共查询到20条相似文献,搜索用时 15 毫秒
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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
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《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
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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
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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
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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
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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
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(25):7232-7235
To enable the investigation of low‐affinity biomolecular complexes with confocal single‐molecule spectroscopy, we have developed a microfluidic device that allows a concentrated sample to be diluted by up to five orders of magnitude within milliseconds, at the physical limit dictated by diffusion. We demonstrate the capabilities of the device by studying the dissociation kinetics and structural properties of low‐affinity protein complexes using single‐molecule two‐color and three‐color Förster resonance energy transfer (FRET). We show that the versatility of the device makes it suitable for studying complexes with dissociation constants from low nanomolar up to 10 μm , thus covering a wide range of biomolecular interactions. The design and precise fabrication of the devices ensure simple yet reliable operation and high reproducibility of the results. 相似文献
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Song Zhang Hu‐jun Qian Zhonghua Liu Hongyu Ju Zhong‐yuan Lu Haiming Zhang Lifeng Chi Shuxun Cui 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(6):1673-1677
Since the discovery of amorphous red phosphorus (a‐red P) in 1847, many possible structures have been proposed. However, the exact molecular structure has not yet been determined because of its amorphous nature. Herein several methods are used to investigate basic properties of a‐red P. Data from scanning tunneling microscopy (STM) and gel permeation chromatography (GPC) confirm that a‐red P is a linear inorganic polymer with a broad molecular weight distribution. The theoretical single‐molecule elasticities of the possible a‐red P structures are obtained by quantum mechanical (QM) calculations. The experimental single‐molecule elasticity of a‐red P measured by single‐molecule AFM matches with the theoretical result of the zig‐zag ladder structure, indicating that a‐red P may adopt this structure. Although this conclusion needs further validation, this fundamental study represents progress towards solving the structure of a‐red P. It is expected that the strategy utilized in this work can be applied to study other inorganic polymers. 相似文献
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Feng Jiang Douglas I. Trupp Norah Algethami Haining Zheng Wenxiang He Afaf Alqorashi Chenxu Zhu Chun Tang Ruihao Li Junyang Liu Hatef Sadeghi Jia Shi Ross Davidson Marcus Korb Alexandre N. Sobolev Masnun Naher Sara Sangtarash Paul J. Low Wenjing Hong Colin J. Lambert 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19163-19169
Together with the more intuitive and commonly recognized conductance mechanisms of charge‐hopping and tunneling, quantum‐interference (QI) phenomena have been identified as important factors affecting charge transport through molecules. Consequently, establishing simple and flexible molecular‐design strategies to understand, control, and exploit QI in molecular junctions poses an exciting challenge. Here we demonstrate that destructive quantum interference (DQI) in meta‐substituted phenylene ethylene‐type oligomers (m‐OPE) can be tuned by changing the position and conformation of methoxy (OMe) substituents at the central phenylene ring. These substituents play the role of molecular‐scale taps, which can be switched on or off to control the current flow through a molecule. Our experimental results conclusively verify recently postulated magic‐ratio and orbital‐product rules, and highlight a novel chemical design strategy for tuning and gating DQI features to create single‐molecule devices with desirable electronic functions. 相似文献
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