Prof. Dr. Johannes Barth
Academic Research Focus
- Fundamental understanding of interface processes
- Control and design of functional nanomaterials
- Control and design of functional nanomaterials
Fields of Application
Nanomaterials
Publications
35.
Y Q Zhang, J Björk, J V Barth
Exploring On-Surface Synthesis under Mild Conditions Journal Article
In: Accounts of Chemical Research, 2025, ISSN: 0001-4842.
@article{nokey,
title = {Exploring On-Surface Synthesis under Mild Conditions},
author = {Y Q Zhang and J Bj\"{o}rk and J V Barth},
url = {\<Go to ISI\>://WOS:001518560000001},
doi = {10.1021/acs.accounts.5c00157},
issn = {0001-4842},
year = {2025},
date = {2025-06-26},
journal = {Accounts of Chemical Research},
abstract = {Bottom-up approaches combining tailor-made molecular precursors and surface-mediated reactions under ultrahigh-vacuum (UHV) conditions attracted significant attention over the past decade as a promising strategy for synthesizing novel, functional, molecule-based materials. These methods have been remarkably successful in creating unconventional covalent products with atomic precision, though largely focusing on one-dimensional (1D) polymeric products. Extending the established protocols to synthesize two-dimensional (2D) covalent architectures presents a major challenge, primarily due to high annealing temperatures required that often entail competing reactions, high defect densities, and structural degradation.In this Account, we highlight the exciting potential of low-temperature (LT) on-surface reactions as an alternative pathway and discuss their largely unexploited capabilities. We summarize major recent advances, focusing on coinage metal surface-assisted chemical transformations at mild conditions in UHV, proceeding frequently near or below room temperature (RT). Special emphasis is placed on alkyne derivatives, either alone or combined with other functional groups, identified as versatile building blocks for next-generation carbon-rich nanomaterials such as graphyne or graphdiyne and their metalated derivatives, which offer immense potential for future technological applications.We discuss four major pathways for initiating LT on-surface reactions of alkyne species, following largely the chronological order of their discovery, and merging insights from high-resolution scanning probe microscopy, X-ray spectroscopies and density functional theory calculations: (i) Conversions catalyzed by in situ generated species and extrinsic elements; (ii) quantum tunneling-mediated reactions; (iii) reaction pathways involving surface-assisted radical or hydrogen transfer processes; and (iv) gas-mediated on-surface reactions. These and other selected examples of LT synthesis protocols offer significant advantages in terms of high selectivity and efficiency, notably enabling the controlled synthesis of extended, regular 2D organometallic and covalent compounds or architectures, and bearing promise for a multitude of all-carbon scaffolds, which currently remain challenging. We aim to inspire the development of functional robust nanoarchitectures with long-range order and atomic-scale precision, contributing to the advancement of molecule-based materials for diverse technological applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Bottom-up approaches combining tailor-made molecular precursors and surface-mediated reactions under ultrahigh-vacuum (UHV) conditions attracted significant attention over the past decade as a promising strategy for synthesizing novel, functional, molecule-based materials. These methods have been remarkably successful in creating unconventional covalent products with atomic precision, though largely focusing on one-dimensional (1D) polymeric products. Extending the established protocols to synthesize two-dimensional (2D) covalent architectures presents a major challenge, primarily due to high annealing temperatures required that often entail competing reactions, high defect densities, and structural degradation.In this Account, we highlight the exciting potential of low-temperature (LT) on-surface reactions as an alternative pathway and discuss their largely unexploited capabilities. We summarize major recent advances, focusing on coinage metal surface-assisted chemical transformations at mild conditions in UHV, proceeding frequently near or below room temperature (RT). Special emphasis is placed on alkyne derivatives, either alone or combined with other functional groups, identified as versatile building blocks for next-generation carbon-rich nanomaterials such as graphyne or graphdiyne and their metalated derivatives, which offer immense potential for future technological applications.We discuss four major pathways for initiating LT on-surface reactions of alkyne species, following largely the chronological order of their discovery, and merging insights from high-resolution scanning probe microscopy, X-ray spectroscopies and density functional theory calculations: (i) Conversions catalyzed by in situ generated species and extrinsic elements; (ii) quantum tunneling-mediated reactions; (iii) reaction pathways involving surface-assisted radical or hydrogen transfer processes; and (iv) gas-mediated on-surface reactions. These and other selected examples of LT synthesis protocols offer significant advantages in terms of high selectivity and efficiency, notably enabling the controlled synthesis of extended, regular 2D organometallic and covalent compounds or architectures, and bearing promise for a multitude of all-carbon scaffolds, which currently remain challenging. We aim to inspire the development of functional robust nanoarchitectures with long-range order and atomic-scale precision, contributing to the advancement of molecule-based materials for diverse technological applications.
34.
D Meier, P Knecht, P Vezzoni Vicente, F Eratam, H Xu, T-L Lee, A Generalov, A Riss, B Yang, F Allegretti, P Feulner, J Reichert, J V Barth, A P Seitsonen, D A Duncan, A C Papageorgiou
Octaethyl vs Tetrabenzo Functionalized Ru Porphyrins on Ag(111): Molecular Conformation, Self-Assembly and Electronic Structure Journal Article
In: The Journal of Physical Chemistry C, vol. 129, no. 1, pp. 858-869, 2025, ISSN: 1932-7447.
@article{nokey,
title = {Octaethyl vs Tetrabenzo Functionalized Ru Porphyrins on Ag(111): Molecular Conformation, Self-Assembly and Electronic Structure},
author = {D Meier and P Knecht and P Vezzoni Vicente and F Eratam and H Xu and T-L Lee and A Generalov and A Riss and B Yang and F Allegretti and P Feulner and J Reichert and J V Barth and A P Seitsonen and D A Duncan and A C Papageorgiou},
url = {https://doi.org/10.1021/acs.jpcc.4c06978},
doi = {10.1021/acs.jpcc.4c06978},
issn = {1932-7447},
year = {2025},
date = {2025-01-09},
journal = {The Journal of Physical Chemistry C},
volume = {129},
number = {1},
pages = {858-869},
abstract = {Metalloporphyrins on interfaces offer a rich playground for functional materials and hence have been subjected to intense scrutiny over the past decades. As the same porphyrin macrocycle on the same surface may exhibit vastly different physicochemical properties depending on the metal center and its substituents, it is vital to have a thorough structural and chemical characterization of such systems. Here, we explore the distinctions arising from coverage and macrocycle substituents on the closely related ruthenium octaethyl porphyrin and ruthenium tetrabenzo porphyrin on Ag(111). Our investigation employs a multitechnique approach in ultrahigh vacuum, combining scanning tunneling microscopy, low-energy electron diffraction, photoelectron spectroscopy, normal incidence X-ray standing wave, and near-edge X-ray absorption fine structure, supported by density functional theory. This methodology allows for a thorough examination of the nuanced differences in the self-assembly, substrate modification, molecular conformation and adsorption height.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Metalloporphyrins on interfaces offer a rich playground for functional materials and hence have been subjected to intense scrutiny over the past decades. As the same porphyrin macrocycle on the same surface may exhibit vastly different physicochemical properties depending on the metal center and its substituents, it is vital to have a thorough structural and chemical characterization of such systems. Here, we explore the distinctions arising from coverage and macrocycle substituents on the closely related ruthenium octaethyl porphyrin and ruthenium tetrabenzo porphyrin on Ag(111). Our investigation employs a multitechnique approach in ultrahigh vacuum, combining scanning tunneling microscopy, low-energy electron diffraction, photoelectron spectroscopy, normal incidence X-ray standing wave, and near-edge X-ray absorption fine structure, supported by density functional theory. This methodology allows for a thorough examination of the nuanced differences in the self-assembly, substrate modification, molecular conformation and adsorption height.
33.
M Rostami, B Yang, F Haag, F Allegretti, L Chi, M Stutzmann, J V Barth
In: Applied Surface Science, vol. 674, pp. 160880, 2024, ISSN: 0169-4332.
@article{nokey,
title = {Influencing the surface quality of free-standing wurtzite gallium nitride in ultra-high vacuum: Stoichiometry control by ammonia and bromine adsorption},
author = {M Rostami and B Yang and F Haag and F Allegretti and L Chi and M Stutzmann and J V Barth},
url = {https://www.sciencedirect.com/science/article/pii/S0169433224015939},
doi = {https://doi.org/10.1016/j.apsusc.2024.160880},
issn = {0169-4332},
year = {2024},
date = {2024-11-15},
journal = {Applied Surface Science},
volume = {674},
pages = {160880},
abstract = {Gallium nitride (GaN), a wide bandgap semiconductor with absorption and emission in the ultraviolet/visible range, is proposed as an alternative to metallic surfaces for assembling organic molecular structures aiming at optoelectronic applications. However, the formation of a persistent surface oxide layer in air considerably limits the use of GaN for well-defined interfaces. In this work, we have investigated, characterized and processed n-type free-standing c-plane hexagonal wurtzite GaN crystals grown by hydride vapor phase epitaxy and ammonothermal growth methods. Surface cleaning and full removal of the oxide layer on GaN surfaces could be reproducibly achieved via sputtering and annealing cycles, as evidenced by X-ray photoelectron spectroscopy and low-energy electron diffraction. Scanning tunneling microscopy, however, indicated substantial roughening of the GaN surface and the formation of unwanted Ga-rich islands and clusters. Although ammonia (NH3) and bromine (Br) treatments compensated the N/Ga atoms ratio reduced by sputtering, the surface morphology remained rough, exhibiting randomly shaped and distributed hillocks. In addition, we studied the effect of electron bombardment on the surface quality of GaN during NH3 annealing, on-surface debromination and polymerization of 1,3,5-tris(4-bromophenyl) benzene on GaN, and the removal of Ga atoms by Br atoms during the desorption.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Gallium nitride (GaN), a wide bandgap semiconductor with absorption and emission in the ultraviolet/visible range, is proposed as an alternative to metallic surfaces for assembling organic molecular structures aiming at optoelectronic applications. However, the formation of a persistent surface oxide layer in air considerably limits the use of GaN for well-defined interfaces. In this work, we have investigated, characterized and processed n-type free-standing c-plane hexagonal wurtzite GaN crystals grown by hydride vapor phase epitaxy and ammonothermal growth methods. Surface cleaning and full removal of the oxide layer on GaN surfaces could be reproducibly achieved via sputtering and annealing cycles, as evidenced by X-ray photoelectron spectroscopy and low-energy electron diffraction. Scanning tunneling microscopy, however, indicated substantial roughening of the GaN surface and the formation of unwanted Ga-rich islands and clusters. Although ammonia (NH3) and bromine (Br) treatments compensated the N/Ga atoms ratio reduced by sputtering, the surface morphology remained rough, exhibiting randomly shaped and distributed hillocks. In addition, we studied the effect of electron bombardment on the surface quality of GaN during NH3 annealing, on-surface debromination and polymerization of 1,3,5-tris(4-bromophenyl) benzene on GaN, and the removal of Ga atoms by Br atoms during the desorption.
32.
P Vezzoni Vicente, T Weiss, D Meier, W Zhao, B S Tömekçe, M G. Cuxart, B P Klein, D A Duncan, T-L Lee, A C Papageorgiou, M Muntwiler, A P Seitsonen, W Auwärter, P Feulner, J V Barth, F Allegretti
Holistic structural understanding of epitaxially-grown Bi/Au(111) moiré superstructures Journal Article
In: Physical Review Materials, vol. 8, no. 10, pp. 104001, 2024.
