C72,La2@C72几何结构和电子性质的计算研究

采用密度泛涵理论(density functional theory,DFT)中的广义梯度近似(generally gradient approximation,GGA)对富勒烯C72和内掺金属La富勒烯La2@C72三种同分异构体的几何结构和电子结构进行研究.发现在C72的三种同分异构体中,满足独立五边形规则(isolated-pentagon-rule,IPR)的C72(D6d)结构最为稳定;在La2@C72三种同分异构体中,有着两对两两相邻五元环(twofused-pentagon)的La2@C72(#10611)结构最为稳定,而满足IPR的La2@C72(D6d)的结构变成了最不稳定结构.从能级图和态密度图分析得知,笼子稳定性的变化与La原子的原子轨道与C72原子轨道之间的杂化有关.Mulliken电荷分析得知,La2@C72(#10611)的两个La原子共转移了约3个电子给C72,并且,它们几乎分布在整个C笼上,形成的电子结构为La23+@C3-72.净自旋分析得知,La2@C72(#10611)中La原子磁性完全淬灭.     

C59N单分子整流器

通过将单个C59N分子置于双势垒隧道结中，从而利用单电子隧穿效应和C59N分子的特殊能级结构，我们成功地实现了一种新型的单分子整流器件．实验中这个整流器件的正向导通电压约为0．5-0．7V，反向击穿电压约为1．6—1．8V．理论分析表明，中性C59N分子的半占据费米能级以及在不同充电情况下费米能级的不对称移动是形成整流效应的主要原因．其构成原理也决定了该器件具有稳定、易重复的特点．     

The Role of Acetylcholine in the Cognitive Function of Frontal Neurons in Monkeys

To study the role of acetylcholine(ACh) in the cognitive function of frontal lobes, ACh and atropine were applied iontophoretically to the task-related neurons recorded from an area around the superior ramus of arcuate sulcus in the frontal cortex of 4 rhesus monkeys during the performance of two tasks. The spontaneous discharges and taskrelated responses of most of the neurons which increased their discharge rate in the delay and differentiation periods of the discrimination response go/no-go task and in the cue and delay periods of the delayed discrimination go/no-go task, were further increased during the application of ACh and suppressed during atropine. These results suggest that ACh may be involved in the excitatory process of the activity of the neurons in the above-mentioned area of frontal cortex to play an important role in the cognitive functions of attention, discrimination and short-term memory.     

Two Thiourea-based Colorimetric Sensors for Anions: Structure and Binding Study

Two colorimetric thiourea-based chemsensors with two relatively rigid arms, 2A and 2B, were synthesized. Their binding abilities with halide anions, AcO^?, [Formula: See Text] were studied by UV-Vis spectroscopy in DMSO. The two sensors showed a notable selective color response to F^? anion from colorless to green-yellow in recognition. The structures of the two sensors and their binding behaviors are discussed. The association constants were calculated by nonlinear fittings of 1:1, 1:2 or 1:1 to 1:2.     

加热状态选择对近沸体系丙烯/丙烷分离能耗影响的探讨

以近沸体系丙烯/丙烷分离为例介绍了化工模拟软件Aspen Plus在化工原理精馏单元的应用,研究了加热状态选择对能耗和年总费用的影响.为了提高学生工程实践能力,探讨了泡点、露点、过冷、过热、气液混合(气化率0.5)等5种进料状态分离丙烯/丙烷对能耗和经济费用的影响,在塔板数、进料板进料温度与压力、塔顶丙烯出料纯度不变条件下,过冷进料的常规工艺流程和泡点塔顶蒸气再压缩热泵工艺流程能耗和年度总费用(TAC)最小.相比常规工艺流程,塔顶蒸气再压缩热泵精馏工艺流程泡点进料可节能65％,年费用节约56％.     

某些含芳碲基或烷碲基的1, 4-苯醌和1, 4-萘醌衍生物

四氯-1,4-苯醌(1)和2,3-二氯-1,4-萘醌(2)中的氯相当活泼,能和许多亲核试剂反应,如醇和酚;硫醇和硫酚;胺及许多含NH的杂环化合物。1和2与磷亲核试剂的反应也是已知的,本文报道1及2和芳碲基或烷碲基亲试剂的反应。     

负载贵金属光催化剂的光催化活性研究

在注入V离子的二氧化钛光催化剂上负载贵金属,制备了在可见光照射下具有高光催化活性的功能型光催化剂,研究在可见光和太阳光照射下丙炔的光催化水解反应，利用这些改性的二氧化钛构筑太阳能到化学能的转换系统.研究结果发现了V/Pt光催化剂在丙炔和水的光催化水解反应中，由于贵金属的存在，有利于促进发生加氢反应；导致丙烯的生成量增加.在可见光下的光催化活性也和负载贵金属所处的氧化状态有着密切的关系，贵金属完全被还原到0价是提高光催化活性的必要条件.     

SnS2/GCP(石墨烯复合粉末)微米复合材料作为锂离子电池负极材料的电化学性能

以石墨烯复合粉末为添加剂,采用一步水热法制备了一种SnS₂/GCP微米复合材料。在所得到的复合材料中,SnS₂纳米片相互缠绕组成多孔球状SnS₂颗粒,石墨烯复合粉末均匀的包裹在球状SnS₂颗粒表面。将所制备的SnS₂/GCP微米复合材料用作锂离子电池负极材料测其电化学性能。结果显示,在0.1 A·g^-1的电流密度下可逆比容量为795.6 mAh·g^-1,循环100次后比容量损失不到1%。相比于SnS₂其比容量和循环稳定性得到了明显改善,主要是由于石墨烯复合粉末的加入,不仅缓解了SnS₂颗粒在充放电过程中的团聚和体积膨胀,而且还提高了SnS₂颗粒的电导率。     

亲锂电解液在LiNi0.6Mn0.2Co0.2O2／Li二次锂金属电池中的电化学性能

金属锂电池被认为是具有良好前景的下一代高能量密度电池。然而,传统的碳酸酯类电解液与锂的亲和性差,在循环过程中由于锂枝晶的生长和固体电解质膜（SEI）的不稳定导致金属锂电池性能快速衰减。采用1.2 mol／L六氟磷酸锂（LiPF₆）／二氟草酸硼酸锂（LiDFOB）／氟代碳酸乙烯酯（FEC）／碳酸二乙酯（DEC）,并添加了双三氟甲磺酰亚胺锂（LiTFSI）作为电解液,对其在LiNi_0.6Mn_0.2Co_0.2O₂／40 μm-Li（单位面积上负／正极材料的实际容量的比N／P＝2.85）电池中的电化学性能进行了研究。LiNi_0.6Mn_0.2Co_0.2O₂／40 μm-Li电池表现出优异的循环稳定性（循环120圈后,容量保持率>93%）和倍率性能（3C倍率下放电比容量为110 mA·h／g）。良好的电化学性能主要归因于该电解液可以在金属锂表面形成致密且稳定的SEI,并抑制锂枝晶的产生。     

Absolute frequency measurement of rubidium 5S-7S two-photon transitions with a femtosecond laser comb

The absolute frequencies of rubidium 5S-7S two-photon transitions at 760 nm are measured to an accuracy of 20 kHz with an optical frequency comb based on a mode-locked femtosecond Ti:sapphire laser. The rubidium 5S-7S two-photon transitions are potential candidates for frequency standards and serve as important optical frequency standards for telecommunication applications. The accuracy of the hyperfine constant of the 7S1/2 state is improved by a factor of 5 in comparison with previous results.