1
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Zhang Y, Liu L, Tu B, Cui B, Guo J, Zhao X, Wang J, Yan Y. An artificial synapse based on molecular junctions. Nat Commun 2023; 14:247. [PMID: 36646674 PMCID: PMC9842743 DOI: 10.1038/s41467-023-35817-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 01/03/2023] [Indexed: 01/18/2023] Open
Abstract
Shrinking the size of the electronic synapse to molecular length-scale, for example, an artificial synapse directly fabricated by using individual or monolayer molecules, is important for maximizing the integration density, reducing the energy consumption, and enabling functionalities not easily achieved by other synaptic materials. Here, we show that the conductance of the self-assembled peptide molecule monolayer could be dynamically modulated by placing electrical biases, enabling us to implement basic synaptic functions. Both short-term plasticity (e.g., paired-pulse facilitation) and long-term plasticity (e.g., spike-timing-dependent plasticity) are demonstrated in a single molecular synapse. The dynamic current response is due to a combination of both chemical gating and coordination effects between Ag+ and hosting groups within peptides which adjusts the electron hopping rate through the molecular junction. In the end, based on the nonlinearity and short-term synaptic characteristics, the molecular synapses are utilized as reservoirs for waveform recognition with 100% accuracy at a small mask length.
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Affiliation(s)
- Yuchun Zhang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Lin Liu
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Bin Tu
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Bin Cui
- School of Physics, Shandong University, Jinan, 250100, China
| | - Jiahui Guo
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xing Zhao
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Jingyu Wang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yong Yan
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China. .,Department of Chemistry, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
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2
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Gupta R, Fereiro JA, Bayat A, Pritam A, Zharnikov M, Mondal PC. Nanoscale molecular rectifiers. Nat Rev Chem 2023; 7:106-122. [PMID: 37117915 DOI: 10.1038/s41570-022-00457-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/30/2022] [Indexed: 01/15/2023]
Abstract
The use of molecules bridged between two electrodes as a stable rectifier is an important goal in molecular electronics. Until recently, however, and despite extensive experimental and theoretical work, many aspects of our fundamental understanding and practical challenges have remained unresolved and prevented the realization of such devices. Recent advances in custom-designed molecular systems with rectification ratios exceeding 105 have now made these systems potentially competitive with existing silicon-based devices. Here, we provide an overview and critical analysis of recent progress in molecular rectification within single molecules, self-assembled monolayers, molecular multilayers, heterostructures, and metal-organic frameworks and coordination polymers. Examples of conceptually important and best-performing systems are discussed, alongside their rectification mechanisms. We present an outlook for the field, as well as prospects for the commercialization of molecular rectifiers.
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3
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Zhao Z, Soni S, Lee T, Nijhuis CA, Xiang D. Smart Eutectic Gallium-Indium: From Properties to Applications. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2203391. [PMID: 36036771 DOI: 10.1002/adma.202203391] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 07/30/2022] [Indexed: 05/27/2023]
Abstract
Eutectic gallium-indium (EGaIn), a liquid metal with a melting point close to or below room temperature, has attracted extensive attention in recent years due to its excellent properties such as fluidity, high conductivity, thermal conductivity, stretchability, self-healing capability, biocompatibility, and recyclability. These features of EGaIn can be adjusted by changing the experimental condition, and various composite materials with extended properties can be further obtained by mixing EGaIn with other materials. In this review, not only the are unique properties of EGaIn introduced, but also the working principles for the EGaIn-based devices are illustrated and the developments of EGaIn-related techniques are summarized. The applications of EGaIn in various fields, such as flexible electronics (sensors, antennas, electronic circuits), molecular electronics (molecular memory, opto-electronic switches, or reconfigurable junctions), energy catalysis (heat management, motors, generators, batteries), biomedical science (drug delivery, tumor therapy, bioimaging and neural interfaces) are reviewed. Finally, a critical discussion of the main challenges for the development of EGaIn-based techniques are discussed, and the potential applications in new fields are prospected.
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Affiliation(s)
- Zhibin Zhao
- Institute of Modern Optics and Center of Single Molecule Sciences, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, 300350, Tianjin, P. R. China
| | - Saurabh Soni
- Department of Molecules and Materials, MESA+ Institute for Nanotechnology, Molecules Center and Center for Brain-Inspired Nano Systems, Faculty of Science and Technology, University of Twente, Enschede, 7500 AE, The Netherlands
| | - Takhee Lee
- Department of Physics and Astronomy, Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Christian A Nijhuis
- Department of Molecules and Materials, MESA+ Institute for Nanotechnology, Molecules Center and Center for Brain-Inspired Nano Systems, Faculty of Science and Technology, University of Twente, Enschede, 7500 AE, The Netherlands
| | - Dong Xiang
- Institute of Modern Optics and Center of Single Molecule Sciences, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, 300350, Tianjin, P. R. China
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4
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Karuppannan SK, Nijhuis CA. A Method to Investigate the Mechanism of Charge Transport Across Bio-Molecular Junctions with Ferritin. Methods Mol Biol 2023; 2671:241-255. [PMID: 37308649 DOI: 10.1007/978-1-0716-3222-2_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
To investigate the mechanisms of charge transport (CT) across biomolecular tunnel junctions, it is required to make electrical contacts by a non-invasive method that leaves the biomolecules unaltered. Although different methods to form biomolecular junctions are available, here we describe the EGaIn-method because it allows us to readily form electrical contacts to monolayers of biomolecules in ordinary laboratory settings and to probe CT as a function of voltage, temperature, or magnetic field. This method relies on a non-Newtonian liquid-metal ally of Ga and In with a few nm thin layer of GaOx floating on its surface giving this material non-Newtonian properties allowing it to be shaped in to cone-shaped tips or stabilized in microchannels. These EGaIn structures form stable contacts to monolayers making it possible to investigate CT mechanisms across biomolecules in great detail.
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Affiliation(s)
- Senthil Kumar Karuppannan
- National Quantum Fables Foundry (NQFF), Institute of Materials Research and Engineering, Singapore, Singapore
| | - Christian A Nijhuis
- Hybrid Materials for Opto-Electronics Group, Department of Molecules and Materials, MESA+ Institute for Nanotechnology, Molecules Center and Center for Brain-Inspired Nano Systems, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands.
