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1.
Guangjun Tian Dexian Sun Yaogang Zhang Xi Yu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):6012-6016
We report an effective modulation of the quantum transport in molecular junctions consisting of aggregation‐induced‐emission(AIE)‐active molecules. Theoretical simulations based on combined density functional theory and rate‐equation method calculations show that the low‐bias conductance of the junction with a single tetraphenylethylene (TPE) molecule can be completely suppressed by strong electron–vibration couplings, that is, the Franck‐Condon blockade effect. It is mainly associated with the low‐energy vibration modes, which is also the origin of the fluorescence quenching of the AIE molecule in solution. We further found that the conductance of the junction can be lifted by restraining the internal motion of the TPE molecule by either methyl substitution on the phenyl group or by aggregation, a mechanism similar to the AIE process. The present work demonstrates the correlation between optical processes of molecules and quantum transport in their junction, and thus opens up a new avenue for the application of AIE‐type molecules in molecular electronics and functional devices. 相似文献
2.
Yuuki Komoto Yasuomi Yamazaki Dr. Yusuke Tamaki Madoka Iwane Prof.Dr. Tomoaki Nishino Prof. Dr. Osamu Ishitani Prof. Dr. Manabu Kiguchi Dr. Shintaro Fujii 《化学:亚洲杂志》2018,13(10):1297-1301
Single‐molecule junctions are of particular interest in molecular electronics. To realize molecular electronic devices, it is crucial that functional single‐molecule junctions are connected to each other by using joint units on the atomic scale. However, good joint units have not been reported because controlling the charge transport directions through the junctions is not trivial. Here, we report a joint unit that controls and changes the charge transport directions through the junctions, by using a ruthenium–tris‐bipyridine (RuBpy) complex. The RuBpy single‐molecule junction was fabricated with scanning tunnelling microscopy‐based break junction techniques. The RuBpy single‐molecule junction showed two distinct high and low conductance states. The two states were characterized by the conductance measurement, the correlation analysis, and the comparative experiment of bipyridine (Bpy), which is the ligand unit of RuBpy. We demonstrate that the Ru complex has multiple charge transport paths, where the charge is carried vertically and horizontally through the complex depending on the path. 相似文献
3.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(48):15580-15584
A key target in molecular electronics has been molecules having switchable electrical properties. Switching between two electrical states has been demonstrated using such stimuli as light, electrochemical voltage, complexation and mechanical modulation. A classic example of the latter is the switching of 4,4′‐bipyridine, leading to conductance modulation of around 1 order of magnitude. Here, we describe the use of side‐group chemistry to control the properties of a single‐molecule electromechanical switch, which can be cycled between two conductance states by repeated compression and elongation. While bulky alkyl substituents inhibit the switching behavior, π‐conjugated side‐groups reinstate it. DFT calculations show that weak interactions between aryl moieties and the metallic electrodes are responsible for the observed phenomenon. This represents a significant expansion of the single‐molecule electronics “tool‐box” for the design of junctions with electromechanical properties. 相似文献
4.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(42):13241-13245
We studied the single‐molecule conductance through an acid oxidant triggered phenothiazine (PTZ‐) based radical junction using the mechanically controllable break junction technique. The electrical conductance of the radical state was enhanced by up to 200 times compared to the neutral state, with high stability lasting for at least two months and high junction formation probability at room‐temperature. Theoretical studies revealed that the conductance increase is due to a significant decrease of the HOMO–LUMO gap and also the enhanced transmission close to the HOMO orbital when the radical forms. The large conductance enhancement induced by the formation of the stable PTZ radical molecule will lead to promising applications in single‐molecule electronics and spintronics. 相似文献
5.
Yonghai Li Masoud Baghernejad Al‐Galiby Qusiy David ZsoltManrique Guanxin Zhang Joseph Hamill Yongchun Fu Peter Broekmann Wenjing Hong Thomas Wandlowski Deqing Zhang Colin Lambert 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(46):13790-13793
We studied charge transport through core‐substituted naphthalenediimide (NDI) single‐molecule junctions using the electrochemical STM‐based break‐junction technique in combination with DFT calculations. Conductance switching among three well‐defined states was demonstrated by electrochemically controlling the redox state of the pendent diimide unit of the molecule in an ionic liquid. The electrical conductances of the dianion and neutral states differ by more than one order of magnitude. The potential‐dependence of the charge‐transport characteristics of the NDI molecules was confirmed by DFT calculations, which account for electrochemical double‐layer effects on the conductance of the NDI junctions. This study suggests that integration of a pendant redox unit with strong coupling to a molecular backbone enables the tuning of charge transport through single‐molecule devices by controlling their redox states. 相似文献
6.