@article{nokey,
title = {Holistic structural understanding of epitaxially-grown Bi/Au(111) moir\'{e} superstructures},
author = {P Vezzoni Vicente and T Weiss and D Meier and W Zhao and B S T\"{o}mek\c{c}e and M G. Cuxart and B P Klein and D A Duncan and T-L Lee and A C Papageorgiou and M Muntwiler and A P Seitsonen and W Auw\"{a}rter and P Feulner and J V Barth and F Allegretti},
url = {https://link.aps.org/doi/10.1103/PhysRevMaterials.8.104001},
doi = {10.1103/PhysRevMaterials.8.104001},
year = {2024},
date = {2024-10-01},
journal = {Physical Review Materials},
volume = {8},
number = {10},
pages = {104001},
abstract = {In light of the recent research interest in low-dimensional bismuth structures as spin-active materials and topological insulators, we present a comprehensive characterization of the Bi/Au(111) interface. The nuanced evolution of Bi phases upon deposition in ultrahigh vacuum (UHV) on a Au(111) surface is investigated from semidisordered clusters to few-layer Bi(110) thin films. Particular attention is devoted to the high-coverage, submonolayer phases, commonly grouped under the (?×√3) nomenclature. We bring forth a new model, refining the current understanding of the Bi/Au(111) interface and demonstrating the existence of submonolayer moir\'{e} superstructures, whose geometry and superperiodicity depend on their coverage. This tuneable periodicity paves the way for their use as tailored buffer and templating layers for epitaxial growth of thin films on Au(111). Finally, we clarify the growth mode of multilayer Bi(110) as bilayer-by-bilayer, allowing precise thickness control of anisotropically strained thin films. This holistic understanding of the structural properties of the material was enabled by the synergy of several experimental techniques, namely low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy and spectroscopy (STM, STS), and x-ray standing waves (XSW), further corroborated by density functional theory (DFT) simulations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In light of the recent research interest in low-dimensional bismuth structures as spin-active materials and topological insulators, we present a comprehensive characterization of the Bi/Au(111) interface. The nuanced evolution of Bi phases upon deposition in ultrahigh vacuum (UHV) on a Au(111) surface is investigated from semidisordered clusters to few-layer Bi(110) thin films. Particular attention is devoted to the high-coverage, submonolayer phases, commonly grouped under the (?×√3) nomenclature. We bring forth a new model, refining the current understanding of the Bi/Au(111) interface and demonstrating the existence of submonolayer moiré superstructures, whose geometry and superperiodicity depend on their coverage. This tuneable periodicity paves the way for their use as tailored buffer and templating layers for epitaxial growth of thin films on Au(111). Finally, we clarify the growth mode of multilayer Bi(110) as bilayer-by-bilayer, allowing precise thickness control of anisotropically strained thin films. This holistic understanding of the structural properties of the material was enabled by the synergy of several experimental techniques, namely low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy and spectroscopy (STM, STS), and x-ray standing waves (XSW), further corroborated by density functional theory (DFT) simulations.
31.
Y Lyu, F Gao, P Cheng, L Chen, S Klyatskaya, M Ruben, J Rosen, J V Barth, J Björk, K Wu, Y-Q Zhang
Unraveling Enyne Bonding via Dehydrogenation–Hydrogenation Processes in On-Surface Synthesis with Terminal Alkynes Journal Article
In: Advanced Materials Interfaces, vol. 11, no. 26, pp. 2400222, 2024, ISSN: 2196-7350.
@article{nokey,
title = {Unraveling Enyne Bonding via Dehydrogenation\textendashHydrogenation Processes in On-Surface Synthesis with Terminal Alkynes},
author = {Y Lyu and F Gao and P Cheng and L Chen and S Klyatskaya and M Ruben and J Rosen and J V Barth and J Bj\"{o}rk and K Wu and Y-Q Zhang},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.202400222},
doi = {https://doi.org/10.1002/admi.202400222},
issn = {2196-7350},
year = {2024},
date = {2024-09-12},
journal = {Advanced Materials Interfaces},
volume = {11},
number = {26},
pages = {2400222},
abstract = {Abstract On-surface reactions of terminal alkynes in ultrahigh vacuum have attracted widespread attention due to their high technological promise. However, employing different precursors and substrate materials often intricate reaction schemes appear far from being well-understood. Thus, recent investigations of alkyne coupling on noble metal surfaces suggest non-dehydrogenative scenarios, contradicting earlier reports. Herein, the study employs noncontact atomic force microscopy (nc-AFM) with high spatial resolution to conclusively characterize exemplary alkyne coupling products. Contrary to initial interpretations proposing dehydrogenative homocoupling on Ag(111), bond-resolved AFM imaging reveals the expression of enyne motifs. Based on complementary, extensive density functional theory calculations, the pertaining reaction mechanisms are explored. It is proposed that enyne formation initiates with a direct carbon\textendashcarbon coupling between two alkyne groups, followed by surface-assisted dehydrogenation-hydrogenation processes. Thereby consecutive steps of atomic hydrogen cleavage, surface migration and recombination to a different carbon atom enable bridging via carbon\textendashcarbon double bonding. The new results shed light on subtle, but crucial surface-mediated hydrogen transfer processes involved in the chemical bond formation, which are suggested to be of general relevance in on-surface synthesis.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract On-surface reactions of terminal alkynes in ultrahigh vacuum have attracted widespread attention due to their high technological promise. However, employing different precursors and substrate materials often intricate reaction schemes appear far from being well-understood. Thus, recent investigations of alkyne coupling on noble metal surfaces suggest non-dehydrogenative scenarios, contradicting earlier reports. Herein, the study employs noncontact atomic force microscopy (nc-AFM) with high spatial resolution to conclusively characterize exemplary alkyne coupling products. Contrary to initial interpretations proposing dehydrogenative homocoupling on Ag(111), bond-resolved AFM imaging reveals the expression of enyne motifs. Based on complementary, extensive density functional theory calculations, the pertaining reaction mechanisms are explored. It is proposed that enyne formation initiates with a direct carbon–carbon coupling between two alkyne groups, followed by surface-assisted dehydrogenation-hydrogenation processes. Thereby consecutive steps of atomic hydrogen cleavage, surface migration and recombination to a different carbon atom enable bridging via carbon–carbon double bonding. The new results shed light on subtle, but crucial surface-mediated hydrogen transfer processes involved in the chemical bond formation, which are suggested to be of general relevance in on-surface synthesis.
30.
S J Riepl, S Kossler, J Braun, J Minár, J V Barth, P Feulner
In: Low Temperature Physics, vol. 50, no. 9, pp. 713-721, 2024, ISSN: 1063-777X.
@article{nokey,
title = {Helium 1s photoemission and photon stimulated desorption of He+ ions by double excitations from adsorbed helium layers: Zero-point motion and matrix effects},
author = {S J Riepl and S Kossler and J Braun and J Min\'{a}r and J V Barth and P Feulner},
url = {https://doi.org/10.1063/10.0028136},
doi = {10.1063/10.0028136},
issn = {1063-777X},
year = {2024},
date = {2024-09-01},
journal = {Low Temperature Physics},
volume = {50},
number = {9},
pages = {713-721},
abstract = {Excited with p-polarized light, the near-edge He 1s photoemission signal from monolayers of He adsorbed on the close-packed surfaces of silver, copper, ruthenium, and platinum shows periodic splitting with photoelectron momentum. By applying a simple single scattering model, we explain this effect by zero-point motion induced variation of the photo hole’s image charge screening and interference of the photoelectron’s final state wavefunction. Relativistic one-step photoemission calculations support this interpretation. In the second part of our study, we investigate neutral double excitations of He bilayers adsorbed on platinum by monitoring the emission of He+ ions. We identify strong matrix and zero-point motion effects, namely resonances absent for isolated He, density and light polarization dependence, line broadening and a correlation of excitation and kinetic ion-energy.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Excited with p-polarized light, the near-edge He 1s photoemission signal from monolayers of He adsorbed on the close-packed surfaces of silver, copper, ruthenium, and platinum shows periodic splitting with photoelectron momentum. By applying a simple single scattering model, we explain this effect by zero-point motion induced variation of the photo hole’s image charge screening and interference of the photoelectron’s final state wavefunction. Relativistic one-step photoemission calculations support this interpretation. In the second part of our study, we investigate neutral double excitations of He bilayers adsorbed on platinum by monitoring the emission of He+ ions. We identify strong matrix and zero-point motion effects, namely resonances absent for isolated He, density and light polarization dependence, line broadening and a correlation of excitation and kinetic ion-energy.
29.
W Zhao, F Haag, I Piquero-Zulaica, Z M Abd El-Fattah, P Pendem, P Vezzoni Vicente, Y-Q Zhang, N Cao, A P Seitsonen, F Allegretti, B Yang, J V Barth
Transmetalation in Surface-Confined Single-Layer Organometallic Networks with Alkynyl–Metal–Alkynyl Linkages Journal Article
In: ACS Nano, vol. 18, no. 31, pp. 20157-20166, 2024, ISSN: 1936-0851.
@article{nokey,
title = {Transmetalation in Surface-Confined Single-Layer Organometallic Networks with Alkynyl\textendashMetal\textendashAlkynyl Linkages},
author = {W Zhao and F Haag and I Piquero-Zulaica and Z M Abd El-Fattah and P Pendem and P Vezzoni Vicente and Y-Q Zhang and N Cao and A P Seitsonen and F Allegretti and B Yang and J V Barth},
url = {https://doi.org/10.1021/acsnano.4c02263},
doi = {10.1021/acsnano.4c02263},
issn = {1936-0851},
year = {2024},
date = {2024-08-06},
journal = {ACS Nano},
volume = {18},
number = {31},
pages = {20157-20166},
abstract = {Transmetalation represents an appealing strategy toward fabricating and tuning functional metal\textendashorganic polymers and frameworks for diverse applications. In particular, building two-dimensional metal\textendashorganic and organometallic networks affords versatile nanoarchitectures of potential interest for nanodevices and quantum technology. The controlled replacement of embedded metal centers holds promise for exploring versatile material varieties by serial modification and different functionalization. Herein, we introduce a protocol for the modification of a single-layer carbon\textendashmetal-based organometallic network via transmetalation. By integrating external Cu atoms into the alkynyl\textendashAg organometallic network constructed with 1,3,5-triethynylbenzene precursors, we successfully realized in situ its highly regular alkynyl\textendashCu counterpart on the Ag(111) surface. While maintaining a similar lattice periodicity and pore morphology to the original alkynyl\textendashAg sheet, the Cu-based network exhibits increased thermal stability, guaranteeing improved robustness for practical implementation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Transmetalation represents an appealing strategy toward fabricating and tuning functional metal–organic polymers and frameworks for diverse applications. In particular, building two-dimensional metal–organic and organometallic networks affords versatile nanoarchitectures of potential interest for nanodevices and quantum technology. The controlled replacement of embedded metal centers holds promise for exploring versatile material varieties by serial modification and different functionalization. Herein, we introduce a protocol for the modification of a single-layer carbon–metal-based organometallic network via transmetalation. By integrating external Cu atoms into the alkynyl–Ag organometallic network constructed with 1,3,5-triethynylbenzene precursors, we successfully realized in situ its highly regular alkynyl–Cu counterpart on the Ag(111) surface. While maintaining a similar lattice periodicity and pore morphology to the original alkynyl–Ag sheet, the Cu-based network exhibits increased thermal stability, guaranteeing improved robustness for practical implementation.
28.
I Piquero-Zulaica, W Hu, A P Seitsonen, F Haag, J Küchle, F Allegretti, Y Lyu, L Chen, K Wu, Z M A El-Fattah, E Aktürk, S Klyatskaya, M Ruben, M Muntwiler, J V Barth, Y-Q Zhang
Unconventional Band Structure via Combined Molecular Orbital and Lattice Symmetries in a Surface-Confined Metallated Graphdiyne Sheet Journal Article
In: Advanced Materials, vol. 36, no. 31, pp. 2405178, 2024, ISSN: 0935-9648.