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5
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Khalid H, Opodi EM, Song X, Wang Z, Li B, Tian L, Yu X, Hu W. Modulated Structure and Rectification Properties of a Molecular Junction by a Mixed Self-Assembled Monolayer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:10893-10901. [PMID: 36007164 DOI: 10.1021/acs.langmuir.2c01751] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The organization of the self-assembled monolayer (SAM) determines its electronic structure and so governs the charge transport process and device performance when adopted into a molecular device. We report a systematic study on the supramolecular structure and rectification performance of the ferrocene (11-ferrocenyl-1-undecanethiol, FUT) based SAM modulated by mixed SAM with inert 1-undecanethiol (C11SH) as diluent. We compared mixed SAMs by two different post assembly strategies, i.e., post assembly of C11SH on FUT SAM and post assembly of FUT on C11SH SAM. The organization and structure of FUT in the mixed SAM were extensively studied by cyclic voltammetry (CV) using the Laviron model. Rectification properties of the mixed SAM obtained using eutectic indium gallium (EGaIn) as the top electrode revealed that the magnitude and stability of the rectification ratio (RR) strongly correlated to not only the amount but also the phase structure and orientation of the FUT in the monolayer, resulting in a tunable RR and increased stability. The mixed monolayer achieved an increased performance relative to pure FUT by post assembling FUT on C11SH SAM, which formed an optimally dense and well-packed monolayer with the FUT head resting on the top of the alkane SAM.
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Affiliation(s)
- Hira Khalid
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
| | - Esther Martine Opodi
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
| | - Xianneng Song
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
| | - Ziyan Wang
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
| | - Baili Li
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
| | - Lixian Tian
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
| | - Xi Yu
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
| | - Wenping Hu
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
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6
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Amini S, Chen X, Chua JQI, Tee JS, Nijhuis CA, Miserez A. Interplay between Interfacial Energy, Contact Mechanics, and Capillary Forces in EGaIn Droplets. ACS APPLIED MATERIALS & INTERFACES 2022; 14:28074-28084. [PMID: 35649179 PMCID: PMC9227710 DOI: 10.1021/acsami.2c04043] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Accepted: 05/16/2022] [Indexed: 06/01/2023]
Abstract
Eutectic gallium-indium (EGaIn) is increasingly employed as an interfacial conductor material in molecular electronics and wearable healthcare devices owing to its ability to be shaped at room temperature, conductivity, and mechanical stability. Despite this emerging usage, the mechanical and physical mechanisms governing EGaIn interactions with surrounding objects─mainly regulated by surface tension and interfacial adhesion─remain poorly understood. Here, using depth-sensing nanoindentation (DSN) on pristine EGaIn/GaOx surfaces, we uncover how changes in EGaIn/substrate interfacial energies regulate the adhesive and contact mechanic behaviors, notably the evolution of EGaIn capillary bridges with distinct capillary geometries and pressures. Varying the interfacial energy by subjecting EGaIn to different chemical environments and by functionalizing the tip with chemically distinct self-assembled monolayers (SAMs), we show that the adhesion forces between EGaIn and the solid substrate can be increased by up to 2 orders of magnitude, resulting in about a 60-fold increase in the elongation of capillary bridges. Our data reveal that by deploying molecular junctions with SAMs of different terminal groups, the trends of charge transport rates, the resistance of monolayers, and the contact interactions between EGaIn and monolayers from electrical characterizations are governed by the interfacial energies as well. This study provides a key understanding into the role of interfacial energy on geometrical characteristics of EGaIn capillary bridges, offering insights toward the fabrication of EGaIn junctions in a controlled fashion.
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Affiliation(s)
- Shahrouz Amini
- Department
of Biomaterials, Max Planck Institute of
Colloids and Interfaces, 14476 Potsdam, Germany
- Biological
and Biomimetic Materials Laboratory, Center for Sustainable Materials
(SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Xiaoping Chen
- Department
of Chemistry and Environment Science, Fujian Province Key Laboratory
of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000, China
- Department
of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Jia Qing Isaiah Chua
- Biological
and Biomimetic Materials Laboratory, Center for Sustainable Materials
(SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Jinq Shi Tee
- Department
of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Christian A. Nijhuis
- Department
of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Centre
for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
- Hybrid Materials
for Opto-Electronics Group, Department of Molecules and Materials,
MESA+ Institute for Nanotechnology and Molecules Centre, Faculty of Science and Technology, University of Twente, 7500 AE Enschede, The Netherlands
| | - Ali Miserez
- Biological
and Biomimetic Materials Laboratory, Center for Sustainable Materials
(SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 639798, Singapore
- School
of Biological Sciences, Nanyang Technological
University (NTU), 60
Nanyang Drive, Singapore 637551, Singapore
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7
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Qiu X, Chiechi RC. Printable logic circuits comprising self-assembled protein complexes. Nat Commun 2022; 13:2312. [PMID: 35484124 PMCID: PMC9050843 DOI: 10.1038/s41467-022-30038-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 04/08/2022] [Indexed: 11/09/2022] Open
Abstract
This paper describes the fabrication of digital logic circuits comprising resistors and diodes made from protein complexes and wired together using printed liquid metal electrodes. These resistors and diodes exhibit temperature-independent charge-transport over a distance of approximately 10 nm and require no encapsulation or special handling. The function of the protein complexes is determined entirely by self-assembly. When induced to self-assembly into anisotropic monolayers, the collective action of the aligned dipole moments increases the electrical conductivity of the ensemble in one direction and decreases it in the other. When induced to self-assemble into isotropic monolayers, the dipole moments are randomized and the electrical conductivity is approximately equal in both directions. We demonstrate the robustness and utility of these all-protein logic circuits by constructing pulse modulators based on AND and OR logic gates that function nearly identically to simulated circuits. These results show that digital circuits with useful functionality can be derived from readily obtainable biomolecules using simple, straightforward fabrication techniques that exploit molecular self-assembly, realizing one of the primary goals of molecular electronics. Proteins are promising molecular materials for next-generation electronic devices. Here, the authors fabricated printable digital logic circuits comprising resistors and diodes from self-assembled photosystem I complexes that enable pulse modulation.
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Affiliation(s)
- Xinkai Qiu
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands. .,Optoelectronics Group, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK.
| | - Ryan C Chiechi
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands. .,Department of Chemistry, North Carolina State University, Raleigh, NC, 27695-8204, United States.
