有机分子电子器件的研究进展

随着传统硅基电子器件的发展日趋受限,以原子和分子作为电子元器件的研究受到了越来越多的重视.概述了分子电子器件的概念和基本原理,详细介绍了分子导线、分子二极管、分子开关、分子存储器件和分子场效应晶体管的工作原理及最近的研究进展.具有π-共轭结构的有机分子体系是构造分子导线的理想单元;分子结的电子结构不对称性是分子具有整流特性的根本原因;轮烷和索烃是构造分子开关的理想单元之一;分子场效应晶体管的工作原理是量子隧穿,主要是金属-绝缘体-金属间的隧穿效应.最后阐述了目前分子电子器件研究中存在的主要问题.     

Molecular Switch Controlled by Pulsed Bias Voltages

Recent experiments have shown that the current–voltage characteristics (I–V) of BPDN‐DT (bipyridyl‐dinitro oligophenylene‐ethynylene dithiol) can be switched in a very controlled manner between “on” and “off” traces by applying a pulse in a bias voltage, V_bias. Here, the polaron formation energies are calculated to check a frequently held belief, namely, that the polaron formation can explain the observed bistability. These results are not consistent with such a mechanism. Instead, a conformational reorientation is proposed. The molecule carries an intrinsic dipole moment, which couples to V_bias. Ramping V_bias exerts a force on the dipole that can reorient (“rotate”) the molecule from the ground state (“off”) into a metastable configuration (“on”) and back. By elaborated electronic structure calculations, a specific path for this rotation is identified through the molecule's conformational phase space. It is shown that this path has sufficiently high barriers to inhibit thermal instability but that the molecule can still be switched in the voltage range of the junction stability. The theoretical I–Vs qualitatively reproduce the key experimental observations. A proposal for the experimental verification of the alternative mechanism of conductance switching is presented.     

涡轮分子增压泵的研究现状与进展

综述了涡轮分子增压泵的研究现状与进展。涡轮分子增压泵是一种动量传输型真空泵，它的出口压力范围可达1000Pa，通过计算流体动力学方法(CFD法)和直接模拟蒙特卡罗法(DSMC)可以模拟计算抽气通道内气体的流动，这两种互补的方法可以研究从粘滞流到分子流的全部抽速曲线，从而指导新型涡轮分子增压泵的设计。     

分子/增压泵的结构、性能及其应用

分子／增压泵是一种最近实现产品化的新一代真空泵，该泵兼有中、高真空泵的性能，能耗低，能获得清洁真空，还能承受大气冲击，应用前景十分广泛。本文详细介绍了分子／增压泵的结构、性能和应用，并与常用的中、高真空泵作比较。最后，介绍了分子／增压泵的一种独特应用——“大型真空设备的冲洗抽气法”，该方法将抽气时间缩短至50％，能耗降至10％～25％。     

分子印迹聚合物

简单介绍了分子印迹聚合物(MIP)的制备及其分子识别机理,重点总结了MIP在分离领域的应用.     

分子泵的世纪回顾与展望

分子泵自1912年诞生以来,至今已快近一个世纪了,它在初期进展较缓慢,在1970年以前,分子泵的应用还仅限于核物理,电真空,表面科学等领域,但近20年来由于半导体产业的兴起和薄膜工业的发展,分子泵才被人们所重视,并得到了兴旺和发达,现代的分子泵已发展到实用和普及的阶段,本文回顾了分子泵分析近百年的发展历史,详细地介绍了分子泵在各个时期的发展状况,对初期的分子泵,涡轮分子泵,磁悬浮轴承和气体静压静轴式涡轮分子泵,复合式分子泵,低温型涡轮分子泵,新型牵引分子泵,陶瓷涡轮分子泵,轴反应生成物的涡轮分子泵和极高真空涡分子泵等做了重点的分析,最后指出分子泵的发展前景。     

