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Krzykawska A, Wróbel M, Kozieł K, Cyganik P. N-Heterocyclic Carbenes for the Self-Assembly of Thin and Highly Insulating Monolayers with High Quality and Stability. ACS NANO 2020; 14:6043-6057. [PMID: 32343123 DOI: 10.1021/acsnano.0c01733] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
As an organic nanostructure, self-assembled monolayers (SAMs) play a central role in many aspects of nanotechnology, including molecular electronics. In this work, we show that SAMs based on N-heterocyclic carbenes on a Au(111) substrate offer a high level of crystallinity and also exhibit the highest possible packing density. As a result of this structural optimization, defect concentrations were reduced by 2-3 orders of magnitude and thermal stability was ∼100 K higher than those of any other SAMs on Au. The conductivity of these SAMs is ∼4 orders of magnitude lower than that of standard alkanethiols of comparable length, which together with very low defect concentration and high thermal stability makes them a highly interesting material for potential application in organic thin film transistors. The self-assembly of such dense, highly crystalline, and notably stable structures is associated with strong C-Au bonding and the rational design of assembled molecules, resulting in the high mobility of both adsorbate and substrate atoms, as confirmed by the size of the molecular domains and the adsorbate-driven modification of the Au(111) substrate, respectively.
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Affiliation(s)
- Anna Krzykawska
- Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Krakow, Poland
| | - Mateusz Wróbel
- Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Krakow, Poland
| | - Krzysztof Kozieł
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland
| | - Piotr Cyganik
- Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Krakow, Poland
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2
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Ghosh M, Yang DS. Structures of self-assembled n-alkanethiols on gold by reflection high-energy electron diffraction. Phys Chem Chem Phys 2020; 22:17325-17335. [DOI: 10.1039/d0cp02866e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structures of long-chain alkanethiols (C18H37SH) chemisorbed on an Au(111) single crystal were investigated using reflection high-energy electron diffraction (RHEED).
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Affiliation(s)
- Mithun Ghosh
- Department of Chemistry
- University of Houston
- Houston
- USA
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3
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Besharat Z, Ghadami Yazdi M, Wakeham D, Johnson M, Rutland MW, Göthelid M, Grönbeck H. Se-C Cleavage of Hexane Selenol at Steps on Au(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:2630-2636. [PMID: 29405715 DOI: 10.1021/acs.langmuir.7b03713] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Selenols are considered as an alternative to thiols in self-assembled monolayers, but the Se-C bond is one limiting factor for their usefulness. In this study, we address the stability of the Se-C bond by a combined experimental and theoretical investigation of gas-phase-deposited hexane selenol (CH3(CH2)5SeH) on Au(111) using photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory (DFT). Experimentally, we find that initial adsorption leaves atomic Se on the surface without any carbon left on the surface, whereas further adsorption generates a saturated selenolate layer. The Se 3d component from atomic Se appears at 0.85 eV lower binding energy than the selenolate-related component. DFT calculations show that the most stable structure of selenols on Au(111) is in the form of RSe-Au-SeR complexes adsorbed on the unreconstructed Au(111) surface. This is similar to thiols on Au(111). Calculated Se 3d core-level shifts between elemental Se and selenolate in this structure nicely reproduce the experimentally recorded shifts. Dissociation of RSeH and subsequent formation of RH are found to proceed with high barriers on defect-free Au(111) terraces, with the highest barrier for scissoring R-Se. However, at steps, these barriers are considerably lower, allowing for Se-C bond breaking and hexane desorption, leaving elemental Se at the surface. Hexane is formed by replacing the Se-C bond with a H-C bond by using the hydrogen liberated from the selenol to selenolate transformation.
