径向电场对纳米管中水分子通量的影响

水分子在纳米通道中的运动对于生命活动、纳米器件的设计等都有着重要的意义. 现在已经证实, 在(6,6)的碳纳米管中, 水分子会以单分子水链的形式协同通过碳纳米管. 但是如何控制水分子的流量仍然是一个困难的课题. 本文研究了在径向电场作用下, 碳纳米管中水分子通量的变化趋势和碳纳米管的开关行为.发现在碳纳米管两端存在200 MPa的压力差时, 电场强度从1 V·nm^-1增加到3 V·nm^-1, 水分子通量线性减小. 当径向电场强度增加到3 V·nm^-1时, 碳纳米管处于关闭状态, 水分子无法通过碳纳米管. 进一步, 我们发现水偶极与碳纳米管管轴夹角的平均值的概率分布和翻转频率都与水分子在纳米管中的个数有很大关系.     

Two-dimensional functional molecular nanoarchitectures – Complementary investigations with scanning tunneling microscopy and X-ray spectroscopy

Functional molecular nanoarchitectures (FMNs) are highly relevant for the development of future nanotechnology devices. Profound knowledge about the atomically controlled construction of such nanoscale assemblies is an indispensable requirement to render the implementation of such components into a real product successful. For exploiting their full potential the architectures’ functionalities have to be characterized in detail including the ways to tailor them. In recent years a plethora of sophisticated constructs were fabricated touching a wide range of research topics.     

Rational design of donor–π–acceptor n-butyl-1,8-naphthalimide-cored branched molecules as charge transport and luminescent materials for organic light-emitting diodes

Four D–π–A bipolar molecules with n-butyl-1,8-naphthalimide (BNI) fragments as acceptors, acetylenes as π-spacers, and different aromatic groups as donors have been designed to explore their optical, electronic, and charge transport properties as charge transport and luminescent materials for organic light-emitting diodes (OLEDs). The frontier molecular orbitals (FMOs) and local density of states analysis have turned out that the vertical electronic transitions of absorption and emission are characterized as intramolecular charge transfer (ICT). The calculated results show that their optical and electronic properties are affected by the different donors of the bipolar molecules. Our results suggest that D–π–A 1,8-naphthalimide derivatives with donors triphenylamine (1), 1-nitrobenzene (2), anisole (3), and 4-phenylbenzo[c][1,2,5]thiadiazole (4) fragments are expected to be promising luminescent materials. Furthermore, 2–4 are expected to be promising candidates for both electron and hole transport materials as well as potential ambipolar charge transport material, whereas BNI and 1 can serve as hole transfer materials only. We have also predicted the mobility of 4 with better performance in three different space groups. On the basis of investigated results, we proposed a rational way for the design of charge transport and/or luminescent materials simultaneously.     

Properties of atoms in electronically excited molecules within the formalism of TDDFT

The topological analysis of the electron density for electronic excited states under the formalism of the quantum theory of atoms in molecules using time‐dependent density functional theory (TDDFT) is presented. Relaxed electron densities for electronic excited states are computed by solving a Z‐vector equation which is obtained by means of the Sternheimer interchange method. This is in contrast to previous work in which the electron density for excited states is obtained using DFT instead of TDDFT, that is, through the imposition of molecular occupancies in accordance with the electron configuration of the excited state under consideration. Once the electron density of the excited state is computed, its topological characterization and the properties of the atoms in molecules are obtained in the same manner that for the ground state. The analysis of the low‐lying singlet and triplet vertical excitations of CO and C₆H₆ are used as representative examples of the application of this methodology. Altogether, it is shown how this procedure provides insights on the changes of the electron density following photoexcitation and it is our hope that it will be useful in the study of different photophysical and photochemical processes. © 2014 Wiley Periodicals, Inc.     

Transformations of iodine species inside elliptical channels of AlPO4‐11 crystals at low temperature: a Raman study

Raman spectra of iodine species confined in one‐dimensional elliptical channels of AlPO₄‐11 (AEL) crystals have been studied from room temperature down to −196 °C. As temperature decreases, thermal fluctuations of individual iodine molecules confined in AEL channels are slowed down and they prefer to rotate to channel axis direction, which increases the population of iodine molecules along channel axis (i.e., lying molecules and chains). Such temperature‐driven orientation transformation of iodine molecules is found to be reversible upon heating up to room temperature. The experimental observations are in good agreement with our theoretical simulations by molecular dynamics on low density iodine‐filled AEL crystals. We thus provide a new way to modulate the orientation of iodine molecules in nanochannels, which may have implications in low‐temperature‐sensitive nanoscale devices. Copyright © 2015 John Wiley & Sons, Ltd.     