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8
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Castilla-Amorós L, Chien TCC, Pankhurst JR, Buonsanti R. Modulating the Reactivity of Liquid Ga Nanoparticle Inks by Modifying Their Surface Chemistry. J Am Chem Soc 2022; 144:1993-2001. [DOI: 10.1021/jacs.1c12880] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Laia Castilla-Amorós
- Laboratory of Nanochemistry for Energy (LNCE), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1950 Sion, Switzerland
| | - Tzu-Chin Chang Chien
- Laboratory of Nanochemistry for Energy (LNCE), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1950 Sion, Switzerland
| | - James R. Pankhurst
- Laboratory of Nanochemistry for Energy (LNCE), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1950 Sion, Switzerland
| | - Raffaella Buonsanti
- Laboratory of Nanochemistry for Energy (LNCE), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1950 Sion, Switzerland
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9
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Han Y, Nickle C, Maglione MS, Karuppannan SK, Casado‐Montenegro J, Qi D, Chen X, Tadich A, Cowie B, Mas‐Torrent M, Rovira C, Cornil J, Veciana J, del Barco E, Nijhuis CA. Bias-Polarity-Dependent Direct and Inverted Marcus Charge Transport Affecting Rectification in a Redox-Active Molecular Junction. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:e2100055. [PMID: 34145786 PMCID: PMC8292891 DOI: 10.1002/advs.202100055] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 04/25/2021] [Indexed: 05/11/2023]
Abstract
This paper describes the transition from the normal to inverted Marcus region in solid-state tunnel junctions consisting of self-assembled monolayers of benzotetrathiafulvalene (BTTF), and how this transition determines the performance of a molecular diode. Temperature-dependent normalized differential conductance analyses indicate the participation of the HOMO (highest occupied molecular orbital) at large negative bias, which follows typical thermally activated hopping behavior associated with the normal Marcus regime. In contrast, hopping involving the HOMO dominates the mechanism of charge transport at positive bias, yet it is nearly activationless indicating the junction operates in the inverted Marcus region. Thus, within the same junction it is possible to switch between Marcus and inverted Marcus regimes by changing the bias polarity. Consequently, the current only decreases with decreasing temperature at negative bias when hopping is "frozen out," but not at positive bias resulting in a 30-fold increase in the molecular rectification efficiency. These results indicate that the charge transport in the inverted Marcus region is readily accessible in junctions with redox molecules in the weak coupling regime and control over different hopping regimes can be used to improve junction performance.
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Affiliation(s)
- Yingmei Han
- Department of ChemistryNational University of Singapore3 Science Drive 3Singapore117543Singapore
| | - Cameron Nickle
- Department of PhysicsUniversity of Central FloridaOrlandoFL32816USA
| | - Maria Serena Maglione
- Institut de Ciència de Materials de Barcelona (ICMAB‐CSIC)/CIBER‐BBNCampus de la UABBellaterra08193Spain
| | | | - Javier Casado‐Montenegro
- Institut de Ciència de Materials de Barcelona (ICMAB‐CSIC)/CIBER‐BBNCampus de la UABBellaterra08193Spain
| | - Dong‐Chen Qi
- Centre for Materials ScienceSchool of Chemistry and PhysicsQueensland University of TechnologyBrisbaneQueensland4001Australia
| | - Xiaoping Chen
- Department of ChemistryNational University of Singapore3 Science Drive 3Singapore117543Singapore
| | - Anton Tadich
- Australian Synchrotron ClaytonVictoria3168Australia
| | - Bruce Cowie
- Australian Synchrotron ClaytonVictoria3168Australia
| | - Marta Mas‐Torrent
- Institut de Ciència de Materials de Barcelona (ICMAB‐CSIC)/CIBER‐BBNCampus de la UABBellaterra08193Spain
| | - Concepció Rovira
- Institut de Ciència de Materials de Barcelona (ICMAB‐CSIC)/CIBER‐BBNCampus de la UABBellaterra08193Spain
| | - Jérôme Cornil
- Laboratory for Chemistry of Novel MaterialsUniversity of MonsPlace du Parc 20MonsB‐7000Belgium
| | - Jaume Veciana
- Institut de Ciència de Materials de Barcelona (ICMAB‐CSIC)/CIBER‐BBNCampus de la UABBellaterra08193Spain
| | | | - Christian A. Nijhuis
- Department of ChemistryNational University of Singapore3 Science Drive 3Singapore117543Singapore
- Centre for Advanced 2D Materials and Graphene Research CenterNational University of Singapore6 Science Drive 2Singapore117546Singapore
- Hybrid Materials for Opto‐Electronics GroupDepartment of Molecules and MaterialsMESA+ Institute for Nanotechnology and Center for Brain‐Inspired Nano SystemsFaculty of Science and TechnologyUniversity of TwenteP.O. Box 217EnschedeAE 7500The Netherlands
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10
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Castilla-Amorós L, Stoian D, Pankhurst JR, Varandili SB, Buonsanti R. Exploring the Chemical Reactivity of Gallium Liquid Metal Nanoparticles in Galvanic Replacement. J Am Chem Soc 2020; 142:19283-19290. [PMID: 33135885 DOI: 10.1021/jacs.0c09458] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Micron/nanosized particles of liquid metals possess intriguing properties and are gaining popularity for applications in various research fields. Nevertheless, the knowledge of their chemistry is still very limited compared to that of other classes of materials. In this work, we explore the reactivity of Ga nanoparticles (NPs) toward a copper molecular precursor to synthesize bimetallic Cu-Ga NPs. Anisotropic Cu-Ga nanodimers, where the two segregated domains of the constituent metals share an interface, form as the reaction product. Through a series of careful experiments, we demonstrate that a galvanic replacement reaction (GRR) between the Ga seeds and a copper-amine complex takes place. We attribute the final morphology of the bimetallic NPs, which is unusual for a GRR, to the presence of the native oxide shell around the Ga NPs and their liquid nature, via a mechanism that resembles the adhesion of bulk Ga drops to solid conductors. On the basis of this new knowledge, we also demonstrate that sequential GRRs to include more metal domains are possible. This study illustrates a new approach to the synthesis of Ga-based metal nanoparticles and provides the basis for its extension to many more systems with increased levels of complexity.