@article{nokey,
title = {Unconventional Band Structure via Combined Molecular Orbital and Lattice Symmetries in a Surface-Confined Metallated Graphdiyne Sheet},
author = {I Piquero-Zulaica and W Hu and A P Seitsonen and F Haag and J K\"{u}chle and F Allegretti and Y Lyu and L Chen and K Wu and Z M A El-Fattah and E Akt\"{u}rk and S Klyatskaya and M Ruben and M Muntwiler and J V Barth and Y-Q Zhang},
url = {https://advanced.onlinelibrary.wiley.com/doi/abs/10.1002/adma.202405178},
doi = {https://doi.org/10.1002/adma.202405178},
issn = {0935-9648},
year = {2024},
date = {2024-08-01},
journal = {Advanced Materials},
volume = {36},
number = {31},
pages = {2405178},
abstract = {Abstract Graphyne (GY) and graphdiyne (GDY)-based monolayers represent the next generation 2D carbon-rich materials with tunable structures and properties surpassing those of graphene. However, the detection of band formation in atomically thin GY/GDY analogues has been challenging, as both long-range order and atomic precision have to be fulfilled in the system. The present work reports direct evidence of band formation in on-surface synthesized metallated Ag-GDY sheets with mesoscopic (≈1 µm) regularity. Employing scanning tunneling and angle-resolved photoemission spectroscopies, energy-dependent transitions of real-space electronic states above the Fermi level and formation of the valence band are respectively observed. Furthermore, density functional theory (DFT) calculations corroborate the observations and reveal that doubly degenerate frontier molecular orbitals on a honeycomb lattice give rise to flat, Dirac and Kagome bands close to the Fermi level. DFT modeling also indicates an intrinsic band gap for the pristine sheet material, which is retained for a bilayer with h-BN, whereas adsorption-induced in-gap electronic states evolve at the synthesis platform with Ag-GDY decorating the (111) facet of silver. These results illustrate the tremendous potential for engineering novel band structures via molecular orbital and lattice symmetries in atomically precise 2D carbon materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Graphyne (GY) and graphdiyne (GDY)-based monolayers represent the next generation 2D carbon-rich materials with tunable structures and properties surpassing those of graphene. However, the detection of band formation in atomically thin GY/GDY analogues has been challenging, as both long-range order and atomic precision have to be fulfilled in the system. The present work reports direct evidence of band formation in on-surface synthesized metallated Ag-GDY sheets with mesoscopic (≈1 µm) regularity. Employing scanning tunneling and angle-resolved photoemission spectroscopies, energy-dependent transitions of real-space electronic states above the Fermi level and formation of the valence band are respectively observed. Furthermore, density functional theory (DFT) calculations corroborate the observations and reveal that doubly degenerate frontier molecular orbitals on a honeycomb lattice give rise to flat, Dirac and Kagome bands close to the Fermi level. DFT modeling also indicates an intrinsic band gap for the pristine sheet material, which is retained for a bilayer with h-BN, whereas adsorption-induced in-gap electronic states evolve at the synthesis platform with Ag-GDY decorating the (111) facet of silver. These results illustrate the tremendous potential for engineering novel band structures via molecular orbital and lattice symmetries in atomically precise 2D carbon materials.
27.
D Potamianos, M Schnitzenbaumer, C Lemell, P Scigalla, F Libisch, E Schock-Schmidtke, M Haimerl, C Schröder, M Schäffer, J T Küchle, J Riemensberger, K Eberle, Y Cui, U Kleineberg, J Burgdörfer, J V Barth, P Feulner, F Allegretti, R Kienberger
Attosecond chronoscopy of the photoemission near a bandgap of a single-element layered dielectric Journal Article
In: Science Advances, vol. 10, no. 26, pp. eado0073, 2024.
@article{nokey,
title = {Attosecond chronoscopy of the photoemission near a bandgap of a single-element layered dielectric},
author = {D Potamianos and M Schnitzenbaumer and C Lemell and P Scigalla and F Libisch and E Schock-Schmidtke and M Haimerl and C Schr\"{o}der and M Sch\"{a}ffer and J T K\"{u}chle and J Riemensberger and K Eberle and Y Cui and U Kleineberg and J Burgd\"{o}rfer and J V Barth and P Feulner and F Allegretti and R Kienberger},
url = {https://www.science.org/doi/abs/10.1126/sciadv.ado0073},
doi = {doi:10.1126/sciadv.ado0073},
year = {2024},
date = {2024-06-26},
journal = {Science Advances},
volume = {10},
number = {26},
pages = {eado0073},
abstract = {We report on the energy dependence of the photoemission time delay from the single-element layered dielectric HOPG (highly oriented pyrolytic graphite). This system offers the unique opportunity to directly observe the Eisenbud-Wigner-Smith (EWS) time delays related to the bulk electronic band structure without being strongly perturbed by ubiquitous effects of transport, screening, and multiple scattering. We find the experimental streaking time shifts to be sensitive to the modulation of the density of states in the high-energy region (E ≈ 100 eV) of the band structure. The present attosecond chronoscopy experiments reveal an energy-dependent increase of the photoemission time delay when the final state energy of the excited electrons lies in the vicinity of the bandgap providing information difficult to access by conventional spectroscopy. Accompanying simulations further corroborate our interpretation. Photoionization timing is exploited for detecting otherwise inaccessible high-energy region band structure features.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report on the energy dependence of the photoemission time delay from the single-element layered dielectric HOPG (highly oriented pyrolytic graphite). This system offers the unique opportunity to directly observe the Eisenbud-Wigner-Smith (EWS) time delays related to the bulk electronic band structure without being strongly perturbed by ubiquitous effects of transport, screening, and multiple scattering. We find the experimental streaking time shifts to be sensitive to the modulation of the density of states in the high-energy region (E ≈ 100 eV) of the band structure. The present attosecond chronoscopy experiments reveal an energy-dependent increase of the photoemission time delay when the final state energy of the excited electrons lies in the vicinity of the bandgap providing information difficult to access by conventional spectroscopy. Accompanying simulations further corroborate our interpretation. Photoionization timing is exploited for detecting otherwise inaccessible high-energy region band structure features.
26.
N Cao, J Björk, E Corral-Rascon, Z Chen, M Ruben, M O Senge, J V Barth, A Riss
The role of aromaticity in the cyclization and polymerization of alkyne-substituted porphyrins on Au(111) Journal Article
In: Nature Chemistry, vol. 15, no. 12, pp. 1765-1772, 2023, ISSN: 1755-4349.
@article{nokey,
title = {The role of aromaticity in the cyclization and polymerization of alkyne-substituted porphyrins on Au(111)},
author = {N Cao and J Bj\"{o}rk and E Corral-Rascon and Z Chen and M Ruben and M O Senge and J V Barth and A Riss},
url = {https://doi.org/10.1038/s41557-023-01327-6},
doi = {10.1038/s41557-023-01327-6},
issn = {1755-4349},
year = {2023},
date = {2023-12-01},
journal = {Nature Chemistry},
volume = {15},
number = {12},
pages = {1765-1772},
abstract = {Aromaticity is an established and widely used concept for the prediction of the reactivity of organic molecules. However, its role remains largely unexplored in on-surface chemistry, where the interaction with the substrate can alter the electronic and geometric structure of the adsorbates. Here we investigate how aromaticity affects the reactivity of alkyne-substituted porphyrin molecules in cyclization and coupling reactions on a Au(111) surface. We examine and quantify the regioselectivity in the reactions by scanning tunnelling microscopy and bond-resolved atomic force microscopy at the single-molecule level. Our experiments show a substantially lower reactivity of carbon atoms that are stabilized by the aromatic diaza[18]annulene pathway of free-base porphyrins. The results are corroborated by density functional theory calculations, which show a direct correlation between aromaticity and thermodynamic stability of the reaction products. These insights are helpful to understand, and in turn design, reactions with aromatic species in on-surface chemistry and heterogeneous catalysis.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Aromaticity is an established and widely used concept for the prediction of the reactivity of organic molecules. However, its role remains largely unexplored in on-surface chemistry, where the interaction with the substrate can alter the electronic and geometric structure of the adsorbates. Here we investigate how aromaticity affects the reactivity of alkyne-substituted porphyrin molecules in cyclization and coupling reactions on a Au(111) surface. We examine and quantify the regioselectivity in the reactions by scanning tunnelling microscopy and bond-resolved atomic force microscopy at the single-molecule level. Our experiments show a substantially lower reactivity of carbon atoms that are stabilized by the aromatic diaza[18]annulene pathway of free-base porphyrins. The results are corroborated by density functional theory calculations, which show a direct correlation between aromaticity and thermodynamic stability of the reaction products. These insights are helpful to understand, and in turn design, reactions with aromatic species in on-surface chemistry and heterogeneous catalysis.
25.
C Schröder, J Riemensberger, R Kuzian, M Ossiander, D Potamianos, F Allegrett, L Bignardi, S Lizzit, A Akil, A Cavalieri, D Menzel, S Neppl, R Ernstorfer, J Braun, H Ebert, J Minar, W Helml, M Jobst, M Gerl, E Bothschafter, A Kim, K Hütten, U Kleineberg, M Schnitzenbaumer, J V Barth, P Feulner, E Krasovskii, R Kienberger
Attosecond dynamics of photoemission over a wide photon energy range Miscellaneous
2023.
@misc{nokey,
title = {Attosecond dynamics of photoemission over a wide photon energy range},
author = {C Schr\"{o}der and J Riemensberger and R Kuzian and M Ossiander and D Potamianos and F Allegrett and L Bignardi and S Lizzit and A Akil and A Cavalieri and D Menzel and S Neppl and R Ernstorfer and J Braun and H Ebert and J Minar and W Helml and M Jobst and M Gerl and E Bothschafter and A Kim and K H\"{u}tten and U Kleineberg and M Schnitzenbaumer and J V Barth and P Feulner and E Krasovskii and R Kienberger},
url = {http://europepmc.org/abstract/PPR/PPR750080
https://doi.org/10.21203/rs.3.rs-3024896/v1},
doi = {10.21203/rs.3.rs-3024896/v1},
year = {2023},
date = {2023-10-01},
urldate = {2023-10-01},
publisher = {Research Square},
abstract = {Dynamics of photoemission from surfaces are usually studied at low photon energies (\<100 eV). Here, we report on new findings on these dynamics observed at a tungsten surface on the attosecond time scale at photon energies exceeding 100 eV, over a range of almost 50 eV. While photoemission, a fundamental process in quantum mechanics, is often described within a semiclassical three-step model, we find that even at high photon energies only a full quantum treatment in one step predicts the measured attosecond dynamics correctly. On this time scale the intuitive, mechanistic interpretation of the photoelectric effect breaks down. This underlines the necessity to further develop experimental and theoretical tools to be used in improving our understanding of the fundamental process of light-matter interaction underlying many methods in extreme ultraviolet and soft x-ray spectroscopy.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Dynamics of photoemission from surfaces are usually studied at low photon energies (<100 eV). Here, we report on new findings on these dynamics observed at a tungsten surface on the attosecond time scale at photon energies exceeding 100 eV, over a range of almost 50 eV. While photoemission, a fundamental process in quantum mechanics, is often described within a semiclassical three-step model, we find that even at high photon energies only a full quantum treatment in one step predicts the measured attosecond dynamics correctly. On this time scale the intuitive, mechanistic interpretation of the photoelectric effect breaks down. This underlines the necessity to further develop experimental and theoretical tools to be used in improving our understanding of the fundamental process of light-matter interaction underlying many methods in extreme ultraviolet and soft x-ray spectroscopy.
24.
N Cao, B Yang, A Riss, J Rosen, J Björk, J V Barth
On-surface synthesis of enetriynes Journal Article
In: Nature Communications, vol. 14, no. 1, pp. 1255, 2023, ISSN: 2041-1723.