Sepideh Afsari Parisa Yasini Haowei Peng John P. Perdew Eric Borguet 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14413-14418
In most junctions built by wiring a single molecule between two electrodes, the electrons flow along only one axis: between the two anchoring groups. However, molecules can be anisotropic, and an orientation‐dependent conductance is expected. Here, we fabricated single‐molecule junctions by using the electrode potential to control the molecular orientation and access individual elements of the conductivity tensor. We measured the conductance in two directions, along the molecular plane as the benzene ring bridges two electrodes using anchoring groups (upright) and orthogonal to the molecular plane with the molecule lying flat on the substrate (planar). The perpendicular (planar) conductance is about 400 times higher than that along the molecular plane (upright). This offers a new method for designing a reversible room‐temperature single‐molecule electromechanical switch that controllably employs the electrode potential to orient the molecule in the junction in either “ON” or “OFF” conductance states. 相似文献
7.
Chun Tang Lijue Chen Longyi Zhang Zhixin Chen Guopeng Li Zhewei Yan Luchun Lin Junyang Liu Longfeng Huang Yiling Ye Yuhui Hua Jia Shi Haiping Xia Wenjing Hong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(31):10711-10715
Molecular components are vital to introduce and manipulate quantum interference (QI) in charge transport through molecular electronic devices. Up to now, the functional molecular units that show QI are mostly found in conventional π‐ and σ‐bond‐based systems; it is thus intriguing to study QI in multicenter bonding systems without both π‐ and σ‐conjugations. Now the presence of QI in multicenter‐bond‐based systems is demonstrated for the first time, through the single‐molecule conductance investigation of carborane junctions. We find that all the three connectivities in carborane frameworks show different levels of destructive QI, which leads to highly suppressed single‐molecule conductance in para‐ and meta‐connected carboranes. The investigation of QI into carboranes provides a promising platform to fabricate molecular electronic devices based on multicenter bonds. 相似文献
8.
Nicol Ferri Norah Algethami Andrea Vezzoli Sara Sangtarash Maeve McLaughlin Hatef Sadeghi Colin J. Lambert Richard J. Nichols Simon J. Higgins 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16736-16742
Single‐molecule junctions that are sensitive to compression or elongation are an emerging class of nanoelectromechanical systems (NEMS). Although the molecule–electrode interface can be engineered to impart such functionality, most studies to date rely on poorly defined interactions. We focused on this issue by synthesizing molecular wires designed to have chemically defined hemilabile contacts based on (methylthio)thiophene moieties. We measured their conductance as a function of junction size and observed conductance changes of up to two orders of magnitude as junctions were compressed and stretched. Localised interactions between weakly coordinating thienyl sulfurs and the electrodes are responsible for the observed effect and allow reversible monodentate?bidentate contact transitions as the junction is modulated in size. We observed an up to ≈100‐fold sensitivity boost of the (methylthio)thiophene‐terminated molecular wire compared with its non‐hemilabile (methylthio)benzene counterpart and demonstrate a previously unexplored application of hemilabile ligands to molecular electronics. 相似文献
9.
Shuning Cai Wenting Deng Feifei Huang Lijue Chen Chun Tang Wenxiang He Shichuan Long Ruihao Li Zhibing Tan Junyang Liu Jia Shi Zitong Liu Zongyuan Xiao Deqing Zhang Wenjing Hong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3869-3873
Photoresponsive molecular systems are essential for molecular optoelectronic devices, but most molecular building blocks are non‐photoresponsive. Employed here is a photoinduced proton transfer (PIPT) strategy to control charge transport through single‐molecule azulene junctions with visible light under ambient conditions, which leads to a reversible and controllable photoresponsive molecular device based on non‐photoresponsive molecules and a photoacid. Also demonstrated is the application of PIPT in two single‐molecule AND gate and OR gate devices with electrical signal as outputs. 相似文献
10.