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Affiliation(s)
- Laia Castilla-Amorós
- Laboratory of Nanochemistry for Energy (LNCE), Department of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1950 Sion, Switzerland
| | - Dragos Stoian
- Laboratory of Nanochemistry for Energy (LNCE), Department of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1950 Sion, Switzerland
| | - James R Pankhurst
- Laboratory of Nanochemistry for Energy (LNCE), Department of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1950 Sion, Switzerland
| | - Seyedeh Behnaz Varandili
- Laboratory of Nanochemistry for Energy (LNCE), Department of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1950 Sion, Switzerland
| | - Raffaella Buonsanti
- Laboratory of Nanochemistry for Energy (LNCE), Department of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1950 Sion, Switzerland
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11
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Qiu X, Chiechi RC. Large-Area Molecular Junctions: Synthesizing Integrated Circuits for Next-Generation Nonvolatile Memory. TRENDS IN CHEMISTRY 2020. [DOI: 10.1016/j.trechm.2020.07.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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12
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Han Y, Nickle C, Zhang Z, Astier HPAG, Duffin TJ, Qi D, Wang Z, Del Barco E, Thompson D, Nijhuis CA. Electric-field-driven dual-functional molecular switches in tunnel junctions. NATURE MATERIALS 2020; 19:843-848. [PMID: 32483243 DOI: 10.1038/s41563-020-0697-5] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 04/28/2020] [Indexed: 05/24/2023]
Abstract
To avoid crosstalk and suppress leakage currents in resistive random access memories (RRAMs), a resistive switch and a current rectifier (diode) are usually combined in series in a one diode-one resistor (1D-1R) RRAM. However, this complicates the design of next-generation RRAM, increases the footprint of devices and increases the operating voltage as the potential drops over two consecutive junctions1. Here, we report a molecular tunnel junction based on molecules that provide an unprecedented dual functionality of diode and variable resistor, resulting in a molecular-scale 1D-1R RRAM with a current rectification ratio of 2.5 × 104 and resistive on/off ratio of 6.7 × 103, and a low drive voltage of 0.89 V. The switching relies on dimerization of redox units, resulting in hybridization of molecular orbitals accompanied by directional ion migration. This electric-field-driven molecular switch operating in the tunnelling regime enables a class of molecular devices where multiple electronic functions are preprogrammed inside a single molecular layer with a thickness of only 2 nm.
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Affiliation(s)
- Yingmei Han
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Cameron Nickle
- Department of Physics, University of Central Florida, Orlando, FL, USA
| | - Ziyu Zhang
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | | | - Thorin J Duffin
- Department of Chemistry, National University of Singapore, Singapore, Singapore
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Singapore
| | - Dongchen Qi
- Centre for Materials Science, School of Chemistry and Physics, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Zhe Wang
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Enrique Del Barco
- Department of Physics, University of Central Florida, Orlando, FL, USA.
| | - Damien Thompson
- Department of Physics, Bernal Institute, University of Limerick, Limerick, Ireland.
| | - Christian A Nijhuis
- Department of Chemistry, National University of Singapore, Singapore, Singapore.
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Singapore.
- Centre for Advanced 2D Materials and Graphene Research Center, National University of Singapore, Singapore, Singapore.
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13
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Qiu X, Ivasyshyn V, Qiu L, Enache M, Dong J, Rousseva S, Portale G, Stöhr M, Hummelen JC, Chiechi RC. Thiol-free self-assembled oligoethylene glycols enable robust air-stable molecular electronics. NATURE MATERIALS 2020; 19:330-337. [PMID: 31959952 DOI: 10.1038/s41563-019-0587-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 12/13/2019] [Indexed: 06/10/2023]
Abstract
Self-assembled monolayers (SAMs) are widely used to engineer the surface properties of metals. The relatively simple and versatile chemistry of metal-thiolate bonds makes thiolate SAMs the preferred option in a range of applications, yet fragility and a tendency to oxidize in air limit their long-term use. Here, we report the formation of thiol-free self-assembled mono- and bilayers of glycol ethers, which bind to the surface of coinage metals through the spontaneous chemisorption of glycol ether-functionalized fullerenes. As-prepared assemblies are bilayers presenting fullerene cages at both the substrate and ambient interface. Subsequent exposure to functionalized glycol ethers displaces the topmost layer of glycol ether-functionalized fullerenes, and the resulting assemblies expose functional groups to the ambient interface. These layers exhibit the key properties of thiolate SAMs, yet they are stable to ambient conditions for several weeks, as shown by the performance of tunnelling junctions formed from SAMs of alkyl-functionalized glycol ethers. Glycol ether-functionalized spiropyrans incorporated into mixed monolayers lead to reversible, light-driven conductance switching. Self-assemblies of glycol ethers are drop-in replacements for thiolate SAMs that retain all of their useful properties while avoiding the drawbacks of metal-thiolate bonds.
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Affiliation(s)
- Xinkai Qiu
- Stratingh Institute for Chemistry, University of Groningen, Groningen, the Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Viktor Ivasyshyn
- Stratingh Institute for Chemistry, University of Groningen, Groningen, the Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Li Qiu
- Stratingh Institute for Chemistry, University of Groningen, Groningen, the Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
- School of Materials Science and Engineering, Yunnan Key Laboratory for Micro/Nano Materials & Technology, Yunnan University, Kunming, China
| | - Mihaela Enache
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Jingjin Dong
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Sylvia Rousseva
- Stratingh Institute for Chemistry, University of Groningen, Groningen, the Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Giuseppe Portale
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Meike Stöhr
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Jan C Hummelen
- Stratingh Institute for Chemistry, University of Groningen, Groningen, the Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Ryan C Chiechi
- Stratingh Institute for Chemistry, University of Groningen, Groningen, the Netherlands.
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands.
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14
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Song H, Kim T, Kang S, Jin H, Lee K, Yoon HJ. Ga-Based Liquid Metal Micro/Nanoparticles: Recent Advances and Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1903391. [PMID: 31583849 DOI: 10.1002/smll.201903391] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 08/21/2019] [Indexed: 05/20/2023]
Abstract
Liquid metals are emerging as fluidic inorganic materials in various research fields. Micro- and nanoparticles of Ga and its alloys have received particular attention in the last decade due to their non toxicity and accessibility in ambient conditions as well as their interesting chemical, physical, mechanical, and electrical properties. Unique features such as a fluidic nature and self-passivating oxide skin make Ga-based liquid metal particles (LMPs) distinguishable from conventional inorganic particles in the context of synthesis and applications. Here, recent advances in the bottom-up and top-down synthetic methods of Ga-based LMPs, their physicochemical properties, and their applications are summarized. Finally, the current status of the LMPs is highlighted and perspectives on future directions are also provided.