@article{nokey,
title = {On-surface synthesis of enetriynes},
author = {N Cao and B Yang and A Riss and J Rosen and J Bj\"{o}rk and J V Barth},
url = {https://doi.org/10.1038/s41467-023-36828-y},
doi = {10.1038/s41467-023-36828-y},
issn = {2041-1723},
year = {2023},
date = {2023-03-06},
journal = {Nature Communications},
volume = {14},
number = {1},
pages = {1255},
abstract = {Belonging to the enyne family, enetriynes comprise a distinct electron-rich all-carbon bonding scheme. However, the lack of convenient synthesis protocols limits the associated application potential within, e.g., biochemistry and materials science. Herein we introduce a pathway for highly selective enetriyne formation via tetramerization of terminal alkynes on a Ag(100) surface. Taking advantage of a directing hydroxyl group, we steer molecular assembly and reaction processes on square lattices. Induced by O2 exposure the terminal alkyne moieties deprotonate and organometallic bis-acetylide dimer arrays evolve. Upon subsequent thermal annealing tetrameric enetriyne-bridged compounds are generated in high yield, readily self-assembling into regular networks. We combine high-resolution scanning probe microscopy, X-ray photoelectron spectroscopy and density functional theory calculations to examine the structural features, bonding characteristics and the underlying reaction mechanism. Our study introduces an integrated strategy for the precise fabrication of functional enetriyne species, thus providing access to a distinct class of highly conjugated π-system compounds.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Belonging to the enyne family, enetriynes comprise a distinct electron-rich all-carbon bonding scheme. However, the lack of convenient synthesis protocols limits the associated application potential within, e.g., biochemistry and materials science. Herein we introduce a pathway for highly selective enetriyne formation via tetramerization of terminal alkynes on a Ag(100) surface. Taking advantage of a directing hydroxyl group, we steer molecular assembly and reaction processes on square lattices. Induced by O2 exposure the terminal alkyne moieties deprotonate and organometallic bis-acetylide dimer arrays evolve. Upon subsequent thermal annealing tetrameric enetriyne-bridged compounds are generated in high yield, readily self-assembling into regular networks. We combine high-resolution scanning probe microscopy, X-ray photoelectron spectroscopy and density functional theory calculations to examine the structural features, bonding characteristics and the underlying reaction mechanism. Our study introduces an integrated strategy for the precise fabrication of functional enetriyne species, thus providing access to a distinct class of highly conjugated π-system compounds.
23.
P Leidinger, M Panighel, V Pérez Dieste, I J Villar-Garcia, P Vezzoni, F Haag, J V Barth, F Allegretti, S Günther, L L Patera
Probing dynamic covalent chemistry in a 2D boroxine framework by in situ near-ambient pressure X-ray photoelectron spectroscopy Journal Article
In: Nanoscale, vol. 15, no. 3, pp. 1068-1075, 2022, ISSN: 2040-3364.
@article{nokey,
title = {Probing dynamic covalent chemistry in a 2D boroxine framework by in situ near-ambient pressure X-ray photoelectron spectroscopy},
author = {P Leidinger and M Panighel and V P\'{e}rez Dieste and I J Villar-Garcia and P Vezzoni and F Haag and J V Barth and F Allegretti and S G\"{u}nther and L L Patera},
url = {http://dx.doi.org/10.1039/D2NR04949J},
doi = {10.1039/D2NR04949J},
issn = {2040-3364},
year = {2022},
date = {2022-12-01},
journal = {Nanoscale},
volume = {15},
number = {3},
pages = {1068-1075},
abstract = {Dynamic covalent chemistry is a powerful approach to design covalent organic frameworks, where high crystallinity is achieved through reversible bond formation. Here, we exploit near-ambient pressure X-ray photoelectron spectroscopy to elucidate the reversible formation of a two-dimensional boroxine framework. By in situ mapping the pressure\textendashtemperature parameter space, we identify the regions where the rates of the condensation and hydrolysis reactions become dominant, being the key to enable the thermodynamically controlled growth of crystalline frameworks.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Dynamic covalent chemistry is a powerful approach to design covalent organic frameworks, where high crystallinity is achieved through reversible bond formation. Here, we exploit near-ambient pressure X-ray photoelectron spectroscopy to elucidate the reversible formation of a two-dimensional boroxine framework. By in situ mapping the pressure–temperature parameter space, we identify the regions where the rates of the condensation and hydrolysis reactions become dominant, being the key to enable the thermodynamically controlled growth of crystalline frameworks.
22.
R M Kluge, R W Haid, A Riss, Y Bao, K Seufert, T O Schmidt, S A Watzele, J V Barth, F Allegretti, W Auwärter, F Calle-Vallejo, A S Bandarenka
A trade-off between ligand and strain effects optimizes the oxygen reduction activity of Pt alloys Journal Article
In: Energy & Environmental Science, vol. 15, no. 12, pp. 5181-5191, 2022, ISSN: 1754-5692.
@article{nokey,
title = {A trade-off between ligand and strain effects optimizes the oxygen reduction activity of Pt alloys},
author = {R M Kluge and R W Haid and A Riss and Y Bao and K Seufert and T O Schmidt and S A Watzele and J V Barth and F Allegretti and W Auw\"{a}rter and F Calle-Vallejo and A S Bandarenka},
url = {http://dx.doi.org/10.1039/D2EE01850K},
doi = {10.1039/D2EE01850K},
issn = {1754-5692},
year = {2022},
date = {2022-10-20},
journal = {Energy \& Environmental Science},
volume = {15},
number = {12},
pages = {5181-5191},
abstract = {To optimize the performance of catalytic materials, it is paramount to elucidate the dependence of the chemical reactivity on the atomic arrangement of the catalyst surface. Therefore, identifying the nature of the active sites that provide optimal binding of reaction intermediates is the first step toward a rational catalyst design. In this work, we focus on the oxygen reduction reaction (ORR), an essential constituent of several energy provision and storage devices. Among the state-of-the-art ORR catalysts are platinum (Pt) and its alloys. The latter benefit from the so-called ligand and strain effects, which influence the electronic properties of the surface. Here, we “visualize” the active sites on Pt3Ni(111) in an acidic medium with a lateral resolution in the nanometre regime via an in situ technique based on electrochemical scanning tunnelling microscopy. In contrast to pure Pt, where the active sites are located at concave sites close to steps, Pt3Ni(111) terraces contain the most active centres, while steps show activity to a comparable or lesser extent. We confirm the experimental findings by a model based on alloy- and strain-sensitive generalized coordination numbers. With this model, we are also able to assess both the composition and the geometric configuration of optimal catalytic active sites on various Pt alloy catalysts. In general, the interplay of ligand effects and lattice compression resulting from the alloying of Pt with 3d transition metals (Ti, Co, Ni, Cu) gradually increases the generalized coordination number of surface Pt atoms, thereby making (111) terraces highly active. This combination of theoretical and experimental tools provides clear strategies to design more efficient Pt alloy electrocatalysts for oxygen reduction.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
To optimize the performance of catalytic materials, it is paramount to elucidate the dependence of the chemical reactivity on the atomic arrangement of the catalyst surface. Therefore, identifying the nature of the active sites that provide optimal binding of reaction intermediates is the first step toward a rational catalyst design. In this work, we focus on the oxygen reduction reaction (ORR), an essential constituent of several energy provision and storage devices. Among the state-of-the-art ORR catalysts are platinum (Pt) and its alloys. The latter benefit from the so-called ligand and strain effects, which influence the electronic properties of the surface. Here, we “visualize” the active sites on Pt3Ni(111) in an acidic medium with a lateral resolution in the nanometre regime via an in situ technique based on electrochemical scanning tunnelling microscopy. In contrast to pure Pt, where the active sites are located at concave sites close to steps, Pt3Ni(111) terraces contain the most active centres, while steps show activity to a comparable or lesser extent. We confirm the experimental findings by a model based on alloy- and strain-sensitive generalized coordination numbers. With this model, we are also able to assess both the composition and the geometric configuration of optimal catalytic active sites on various Pt alloy catalysts. In general, the interplay of ligand effects and lattice compression resulting from the alloying of Pt with 3d transition metals (Ti, Co, Ni, Cu) gradually increases the generalized coordination number of surface Pt atoms, thereby making (111) terraces highly active. This combination of theoretical and experimental tools provides clear strategies to design more efficient Pt alloy electrocatalysts for oxygen reduction.
21.
A Badami-Behjat, P S Deimel, F Allegretti, E Ringel, K Mahata, M Schmittel, J V Barth, W M Heckl, M Lackinger
In: Chemistry of Materials, vol. 34, no. 19, pp. 8876-8884, 2022, ISSN: 0897-4756.
@article{nokey,
title = {Versatile Role of Molecule\textendashSurface Interactions for Monolayer Self-Assembly at Liquid\textendashSolid Interfaces: Substrate-Induced Polymorphism, Thermodynamic Stability, and New Polymorphs},
author = {A Badami-Behjat and P S Deimel and F Allegretti and E Ringel and K Mahata and M Schmittel and J V Barth and W M Heckl and M Lackinger},
url = {https://doi.org/10.1021/acs.chemmater.2c02177},
doi = {10.1021/acs.chemmater.2c02177},
issn = {0897-4756},
year = {2022},
date = {2022-10-11},
journal = {Chemistry of Materials},
volume = {34},
number = {19},
pages = {8876-8884},
abstract = {Self-assembly of supramolecular monolayers at liquid\textendashsolid interfaces has matured into an established research field. Numerous studies unveiled crucial influences of solvent, solute concentration, and temperature on the kinetics and thermodynamics of monolayer formation and their specific role for structure selection. Yet, almost all experiments are carried out on highly inert graphite surfaces that are straightforward to prepare. However, the strong focus on graphite leaves the crucial impact of the underlying surface severely underexplored. Here, we show that passivation of Au(111) with a chemisorbed monolayer of iodine atoms renders it sufficiently inert for studies at liquid\textendashsolid interfaces, even at elevated temperatures. By using aromatic homologues of benzene tricarboxylic acids as a well-explored model system and by a one-to-one comparison to graphite, we unveil that molecule\textendashsurface interactions can cause substrate-induced polymorphism, crucially affect the supramolecular monolayer’s thermodynamic stability, or even result in the emergence of new polymorphs. These experiments underscore a decisive and specific thermodynamic influence of the underlying surface. We expect our study to stimulate further research on the surface influence on interfacial monolayers by employing this accessible and easy-to-prepare surface with the aim to establish a new lever for steering supramolecular self-assembly.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Self-assembly of supramolecular monolayers at liquid–solid interfaces has matured into an established research field. Numerous studies unveiled crucial influences of solvent, solute concentration, and temperature on the kinetics and thermodynamics of monolayer formation and their specific role for structure selection. Yet, almost all experiments are carried out on highly inert graphite surfaces that are straightforward to prepare. However, the strong focus on graphite leaves the crucial impact of the underlying surface severely underexplored. Here, we show that passivation of Au(111) with a chemisorbed monolayer of iodine atoms renders it sufficiently inert for studies at liquid–solid interfaces, even at elevated temperatures. By using aromatic homologues of benzene tricarboxylic acids as a well-explored model system and by a one-to-one comparison to graphite, we unveil that molecule–surface interactions can cause substrate-induced polymorphism, crucially affect the supramolecular monolayer’s thermodynamic stability, or even result in the emergence of new polymorphs. These experiments underscore a decisive and specific thermodynamic influence of the underlying surface. We expect our study to stimulate further research on the surface influence on interfacial monolayers by employing this accessible and easy-to-prepare surface with the aim to establish a new lever for steering supramolecular self-assembly.
20.