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Affiliation(s)
- Zahra Besharat
- Material Physics, MNF, SCI, KTH Royal Institute of Technology , Stockholm SE-164 40, Sweden
- Department of Chemistry, Division of Surface and Corrosion Science, KTH Royal Institute of Technology , Stockholm SE-100 44, Sweden
| | - Milad Ghadami Yazdi
- Material Physics, MNF, SCI, KTH Royal Institute of Technology , Stockholm SE-164 40, Sweden
| | - Deborah Wakeham
- Department of Chemistry, Division of Surface and Corrosion Science, KTH Royal Institute of Technology , Stockholm SE-100 44, Sweden
| | - Magnus Johnson
- Department of Chemistry, Division of Surface and Corrosion Science, KTH Royal Institute of Technology , Stockholm SE-100 44, Sweden
| | - Mark W Rutland
- Department of Chemistry, Division of Surface and Corrosion Science, KTH Royal Institute of Technology , Stockholm SE-100 44, Sweden
- Chemistry, Materials and Surfaces, SP Technical Research Institute of Sweden , Box 5607, Stockholm SE-114 86, Sweden
| | - Mats Göthelid
- Material Physics, MNF, SCI, KTH Royal Institute of Technology , Stockholm SE-164 40, Sweden
| | - Henrik Grönbeck
- Department of Physics and Competence Centre for Catalysis, Chalmers University of Technology , Göteborg SE-412 96, Sweden
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4
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Olivieri G, Goel A, Kleibert A, Cvetko D, Brown MA. Quantitative ionization energies and work functions of aqueous solutions. Phys Chem Chem Phys 2018; 18:29506-29515. [PMID: 27747349 DOI: 10.1039/c6cp05682b] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Despite the ubiquitous nature of aqueous solutions across the chemical, biological and environmental sciences our experimental understanding of their electronic structure is rudimentary-qualitative at best. One of the most basic and seemingly straightforward properties of aqueous solutions-ionization energies-are (qualitatively) tabulated at the water-air interface for a mere handful of solutes, and the manner in which these results are obtained assume the aqueous solutions behave like a gas in the photoelectron experiment (where the vacuum levels of the aqueous solution and of the photoelectron analyzer are equilibrated). Here we report the experimental measure of a sizeable offset (ca. 0.6 eV) between the vacuum levels of an aqueous solution (0.05 M NaCl) and that of our photoelectron analyzer, indicating a breakdown of the gas-like vacuum level alignment assumption for the aqueous solution. By quantifying the vacuum level offset as a function of solution chemical composition our measurements enable, for the first time, quantitative determination of ionization energies in liquid solutions. These results reveal that the ionization energy of liquid water is not independent of the chemical composition of the solution as is usually inferred in the literature, a finding that has important ramifications as measured ionization energies are frequently used to validate theoretical models that posses the ability to provide microscopic insight not directly available by experiment. Finally, we derive the work function, or the electrochemical potential of the aqueous solution and show that it too varies with the chemical composition of the solution.
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Affiliation(s)
- Giorgia Olivieri
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, Switzerland.
| | - Alok Goel
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, Switzerland.
| | - Armin Kleibert
- Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland
| | - Dean Cvetko
- Faculty for Mathematics and Physics, University of Ljubljana and Jožef Stefan Institute, Ljubljana, Slovenia
| | - Matthew A Brown
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, Switzerland.
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5
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Chen J, Wang Z, Oyola-Reynoso S, Thuo MM. Properties of Self-Assembled Monolayers Revealed via Inverse Tensiometry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:13451-13467. [PMID: 28777587 DOI: 10.1021/acs.langmuir.7b01937] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Self-assembled monolayers (SAMs) have emerged as a simple platform technology and hence have been broadly studied. With advances in state-of-the-art fabrication and characterization methods, new insights into SAM structure and related properties have been delineated, albeit with some discrepancies and/or incoherencies. Some discrepancies, especially between experimental and theoretical work, are in part due to the misunderstanding of subtle structural features such as phase evolution and SAM quality. Recent work has, however, shown that simple techniques, such as the measurement of static contact angles, can be used to delineate otherwise complex properties of the SAM, especially when complemented by other more advanced techniques. In this article, we highlight the effect of nanoscale substrate asperities and molecular chain length on the SAM structure and associated properties. First, surfaces with tunable roughness are prepared on both Au and Ag, and their corresponding n-alkanethiolate SAMs are characterized through wetting and spectroscopy. From these data, chain-length- and substrate-morphology-dependent limits to the odd-even effect (structure and properties vary with the number of carbons in the molecules and the nature of the substrate), parametrization of gauche defect densities, and structural phase evolution (liquidlike, waxy, crystalline interfaces) are deduced. An evaluation of the correlation between the effect of roughness and the components of surface tension (polar-γp and dispersive-γd) reveals that wetting, at nanoscale rough surfaces, evolves proportionally with the ratio of the two components of surface tension. The evolution of conformational order is captured over a range of molecular lengths and parametrized through a dimensionless number, χc. By deploying a well-known tensiometry technique (herein the liquid is used to characterize the solid, hence the term inverse tensiometry) to characterize SAMs, we demonstrate that complex molecular-level phenomena in SAMs can be understood through simplicity.