高分子材料模拟中的分子力学法和力场

比较了分子模拟中两种基本方法，量子力学和分子力学法，详细介绍了在高分子模拟中应用较多的分子力学法和力场，并预测了未来的发展趋势。     

Design of Bistable Gold@Spin‐Crossover Core–Shell Nanoparticles Showing Large Electrical Responses for the Spin Switching

A simple chemical protocol to prepare core–shell gold@spin‐crossover (Au@SCO) nanoparticles (NPs) based on the 1D spin‐crossover [Fe(Htrz)₂(trz)](BF₄) coordination polymer is reported. The synthesis relies on a two‐step approach consisting of a partial surface ligand substitution of the citrate‐stabilized Au NPs followed by the controlled growth of a very thin layer of the SCO polymer. As a result, colloidally stable core@shell spherical NPs with a Au core of ca. 12 nm and a thin SCO shell 4 nm thick, are obtained, exhibiting a narrow distribution in sizes. Differential scanning calorimetry proves that a cooperative spin transition in the range 340–360 K is maintained in these Au@SCO NPs, in full agreement with the values reported for pristine 4 nm SCO NPs. Temperature‐dependent charge‐transport measurements of an electrical device based on assemblies of these Au@SCO NPs also support this spin transition. Thus, a large change in conductance upon spin state switching, as compared with other memory devices based on the pristine SCO NPs, is detected. This results in a large improvement in the sensitivity of the device to the spin transition, with values for the ON/OFF ratio which are an order of magnitude better than the best ones obtained in previous SCO devices.     

Vision Statement: Materials in Motion

At the dawn of a new era of interactive and responsive materials and dynamic molecular systems there is ample opportunity to raise the level of complexity enabling mechanical motion, autonomous behavior, or interactive self-regulatory functions. Some of the major challenges and opportunities are discussed with a brief perspective toward future developments on responsive materials.     

聚合物中小分子扩散的分子动力学模拟

采用分子动力学(MD)方法,以研究低聚体在聚甲基丙烯酸甲酯中的扩散为例,通过分析高分子链长、低聚体含量、聚合度和温度对扩散系数的影响,揭示小分子在聚合物中扩散过程.通过比较扩散系数的模拟值与实验值,发现两者比值在4左右.为获得小分子在聚合物中的扩散系数提供了一种较好的方法.     

Tip-Induced Inversion of the Chirality of a Molecule's Adsorption Potential Probed by the Switching Directionality

The switching behavior of surface-supported molecular units excited by current, light, or mechanical forces is determined by the shape of the adsorption potential. The ability to tailor the energy landscape in which a molecule resides at a surface gives the possibility of imposing a desired response, which is of paramount importance for the realization of molecular electronic units. Here, by means of scanning tunneling microscopy, a triazatruxene (TAT) molecule on Ag(111) is studied, which shows a switching behavior characterized by transitions of the molecule between three states, and which is attributed to three energetically degenerate bonding configurations. Upon tunneling current injection, the system can be excited and continuously driven, showing a switching directionality close to 100%. Two surface enantiomers of TAT show opposite switching directions pointing at the chirality of the energy landscape of the adsorption potential as a key ingredient for directional switching. Further, it is shown that by tuning the tunneling parameters, the symmetry of the adsorption potential can be controllably adjusted, leading to a suppression of the directionality or an inversion of the switching direction. The findings represent a molecule-surface model system exhibiting unprecedented control of the shape of its adsorption potential.     

Recent Advances in Molecular Spintronics: Multifunctional Spintronic Devices

The field of spintronics has triggered an enormous revolution in information storage since the first observation of giant magnetoresistance (GMR). Molecular semiconductors are characterized by having very long spin relaxation times up to milliseconds, and are thus widely considered to hold immense potential for spintronic applications. Along with the development of molecular spintronics, it is clear that the study of multipurpose spintronic devices has gradually grown into a new research and development direction. The abundant photoelectric properties of molecular semiconductors and the intriguing functionality of the spinterface, together with novel designs of device structures, have promoted the integration of multiple functions and different mechanisms into discrete spintronic devices. Here, according to the different relationships between the integrated mechanisms, multifunctional molecular spintronic devices containing parallel and interactive types are highlighted. This is followed by the introduction of pure‐spin‐current‐type molecular spintronic devices that have already demonstrated great potential for multifunction exploration. Finally, the challenges and outlook that make this field young and energetic are outlined.     