J T Küchle, A Baklanov, A P Seitsonen, P T P Ryan, P Feulner, P Pendem, T-L Lee, M Muntwiler, M Schwarz, F Haag, J V Barth, W Auwärter, D A Duncan, F Allegretti
Silicene’s pervasive surface alloy on Ag(111): a scaffold for two-dimensional growth Journal Article
In: 2D Materials, vol. 9, no. 4, pp. 045021, 2022, ISSN: 2053-1583.
@article{nokey,
title = {Silicene’s pervasive surface alloy on Ag(111): a scaffold for two-dimensional growth},
author = {J T K\"{u}chle and A Baklanov and A P Seitsonen and P T P Ryan and P Feulner and P Pendem and T-L Lee and M Muntwiler and M Schwarz and F Haag and J V Barth and W Auw\"{a}rter and D A Duncan and F Allegretti},
url = {https://dx.doi.org/10.1088/2053-1583/ac8a01},
doi = {10.1088/2053-1583/ac8a01},
issn = {2053-1583},
year = {2022},
date = {2022-09-06},
journal = {2D Materials},
volume = {9},
number = {4},
pages = {045021},
abstract = {Silicene, the two-dimensional (2D) allotrope of silicon, is a promising material for electronics. So far, the most direct synthesis strategy has been to grow it epitaxially on metal surfaces; however, the effect of the strong silicon-metal interaction on the structure and electronic properties of the metal-supported silicene is generally poorly understood. In this work, we consider the -silicene monolayer (ML) grown on Ag(111), probably the most illustrious representative of the 2D silicon family, and show that our experimental results refute the common interpretation of this system as a simple buckled, honeycomb ML with a sharp interface to the Ag substrate. Instead, the presented analysis demonstrates the pervasive presence of a second silicon species, which we conclude to be a Si\textendashAg alloy stacked between the 2D silicene and the silver substrate and scaffolding the 2D silicene layer. These findings question the current structural understanding of the silicene/Ag(111) interface and may raise expectations of analogous alloy systems in the stabilization of other 2D materials grown epitaxially on metal surfaces.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Silicene, the two-dimensional (2D) allotrope of silicon, is a promising material for electronics. So far, the most direct synthesis strategy has been to grow it epitaxially on metal surfaces; however, the effect of the strong silicon-metal interaction on the structure and electronic properties of the metal-supported silicene is generally poorly understood. In this work, we consider the -silicene monolayer (ML) grown on Ag(111), probably the most illustrious representative of the 2D silicon family, and show that our experimental results refute the common interpretation of this system as a simple buckled, honeycomb ML with a sharp interface to the Ag substrate. Instead, the presented analysis demonstrates the pervasive presence of a second silicon species, which we conclude to be a Si–Ag alloy stacked between the 2D silicene and the silver substrate and scaffolding the 2D silicene layer. These findings question the current structural understanding of the silicene/Ag(111) interface and may raise expectations of analogous alloy systems in the stabilization of other 2D materials grown epitaxially on metal surfaces.
19.
D Meier, B Schoof, J Wang, X Li, A Walz, A Huettig, H Schlichting, F Rosu, V Gabelica, V Maurizot, J Reichert, A C Papageorgiou, I Huc, J V Barth
Structural adaptations of electrosprayed aromatic oligoamide foldamers on Ag(111) Journal Article
In: Chemical Communications, vol. 58, no. 64, pp. 8938-8941, 2022, ISSN: 1359-7345.
@article{nokey,
title = {Structural adaptations of electrosprayed aromatic oligoamide foldamers on Ag(111)},
author = {D Meier and B Schoof and J Wang and X Li and A Walz and A Huettig and H Schlichting and F Rosu and V Gabelica and V Maurizot and J Reichert and A C Papageorgiou and I Huc and J V Barth},
url = {http://dx.doi.org/10.1039/D2CC03286D},
doi = {10.1039/D2CC03286D},
issn = {1359-7345},
year = {2022},
date = {2022-07-11},
journal = {Chemical Communications},
volume = {58},
number = {64},
pages = {8938-8941},
abstract = {Aromatic foldamers are promising for applications such as molecular recognition and molecular machinery. For many of these, defect free, 2D-crystaline monolayers are needed. To this end, submonolayers were prepared in ultra-high vacuum (UHV) on Ag(111) via electrospray controlled ion beam deposition (ES-CIBD). On the surface, the unfolded state is unambiguously identified by real-space single-molecule imaging using scanning tunnelling microscopy (STM) and it is found to assemble in regular structures.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Aromatic foldamers are promising for applications such as molecular recognition and molecular machinery. For many of these, defect free, 2D-crystaline monolayers are needed. To this end, submonolayers were prepared in ultra-high vacuum (UHV) on Ag(111) via electrospray controlled ion beam deposition (ES-CIBD). On the surface, the unfolded state is unambiguously identified by real-space single-molecule imaging using scanning tunnelling microscopy (STM) and it is found to assemble in regular structures.
18.
A Walz, K Stoiber, A Huettig, H Schlichting, J V Barth
In: Analytical Chemistry, vol. 94, no. 22, pp. 7767-7778, 2022, ISSN: 0003-2700.
@article{nokey,
title = {Navigate Flying Molecular Elephants Safely to the Ground: Mass-Selective Soft Landing up to the Mega-Dalton Range by Electrospray Controlled Ion-Beam Deposition},
author = {A Walz and K Stoiber and A Huettig and H Schlichting and J V Barth},
url = {https://doi.org/10.1021/acs.analchem.1c04495},
doi = {10.1021/acs.analchem.1c04495},
issn = {0003-2700},
year = {2022},
date = {2022-06-07},
journal = {Analytical Chemistry},
volume = {94},
number = {22},
pages = {7767-7778},
abstract = {The prototype of a highly versatile and efficient preparative mass spectrometry system used for the deposition of molecules in ultrahigh vacuum (UHV) is presented, along with encouraging performance data obtained using four model species that are thermolabile or not sublimable. The test panel comprises two small organic compounds, a small and very large protein, and a large DNA species covering a 4-log mass range up to 1.7 MDa as part of a broad spectrum of analyte species evaluated to date. Three designs of innovative ion guides, a novel digital mass-selective quadrupole (dQMF), and a standard electrospray ionization (ESI) source are combined to an integrated device, abbreviated electrospray controlled ion-beam deposition (ES-CIBD). Full control is achieved by (i) the square-wave-driven radiofrequency (RF) ion guides with steadily tunable frequencies, including a dQMF allowing for investigation, purification, and deposition of a virtually unlimited m/z range, (ii) the adjustable landing energy of ions down to ∼2 eV/z enabling integrity-preserving soft landing, (iii) the deposition in UHV with high ion beam intensity (up to 3 nA) limiting contaminations and deposition time, and (iv) direct coverage control via the deposited charge. The maximum resolution of R = 650 and overall efficiency up to Ttotal = 4.4% calculated from the solution to UHV deposition are advantageous, whereby the latter can be further enhanced by optimizing ionization performance. In the setup presented, a scanning tunneling microscope (STM) is attached for in situ UHV investigations of deposited species, demonstrating a selective, structure-preserving process and atomically clean layers.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The prototype of a highly versatile and efficient preparative mass spectrometry system used for the deposition of molecules in ultrahigh vacuum (UHV) is presented, along with encouraging performance data obtained using four model species that are thermolabile or not sublimable. The test panel comprises two small organic compounds, a small and very large protein, and a large DNA species covering a 4-log mass range up to 1.7 MDa as part of a broad spectrum of analyte species evaluated to date. Three designs of innovative ion guides, a novel digital mass-selective quadrupole (dQMF), and a standard electrospray ionization (ESI) source are combined to an integrated device, abbreviated electrospray controlled ion-beam deposition (ES-CIBD). Full control is achieved by (i) the square-wave-driven radiofrequency (RF) ion guides with steadily tunable frequencies, including a dQMF allowing for investigation, purification, and deposition of a virtually unlimited m/z range, (ii) the adjustable landing energy of ions down to ∼2 eV/z enabling integrity-preserving soft landing, (iii) the deposition in UHV with high ion beam intensity (up to 3 nA) limiting contaminations and deposition time, and (iv) direct coverage control via the deposited charge. The maximum resolution of R = 650 and overall efficiency up to Ttotal = 4.4% calculated from the solution to UHV deposition are advantageous, whereby the latter can be further enhanced by optimizing ionization performance. In the setup presented, a scanning tunneling microscope (STM) is attached for in situ UHV investigations of deposited species, demonstrating a selective, structure-preserving process and atomically clean layers.
17.
N Li, R Guo, A L Oechsle, M A Reus, S Liang, L Song, K Wang, D Yang, F Allegretti, A Kumar, M Nuber, J Berger, S Bernstorff, H Iglev, J Hauer, R A Fischer, J V Barth, P Müller-Buschbaum
Operando Study of Structure Degradation in Solid-State Dye-Sensitized Solar Cells with a TiO2 Photoanode Having Ordered Mesopore Arrays Journal Article
In: Solar RRL, vol. n/a, no. n/a, pp. 2200373, 2022, ISSN: 2367-198X.
@article{nokey,
title = {Operando Study of Structure Degradation in Solid-State Dye-Sensitized Solar Cells with a TiO2 Photoanode Having Ordered Mesopore Arrays},
author = {N Li and R Guo and A L Oechsle and M A Reus and S Liang and L Song and K Wang and D Yang and F Allegretti and A Kumar and M Nuber and J Berger and S Bernstorff and H Iglev and J Hauer and R A Fischer and J V Barth and P M\"{u}ller-Buschbaum},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/solr.202200373},
doi = {https://doi.org/10.1002/solr.202200373},
issn = {2367-198X},
year = {2022},
date = {2022-05-31},
journal = {Solar RRL},
volume = {n/a},
number = {n/a},
pages = {2200373},
abstract = {Via operando grazing-incidence small-angle X-ray scattering, the degradation mechanisms of solid-state dye-sensitized solar cells (ssDSSCs) using two types of ordered mesoporous TiO2 scaffolds with different pore sizes, and an exemplary dye D205, are investigated. The temporal evolution of the inner morphology shows a strong impact on device performance. The photoinduced dye aggregation on the TiO2 surface leads to an increase in the domain radius but a decreased spatial order of the photoactive layer during the burn-in stage. This dye aggregation on the TiO2 surface causes the short-circuit current density loss, which plays a major role in the power conversion efficiency decay. Finally, it is found that a larger surface area in the small-pore sample yields a faster short-circuit current density decay as compared with the big-pore sample. Therefore, a control of dye aggregation and the pore size of TiO2 photoelectrodes is crucial for the stability of TiO2-based ssDSSCs.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Via operando grazing-incidence small-angle X-ray scattering, the degradation mechanisms of solid-state dye-sensitized solar cells (ssDSSCs) using two types of ordered mesoporous TiO2 scaffolds with different pore sizes, and an exemplary dye D205, are investigated. The temporal evolution of the inner morphology shows a strong impact on device performance. The photoinduced dye aggregation on the TiO2 surface leads to an increase in the domain radius but a decreased spatial order of the photoactive layer during the burn-in stage. This dye aggregation on the TiO2 surface causes the short-circuit current density loss, which plays a major role in the power conversion efficiency decay. Finally, it is found that a larger surface area in the small-pore sample yields a faster short-circuit current density decay as compared with the big-pore sample. Therefore, a control of dye aggregation and the pore size of TiO2 photoelectrodes is crucial for the stability of TiO2-based ssDSSCs.
16.
W Ran, A Walz, K Stoiber, P Knecht, H Xu, A C Papageorgiou, A Huettig, D Cortizo-Lacalle, J P Mora-Fuentes, A Mateo-Alonso, H Schlichting, J Reichert, J V Barth
In: Angewandte Chemie International Edition, vol. n/a, no. n/a, 2022, ISSN: 1433-7851.