固态氧化物电解池中碳-分子电化学转化为可再生燃料

近年来,随着社会环保意识的迅速提高以及对可再生能源利用能力的大幅增强,以燃料电池和电解池为代表的电化学技术已经逐渐在能源的存储、转化和利用方面发挥着不可或缺的独特作用.其中,固态氧化物电解池经过多年的发展,在装置成本和工作效率上取得了长足的进步,在储能转化方面具有重要的潜力.与此同时,伴随着《巴黎协定》签订以来各国的“碳中和”路线图逐渐出台,利用相对廉价易得的可再生电能,将二氧化碳(CO₂)和甲烷(CH₄)等碳-(C1)分子电解转化为高附加值的可再生燃料(如水煤气、乙烯等),对于碳中和目标的实现具有重要的意义.因此,C1分子电化学转化的研究成为了当下重点关注的研究领域,许多重要的研究成果和技术进步在过去几年中不断涌现.固态氧化物电解池作为一种代表性的C1分子电解和转化平台,也日渐引起相关领域研究人员的关注和兴趣.与传统的C1分子催化转化方法相比,基于固态氧化物电解池的电解转化技术具有两个重要优点:高能量转换效率与体系抗中毒能力.这两个特性作为体系稳健性的基石,保障了C1分子转化为可再生燃料的反应过程的长期可持续性.本文首先简要回顾了固态氧化物电解池的前沿技术与发展,并从电解池系统分类、反应体系的特征和反应体系发展的前景与挑战这三个方面,简要介绍了近年来基于固态氧化物电解池体系的C1分子电化学转化的代表性工作.CO₂与CH₄作为廉价易得的C1分子的代表,其转化因其反应分子惰性及反应过程不可控性而广受研究者关注,本文重点关注了在固态氧化物电解池中CO₂,CO₂/H₂O和CH₄三个体系的电化学反应过程和近期研究进展,希望可为相关研究人员未来设计更合适的催化剂和构建更优的电解池结构提供有益的参考.本文还针对目前固态氧化物电解池体系在C1分子转化领域所面临的挑战,提出了未来的一些可能的研究方向,以期助力研究者在不远的将来实现C1分子电解生产可再生燃料的实用化.     

基于创新能力培养的化学专业本科实验教学新体系的构建与实践

课程体系是人才培养的载体。为了更好地培养拔尖创新人才,南京大学化学国家级实验教学示范中心依据化学学科的特点和发展趋势,以科学内容的内在联系和研究规律为主线构建了“化学实验基础?化学合成与表征+化学原理与测量?化学功能分子实验+化学生物学综合实验+基于项目的研究实验”实验课程新体系,按照一流课程建设要求(高阶性、创新性和挑战度)对实验教学内容进行了优化,并建立起与之相适应的实验教学平台。新课程体系综合考虑了化学一级学科的整体性和关联学科的交叉性,在南京大学化学化工学院“拔尖计划”和“强基计划”学生中实施,教学效果显著。     

Applications of single-drop microextraction in analytical chemistry: A review

Single-drop microextraction (SDME) has been recognized as one of the simple miniaturized sample preparation tools for the isolation and preconcentration of several analytes from a complex sample matrix. In this review, we explored the applications of SDME coupled with various analytical techniques (spectroscopy, chromatography, and mass spectrometry) for the analysis of organic molecules, inorganic ions, and biomolecules from various sample matrices including food, environmental, clinical, pharmaceutical, and industrial samples. Also, it summarizes the use of nanoparticles in SDME combined with various analytical tools for the rapid analysis of several trace-level target analytes. An overview of ionic liquids, deep eutectic solvents, and SUPRAS, which improved the selectivity and sensitivity of various analytical techniques toward several analytes, as promising extracting solvent systems in SDME is also included. Finally, discussed the impressive analytical features and future perspectives of SDME in this review article.     

Diboron Bonds Between BX3 (X=H,F, CH3) and BYZ2 (Y=H,F; Z=CO,N2, CNH)

The ability of B atoms on two different molecules to engage with one another in a noncovalent diboron bond is studied by ab initio calculations. Due to electron donation from its substituents, the trivalent B atom of BYZ₂ (Z=CO, N₂, and CNH; Y=H and F) has the ability to in turn donate charge to the B of a BX₃ molecule (X=H, F, and CH₃), thus forming a B⋅⋅⋅B diboron bond. These bonds are of two different strengths and character. BH(CO)₂ and BH(CNH)₂, and their fluorosubstituted analogues BF(CO)₂ and BF(CNH)₂, engage in a typical noncovalent bond with B(CH₃)₃ and BF₃, with interaction energies in the 3–8 kcal/mol range. Certain other combinations result in a much stronger diboron bond, in the 26–44 kcal/mol range, and with a high degree of covalent character. Bonds of this type occur when BH₃ is added to BH(CO)₂, BH(CNH)₂, BH(N₂)₂, and BF(CO)₂, or in the complexes of BH(N₂)₂ with B(CH₃)₃ and BF₃. The weaker noncovalent bonds are held together by roughly equal electrostatic and dispersion components, complemented by smaller polarization energy, while polarization is primarily responsible for the stronger ones.