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Affiliation(s)
- Hyunsun Song
- Department of Chemistry and Research Institute for Natural Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Taekyung Kim
- Department of Chemistry and Research Institute for Natural Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Seohyun Kang
- Department of Chemistry and Research Institute for Natural Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Haneul Jin
- Department of Chemistry and Research Institute for Natural Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Kwangyeol Lee
- Department of Chemistry and Research Institute for Natural Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Hyo Jae Yoon
- Department of Chemistry and Research Institute for Natural Sciences, Korea University, Seoul, 02841, Republic of Korea
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15
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Chen X, Hu H, Trasobares J, Nijhuis CA. Rectification Ratio and Tunneling Decay Coefficient Depend on the Contact Geometry Revealed by in Situ Imaging of the Formation of EGaIn Junctions. ACS APPLIED MATERIALS & INTERFACES 2019; 11:21018-21029. [PMID: 31117425 DOI: 10.1021/acsami.9b02033] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
This paper describes how the intensive (tunneling decay coefficient β and rectification ratio R) and extensive (current density J) properties of Ag-S(CH2) n-1CH3//GaO x/EGaIn junctions ( n = 10, 14, 18) and molecular diodes of the form of Ag-S(CH2)11Fc//GaO x/EGaIn depend on Ageo, the contact area between the self-assembled monolayer and the cone-shaped EGaIn tip. Large junctions with Ageo ≥ 1000 μm2 are unreliable and defects, such as pinholes, dominate the charge transport characteristics. For S(CH2)11Fc SAMs, R decreases from 130 to unity with increasing Ageo due to an increase in the leakage current (the current flowing across the junction at reverse bias when the diodes block current flow). The value of β decreases from 1.00 ± 0.06 n-1 to 0.70 ± 0.03 n-1 with increasing Ageo which also indicates that large junctions suffer from defects. Small junctions with Ageo ≤ 300 μm2 are not stable due to the high surface tension of the bulk EGaIn resulting in unstable EGaIn tips. In addition, the contact area for such small junctions is dominated by the rough tip apex reducing the effective contact area and reproducibility significantly. The contact area of very large junctions is dominated by the relatively smooth side walls of the tips. Our findings show that there is an optimum range for the value of Ageo between 300-500 μm2 where the electrical properties of the junctions are dominated by molecular effects. In this range of Ageo, the value of J (defined by I/ Ageo where I is the measured current) increases with Ageo until it plateaus for junctions with Ageo > 1000 μm2 in agreement with recently reported findings by the Whitesides group. In this regime reproducible measurements of J can be obtained provided Ageo is kept constant.
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Affiliation(s)
- Xiaoping Chen
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
| | - Hongting Hu
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
| | - Jorge Trasobares
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
| | - Christian A Nijhuis
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
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16
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Cai S, Deng W, Huang F, Chen L, Tang C, He W, Long S, Li R, Tan Z, Liu J, Shi J, Liu Z, Xiao Z, Zhang D, Hong W. Light‐Driven Reversible Intermolecular Proton Transfer at Single‐Molecule Junctions. Angew Chem Int Ed Engl 2019; 58:3829-3833. [DOI: 10.1002/anie.201813137] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 01/07/2019] [Indexed: 12/30/2022]
Affiliation(s)
- Shuning Cai
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Wenting Deng
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Feifei Huang
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Lijue Chen
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Chun Tang
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Wenxiang He
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Shichuan Long
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Ruihao Li
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Zhibing Tan
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Junyang Liu
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Jia Shi
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Zitong Liu
- Beijing National Laboratory for Molecular SciencesCAS Key Laboratory of Organic SolidsCAS Center of Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of Sciences Beijing 100190 China
| | - Zongyuan Xiao
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Deqing Zhang
- Beijing National Laboratory for Molecular SciencesCAS Key Laboratory of Organic SolidsCAS Center of Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of Sciences Beijing 100190 China
| | - Wenjing Hong
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
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17
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Cai S, Deng W, Huang F, Chen L, Tang C, He W, Long S, Li R, Tan Z, Liu J, Shi J, Liu Z, Xiao Z, Zhang D, Hong W. Light‐Driven Reversible Intermolecular Proton Transfer at Single‐Molecule Junctions. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201813137] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Shuning Cai
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Wenting Deng
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Feifei Huang
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Lijue Chen
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Chun Tang
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Wenxiang He
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Shichuan Long
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Ruihao Li
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Zhibing Tan
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Junyang Liu
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Jia Shi
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Zitong Liu
- Beijing National Laboratory for Molecular SciencesCAS Key Laboratory of Organic SolidsCAS Center of Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of Sciences Beijing 100190 China
| | - Zongyuan Xiao
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
| | - Deqing Zhang
- Beijing National Laboratory for Molecular SciencesCAS Key Laboratory of Organic SolidsCAS Center of Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of Sciences Beijing 100190 China
| | - Wenjing Hong
- State Key Laboratory of Physical Chemistry of Solid SurfacesCollege of Chemistry and Chemical Engineering, iChEMXiamen University Xiamen 361005 China
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18
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Ai Y, Kovalchuk A, Qiu X, Zhang Y, Kumar S, Wang X, Kühnel M, Nørgaard K, Chiechi RC. In-Place Modulation of Rectification in Tunneling Junctions Comprising Self-Assembled Monolayers. NANO LETTERS 2018; 18:7552-7559. [PMID: 30398891 PMCID: PMC6295922 DOI: 10.1021/acs.nanolett.8b03042] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 09/27/2018] [Indexed: 05/25/2023]
Abstract
This paper describes tunneling junctions comprising self-assembled monolayers that can be converted between resistor and diode functionality in-place. The rectification ratio is affected by the hydration of densely packed carboxylic acid groups at the interface between the top-contact and the monolayer. We studied this process by treatment with water and a water scavenger using three different top-contacts, eutectic Ga-In (EGaIn), conducting-probe atomic force microscopy (CP-AFM), and reduced graphene oxide (rGO), demonstrating that the phenomena is molecular in nature and is not platform-speciffc. We propose a mechanism in which the tunneling junctions convert to diode behavior through the lowering of the LUMO, which is suffcient to bring it close to resonance at positive bias, potentially assisted by a Stark shift. This shift in energy is supported by calculations and a change in polarization observed by X-ray photoelectron spectroscopy and Kelvin probe measurements. We demonstrate light-driven modulation using spiropyran as a photoacid, suggesting that any chemical process that is coupled to the release of small molecules that can tightly bind carboxylic acid groups can be used as an external stimulus to modulate rectification. The ability to convert a tunneling junction reversibly between a diode and a resistor via an effect that is intrinsic to the molecules in the junction extends the possible applications of Molecular Electronics to reconfigurable circuits and other new functionalities that do not have direct analogs in conventional semiconductor devices.