@article{nokey,
title = {Depositing Molecular Graphene Nanoribbons on Ag(111) by Electrospray - Controlled Ion Beam Deposition: Self-assembly and On-Surface Transformations},
author = {W Ran and A Walz and K Stoiber and P Knecht and H Xu and A C Papageorgiou and A Huettig and D Cortizo-Lacalle and J P Mora-Fuentes and A Mateo-Alonso and H Schlichting and J Reichert and J V Barth},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202111816},
doi = {https://doi.org/10.1002/anie.202111816},
issn = {1433-7851},
year = {2022},
date = {2022-01-25},
journal = {Angewandte Chemie International Edition},
volume = {n/a},
number = {n/a},
abstract = {The chemical processing of low dimensional carbon nanostructures is crucial for their integration in future devices. Here we apply a new methodology in atomically precise engineering by combining multistep solution synthesis of N-doped molecular graphene nanoribbons (GNRs) with mass-selected ultra-high vacuum electrospray - controlled ion beam deposition on surfaces and real space visualisation by scanning tunnelling microscopy. We demonstrate how this method yields solely a controllable amount of single, otherwise unsublimable, GNRs of 2.9 nm length on a planar Ag(111) surface. This methodology allows for further processing by employing on-surface synthesis protocols and exploiting the reactivity of the substrate. Following multiple chemical transformations, the GNRs provide reactive building blocks to form extended, metal-organic coordination polymers.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The chemical processing of low dimensional carbon nanostructures is crucial for their integration in future devices. Here we apply a new methodology in atomically precise engineering by combining multistep solution synthesis of N-doped molecular graphene nanoribbons (GNRs) with mass-selected ultra-high vacuum electrospray - controlled ion beam deposition on surfaces and real space visualisation by scanning tunnelling microscopy. We demonstrate how this method yields solely a controllable amount of single, otherwise unsublimable, GNRs of 2.9 nm length on a planar Ag(111) surface. This methodology allows for further processing by employing on-surface synthesis protocols and exploiting the reactivity of the substrate. Following multiple chemical transformations, the GNRs provide reactive building blocks to form extended, metal-organic coordination polymers.
15.
D Meier, A K Adak, P Knecht, J Reichert, S Mondal, N Suryadevara, S K Kuppusamy, K Eguchi, M K Muntwiler, F Allegretti, M Ruben, J V Barth, S Narasimhan, A C Papageorgiou
Rotation in an Enantiospecific Self-Assembled Array of Molecular Raffle Wheels Journal Article
In: Angewandte Chemie International Edition, vol. 60, no. 52, pp. 26932-26938, 2021, ISSN: 1433-7851.
@article{nokey,
title = {Rotation in an Enantiospecific Self-Assembled Array of Molecular Raffle Wheels},
author = {D Meier and A K Adak and P Knecht and J Reichert and S Mondal and N Suryadevara and S K Kuppusamy and K Eguchi and M K Muntwiler and F Allegretti and M Ruben and J V Barth and S Narasimhan and A C Papageorgiou},
url = {https://doi.org/10.1002/anie.202107708},
doi = {https://doi.org/10.1002/anie.202107708},
issn = {1433-7851},
year = {2021},
date = {2021-12-20},
journal = {Angewandte Chemie International Edition},
volume = {60},
number = {52},
pages = {26932-26938},
abstract = {Abstract Tailored nano-spaces can control enantioselective adsorption and molecular motion. We report on the spontaneous assembly of a dynamic system?a rigid kagome network with each pore occupied by a guest molecule?employing solely 2,6-bis(1H-pyrazol-1-yl)pyridine-4-carboxylic acid on Ag(111). The network cavity snugly hosts the chemically modified guest, bestows enantiomorphic adsorption and allows selective rotational motions. Temperature-dependent scanning tunnelling microscopy studies revealed distinct anchoring orientations of the guest unit switching with a 0.95?eV thermal barrier. H-bonding between the guest and the host transiently stabilises the rotating guest, as the flapper on a raffle wheel. Density functional theory investigations unravel the detailed molecular pirouette of the guest and how the energy landscape is determined by H-bond formation and breakage. The origin of the guest's enantiodirected, dynamic anchoring lies in the specific interplay of the kagome network and the silver surface.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Tailored nano-spaces can control enantioselective adsorption and molecular motion. We report on the spontaneous assembly of a dynamic system?a rigid kagome network with each pore occupied by a guest molecule?employing solely 2,6-bis(1H-pyrazol-1-yl)pyridine-4-carboxylic acid on Ag(111). The network cavity snugly hosts the chemically modified guest, bestows enantiomorphic adsorption and allows selective rotational motions. Temperature-dependent scanning tunnelling microscopy studies revealed distinct anchoring orientations of the guest unit switching with a 0.95?eV thermal barrier. H-bonding between the guest and the host transiently stabilises the rotating guest, as the flapper on a raffle wheel. Density functional theory investigations unravel the detailed molecular pirouette of the guest and how the energy landscape is determined by H-bond formation and breakage. The origin of the guest's enantiodirected, dynamic anchoring lies in the specific interplay of the kagome network and the silver surface.
14.
N Cao, A Riss, E Corral-Rascon, A Meindl, W Auwärter, M O Senge, M Ebrahimi, J V Barth
Surface-confined formation of conjugated porphyrin-based nanostructures on Ag(111) Journal Article
In: Nanoscale, vol. 13, no. 47, pp. 19884-19889, 2021, ISSN: 2040-3364.
@article{nokey,
title = {Surface-confined formation of conjugated porphyrin-based nanostructures on Ag(111)},
author = {N Cao and A Riss and E Corral-Rascon and A Meindl and W Auw\"{a}rter and M O Senge and M Ebrahimi and J V Barth},
url = {http://dx.doi.org/10.1039/D1NR06451G},
doi = {10.1039/D1NR06451G},
issn = {2040-3364},
year = {2021},
date = {2021-11-25},
journal = {Nanoscale},
volume = {13},
number = {47},
pages = {19884-19889},
abstract = {Porphyrin-based oligomers were synthesized from the condensation of adsorbed 4-benzaldehyde-substituted porphyrins through the formation of CC linkages, following a McMurry-type coupling scheme. Scanning tunneling microscopy, non-contact atomic force microscopy, and X-ray photoelectron spectroscopy data evidence both the dissociation of aldehyde groups and the formation of CC linkages. Our approach provides a path for the on-surface synthesis of porphyrin-based oligomers coupled by CC bridges \textendash as a means to create functional conjugated nanostructures.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Porphyrin-based oligomers were synthesized from the condensation of adsorbed 4-benzaldehyde-substituted porphyrins through the formation of CC linkages, following a McMurry-type coupling scheme. Scanning tunneling microscopy, non-contact atomic force microscopy, and X-ray photoelectron spectroscopy data evidence both the dissociation of aldehyde groups and the formation of CC linkages. Our approach provides a path for the on-surface synthesis of porphyrin-based oligomers coupled by CC bridges – as a means to create functional conjugated nanostructures.
13.
J D Bartl, C Thomas, A Henning, M F Ober, G Savasci, B Yazdanshenas, P S Deimel, E Magnano, F Bondino, P Zeller, L Gregoratti, M Amati, C Paulus, F Allegretti, A Cattani-Scholz, J V Barth, C Ochsenfeld, B Nickel, I D Sharp, M Stutzmann, B Rieger
Modular Assembly of Vibrationally and Electronically Coupled Rhenium Bipyridine Carbonyl Complexes on Silicon Journal Article
In: Journal of the American Chemical Society, vol. 143, pp. 19505, 2021, ISSN: 0002-7863.
@article{nokey,
title = {Modular Assembly of Vibrationally and Electronically Coupled Rhenium Bipyridine Carbonyl Complexes on Silicon},
author = {J D Bartl and C Thomas and A Henning and M F Ober and G Savasci and B Yazdanshenas and P S Deimel and E Magnano and F Bondino and P Zeller and L Gregoratti and M Amati and C Paulus and F Allegretti and A Cattani-Scholz and J V Barth and C Ochsenfeld and B Nickel and I D Sharp and M Stutzmann and B Rieger},
url = {https://doi.org/10.1021/jacs.1c09061},
doi = {10.1021/jacs.1c09061},
issn = {0002-7863},
year = {2021},
date = {2021-11-12},
urldate = {2021-11-12},
journal = {Journal of the American Chemical Society},
volume = {143},
pages = {19505},
abstract = {Hybrid inorganic/organic heterointerfaces are promising systems for next-generation photocatalytic, photovoltaic, and chemical-sensing applications. Their performance relies strongly on the development of robust and reliable surface passivation and functionalization protocols with (sub)molecular control. The structure, stability, and chemistry of the semiconductor surface determine the functionality of the hybrid assembly. Generally, these modification schemes have to be laboriously developed to satisfy the specific chemical demands of the semiconductor surface. The implementation of a chemically independent, yet highly selective, standardized surface functionalization scheme, compatible with nanoelectronic device fabrication, is of utmost technological relevance. Here, we introduce a modular surface assembly (MSA) approach that allows the covalent anchoring of molecular transition-metal complexes with sub-nanometer precision on any solid material by combining atomic layer deposition (ALD) and selectively self-assembled monolayers of phosphonic acids. ALD, as an essential tool in semiconductor device fabrication, is used to grow conformal aluminum oxide activation coatings, down to sub-nanometer thicknesses, on silicon surfaces to enable a selective step-by-step layer assembly of rhenium(I) bipyridine tricarbonyl molecular complexes. The modular surface assembly of molecular complexes generates precisely structured spatial ensembles with strong intermolecular vibrational and electronic coupling, as demonstrated by infrared spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy analysis. The structure of the MSA can be chosen to avoid electronic interactions with the semiconductor substrate to exclusively investigate the electronic interactions between the surface-immobilized molecular complexes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hybrid inorganic/organic heterointerfaces are promising systems for next-generation photocatalytic, photovoltaic, and chemical-sensing applications. Their performance relies strongly on the development of robust and reliable surface passivation and functionalization protocols with (sub)molecular control. The structure, stability, and chemistry of the semiconductor surface determine the functionality of the hybrid assembly. Generally, these modification schemes have to be laboriously developed to satisfy the specific chemical demands of the semiconductor surface. The implementation of a chemically independent, yet highly selective, standardized surface functionalization scheme, compatible with nanoelectronic device fabrication, is of utmost technological relevance. Here, we introduce a modular surface assembly (MSA) approach that allows the covalent anchoring of molecular transition-metal complexes with sub-nanometer precision on any solid material by combining atomic layer deposition (ALD) and selectively self-assembled monolayers of phosphonic acids. ALD, as an essential tool in semiconductor device fabrication, is used to grow conformal aluminum oxide activation coatings, down to sub-nanometer thicknesses, on silicon surfaces to enable a selective step-by-step layer assembly of rhenium(I) bipyridine tricarbonyl molecular complexes. The modular surface assembly of molecular complexes generates precisely structured spatial ensembles with strong intermolecular vibrational and electronic coupling, as demonstrated by infrared spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy analysis. The structure of the MSA can be chosen to avoid electronic interactions with the semiconductor substrate to exclusively investigate the electronic interactions between the surface-immobilized molecular complexes.
12.
J Mahl, O Gessner, J V Barth, P Feulner, S Neppl
Strong Potential Gradients and Electron Confinement in ZnO Nanoparticle Films: Implications for Charge-Carrier Transport and Photocatalysis Journal Article
In: ACS Applied Nano Materials, vol. 4, no. 11, pp. 12213-12221, 2021.