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Affiliation(s)
- Jiahao Chen
- Department of Materials Science and Engineering, Iowa State University , 2220 Hoover Hall, Ames, Iowa 50011, United States
| | - Zhengjia Wang
- Department of Materials Science and Engineering, Iowa State University , 2220 Hoover Hall, Ames, Iowa 50011, United States
| | - Stephanie Oyola-Reynoso
- Department of Materials Science and Engineering, Iowa State University , 2220 Hoover Hall, Ames, Iowa 50011, United States
| | - Martin M Thuo
- Department of Materials Science and Engineering, Iowa State University , 2220 Hoover Hall, Ames, Iowa 50011, United States
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Slaughter LS, Cheung KM, Kaappa S, Cao HH, Yang Q, Young TD, Serino AC, Malola S, Olson JM, Link S, Häkkinen H, Andrews AM, Weiss PS. Patterning of supported gold monolayers via chemical lift-off lithography. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2017; 8:2648-2661. [PMID: 29259879 PMCID: PMC5727779 DOI: 10.3762/bjnano.8.265] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 11/24/2017] [Indexed: 05/19/2023]
Abstract
The supported monolayer of Au that accompanies alkanethiolate molecules removed by polymer stamps during chemical lift-off lithography is a scarcely studied hybrid material. We show that these Au-alkanethiolate layers on poly(dimethylsiloxane) (PDMS) are transparent, functional, hybrid interfaces that can be patterned over nanometer, micrometer, and millimeter length scales. Unlike other ultrathin Au films and nanoparticles, lifted-off Au-alkanethiolate thin films lack a measurable optical signature. We therefore devised fabrication, characterization, and simulation strategies by which to interrogate the nanoscale structure, chemical functionality, stoichiometry, and spectral signature of the supported Au-thiolate layers. The patterning of these layers laterally encodes their functionality, as demonstrated by a fluorescence-based approach that relies on dye-labeled complementary DNA hybridization. Supported thin Au films can be patterned via features on PDMS stamps (controlled contact), using patterned Au substrates prior to lift-off (e.g., selective wet etching), or by patterning alkanethiols on Au substrates to be reactive in selected regions but not others (controlled reactivity). In all cases, the regions containing Au-alkanethiolate layers have a sub-nanometer apparent height, which was found to be consistent with molecular dynamics simulations that predicted the removal of no more than 1.5 Au atoms per thiol, thus presenting a monolayer-like structure.
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Affiliation(s)
- Liane S Slaughter
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Kevin M Cheung
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Sami Kaappa
- Department of Physics, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland
| | - Huan H Cao
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Qing Yang
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Thomas D Young
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Andrew C Serino
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Sami Malola
- Department of Physics, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland
| | - Jana M Olson
- Department of Chemistry, Rice University, Houston, Texas, 77005, USA
| | - Stephan Link
- Department of Chemistry, Rice University, Houston, Texas, 77005, USA
- Department of Electrical and Computer Engineering, Rice University, Houston, Texas, 77005, USA
| | - Hannu Häkkinen
- Department of Physics, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland
- Department of Chemistry, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland
| | - Anne M Andrews
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, and Hatos Center for Neuropharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Paul S Weiss
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
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7
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Zhukhovitskiy AV, MacLeod MJ, Johnson JA. Carbene Ligands in Surface Chemistry: From Stabilization of Discrete Elemental Allotropes to Modification of Nanoscale and Bulk Substrates. Chem Rev 2015; 115:11503-32. [DOI: 10.1021/acs.chemrev.5b00220] [Citation(s) in RCA: 223] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Aleksandr V. Zhukhovitskiy
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Michelle J. MacLeod
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Jeremiah A. Johnson
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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8
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Jia J, Kara A, Pasquali L, Bendounan A, Sirotti F, Esaulov VA. On sulfur core level binding energies in thiol self-assembly and alternative adsorption sites: An experimental and theoretical study. J Chem Phys 2015; 143:104702. [PMID: 26374051 DOI: 10.1063/1.4929350] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Characteristic core level binding energies (CLBEs) are regularly used to infer the modes of molecular adsorption: orientation, organization, and dissociation processes. Here, we focus on a largely debated situation regarding CLBEs in the case of chalcogen atom bearing molecules. For a thiol, this concerns the case when the CLBE of a thiolate sulfur at an adsorption site can be interpreted alternatively as due to atomic adsorption of a S atom, resulting from dissociation. Results of an investigation of the characteristics of thiol self-assembled monolayers (SAMs) obtained by vacuum evaporative adsorption are presented along with core level binding energy calculations. Thiol ended SAMs of 1,4-benzenedimethanethiol (BDMT) obtained by evaporation on Au display an unconventional CLBE structure at about 161.25 eV, which is close to a known CLBE of a S atom on Au. Adsorption and CLBE calculations for sulfur atoms and BDMT molecules are reported and allow delineating trends as a function of chemisorption on hollow, bridge, and atop sites and including the presence of adatoms. These calculations suggest that the 161.25 eV peak is due to an alternative adsorption site, which could be associated to an atop configuration. Therefore, this may be an alternative interpretation, different from the one involving the adsorption of atomic sulfur resulting from the dissociation process of the S-C bond. Calculated differences in S(2p) CLBEs for free BDMT molecules, SH group sulfur on top of the SAM, and disulfide are also reported to clarify possible errors in assignments.
