breakup of ⁵Li, produced by n-transfer to the target, into α + p and to similar processes with ⁷Li beam. The cross-sections with ⁶Li, S _α = 1.475 MeV, are systematically larger than the ⁷Li ones. This reflects, most likely, the higher binding energy of ⁷Li, S _α = 2.468 MeV. Theoretical predictions for the ⁶Li + ²⁰⁸Pb system which include for ⁶Li breakup to continuum states within a continuum discretized coupled-channels approach (CDCC) and resonant breakup plus n-transfer with DWBA reproduce the angular distribution shapes but still underestimate the cross-sections by a factor ∼ 3. Received: 15 January 2001 / Accepted: 3 March 2001     

Enhanced room temperature ferromagnetism and photoluminescence behavior of Cu-doped ZnO co-doped with Mn

Cu, Mn co-doped ZnO nanoparticles were successfully synthesized by the sol–gel technique. XRD pattern described that Mn-doping did not affect the hexagonal wurtzite structure of the samples and no secondary phases were found. The reduced crystallite size at Mn=2% is due to the suppression of grain surface growth by foreign impurity. The enhancement of crystal size after Mn=2% is due to the expansion of lattice volume produced by the distortion around the dopant ion. The better dielectric constant and conductivity noticed at Mn=2% are explained by charge carrier density and crystallite size. The suppression of broad UV band by Mn-doping is discussed based on the generation of non-radiative recombination centers. Hysteresis loop showed the clear room temperature ferromagnetism in all the samples and the magnetization increased with Mn-doping. Better electrical and magnetic behavior of Zn_0.94Cu_0.04Mn_0.02O sample is suggested for effective opto-magnetic devices.     

Quantum entanglement in a molecular magnet with itinerant electrons

We study the behaviors of pairwise and multipartite entanglement in a molecular magnet with itinerant electrons. In different ground states, the ratio of pairwise to multipartite entanglement is different. The monogamy of quantum entanglement is shown. Both charge correlation and spin correlation play important roles in the entanglement. The entanglements are generally suppressed by the on-site repulsion U and are mainly determined by spin correlation for large U and by charge correlation for small U. At finite temperature, in general, the thermal fluctuation suppresses the entanglements. However, in some cases, the multipartite entanglement can be enhanced by increasing temperature. Comparing the Heisenberg model with the Hubbard model, it is found that thermal entanglement in the itinerant electron system is more robust because charge correlation can survive at much higher temperature than spin correlation.     

Generation of maximally entangled atom pairs in driven dissipative cavity QED systems

We investigate the entanglement of an open tripartite system where a cavity field mode in thermal equilibrium is off-resonantly coupled with two atoms that are simultaneously driven by a resonant coherent field. For moderately detuned atom-field coupling and strong atomic driving we show the generation, at given interaction times and for low enough cavity decay rates, of atomic Bell states and of Bell state superpositions relevant for quantum gates implementation. The system can oscillate between bi-separable and fully separable states. Also we describe the distribution of quantum correlations between the atom-atom and the two atom-field subsystems. In the dispersive coupling regime with strongly driven atoms we show the generation of nearly stationary Bell states which remain protected from cavity dissipation.     

掺杂ZnSe/BeTe Ⅱ型量子阱结构中带电激子的磁场效应

报道了n型掺杂ZnSe/BeTe/ZnSe Ⅱ型量子阱(type-Ⅱ QW)在极低温 (5—10 K)条件下的各种光学性质. 磁场中(Farada配置)ZnSe层的反射光谱展示了一个典型的负的带电激子(X^-)的跃迁特征. 对于空间间接光致发光(spacially indirect PL)光谱,它的主发光峰显示了一个反玻尔兹曼分布的非对称性,并且在磁场中(Voigt配置)它的峰值能量随磁场的增加而降低. 这些实验结果显示了该掺杂样品的空间间接PL是来自Ⅱ型QW结构所特有的带电激子的跃迁. 关键词： 光致发光 二维电子气 带电激子 Ⅱ型量子阱     

ICP—AES法同时测定硼铁中的主要成分及杂质

本文研究了用ＩＣＰ－ＡＥＳ法同时测定硼铁中的主要成分Ｂ、Ｆｅ及杂质元素、Ａｌ、Ｍｎ，Ｓｉ的方法。采用碱熔融法分解样品，选Ｃｄ作为内标元素。