@article{nokey,
title = {Strong Potential Gradients and Electron Confinement in ZnO Nanoparticle Films: Implications for Charge-Carrier Transport and Photocatalysis},
author = {J Mahl and O Gessner and J V Barth and P Feulner and S Neppl},
url = {https://doi.org/10.1021/acsanm.1c02730},
doi = {10.1021/acsanm.1c02730},
year = {2021},
date = {2021-11-11},
journal = {ACS Applied Nano Materials},
volume = {4},
number = {11},
pages = {12213-12221},
abstract = {Zinc oxide (ZnO) nanomaterials are promising components for chemical and biological sensors and photocatalytic conversion and operate as electron collectors in photovoltaic technologies. Many of these applications involve nanostructures in contact with liquids or exposed to ambient atmosphere. Under these conditions, single-crystal ZnO surfaces are known to form narrow electron accumulation layers with few nanometer spatial penetration into the bulk. A key question is to what extent such pronounced surface potential gradients can develop in the nanophases of ZnO, where they would dominate the catalytic activity by modulating charge-carrier mobility and lifetimes. Here, we follow the temperature-dependent surface electronic structure of nanoporous ZnO with photoemission spectroscopy to reveal a sizable, spatially averaged downward band bending for the hydroxylated state and a conservative upper bound of \<6 nm for the spatial extent of the associated potential gradient. This nanoscale confinement of conduction-band electrons to the nanoparticle film surface is crucial for a microscopic understanding and further optimization of charge transport and photocatalytic function in complex ZnO nanomaterials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Zinc oxide (ZnO) nanomaterials are promising components for chemical and biological sensors and photocatalytic conversion and operate as electron collectors in photovoltaic technologies. Many of these applications involve nanostructures in contact with liquids or exposed to ambient atmosphere. Under these conditions, single-crystal ZnO surfaces are known to form narrow electron accumulation layers with few nanometer spatial penetration into the bulk. A key question is to what extent such pronounced surface potential gradients can develop in the nanophases of ZnO, where they would dominate the catalytic activity by modulating charge-carrier mobility and lifetimes. Here, we follow the temperature-dependent surface electronic structure of nanoporous ZnO with photoemission spectroscopy to reveal a sizable, spatially averaged downward band bending for the hydroxylated state and a conservative upper bound of <6 nm for the spatial extent of the associated potential gradient. This nanoscale confinement of conduction-band electrons to the nanoparticle film surface is crucial for a microscopic understanding and further optimization of charge transport and photocatalytic function in complex ZnO nanomaterials.
11.
B Yang, K Niu, F Haag, N Cao, J Zhang, H Zhang, Q Li, F Allegretti, J Björk, J V Barth, L Chi
Abiotic Formation of an Amide Bond via Surface-Supported Direct Carboxyl–Amine Coupling Journal Article
In: Angewandte Chemie International Edition, vol. 61, no. 5, pp. e202113590, 2021, ISSN: 1433-7851.
@article{nokey,
title = {Abiotic Formation of an Amide Bond via Surface-Supported Direct Carboxyl\textendashAmine Coupling},
author = {B Yang and K Niu and F Haag and N Cao and J Zhang and H Zhang and Q Li and F Allegretti and J Bj\"{o}rk and J V Barth and L Chi},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202113590},
doi = {https://doi.org/10.1002/anie.202113590},
issn = {1433-7851},
year = {2021},
date = {2021-10-28},
journal = {Angewandte Chemie International Edition},
volume = {61},
number = {5},
pages = {e202113590},
abstract = {Abstract Amide bond formation is one of the most important reactions in biochemistry, notably being of crucial importance for the origin of life. Herein, we combine scanning tunneling microscopy and X-ray photoelectron spectroscopy studies to provide evidence for thermally activated abiotic formation of amide bonds between adsorbed precursors through direct carboxyl\textendashamine coupling under ultrahigh-vacuum conditions by means of on-surface synthesis. Complementary insights from temperature-programmed desorption measurements and density functional theory calculations reveal the competition between cross-coupling amide formation and decarboxylation reactions on the Au(111) surface. Furthermore, we demonstrate the critical influence of the employed metal support: whereas on Au(111) the coupling readily occurs, different reaction scenarios prevail on Ag(111) and Cu(111). The systematic experiments signal that archetypical bio-related molecules can be abiotically synthesized in clean environments without water or oxygen.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Amide bond formation is one of the most important reactions in biochemistry, notably being of crucial importance for the origin of life. Herein, we combine scanning tunneling microscopy and X-ray photoelectron spectroscopy studies to provide evidence for thermally activated abiotic formation of amide bonds between adsorbed precursors through direct carboxyl–amine coupling under ultrahigh-vacuum conditions by means of on-surface synthesis. Complementary insights from temperature-programmed desorption measurements and density functional theory calculations reveal the competition between cross-coupling amide formation and decarboxylation reactions on the Au(111) surface. Furthermore, we demonstrate the critical influence of the employed metal support: whereas on Au(111) the coupling readily occurs, different reaction scenarios prevail on Ag(111) and Cu(111). The systematic experiments signal that archetypical bio-related molecules can be abiotically synthesized in clean environments without water or oxygen.
10.
F Haag, P S Deimel, P Knecht, L Niederegger, K Seufert, M G. Cuxart, Y Bao, A C Papageorgiou, M Muntwiler, W Auwärter, C R Hess, J V Barth, F Allegretti
The Flexible On-Surface Self-Assembly of a Low-Symmetry Mabiq Ligand: An Unconventional Metal-Assisted Phase Transformation on Ag(111) Journal Article
In: The Journal of Physical Chemistry C, vol. 125, no. 42, pp. 23178-23191, 2021, ISSN: 1932-7447.
@article{nokey,
title = {The Flexible On-Surface Self-Assembly of a Low-Symmetry Mabiq Ligand: An Unconventional Metal-Assisted Phase Transformation on Ag(111)},
author = {F Haag and P S Deimel and P Knecht and L Niederegger and K Seufert and M G. Cuxart and Y Bao and A C Papageorgiou and M Muntwiler and W Auw\"{a}rter and C R Hess and J V Barth and F Allegretti},
url = {https://doi.org/10.1021/acs.jpcc.1c07400},
doi = {10.1021/acs.jpcc.1c07400},
issn = {1932-7447},
year = {2021},
date = {2021-10-12},
journal = {The Journal of Physical Chemistry C},
volume = {125},
number = {42},
pages = {23178-23191},
abstract = {The self-assembly of metal\textendashorganic complexes and networks of increasing complexity on solid surfaces is important for their application in a variety of fields, such as catalysis, sensing, and molecular magnetism. Here, we have selected a low-symmetry, free-base macrocyclic biquinazoline ligand, H-Mabiq, which upon metalation has the potential to incorporate cations in two different coordination sites, affording multi-valency and multi-electron transfer capacity. We show that H-Mabiq molecules readily self-assemble onto the Ag(111) surface at room temperature, forming a well-ordered monolayer of closely packed molecules. Upon increasing the temperature, a new phase with a different long-range order and molecular packing is obtained. By means of scanning tunneling microscopy and photoelectron spectroscopy, we show that this new phase is characterized by a distinctive silver-bridged dimeric motif, entailing a Ag adatom accommodated at the peripheral coordination site of two opposing H-Mabiq molecules. Thus, the present work reveals the ability of the bio-inspired Mabiq ligands to form surface-confined two-dimensional assemblies incorporating metal adatoms. The results bode promise for the use of metal-containing Mabiq compounds to engineer regular bimetallic arrays with atomic precision.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The self-assembly of metal–organic complexes and networks of increasing complexity on solid surfaces is important for their application in a variety of fields, such as catalysis, sensing, and molecular magnetism. Here, we have selected a low-symmetry, free-base macrocyclic biquinazoline ligand, H-Mabiq, which upon metalation has the potential to incorporate cations in two different coordination sites, affording multi-valency and multi-electron transfer capacity. We show that H-Mabiq molecules readily self-assemble onto the Ag(111) surface at room temperature, forming a well-ordered monolayer of closely packed molecules. Upon increasing the temperature, a new phase with a different long-range order and molecular packing is obtained. By means of scanning tunneling microscopy and photoelectron spectroscopy, we show that this new phase is characterized by a distinctive silver-bridged dimeric motif, entailing a Ag adatom accommodated at the peripheral coordination site of two opposing H-Mabiq molecules. Thus, the present work reveals the ability of the bio-inspired Mabiq ligands to form surface-confined two-dimensional assemblies incorporating metal adatoms. The results bode promise for the use of metal-containing Mabiq compounds to engineer regular bimetallic arrays with atomic precision.
9.
E Rheinfrank, M Pörtner, M D C Nuñez Beyerle, F Haag, P S Deimel, F Allegretti, K Seufert, J V Barth, M-L Bocquet, P Feulner, W Auwärter
Actinide Coordination Chemistry on Surfaces: Synthesis, Manipulation, and Properties of Thorium Bis(porphyrinato) Complexes Journal Article
In: Journal of the American Chemical Society, vol. 143, no. 36, pp. 14581-14591, 2021, ISSN: 0002-7863.
@article{nokey,
title = {Actinide Coordination Chemistry on Surfaces: Synthesis, Manipulation, and Properties of Thorium Bis(porphyrinato) Complexes},
author = {E Rheinfrank and M P\"{o}rtner and M D C Nu\~{n}ez Beyerle and F Haag and P S Deimel and F Allegretti and K Seufert and J V Barth and M-L Bocquet and P Feulner and W Auw\"{a}rter},
url = {https://doi.org/10.1021/jacs.1c04982},
doi = {10.1021/jacs.1c04982},
issn = {0002-7863},
year = {2021},
date = {2021-09-03},
journal = {Journal of the American Chemical Society},
volume = {143},
number = {36},
pages = {14581-14591},
abstract = {Actinide-based metal\textendashorganic complexes and coordination architectures encompass intriguing properties and functionalities but are still largely unexplored on surfaces. We introduce the in situ synthesis of actinide tetrapyrrole complexes under ultrahigh-vacuum conditions, on both a metallic support and a 2D material. Specifically, exposure of a tetraphenylporphyrin (TPP) multilayer to an elemental beam of thorium followed by a temperature-programmed reaction and desorption of surplus molecules yields bis(porphyrinato)thorium (Th(TPP)2) assemblies on Ag(111) and hexagonal boron nitride/Cu(111). A multimethod characterization including X-ray photoelectron spectroscopy, scanning tunneling microscopy, temperature-programmed desorption, and complementary density functional theory modeling provides insights into conformational and electronic properties. Supramolecular assemblies of Th(TPP)2 as well as individual double-deckers are addressed with submolecular precision, e.g., demonstrating the reversible rotation of the top porphyrin in Th(TPP)2 by molecular manipulation. Our findings thus demonstrate prospects for actinide-based functional nanoarchitectures.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Actinide-based metal–organic complexes and coordination architectures encompass intriguing properties and functionalities but are still largely unexplored on surfaces. We introduce the in situ synthesis of actinide tetrapyrrole complexes under ultrahigh-vacuum conditions, on both a metallic support and a 2D material. Specifically, exposure of a tetraphenylporphyrin (TPP) multilayer to an elemental beam of thorium followed by a temperature-programmed reaction and desorption of surplus molecules yields bis(porphyrinato)thorium (Th(TPP)2) assemblies on Ag(111) and hexagonal boron nitride/Cu(111). A multimethod characterization including X-ray photoelectron spectroscopy, scanning tunneling microscopy, temperature-programmed desorption, and complementary density functional theory modeling provides insights into conformational and electronic properties. Supramolecular assemblies of Th(TPP)2 as well as individual double-deckers are addressed with submolecular precision, e.g., demonstrating the reversible rotation of the top porphyrin in Th(TPP)2 by molecular manipulation. Our findings thus demonstrate prospects for actinide-based functional nanoarchitectures.
8.
F Bischoff, A Riss, G S Michelitsch, J Ducke, J V Barth, K Reuter, W Auwärter
Surface-Mediated Ring-Opening and Porphyrin Deconstruction via Conformational Distortion Journal Article
In: Journal of the American Chemical Society, vol. 143, no. 37, pp. 15131-15138, 2021, ISSN: 0002-7863.