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Affiliation(s)
- Juanjuan Jia
- Institut des Sciences Moléculaires d'Orsay, Université-Paris Sud, 91405 Orsay, France
| | - Abdelkader Kara
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Luca Pasquali
- Dipartimento di Ingegneria "E. Ferrari," Università di Modena e Reggio Emilia, Via Vignolese 905, 41125 Modena, Italy
| | - Azzedine Bendounan
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex, France
| | - Fausto Sirotti
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex, France
| | - Vladimir A Esaulov
- Institut des Sciences Moléculaires d'Orsay, Université-Paris Sud, 91405 Orsay, France
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9
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Pal NK, Kryschi C. A facile one-pot synthesis of blue and red luminescent thiol stabilized gold nanoclusters: a thorough optical and microscopy study. Phys Chem Chem Phys 2015. [DOI: 10.1039/c5cp01773d] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Ultrasmall blue and red luminescent 1-dodecanethiol terminated gold clusters were synthesized concurrently at the same pot using a simple two step process.
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Affiliation(s)
- Nabin Kumar Pal
- Department of Chemistry and Pharmacy and ICMM
- Friedrich-Alexander-University of Erlangen-Nuremberg
- Erlangen
- Germany
| | - Carola Kryschi
- Department of Chemistry and Pharmacy and ICMM
- Friedrich-Alexander-University of Erlangen-Nuremberg
- Erlangen
- Germany
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10
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Carro P, Torrelles X, Salvarezza RC. A novel model for the (√3 × √3)R30° alkanethiolate–Au(111) phase based on alkanethiolate–Au adatom complexes. Phys Chem Chem Phys 2014; 16:19017-23. [DOI: 10.1039/c4cp01255k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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11
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Sørensen SG, Füchtbauer HG, Tuxen AK, Walton AS, Lauritsen JV. Structure and electronic properties of in situ synthesized single-layer MoS2 on a gold surface. ACS NANO 2014; 8:6788-96. [PMID: 24938884 DOI: 10.1021/nn502812n] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
When transition metal sulfides such as MoS2 are present in the single-layer form, the electronic properties change in fundamental ways, enabling them to be used, e.g., in two-dimensional semiconductor electronics, optoelectronics, and light harvesting. The change is related to a subtle modification of the band structure due to confinement in the direction perpendicular to the sheets, and there is a considerable interest in understanding how this modification can be controlled and adjusted to generate 2D-materials with functional properties. In this article we report a synthesis procedure together with scanning tunneling microscopy and X-ray photoelectron spectroscopy characterization of two-dimensional single-layer islands of MoS2 synthesized directly on a gold single crystal substrate. Thanks to a periodic modulation of the atom stacking induced by the lattice mismatch, we observe a structural buckling of the MoS2 layer resulting in a characteristic moiré pattern. X-ray photoelectron spectroscopy indicates that the system develops the characteristics of n-doped MoS2 due to electron donation. Scanning tunneling spectroscopy furthermore reflects a convolution of MoS2 and Au donor states where the MoS2 band structure appears modified at the band gap edges. This electronic effect is further modulated by the moiré periodicity and leads to small substrate-induced electronic perturbations near the conduction band minimum in the band gap of MoS2. The results may be highly relevant in the context of nanopatterned two-dimensional materials on metal surfaces, and we propose the MoS2/Au system in this article as a promising candidate to further explore the properties of supported 2D transition-metal dichalcogenides.
