Progress of Jinping Underground laboratory for Nuclear Astrophysics (JUNA)

Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of~(25)Mg(p,γ)~(26)Al,~(19)F(p,α)~(16)O,~(13)C(α,n)~(16)O and ~(12)C(α,γ)~(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.     

Synthesis of perylene-bridged bis(dibenzo-24-crown-8) and its assembly behavior with a fullerene-based secondary dibenzylammonium salt

This paper reports the synthesis of a perylene-bridged bis(crown ether) through the condensation reaction between primary amine-armed dibenzo-24-crown-8 and 3,4,9,10-perylenetetracarboxylic dianhydride. Pseudorotaxane with a perylene moiety at the wheel and a fullerene unit in the middle of the axle was prepared, which was evidenced by ¹H NMR and fluorescence experiments. Subsequent investigations show that the formation and disassociation of the pseudorotaxane can be controlled by the alternating addition of KPF₆ and 18-crown-6, following the change of the florescence intensity of perylene.

     

电泳技术在纳米颗粒分离中的应用

合成纳米颗粒常在尺寸和形状方面具有广泛分布.在很多实验中,需要利用一定大小及形状的纳米颗粒的独特物理化学性质,因此,简便快速的纳米颗粒分离技术越来越受到诸多科学领域的重视.电泳技术以其高分辨率,被广泛用于多种生物大分子如核酸、蛋白质等的分离纯化.纳米颗粒在尺寸上与生物体中的蛋白复合物、细胞器和微生物等十分接近,考虑到带电纳米颗粒与生物分子在电场中的运动行为的相似性,运用电泳技术进行纳米颗粒的鉴定、分离和纯化是一种新的思路,并取得了良好的实验结果.本文主要介绍了琼脂糖凝胶电泳、毛细管电泳以及其他一些电泳技术在纳米颗粒分离中的研究进展.     

纳米结构ZnO在TiO_2薄膜上的电化学沉积及其表征

在三电极体系中,以硝酸锌水溶液作为电解液,采用阴极还原电沉积法成功实现了一维纳米结构ZnO阵列在TiO2纳米粒子/ITO导电玻璃薄膜基底上的沉积,并通过XRD、SEM、EDS和PL光谱等方法对样品进行了表征.重点研究了薄膜基底、电解液浓度、沉积时间、六次亚甲基四胺(HMT)的引入对ZnO沉积及其发光性质的影响.结果显示:与ITO玻璃基底相比,ZnO更易于在TiO2纳米粒子薄膜上实现电化学沉积.ZnO属于六方晶系的铅锌矿结构,并且沿着c-轴方向表现出明显的择优化生长,以形成垂直于基底的ZnO纳米棒阵列.延长沉积时间、增加电解液浓度和引入一定量的HMT等均对ZnO的生长有促进作用,进而使其纳米棒的结晶度和取向程度提高,进而解释了所得的薄膜分别约在375和520nm处表现出ZnO的强而窄的带边紫外光发射峰和弱而宽的表面态绿光发射带.     

二萘嵌苯桥联双二苯并24冠8的合成及其与富勒烯二级铵盐的组装行为

通过端基为伯胺的臂式二苯并24冠8与苝四甲酸二酐衍生物的缩合反应合成了二萘嵌苯桥联的双冠醚主体.利用核磁、荧光等手段研究了其与富勒烯二级铵盐客体形成准轮烷的组装行为.结果表明,24冠8大环可以键合二级铵盐客体,形成轮上有二萘嵌苯和轴上有富勒烯的准轮烷,KPF6和18冠6的加入可以调控准轮烷的解离和形成,并伴随着荧光强度的改变.     

论文Eu(Ⅲ)在Na基高庙子膨润土上的吸附作用:实验和构模研究

采用连续电位滴定法研究了不同离子强度下Na基高庙子膨润土(Na-BNT)的表面酸、碱性质;用批式法研究了温度为22±2℃时,离子强度从0.001到0.5mol/L、Eu(Ⅲ)浓度从10-9到10-4mol/L、pH从3到10.5的广泛实验条件下,Eu(Ⅲ)在Na-BNT上的吸附作用;通过考虑发生在层间位点(layersites)和边位点(edgesites)上的表面反应,对比了双层静电模型与非静电模型对宏观实验数据的描述,结果表明,双层静电模型可以描述Na基高庙子膨润土的表面酸碱性质,但对除I=0.1mol/L以外其他离子强度下Eu(Ⅲ)的吸附难以作出合理描述;非静电模型可以定量描述广泛实验条件下Eu(Ⅲ)在Na基高庙子膨润土上的吸附作用,但对pH>8时Na基高庙子膨润土的表面酸碱性质的描述不够理想;研究结果为解释和预测+3价镧系和锕系元素在高庙子膨润土上的吸附作用提供了模型参考.     

Electrochemical deposition of nano-structured ZnO on the nanocrystalline TiO2 film and its characterization

One-dimensional structure of ZnO nanorod arrays on nanocrystalline TiO₂/ITO conductive glass substrates has been fabricated by cathodic reduction electrochemical deposition methods in the three-electrode system, with zinc nitrate aqueous solution as the electrolyte, and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and photoluminescence (PL) spectra. The effects of film substrates, electrolyte concentration, deposition time, and methenamine (HMT) addition on ZnO deposition and its luminescent property were investigated in detail. The results show that, compared with on the ITO glass substrate, ZnO is much easily achieved by electrochemical deposition on the TiO₂ nanoparticle thin films. ZnO is hexagonally structured wurtzite with the c-axis preferred growth, and further forms nanorod arrays vertically on the substrates. It is favorable to the growth of ZnO to extend the deposition time, to increase the electrolyte concentration, and to add a certain amount of HMT in the system, consequently improving the crystallinity and orientation of ZnO arrays. It is demonstrated that the obtained ZnO arrays with high crystallinity and good orientation display strong band-edge UV (375 nm) and weak surface-state-related green (520 nm) emission peaks.     

新的质量标度下奇异夸克物质的电荷与临界密度

应用自恰的热力学方式确定夸克质量公式中的参数,并进一步证明,在新的质量标度下,适量的负电荷仍然可以降低奇异夸克物质的临界密度,从而有利于在重离子碰撞实验中寻找strangelets.当然,过量的负电荷仍将使味平衡成为不可能.