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Affiliation(s)
- Yong Ai
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747
AG Groningen, The Netherlands
| | - Andrii Kovalchuk
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747
AG Groningen, The Netherlands
| | - Xinkai Qiu
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747
AG Groningen, The Netherlands
| | - Yanxi Zhang
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747
AG Groningen, The Netherlands
| | - Sumit Kumar
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747
AG Groningen, The Netherlands
| | - Xintai Wang
- Nano-Science
Center & Department of Chemistry, University
of Copenhagen, Universitetsparken
5, DK-2100 Copenhagen, Denmark
| | - Martin Kühnel
- Nano-Science
Center & Department of Chemistry, University
of Copenhagen, Universitetsparken
5, DK-2100 Copenhagen, Denmark
| | - Kasper Nørgaard
- Nano-Science
Center & Department of Chemistry, University
of Copenhagen, Universitetsparken
5, DK-2100 Copenhagen, Denmark
| | - Ryan C. Chiechi
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747
AG Groningen, The Netherlands
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19
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Aragonès AC, Darwish N, Ciampi S, Jiang L, Roesch R, Ruiz E, Nijhuis CA, Díez-Pérez I. Control over Near-Ballistic Electron Transport through Formation of Parallel Pathways in a Single-Molecule Wire. J Am Chem Soc 2018; 141:240-250. [DOI: 10.1021/jacs.8b09086] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Albert C. Aragonès
- Department of Chemistry, Faculty of Natural & Mathematical Sciences, King’s College London, Britannia House, 7 Trinity Street, London SE1 1DB, United Kingdom
- Institut de Química Teòrica i Computacional (IQTC), Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| | - Nadim Darwish
- School of Molecular and Life Sciences, Curtin University, Bentley WA 6102, Australia
| | - Simone Ciampi
- School of Molecular and Life Sciences, Curtin University, Bentley WA 6102, Australia
| | - Li Jiang
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
| | - Raphael Roesch
- Center for Biosensors and Bioelectronics, Biodesign Institute, Arizona State University, Tempe, Arizona 85287, United States
| | - Eliseo Ruiz
- Institut de Química Teòrica i Computacional (IQTC), Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
- Departament de Química Inorgànica i Orgànica, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| | - Christian A. Nijhuis
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117546
| | - Ismael Díez-Pérez
- Department of Chemistry, Faculty of Natural & Mathematical Sciences, King’s College London, Britannia House, 7 Trinity Street, London SE1 1DB, United Kingdom
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20
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Chen YL, Nguyen Y, Wu SE, Chun YC, Chuang C, Hsieh YP, Hofmann M. Patterned liquid metal contacts for high density, stick-and-peel 2D material device arrays. NANOSCALE 2018; 10:14510-14515. [PMID: 30024009 DOI: 10.1039/c8nr02979b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Two-dimensional materials have shown great promise to enable novel wearable electronic devices ranging from sensors to energy generators. These developments are due to their high mechanical robustness, which allow them to retain high performance even at large deformations. Under these conditions, however, good electrical contacts become an important issue that cannot be addressed with conventional materials. Liquid metals could overcome this limitation by providing soft and compliant electrodes but to date no realistic heterointegration of nanomaterials and complex liquid metal contacts has been attempted. We here demonstrate the application of micrometer-sized electrical contacts to flexible, fragile and rough 2D materials using patterned liquid metal contacts. A novel deposition method enables the scalable and facile production of large arrays of contacts in arbitrary geometries. This ability permitted the single-step, fabrication-free and contamination-free production of concentric liquid metal-contacted graphene field effect transistors of comparable performance to traditional devices. We demonstrate that the contacts can be removed without damaging the 2D materials allowing the contacts to be reused. Finally, good contact could be made to complex morphologies and three-dimensional substrates, which highlights the potential of our approach to the characterization and application of nanomaterials in electronics.
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Affiliation(s)
- Yen-Lin Chen
- Department of Materials Science, National Cheng Kung University, Tainan 70101, Taiwan
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21
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Schmitz S, Kovalchuk A, Martín-Rodríguez A, van Leusen J, Izarova NV, Bourone SDM, Ai Y, Ruiz E, Chiechi RC, Kögerler P, Monakhov KY. Element-Selective Molecular Charge Transport Characteristics of Binuclear Copper(II)-Lanthanide(III) Complexes. Inorg Chem 2018; 57:9274-9285. [DOI: 10.1021/acs.inorgchem.8b01279] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sebastian Schmitz
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
| | - Andrew Kovalchuk
- Stratingh Institute for Chemistry & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747 AG, Netherlands
| | - Alejandro Martín-Rodríguez
- Departament de Química Inorgànica i Orgànica and Institut de Química Teòrica i Computacional, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| | - Jan van Leusen
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
| | - Natalya V. Izarova
- Jülich-Aachen Research Alliance (JARA-FIT) and Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52425 Jülich, Germany
| | - Svenja D. M. Bourone
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
| | - Yong Ai
- Stratingh Institute for Chemistry & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747 AG, Netherlands
| | - Eliseo Ruiz
- Departament de Química Inorgànica i Orgànica and Institut de Química Teòrica i Computacional, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| | - Ryan C. Chiechi
- Stratingh Institute for Chemistry & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747 AG, Netherlands
| | - Paul Kögerler
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
- Jülich-Aachen Research Alliance (JARA-FIT) and Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52425 Jülich, Germany
| | - Kirill Yu. Monakhov
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
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22
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Xie Z, Bâldea I, Frisbie CD. Why one can expect large rectification in molecular junctions based on alkane monothiols and why rectification is so modest. Chem Sci 2018; 9:4456-4467. [PMID: 29896387 PMCID: PMC5956982 DOI: 10.1039/c8sc00938d] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 04/07/2018] [Indexed: 11/23/2022] Open
Abstract
Many attempts to obtain high current rectification ratios (RRs) in molecular electronics are triggered by a potentiometer rule argument, which predicts that a strongly asymmetric location of the dominant molecular orbital yields large RR-values. Invoking this argument, molecular junctions based on alkane monothiols (CnT) can be expected to exhibit high RRs; the HOMO of these molecules is localized on the thiol terminal group bonded to one electrode. The extensive current-voltage (I-V) results for CP-AFM (conducting probe atomic force microscope) CnT junctions of various molecular lengths (n = 7, 8, 9, 10, and 12) and different metallic contacts (Ag, Au, and Pt) are consistent with conduction dominated by the HOMO, but the measured RR ∼ 1.5 is much smaller than that predicted by the potentiometer rule framework. Further, the linear shift in the HOMO position with applied bias, γ, which gives rise to rectification, is also smaller than expected, and critically, γ has the opposite sign from potentiometer rule predictions. Companion ab initio OVGF (outer valence Green's function) quantum chemical calculations provide important insight. Namely, a linear Stark shift γm is calculated for the HOMO of CnT molecules for electric field strengths (106-107 V cm-1) typical of molecular junctions, and the sign of γm matches the sign of the experimental γ for junctions derived from transport measurements, suggesting that the Stark effect plays an important role. However, the magnitude of the measured γ is only 10-15% of the computed value γm. We propose that this implies that the contacts are far from optimal; they substantially screen the effect of the applied bias, possibly via molecule-electrode interface states. We predict that, with optimized contacts, the rectification ratios in CnT-based junctions can reach reasonably high values (RR ≈ 500). We believe that Stark shifts and limited current rectification due to non-ideal contacts discussed here for the specific case of alkane monothiol junctions are issues of general interest for molecular electronics that deserve further consideration.