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Affiliation(s)
- Signe G Sørensen
- Interdisciplinary Nanoscience Center, Aarhus University , DK-8000 Aarhus C, Denmark
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12
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Caprile L, Cossaro A, Falletta E, Della Pina C, Cavalleri O, Rolandi R, Terreni S, Ferrando R, Rossi M, Floreano L, Canepa M. Interaction of L-cysteine with naked gold nanoparticles supported on HOPG: a high resolution XPS investigation. NANOSCALE 2012; 4:7727-7734. [PMID: 23135640 DOI: 10.1039/c2nr32741d] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report the results of a synchrotron-based high-resolution XPS study of the interaction of L-cysteine (Cys) with well-characterized colloidal gold nanoparticles (NPs, typical size 3-4 nm), which were pre-deposited on highly oriented pyrolytic graphite and then brought into contact with the aqueous solution of Cys by drop-casting. By comparison with data previously obtained for Cys deposition on flat Au substrates (single crystals and high quality films), we demonstrate the formation of a strong Cys/NP thiolate bond. The analysis of the line shape and adsorbate-induced Au 4f core level shift, backed by simulations of the NP structure, reveals the interaction of Cys with low-coordinated Au atoms belonging to the NP edge and corners. The analysis of the N 1s core-level indicates that neutral molecules are the most abundant species. The small facet size limits the formation of extended networks of zwitterionic molecules, typical of single crystal surfaces. This study provides a spectroscopic insight into the intense poisoning effect caused by a limited amount of Cys on Au catalysts described in previous reports.
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Affiliation(s)
- Laura Caprile
- CNISM and Dipartimento di Fisica, Universitá di Genova, via Dodecaneso 33, Genova, Italy
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13
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Houmam A, Muhammad H, Koczkur KM. Rapid formation of a dense sulfur layer on gold through use of triphenylmethane sulfenyl chloride as a precursor. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:16881-16889. [PMID: 23131048 DOI: 10.1021/la3032607] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The use of triphenylmethane sulfenyl chloride as a new precursor leads to the efficient deposition of sulfur on polycrystalline gold and Au(111) substrates. The modified surfaces are characterized using X-ray photoelectron spectroscopy (XPS), electrochemistry and scanning tunneling microscopy (STM). The XPS data shows the rapid deposition of polymeric sulfur within very short times. Electrochemical stripping cyclic voltammetry (CV) confirms the rapid deposition and shows that high coverage values are achieved. STM imaging shows the formation of a wide range sulfur layer and production of the well-known etch pits. High-resolution STM images confirm the high density of the sulfur layers and show formation of a long-range phase consisting of rhombus structures close to the previously described rectangular structures along with other parallelograms and partial parallelograms. The present results do not show the initial formation of any organic self-assembled monolayer (SAM) indicating that the formation of polymeric sulfur does not result from the decomposition of an initial SAM as previously observed with alkyl and aryl thiolate-based SAMs. The suggested mechanism involves an initial reductive process similar to the one reported for thiocyanates and sulfenyl chlorides. This is followed by the dissociation of the Ph(3)C-S bond, leaving only sulfur on the surface, through a process leading to the recombination of the remaining fragments to yield triphenylmethyl chloride.
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Affiliation(s)
- Abdelaziz Houmam
- Electrochemical Technology Centre, Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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14
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Cometto FP, Patrito EM, Paredes Olivera P, Zampieri G, Ascolani H. Electrochemical, high-resolution photoemission spectroscopy and vdW-DFT study of the thermal stability of benzenethiol and benzeneselenol monolayers on Au(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:13624-13635. [PMID: 22946792 DOI: 10.1021/la3024937] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The preparation and thermal stability of benzenethiol and benzeneselenol self-assembled monolayers (SAMs) grown on Au(111) have been investigated by electrochemical experiments and high-resolution photoemission spectroscopy. Both techniques confirm the formation of monolayers with high packing densities (θ = 0.27-0.29 ML) and good degrees of order in both cases. Despite many similarities between the two SAMs, the thermal desorption is distinctly different: whereas the benzenethiol SAM desorbs in a single steplike process, the desorption of the benzeneselenol SAM occurs with a much lower activation energy and involves the cleavage of some Se-C bonds and a change in molecular configuration from standing up to lying down. This behavior is explained by considering the different nature of the bonding of the headgroup with the metal surface and with the phenyl ring. Density functional theory calculations show that the breakage of the Se-C bond has a lower activation energy barrier than the breakage of the S-C bond.
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Affiliation(s)
- F P Cometto
- Departamento de Fisico Química, Instituto de Fisicoquímica de Córdoba, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
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15
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Grönbeck H. The bonding in thiolate protected gold nanoparticles from Au4f photoemission core level shifts. NANOSCALE 2012; 4:4178-4182. [PMID: 22635169 DOI: 10.1039/c2nr30903c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Density functional theory calculations are used to evaluate Au4f core level shifts of methyl thiolate protected Au(25), Au(102) and Au(144) nanoparticles. The shifts are found to provide sensitive fingerprints of the chemical environment. In particular, Au atoms in protective gold-thiolate complexes have higher binding energies than Au atoms with solely metal neighbors. The core level shifts for the nanoparticles are compared to the corresponding results for methyl thiolates adsorbed on Au(111) and implications for the understanding of the gold-sulfur bond is discussed.