Understanding electron transport through a single molecule bridging between metal electrodes is a central issue in the field of molecular electronics. This review covers the fabrication and electron‐transport properties of single π‐conjugated molecule junctions, which include benzene, fullerene, and π‐stacked molecules. The metal/molecule interface plays a decisive role in determining the stability and conductivity of single‐molecule junctions. The effect of the metal–molecule contact on the conductance of the single π‐conjugated molecule junction is reviewed. The characterization of the single benzene molecule junction is also discussed using inelastic electron tunneling spectroscopy and shot noise. Finally, electron transport through the π‐stacked system using π‐stacked aromatic molecules enclosed within self‐assembled coordination cages is reviewed. The electron transport in the π‐stacked systems is found to be efficient at the single‐molecule level, thus providing insight into the design of conductive materials. 相似文献
11.
Chao Zhan Gan Wang Xia‐Guang Zhang Zhi‐Hao Li Jun‐Ying Wei Yu Si Yang Yang Wenjing Hong Zhong‐Qun Tian 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(41):14676-14680
Adsorption plays a critical role in surface and interface processes. Fractional surface coverage and adsorption free energy are two essential parameters of molecular adsorption. However, although adsorption at the solid–gas interface has been well‐studied, and some adsorption models were proposed more than a century ago, challenges remain for the experimental investigation of molecular adsorption at the solid–liquid interface. Herein, we report the statistical and quantitative single‐molecule measurement of adsorption at the solid–liquid interface by using the single‐molecule break junction technique. The fractional surface coverage was extracted from the analysis of junction formation probability so that the adsorption free energy could be calculated by referring to the Langmuir isotherm. In the case of three prototypical molecules with terminal methylthio, pyridyl, and amino groups, the adsorption free energies were found to be 32.5, 33.9, and 28.3 kJ mol?1, respectively, which are consistent with DFT calculations. 相似文献
12.
Multichannel Conductance of Folded Single‐Molecule Wires Aided by Through‐Space Conjugation 下载免费PDF全文
Long Chen Ya‐Hao Wang Bairong He Han Nie Dr. Rongrong Hu Prof. Fei Huang Prof. Anjun Qin Dr. Xiao‐Shun Zhou Prof. Zujin Zhao Prof. Ben Zhong Tang 《Angewandte Chemie (International ed. in English)》2015,54(14):4231-4235
Deciphering charge transport through multichannel pathways in single‐molecule junctions is of high importance to construct nanoscale electronic devices and deepen insight into biological redox processes. Herein, we report two tailor‐made folded single‐molecule wires featuring intramolecular π–π stacking interactions. The scanning tunneling microscope (STM) based break‐junction technique and theoretical calculations show that through‐bond and through‐space conjugations are integrated into one single‐molecule wire, allowing for two simultaneous conducting channels in a single‐molecule junction. These folded molecules with stable π–π stacking interaction offer conceptual advances in single‐molecule multichannel conductance, and are perfect models for conductance studies in biological systems, organic thin films, and π‐stacked columnar aggregates. 相似文献
13.
Dr. Keiichi Katoh Hironari Isshiki Prof. Tadahiro Komeda Prof. Masahiro Yamashita 《化学:亚洲杂志》2012,7(6):1154-1169
Unlike electronics, which is based on the freedom of the charge of an electron whose memory is volatile, spintronics is based on the freedom of the charge, spin, and orbital of an electron whose memory is non‐volatile. Although in most GMR, TMR, and CMR systems, bulk or classical magnets that are composed of transition metals are used, this Focus Review considers the growing use of single‐molecule magnets (SMMs) that are composed of multinuclear metal complexes and nanosized magnets, which exhibit slow magnetic‐relaxation processes and quantum tunneling. Molecular spintronics, which combines spintronics and molecular electronics, is an emerging field of research. Using molecules is advantageous because their electronic and magnetic properties can be manipulated under specific conditions. Herein, recent developments in [LnPc]‐based multiple‐decker SMMs on surfaces for molecular spintronic devices are presented. First, we discuss the strategies for preparing single‐molecular‐memory devices by using SMMs. Next, we focus on the switching of the Kondo signal of [LnPc]‐based multiple‐decker SMMs that are adsorbed onto surfaces, their characterization by using STM and STS, and the relationship between the molecular structure, the electronic structure, and the Kondo resonance of [TbPc2]. Finally, the field‐effect‐transistor (FET) properties of surface‐adsorbed [LnPc2] and [Ln2Pc3] cast films are reported, which is the first step towards controlling SMMs through their spins for applications in single‐molecular memory and spintronics devices. 相似文献
14.