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Affiliation(s)
- Zuoti Xie
- Department of Chemical Engineering and Materials Science , Department of Chemistry , University of Minnesota , Minneapolis , Minnesota 55455 , USA .
| | - Ioan Bâldea
- Theoretische Chemie , Universität Heidelberg , INF 229 , D-69120 Heidelberg , Germany .
| | - C Daniel Frisbie
- Department of Chemical Engineering and Materials Science , Department of Chemistry , University of Minnesota , Minneapolis , Minnesota 55455 , USA .
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23
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Yuan L, Wang L, Garrigues AR, Jiang L, Annadata HV, Anguera Antonana M, Barco E, Nijhuis CA. Transition from direct to inverted charge transport Marcus regions in molecular junctions via molecular orbital gating. NATURE NANOTECHNOLOGY 2018; 13:322-329. [PMID: 29581549 DOI: 10.1038/s41565-018-0068-4] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 01/17/2018] [Indexed: 05/25/2023]
Abstract
Solid-state molecular tunnel junctions are often assumed to operate in the Landauer regime, which describes essentially activationless coherent tunnelling processes. In solution, on the other hand, charge transfer is described by Marcus theory, which accounts for thermally activated processes. In practice, however, thermally activated transport phenomena are frequently observed also in solid-state molecular junctions but remain poorly understood. Here, we show experimentally the transition from the Marcus to the inverted Marcus region in a solid-state molecular tunnel junction by means of intra-molecular orbital gating that can be tuned via the chemical structure of the molecule and applied bias. In the inverted Marcus region, charge transport is incoherent, yet virtually independent of temperature. Our experimental results fit well to a theoretical model that combines Landauer and Marcus theories and may have implications for the interpretation of temperature-dependent charge transport measurements in molecular junctions.
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Affiliation(s)
- Li Yuan
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Lejia Wang
- Department of Chemistry, National University of Singapore, Singapore, Singapore
- School of Materials and Chemical Engineering, Ningbo University of Technology, Ningbo, China
| | - Alvar R Garrigues
- Department of Physics, University of Central Florida, Orlando, Florida, USA
| | - Li Jiang
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | | | | | - Enrique Barco
- Department of Physics, University of Central Florida, Orlando, Florida, USA.
| | - Christian A Nijhuis
- Department of Chemistry, National University of Singapore, Singapore, Singapore.
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore.
- NUSNNI-Nanocore, National University of Singapore, Singapore, Singapore.
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24
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Sangeeth CSS, Jiang L, Nijhuis CA. Bottom-electrode induced defects in self-assembled monolayer (SAM)-based tunnel junctions affect only the SAM resistance, not the contact resistance or SAM capacitance. RSC Adv 2018; 8:19939-19949. [PMID: 35541643 PMCID: PMC9080736 DOI: 10.1039/c8ra01513a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 05/14/2018] [Indexed: 12/22/2022] Open
Abstract
In large area molecular junctions, defects are always present and can be caused by impurities and/or defects in the electrode materials and/or SAMs, but how they affect the electrical characteristics of junctions has rarely been studied. Usually, junctions are characterized by two-terminal current–voltage measurements where only the total current across the junction is measured, but with these methods one cannot distinguish how the individual components of the junctions are altered by the defects. Here we show that the roughness of the bottom-electrode is a crucial factor in determining the electrical properties of self-assembled monolayer (SAM)-based junctions. We used potentiodynamic impedance spectroscopy to reveal which components of the junctions are altered by defective bottom electrodes because this method allows for direct determination of all components that impede charge transport in the equivalent circuit of the junctions. We intentionally introduced defects via the roughness of the bottom electrode and found that these defects lower the SAM resistance but they do not alter the capacitance of the SAM or the contact resistance of the junction. In other words, defective junctions can be seen as “leaky capacitors” resulting in an underestimation of the SAM resistance of two orders of magnitude. These results help to improve the interpretation of data generated by SAM-based junctions and explain in part the observed large spread of reported tunneling rates for the same molecules measured across different platforms. In large area molecular junctions, defects are always present and can be caused by impurities and/or defects in the electrode materials and/or SAMs, but how they affect the electrical characteristics of junctions has rarely been studied.![]()
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Affiliation(s)
| | - Li Jiang
- Department of Chemistry
- National University of Singapore
- Singapore 117543
- Singapore
| | - Christian A. Nijhuis
- Department of Chemistry
- National University of Singapore
- Singapore 117543
- Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre
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25
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Jeong H, Kim D, Xiang D, Lee T. High-Yield Functional Molecular Electronic Devices. ACS NANO 2017; 11:6511-6548. [PMID: 28578582 DOI: 10.1021/acsnano.7b02967] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
An ultimate goal of molecular electronics, which seeks to incorporate molecular components into electronic circuit units, is to generate functional molecular electronic devices using individual or ensemble molecules to fulfill the increasing technical demands of the miniaturization of traditional silicon-based electronics. This review article presents a summary of recent efforts to pursue this ultimate aim, covering the development of reliable device platforms for high-yield ensemble molecular junctions and their utilization in functional molecular electronic devices, in which distinctive electronic functionalities are observed due to the functional molecules. In addition, other aspects pertaining to the practical application of molecular devices such as manufacturing compatibility with existing complementary metal-oxide-semiconductor technology, their integration, and flexible device applications are also discussed. These advances may contribute to a deeper understanding of charge transport characteristics through functional molecular junctions and provide a desirable roadmap for future practical molecular electronics applications.