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Affiliation(s)
- Henrik Grönbeck
- Department of Applied Physics and Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
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16
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17
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Houmam A, Koczkur KM, Moula G, Hamed EM. New Insights into Sulfur Deposition on Gold Using Dithiobisphthalimide as a New Precursor. Chemphyschem 2012; 13:1240-5. [DOI: 10.1002/cphc.201100768] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Indexed: 11/07/2022]
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18
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On the kinetics and thermodynamics of S–X (X = H, CH3, SCH3, COCH3, and CN) cleavage in the formation of self-assembled monolayers of alkylthiols on Au(111). Theor Chem Acc 2012. [DOI: 10.1007/s00214-012-1150-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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19
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Wang ZW, Palmer RE. Mass spectrometry and dynamics of gold adatoms observed on the surface of size-selected Au nanoclusters. NANO LETTERS 2012; 12:91-95. [PMID: 22126627 DOI: 10.1021/nl2037112] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report the imaging, mass spectrum, and dynamical behavior of adatoms and small clusters observed on the surface facets of size-selected, truncated octahedral gold clusters, Au(N) (N = 923 ± 23), via aberration-corrected scanning transmission electron microscopy. Our quantitative atom counting measurements show that most (~70%) of the species on the surface are single Au adatoms. Such species are now proposed as key elements of the atomic structure of both monolayer-protected nanoclusters (nanoparticles) and self-assembled monolayers and may also play a role in gold nanocatalysis. The adatoms are found on both {100} and {111} facets with similar probabilities.
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Affiliation(s)
- Z W Wang
- Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, B15 2TT, United Kingdom
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20
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Matharu Z, Bandodkar AJ, Gupta V, Malhotra BD. Fundamentals and application of ordered molecular assemblies to affinity biosensing. Chem Soc Rev 2012; 41:1363-402. [DOI: 10.1039/c1cs15145b] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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21
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Houmam A, Muhammad H, Koczkur KM. Physical structure of standing-up aromatic SAMs revealed by scanning tunneling microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:13544-13553. [PMID: 21970561 DOI: 10.1021/la202928z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Long-range-ordered aromatic SAMs are formed on Au(111) using 4-nitrophenyl sulfenyl chloride as a precursor. Although the main structure is a √3 × √3 with a molecular density similar to that usually found for aliphatic SAMs, particular spots presenting specific shapes are also observed by STM. These include hexagons, partial hexagons, parallelograms, and zigzags resulting from specific arrangements of adsorbed molecules. These molecular arrangements are reversible as they form and dissociate or "vanish" in various areas on the surface. STM shows that these particular structures provide some order to their surrounding because areas void of these structures look less ordered. More interestingly, STM shows submolecular details of the molecules involved in forming these structures, hence providing direct experimental evidence for the ability of the STM to provide physical structure information of standing up SAMs. This is indeed a heavily debated question, and this work reports the first experimental example where submolecular physical structure is revealed by STM for standing-up SAMs.
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Affiliation(s)
- Abdelaziz Houmam
- Electrochemical Technology Centre, Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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22
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Ryu S, Kang JW, Han YK, Lee YS. Structures of Butylthiolate Self-Assembled Monolayers on Au(111) with Gold Adatoms. B KOREAN CHEM SOC 2011. [DOI: 10.5012/bkcs.2011.32.10.3614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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23
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Koczkur KM, Hamed EM, Houmam A. Sulfur multilayer formation on Au(111): new insights from the study of hexamethyldisilathiane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:12270-12274. [PMID: 21916512 DOI: 10.1021/la202591j] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Hexamethyldisilathiane was successfully used as a new precursor for the formation of S layers on Au and to study their interaction. Characterization of the S modified gold surface was done by X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and scanning tunneling microscopy (STM). Key findings include the direct observation by STM of (i) coexistence of different phases, (ii) multiple sulfur layers formation, (ii) formation of rectangular structures not only on the adlayer but also on the top layer, and (iv) rectangular structure mobility on different layers. These results provide clear evidence regarding the adsorbate nature of the rectangular structures, solving a highly debated question.