Epitope Imprinting Technology: Progress,Applications, and Perspectives toward Artificial Antibodies

Epitope imprinting is a promising tool to generate antibody‐like specific recognition sites. Recently, because of the ease of obtaining templates, the flexibility in selecting monomers, their resistance to harsh environments, and the high specificity toward targets, epitope‐imprinted materials have attracted much attention in various fields, such as bioanalysis, clinical therapy, and pharmacy. Here, the discussion is focused on the current representative epitope imprinting technologies, including epitope bulk imprinting and epitope surface imprinting. Moreover, the application of epitope‐imprinted materials to the recognition of peptides, proteins, and cells is reviewed. Finally, the remaining challenges arising from the intrinsic properties of epitope imprinting are discussed, and future development in the field is prospected.     

Simple and universal platform for logic gate operations based on molecular beacon probes

A new platform technology is herein described with which to construct molecular logic gates by employing the hairpin-structured molecular beacon probe as a basic work unit. In this logic gate operation system, single-stranded DNA is used as the input to induce a conformational change in a molecular beacon probe through a sequence-specific interaction. The fluorescent signal resulting from the opening of the molecular beacon probe is then used as the output readout. Importantly, because the logic gates are based on DNA, thus permitting input/output homogeneity to be preserved, their wiring into multi-level circuits can be achieved by combining separately operated logic gates or by designing the DNA output of one gate as the input to the other. With this novel strategy, a complete set of two-input logic gates is successfully constructed at the molecular level, including OR, AND, XOR, INHIBIT, NOR, NAND, XNOR, and IMPLICATION. The logic gates developed herein can be reversibly operated to perform the set-reset function by applying an additional input or a removal strand. Together, these results introduce a new platform technology for logic gate operation that enables the higher-order circuits required for complex communication between various computational elements.     

Electric‐Field‐Controlled Dopant Distribution in Organic Semiconductors

Stable electrical doping of organic semiconductors is fundamental for the functionality of high performance devices. It is known that dopants can be subjected to strong diffusion in certain organic semiconductors. This work studies the impact of operating conditions on thin films of the polymer poly(3‐hexylthiophene) (P3HT) and the small molecule Spiro‐MeOTAD, doped with two differently sized p‐type dopants. The negatively charged dopants can drift upon application of an electric field in thin films of doped P3HT over surprisingly large distances. This drift is not observed in the small molecule Spiro‐MeOTAD. Upon the dopants’ directional movement in P3HT, a dedoped region forms at the negatively biased electrode, increasing the overall resistance of the thin film. In addition to electrical measurements, optical microscopy, spatially resolved infrared spectroscopy, and scanning Kelvin probe microscopy are used to investigate the drift of dopants. Dopant mobilities of 10^?9 to 10^?8 cm² V^?1 s^?1 are estimated. This drift over several micrometers is reversible and can be controlled. Furthermore, this study presents a novel memory device to illustrate the applicability of this effect. The results emphasize the importance of dynamic processes under operating conditions that must be considered even for single doped layers.     

分子模拟预测小分子在高分子中扩散行为的研究进展

分子模拟可探究微小时间尺度内体系的动态行为,是研究高分子溶液中扩散现象的有效工具。介绍了用于计算化学和材料科学领域的计算软件,以及可用于高分子体系的分子力场。较为详细地综述了近年来用分子模拟技术研究小分子在聚硅氧烷类、聚酰亚胺类、聚烯烃类等高分子中扩散行为的进展,并指出其发展前景。