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Affiliation(s)
- Hyunhak Jeong
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University , Seoul 08826, Korea
| | - Dongku Kim
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University , Seoul 08826, Korea
| | - Dong Xiang
- Key Laboratory of Optical Information Science and Technology, Institute of Modern Optics, College of Electronic Information and Optical Engineering, Nankai University , Tianjin 300071, China
| | - Takhee Lee
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University , Seoul 08826, Korea
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26
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Zhang Y, Qiu X, Gordiichuk P, Soni S, Krijger TL, Herrmann A, Chiechi RC. Mechanically and Electrically Robust Self-Assembled Monolayers for Large-Area Tunneling Junctions. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2017; 121:14920-14928. [PMID: 28729893 PMCID: PMC5512119 DOI: 10.1021/acs.jpcc.7b03853] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 06/12/2017] [Indexed: 05/28/2023]
Abstract
This paper examines the relationship between mechanical deformation and the electronic properties of self-assembled monolayers (SAMs) of the oligothiophene 4-([2,2':5',2″:5″,2‴-quaterthiophen]-5-yl)butane-1-thiol (T4C4) in tunneling junctions using conductive probe atomic force microscopy (CP-AFM) and eutectic Ga-In (EGaIn). We compared shifts in conductivity, transition voltages of T4C4 with increasing AFM tip loading force to alkanethiolates. While these shifts result from an increasing tilt angle from penetration of the SAM by the AFM tip for the latter, we ascribe them to distortions of the π system present in T4C4, which is more mechanically robust than alkanethiolates of comparable length; SAMs comprising T4C4 shows about five times higher Young's modulus than alkanethiolates. Density functional theory calculations confirm that mechanical deformations shift the barrier height due to changes in the frontier orbitals caused by small rearrangements to the conformation of the quaterthiophene moiety. The mechanical robustness of T4C4 manifests as an increased tolerance to high bias in large-area EGaIn junctions suggesting that electrostatic pressure plays a significant role in the shorting of molecular junctions at high bias.
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Affiliation(s)
- Yanxi Zhang
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Xinkai Qiu
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Pavlo Gordiichuk
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Saurabh Soni
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Theodorus L. Krijger
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Andreas Herrmann
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Ryan C. Chiechi
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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27
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Xie Z, Bâldea I, Demissie AT, Smith CE, Wu Y, Haugstad G, Frisbie CD. Exceptionally Small Statistical Variations in the Transport Properties of Metal–Molecule–Metal Junctions Composed of 80 Oligophenylene Dithiol Molecules. J Am Chem Soc 2017; 139:5696-5699. [DOI: 10.1021/jacs.7b01918] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
| | - Ioan Bâldea
- Theoretical
Chemistry, Heidelberg University, INF 229, D-69120 Heidelberg, Germany
- Institute of Space Sciences, NILPRP, RO 077125 Bucharest-Măgurele, Romania
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28
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Thompson D, Nijhuis CA. Even the Odd Numbers Help: Failure Modes of SAM-Based Tunnel Junctions Probed via Odd-Even Effects Revealed in Synchrotrons and Supercomputers. Acc Chem Res 2016; 49:2061-2069. [PMID: 27598413 DOI: 10.1021/acs.accounts.6b00256] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This Account describes a body of research in atomic level design, synthesis, physicochemical characterization, and macroscopic electrical testing of molecular devices made from ferrocene-functionalized alkanethiol molecules, which are molecular diodes, with the aim to identify, and resolve, the failure modes that cause leakage currents. The mismatch in size between the ferrocene headgroup and alkane rod makes waxlike highly dynamic self-assembled monolayers (SAMs) on coinage metals that show remarkable atomic-scale sensitivity in their electrical properties. Our results make clear that molecular tunnel junction devices provide an excellent testbed to probe the electronic and supramolecular structures of SAMs on inorganic substrates. Contacting these SAMs to a eutectic "EGaIn" alloy top-electrode, we designed highly stable long-lived molecular switches of the form electrode-SAM-electrode with robust rectification ratios of up to 3 orders of magnitude. The graphic that accompanies this conspectus displays a computed SAM packing structure, illustrating the lollipop shape of the molecules that gives dynamic SAM supramolecular structures and also the molecule-electrode van der Waals (vdW) contacts that must be controlled to form good SAM-based devices. In this Account, we first trace the evolution of SAM-based electronic devices and rationalize their operation using energy level diagrams. We describe the measurement of device properties using near edge X-ray absorption fine structure spectroscopy, cyclic voltammetry, and X-ray photoelectron spectroscopy complemented by molecular dynamics and electronic structure calculations together with large numbers of electrical measurements. We discuss how data obtained from these combined experimental/simulation codesign studies demonstrate control over the supramolecular and electronic structure of the devices, tuning odd-even effects to optimize inherent packing tendencies of the molecules in order to minimize leakage currents in the junctions. It is now possible, but still very costly to create atomically smooth electrodes and we discuss progress toward masking electrode imperfections using cooperative molecule-electrode contacts that are only accessible by dynamic SAM structures. Finally, the unique ability of SAM devices to achieve simultaneously high and atom-sensitive electrical switching is summarized and discussed. While putting these structures to work as real world electronic devices remains very challenging, we speculate on the scientific and technological advances that are required to further improve electronic and supramolecular structure, toward the creation of high yields of long-lived molecular devices with (very) large, reproducible rectification ratios.
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Affiliation(s)
- Damien Thompson
- Department
of Physics, Bernal Institute, University of Limerick, Limerick V94 T9PX, Ireland
| | - Christian A. Nijhuis
- Department
of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117546
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29
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Kumar S, van Herpt J, Gengler RYN, Feringa BL, Rudolf P, Chiechi RC. Mixed Monolayers of Spiropyrans Maximize Tunneling Conductance Switching by Photoisomerization at the Molecule-Electrode Interface in EGaIn Junctions. J Am Chem Soc 2016; 138:12519-26. [PMID: 27602432 PMCID: PMC5053170 DOI: 10.1021/jacs.6b06806] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Indexed: 01/19/2023]
Abstract
This paper describes the photoinduced switching of conductance in tunneling junctions comprising self-assembled monolayers of a spiropyran moiety using eutectic Ga-In top contacts. Despite separation of the spiropyran unit from the electrode by a long alkyl ester chain, we observe an increase in the current density J of a factor of 35 at 1 V when the closed form is irradiated with UV light to induce the ring-opening reaction, one of the highest switching ratios reported for junctions incorporating self-assembled monolayers. The magnitude of switching of hexanethiol mixed monolayers was higher than that of pure spiropyran monolayers. The first switching event recovers 100% of the initial value of J and in the mixed-monolayers subsequent dampening is not the result of degradation of the monolayer. The observation of increased conductivity is supported by zero-bias DFT calculations showing a change in the localization of the density of states near the Fermi level as well as by simulated transmission spectra revealing positive resonances that broaden and shift toward the Fermi level in the open form.
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Affiliation(s)
- Sumit Kumar
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Jochem
T. van Herpt
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Régis Y. N. Gengler
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Ben L. Feringa
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Petra Rudolf
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Ryan C. Chiechi
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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