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Affiliation(s)
- Kallum M Koczkur
- Department of Chemistry, Electrochemical Technology Centre, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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24
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Ataman E, Isvoranu C, Knudsen J, Schulte K, Andersen JN, Schnadt J. Modification of the size of supported clusters by coadsorption of an organic compound: gold and L-cysteine on rutile TiO2(110). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:11466-11474. [PMID: 21806065 DOI: 10.1021/la201923y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Using X-ray photoelectron spectroscopy we studied the coadsorption of the amino acid L-cysteine and gold on a rutile TiO(2)(110) surface under ultrahigh vacuum conditions. Irrespective of the deposition order, i.e., irrespective of whether L-cysteine or gold is deposited first, the primary interaction between L-cysteine and the gold clusters formed at the surface takes place through the deprotonated thiol group of the molecule. The deposition order, however, has a profound influence on the size of the gold clusters as well as their location on the surface. If L-cysteine is deposited first the clusters are smaller by a factor two to three compared to gold deposited onto the pristine TiO(2)(110) surface and then covered by L-cysteine. Further, in the former case the clusters cover the molecules and thus form the outermost layer of the sample. We also find that above a minimum gold cluster size the gold cluster/L-cysteine bond is stronger than the L-cysteine/surface bridging oxygen vacancy bond, which, in turn, is stronger than the gold cluster/vacancy bond.
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Affiliation(s)
- Evren Ataman
- Division of Synchrotron Radiation Research, Department of Physics, Lund University, Box 118, 221 00 Lund, Sweden
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25
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Järvi TT, van Duin ACT, Nordlund K, Goddard WA. Development of Interatomic ReaxFF Potentials for Au–S–C–H Systems. J Phys Chem A 2011; 115:10315-22. [DOI: 10.1021/jp201496x] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Tommi T. Järvi
- Fraunhofer Institute for Mechanics of Materials IWM, Freiburg, Germany
| | - Adri C. T. van Duin
- Department of Mechanical
and Nuclear Engineering, Pennsylvania State University, University Park, Pennsylvania, United States
| | - Kai Nordlund
- Department of Physics, University of Helsinki, Finland
| | - William A. Goddard
- Materials and Process Simulation
Center, California Institute of Technology, Pasadena, California, United States
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26
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Pasquali L, Terzi F, Seeber R, Nannarone S, Datta D, Dablemont C, Hamoudi H, Canepa M, Esaulov VA. UPS, XPS, and NEXAFS study of self-assembly of standing 1,4-benzenedimethanethiol SAMs on gold. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:4713-4720. [PMID: 21405080 DOI: 10.1021/la105063u] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We report a study of the self-assembly of 1,4-benzenedimethanethiol monolayers on gold formed in n-hexane solution held at 60 °C for 30 min and in dark conditions. The valence band characteristics, the thickness of the layer, and the orientation of the molecules were analyzed at a synchrotron using high resolution photoelectron spectroscopy and near edge X-ray adsorption spectroscopy. These measurements unambiguously attest the formation of a single layer with molecules arranged in the upright position and presenting a free -SH group at the outer interface. Near edge X-ray absorption fine structure (NEXAFS) measurements suggest that the molecular axis is oriented at 24° with respect to the surface normal. In addition, valence band features could be successfully associated to specific molecular orbital contributions thanks to the comparison with theoretically calculated density of states projected on the different molecular units.
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Affiliation(s)
- Luca Pasquali
- Dipartimento di Ingegneria dei Materiali e dell'Ambiente, Università di Modena e Reggio Emilia, Via Vignolese 905, 41100 Modena, Italy
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27
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Li F, Tang L, Zhou W, Guo Q. Relationship between the c(4×2) and the (√3×√3)R30° phases in alkanethiol self-assembled monolayers on Au(111). Phys Chem Chem Phys 2011; 13:11958-64. [DOI: 10.1039/c1cp00037c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Rajaraman G, Caneschi A, Gatteschi D, Totti F. A periodic mixed gaussians–plane waves DFT study on simple thiols on Au(111): adsorbate species, surface reconstruction, and thiols functionalization. Phys Chem Chem Phys 2011; 13:3886-95. [DOI: 10.1039/c0cp02042g] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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29
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Heimel G, Rissner F, Zojer E. Modeling the electronic properties of pi-conjugated self-assembled monolayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2010; 22:2494-513. [PMID: 20414885 DOI: 10.1002/adma.200903855] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The modification of electrode surfaces by depositing self-assembled monolayers (SAMs) provides the possibility for controlled adjustment of various key parameters in organic and molecular electronic devices. Most important among them are the work function of the electrode and the relative alignment of its Fermi level with the conducting states in the SAM itself and with those in a subsequently deposited organic semiconductor. For the efficient application of such interface modifications it is crucial to reach a proper understanding of the relation between the chemical structure of a molecule, its molecular electronic characteristics, and the properties of the SAM formed by such molecules. Over the past years, quantum-mechanical calculations have proven to be a valuable tool for reaching a fundamental understanding of the relevant structure-property relations. Here, we provide a review over the field and report on recent progress in the modeling of the interfacial electronic properties of pi-conjugated SAMs. In addition to the insight that can be gained from simple electrostatic considerations, we focus on the quantum-mechanical description of the roles played by substituents, molecular backbones, chemical anchoring groups, and the packing density of molecules on the surface. Furthermore, we explicitly address the energy-level alignment at the interface between a prototypical organic semiconductor and a SAM-covered metal electrode and describe an approach suitable for extending the metallic character of the substrate onto the monolayer.