《化学:亚洲杂志》2017,12(7):730-733
An interesting physical phenomenon, electroluminescence, that was originally observed with a hydrocarbon molecule has recently been developed into highly efficient organic light‐emitting devices. These modern devices have evolved through the development of multi‐element molecular materials for specific roles, and hydrocarbon devices have been left unexplored. In this study, we report an efficient organic light‐emitting device composed solely of hydrocarbon materials. The electroluminescence was achieved in the blue region by efficient fluorescence and charge recombination within a simple single‐layer architecture of macrocyclic aromatic hydrocarbons. This study may stimulate further studies on hydrocarbons to uncover their full potential as electronic materials. 相似文献
15.
Polymer brushes have been widely used as functional surface coatings for broad applications including antifouling, energy storage, and lubrications. Understanding the molecule dynamics at polymer brush interfaces is important in unraveling the structure–property relationships in these materials and establishing a new materials design paradigm of novel functional polymer thin films with efficient interfacial transport. By applying modern fluorescence‐based single‐molecule spectroscopic and microscopic techniques, molecule dynamics at varied polymer brush interfaces have been experimentally investigated in recent years. New insights are given to the understandings of some unique and unusual materials properties of polymer brush thin films. This review summarizes some recent studies of molecular diffusion at polymer brush interfaces, highlights some new understandings of the interfacial properties of polymer brushes, and discusses future research opportunities in this field. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014 , 52, 85–103 相似文献
16.
State‐of‐the‐art applications of cyclodextrins as functional monomers in molecular imprinting techniques: a review 下载免费PDF全文
Sovichea Lay Xiaofeng Ni Haining Yu Shengrong Shen 《Journal of separation science》2016,39(12):2321-2331
As a versatile tool in separation science, cyclodextrins and their derivatives, known as emerging functional monomers, have been used extensively in molecular imprinting techniques. The attributes of cyclodextrins and their derivatives are widely known to form host–guest inclusion complex processes between the polymer and template. The exploitation of the imprinting technique could produce a product of molecularly imprinted polymers, which are very robust with long‐term stability, reliability, cost‐efficiency, and selectivity. Hence, molecularly imprinted polymers have gained popularity in chemical separation and analysis. Molecularly imprinted polymers containing either cyclodextrin or its derivatives demonstrate superior binding effects for a target molecule. As noted in the previous studies, the functional monomers of cyclodextrins and their derivatives have been used in molecular imprinting for selective separation with a wide range of chemical compounds, including steroidals, amino acids, polysaccharides, drugs, plant hormones, proteins, pesticides, and plastic additives. Therefore, the main goal of this review is to illustrate the exotic applications of imprinting techniques employing cyclodextrins and their derivatives as single or binary functional monomers in synthesizing molecularly imprinted polymers in areas of separation science by reviewing some of the latest studies reported in the literature. 相似文献
17.
Ta‐Cheng Ting Dr. Liang‐Yan Hsu Dr. Min‐Jie Huang Er‐Chien Horng Dr. Hao‐Cheng Lu Chan‐Hsiang Hsu Dr. Ching‐Hong Jiang Prof. Bih‐Yaw Jin Prof. Shie‐Ming Peng Prof. Chun‐hsien Chen 《Angewandte Chemie (International ed. in English)》2015,54(52):15734-15738
The use of single‐molecule junctions for various functions constitutes a central goal of molecular electronics. The functional features and the efficiency of electron transport are dictated by the degree of energy‐level alignment (ELA), that is, the offset potential between the electrode Fermi level and the frontier molecular orbitals. Examples manifesting ELA are rare owing to experimental challenges and the large energy barriers of typical model compounds. In this work, single‐molecule junctions of organometallic compounds with five metal centers joined in a collinear fashion were analyzed. The single‐molecule i–V scans could be conducted in a reliable manner, and the EFMO levels were electrochemically accessible. When the electrode Fermi level (EF) is close to the frontier orbitals (EFMO) of the bridging molecule, larger conductance was observed. The smaller |EF?EFMO| gap was also derived quantitatively, unambiguously confirming the ELA. The mechanism is described in terms of a two‐level model involving co‐tunneling and sequential tunneling processes. 相似文献
18.