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Affiliation(s)
- Georg Heimel
- Institut für Physik, Humboldt-Universität zu Berlin, Newtonstrasse 15, 12489 Berlin, Germany.
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30
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Vericat C, Vela ME, Benitez G, Carro P, Salvarezza RC. Self-assembled monolayers of thiols and dithiols on gold: new challenges for a well-known system. Chem Soc Rev 2010; 39:1805-34. [PMID: 20419220 DOI: 10.1039/b907301a] [Citation(s) in RCA: 767] [Impact Index Per Article: 54.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Self-assembled monolayers (SAMs) of alkanethiols and dialkanethiols on gold are key elements for building many systems and devices with applications in the wide field of nanotechnology. Despite the progress made in the knowledge of these fascinating two-dimensional molecular systems, there are still several "hot topics" that deserve special attention in order to understand and to control their physical and chemistry properties at the molecular level. This critical review focuses on some of these topics, including the nature of the molecule-gold interface, whose chemistry and structure remain elusive, the self-assembly process on planar and irregular surfaces, and on nanometre-sized objects, and the chemical reactivity and thermal stability of these systems in ambient and aqueous solutions, an issue which seriously limits their technological applications (375 references).
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Affiliation(s)
- C Vericat
- Instituto de Investigaciones Fisicoquímicas Teóricasy Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET, Sucursal 4 Casilla de Correo 16, (1900) La Plata, Argentina
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31
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Voznyy O, Dubowski JJ, Yates JT, Maksymovych P. The role of gold adatoms and stereochemistry in self-assembly of methylthiolate on Au(111). J Am Chem Soc 2010; 131:12989-93. [PMID: 19737018 DOI: 10.1021/ja902629y] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
On the basis of high resolution STM images and DFT modeling, we have resolved low- and high-coverage structures of methylthiolate (CH(3)S) self-assembled on the Au(111) surface. The key new finding is that the building block of all these structures has the same stoichiometry of two thiolate species joined by a gold adatom. The self-arrangement of the methylthiolate-adatom complexes on the surface depends critically on their stereochemical properties. Variations of the latter can produce local ordering of adatom complexes with either (3 x 4) or (3 x 4 square root(3)) periodicity. A possible structural connection between the (3 x 4 square root(3)) structure and commonly observed (square root(3) x square root(3))R30 degrees phase in methylthiolate self-assembled monolayers is developed by taking into account the reduction in the long-range order and stereochemical isomerization at high coverage. We also suggest how the observed self-arrangements of methylthiolate may be related to the c(4 x 2) phase of its longer homologues.
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Affiliation(s)
- Oleksandr Voznyy
- Department of Electrical and Computer Engineering, Centre of Excellence for Information Engineering (CEGI), Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada.
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32
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Rajaraman G, Caneschi A, Gatteschi D, Totti F. A DFT exploration of the organization of thiols on Au(111): a route to self-assembled monolayer of magnetic molecules. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/c0jm02481c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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33
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Cossaro A, Floreano L, Verdini A, Casalis L, Morgante A. Comment on "local methylthiolate adsorption geometry on au(111) from photoemission core-level shifts". PHYSICAL REVIEW LETTERS 2009; 103:119601-119602. [PMID: 19792410 DOI: 10.1103/physrevlett.103.119601] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Indexed: 05/28/2023]
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34
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Jiang DE, Dai S. Cis–trans conversion of the CH3S–Au–SCH3 complex on Au(111). Phys Chem Chem Phys 2009; 11:8601-5. [DOI: 10.1039/b902966d] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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