Dr. Zhihai Li Dr. Manuel Smeu Sepideh Afsari Dr. Yangjun Xing Prof. Mark A. Ratner Prof. Eric Borguet 《Angewandte Chemie (International ed. in English)》2014,53(4):1098-1102
Sensors play a significant role in the detection of toxic species and explosives, and in the remote control of chemical processes. In this work, we report a single‐molecule‐based pH switch/sensor that exploits the sensitivity of dye molecules to environmental pH to build metal–molecule–metal (m‐M‐m) devices using the scanning tunneling microscopy (STM) break junction technique. Dyes undergo pH‐induced electronic modulation due to reversible structural transformation between a conjugated and a nonconjugated form, resulting in a change in the HOMO–LUMO gap. The dye‐mediated m‐M‐m devices react to environmental pH with a high on/off ratio (≈100:1) of device conductivity. Density functional theory (DFT) calculations, carried out under the non‐equilibrium Green’s function (NEGF) framework, model charge transport through these molecules in the two possible forms and confirm that the HOMO–LUMO gap of dyes is nearly twice as large in the nonconjugated form as in the conjugated form. 相似文献
19.
Ana Martín‐Lasanta Dr. Delia Miguel Trinidad García Prof. Dr. Juan A. López‐Villanueva Prof. Dr. Salvador Rodríguez‐Bolívar Dr. Francisco M. Gómez‐Campos Prof. Dr. Elena Buñuel Prof. Dr. Diego J. Cárdenas Dr. Luis Álvarez de Cienfuegos Prof. Dr. Juan M. Cuerva 《Chemphyschem》2012,13(3):860-868
One of the central issues of molecular electronics (ME) is the study of the molecule–metal electrode contacts, and their implications for the conductivity, charge‐transport mechanism, and mechanical stability. In fact, stochastic on/off switching (blinking) reported in STM experiments is a major problem of single‐molecule devices, and challenges the stability and reliability of these systems. Surprisingly, the ambiguous STM results all originate from devices that bind to the metallic electrode through a one‐atom connection. In the present work, DFT is employed to study and compare the properties of a set of simple acenes that bind to metallic electrodes with an increasing number of connections, in order to determine whether the increasing numbers of anchoring groups have a direct repercussion on the stability of these systems. The conductivities of the three polycyclic aromatic hydrocarbons are calculated, as well as their transmission spectra and current profiles. The thermal and mechanical stability of these systems is studied by pulling and pushing the metal–molecule connection. The results show that molecules with more than one connection per electrode exhibit greater electrical efficiency and current stability. 相似文献
20.
《Chemphyschem》2003,4(12):1335-1339
This article describes two‐terminal molecular switch tunnel junctions (MSTJs) which incorporate a semiconducting, single‐walled carbon nanotube (SWNT) as the bottom electrode. The nanotube interacts noncovalently with a monolayer of bistable, nondegenerate [2]catenane tetracations, self‐organized by their supporting amphiphilic dimyristoylphosphatidyl anions which shield the mechanically switchable tetracations from a two‐micrometer wide metallic top electrode. The resulting 0.002 μm2 area tunnel junction addresses a nanometer wide row of ≈2000 molecules. Active and remnant current–voltage measurements demonstrated that these devices can be reconfigurably switched and repeatedly cycled between high and low current states under ambient conditions. Control compounds, including a degenerate [2]catenane, were explored in support of the mechanical origin of the switching signature. These SWNT‐based MSTJs operate like previously reported silicon‐based MSTJs, but differently from similar devices incorporating bottom metal electrodes. The relevance of these results with respect to the choice of electrode materials for molecular electronics devices is discussed. 相似文献