@article{nokey,
title = {Surface-Mediated Ring-Opening and Porphyrin Deconstruction via Conformational Distortion},
author = {F Bischoff and A Riss and G S Michelitsch and J Ducke and J V Barth and K Reuter and W Auw\"{a}rter},
url = {https://doi.org/10.1021/jacs.1c05348},
doi = {10.1021/jacs.1c05348},
issn = {0002-7863},
year = {2021},
date = {2021-09-02},
urldate = {2021-09-02},
journal = {Journal of the American Chemical Society},
volume = {143},
number = {37},
pages = {15131-15138},
abstract = {The breakdown of macrocyclic compounds is of utmost importance in manifold biological and chemical processes, usually proceeding via oxygenation-induced ring-opening reactions. Here, we introduce a surface chemical route to selectively break a prototypical porphyrin species, cleaving off one pyrrole unit and affording a tripyrrin derivative. This pathway, operational in an ultrahigh vacuum environment at moderate temperature is enabled by a distinct molecular conformation achieved via the specific interaction between the porphyrin and its copper support. We provide an atomic-level characterization of the surface-anchored tripyrrin, its reaction intermediates, and byproducts by bond-resolved atomic force microscopy, unequivocally identifying the molecular skeletons. The ring-opening is rationalized by the distortion reducing the macrocycle’s stability. Our findings open a route to steer ring-opening reactions by conformational design and to study intriguing tetrapyrrole catabolite analogues on surfaces.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The breakdown of macrocyclic compounds is of utmost importance in manifold biological and chemical processes, usually proceeding via oxygenation-induced ring-opening reactions. Here, we introduce a surface chemical route to selectively break a prototypical porphyrin species, cleaving off one pyrrole unit and affording a tripyrrin derivative. This pathway, operational in an ultrahigh vacuum environment at moderate temperature is enabled by a distinct molecular conformation achieved via the specific interaction between the porphyrin and its copper support. We provide an atomic-level characterization of the surface-anchored tripyrrin, its reaction intermediates, and byproducts by bond-resolved atomic force microscopy, unequivocally identifying the molecular skeletons. The ring-opening is rationalized by the distortion reducing the macrocycle’s stability. Our findings open a route to steer ring-opening reactions by conformational design and to study intriguing tetrapyrrole catabolite analogues on surfaces.
7.
N Li, R Guo, W Chen, V Körstgens, J E Heger, S Liang, C J Brett, M A Hossain, J Zheng, P S Deimel, A Buyruk, F Allegretti, M Schwartzkopf, J G C Veinot, G Schmitz, J V Barth, T Ameri, S V Roth, P Müller-Buschbaum
In: Advanced Functional Materials, vol. 31, iss. 34, pp. 2102105, 2021, ISSN: 1616-301X.
@article{,
title = {Tailoring Ordered Mesoporous Titania Films via Introducing Germanium Nanocrystals for Enhanced Electron Transfer Photoanodes for Photovoltaic Applications},
author = {N Li and R Guo and W Chen and V K\"{o}rstgens and J E Heger and S Liang and C J Brett and M A Hossain and J Zheng and P S Deimel and A Buyruk and F Allegretti and M Schwartzkopf and J G C Veinot and G Schmitz and J V Barth and T Ameri and S V Roth and P M\"{u}ller-Buschbaum},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202102105},
doi = {https://doi.org/10.1002/adfm.202102105},
issn = {1616-301X},
year = {2021},
date = {2021-06-17},
urldate = {2021-06-17},
journal = {Advanced Functional Materials},
volume = {31},
issue = {34},
pages = {2102105},
abstract = {Abstract Based on a diblock-copolymer templated sol\textendashgel synthesis, germanium nanocrystals (GeNCs) are introduced to tailor mesoporous titania (TiO2) films for obtaining more efficient anodes for photovoltaic applications. After thermal annealing in air, the hybrid films with different GeNC content are investigated and compared with films undergoing an argon atmosphere annealing. The surface and inner morphologies of the TiO2/GeOx nanocomposite films are probed via scanning electron microscopy and grazing-incidence small-angle X-ray scattering. The crystal phase, chemical composition, and optical properties of the nanocomposite films are examined with transmission electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet\textendashvisible spectroscopy. Special focus is set on the air-annealed nanocomposite films since they hold greater promise for photovoltaics. Specifically, the charge\textendashcarrier dynamics of these air-annealed nanocomposite films are studied, and it is found that, compared with pristine TiO2 photoanodes, the GeNC addition enhances the electron transfer, yielding an increase in the short-circuit photocurrent density of exemplary perovskite solar cells and thus, an enhanced device efficiency as well as a significantly reduced hysteresis.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Based on a diblock-copolymer templated sol–gel synthesis, germanium nanocrystals (GeNCs) are introduced to tailor mesoporous titania (TiO2) films for obtaining more efficient anodes for photovoltaic applications. After thermal annealing in air, the hybrid films with different GeNC content are investigated and compared with films undergoing an argon atmosphere annealing. The surface and inner morphologies of the TiO2/GeOx nanocomposite films are probed via scanning electron microscopy and grazing-incidence small-angle X-ray scattering. The crystal phase, chemical composition, and optical properties of the nanocomposite films are examined with transmission electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet–visible spectroscopy. Special focus is set on the air-annealed nanocomposite films since they hold greater promise for photovoltaics. Specifically, the charge–carrier dynamics of these air-annealed nanocomposite films are studied, and it is found that, compared with pristine TiO2 photoanodes, the GeNC addition enhances the electron transfer, yielding an increase in the short-circuit photocurrent density of exemplary perovskite solar cells and thus, an enhanced device efficiency as well as a significantly reduced hysteresis.
6.
P Knecht, J Reichert, P S Deimel, P Feulner, F Haag, F Allegretti, M Garnica, M Schwarz, W Auwärter, P T P Ryan, T-L Lee, D A Duncan, A P Seitsonen, J V Barth, A C Papageorgiou
Conformational Control of Chemical Reactivity for Surface-Confined Ru-Porphyrins Journal Article
In: Angewandte Chemie International Edition, vol. 60, no. 30, pp. 16561-16567, 2021, ISSN: 1433-7851.
@article{nokey,
title = {Conformational Control of Chemical Reactivity for Surface-Confined Ru-Porphyrins},
author = {P Knecht and J Reichert and P S Deimel and P Feulner and F Haag and F Allegretti and M Garnica and M Schwarz and W Auw\"{a}rter and P T P Ryan and T-L Lee and D A Duncan and A P Seitsonen and J V Barth and A C Papageorgiou},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202104075},
doi = {https://doi.org/10.1002/anie.202104075},
issn = {1433-7851},
year = {2021},
date = {2021-05-03},
journal = {Angewandte Chemie International Edition},
volume = {60},
number = {30},
pages = {16561-16567},
abstract = {Abstract We assess the crucial role of tetrapyrrole flexibility in the CO ligation to distinct Ru-porphyrins supported on an atomistically well-defined Ag(111) substrate. Our systematic real-space visualisation and manipulation experiments with scanning tunnelling microscopy directly probe the ligation, while bond-resolving atomic force microscopy and X-ray standing-wave measurements characterise the geometry, X-ray and ultraviolet photoelectron spectroscopy the electronic structure, and temperature-programmed desorption the binding strength. Density-functional-theory calculations provide additional insight into the functional interface. We unambiguously demonstrate that the substituents regulate the interfacial conformational adaptability, either promoting or obstructing the uptake of axial CO adducts.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract We assess the crucial role of tetrapyrrole flexibility in the CO ligation to distinct Ru-porphyrins supported on an atomistically well-defined Ag(111) substrate. Our systematic real-space visualisation and manipulation experiments with scanning tunnelling microscopy directly probe the ligation, while bond-resolving atomic force microscopy and X-ray standing-wave measurements characterise the geometry, X-ray and ultraviolet photoelectron spectroscopy the electronic structure, and temperature-programmed desorption the binding strength. Density-functional-theory calculations provide additional insight into the functional interface. We unambiguously demonstrate that the substituents regulate the interfacial conformational adaptability, either promoting or obstructing the uptake of axial CO adducts.
5.
P Knecht, B Zhang, J Reichert, D A Duncan, M Schwarz, F Haag, P T P Ryan, T-L Lee, P S Deimel, P Feulner, F Allegretti, W Auwärter, G Médard, A P Seitsonen, J V Barth, A C Papageorgiou
Assembly and Manipulation of a Prototypical N-Heterocyclic Carbene with a Metalloporphyrin Pedestal on a Solid Surface Journal Article
In: Journal of the American Chemical Society, vol. 143, no. 11, pp. 4433-4439, 2021, ISSN: 0002-7863.
@article{nokey,
title = {Assembly and Manipulation of a Prototypical N-Heterocyclic Carbene with a Metalloporphyrin Pedestal on a Solid Surface},
author = {P Knecht and B Zhang and J Reichert and D A Duncan and M Schwarz and F Haag and P T P Ryan and T-L Lee and P S Deimel and P Feulner and F Allegretti and W Auw\"{a}rter and G M\'{e}dard and A P Seitsonen and J V Barth and A C Papageorgiou},
url = {https://doi.org/10.1021/jacs.1c01229},
doi = {10.1021/jacs.1c01229},
issn = {0002-7863},
year = {2021},
date = {2021-03-11},
journal = {Journal of the American Chemical Society},
volume = {143},
number = {11},
pages = {4433-4439},
abstract = {The controlled arrangement of N-heterocyclic carbenes (NHCs) on solid surfaces is a current challenge of surface functionalization. We introduce a strategy of using Ru porphyrins in order to control both the orientation and lateral arrangement of NHCs on a planar surface. The coupling of the NHC to the Ru porphyrin is a facile process which takes place on the interface: we apply NHCs as functional, robust pillars on well-defined, preassembled Ru porphyrin monolayers on silver and characterize these interfaces with atomic precision via a battery of experimental techniques and theoretical considerations. The NHCs assemble at room temperature modularly and reversibly on the Ru porphyrin arrays. We demonstrate a selective and complete functionalization of the Ru centers. With its binding, the NHC modifies the interaction of the Ru porphyrin with the Ag surface, displacing the Ru atom by 1 r{A} away from the surface. This arrangement of NHCs allows us to address individual ligands by controlled manipulation with the tip of a scanning tunneling microscope, creating patterned structures on the nanometer scale.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The controlled arrangement of N-heterocyclic carbenes (NHCs) on solid surfaces is a current challenge of surface functionalization. We introduce a strategy of using Ru porphyrins in order to control both the orientation and lateral arrangement of NHCs on a planar surface. The coupling of the NHC to the Ru porphyrin is a facile process which takes place on the interface: we apply NHCs as functional, robust pillars on well-defined, preassembled Ru porphyrin monolayers on silver and characterize these interfaces with atomic precision via a battery of experimental techniques and theoretical considerations. The NHCs assemble at room temperature modularly and reversibly on the Ru porphyrin arrays. We demonstrate a selective and complete functionalization of the Ru centers. With its binding, the NHC modifies the interaction of the Ru porphyrin with the Ag surface, displacing the Ru atom by 1 Å away from the surface. This arrangement of NHCs allows us to address individual ligands by controlled manipulation with the tip of a scanning tunneling microscope, creating patterned structures on the nanometer scale.
4.
X Jiang, H Kim, P S Deimel, W Chen, W Cao, D Yang, S Yin, R Schaffrinna, F Allegretti, J V Barth, M Schwager, H Tang, K Wang, M Schwartzkopf, S V Roth, P Müller-Buschbaum
In: Journal of Materials Chemistry A, vol. 8, no. 44, pp. 23628-23636, 2020, ISSN: 2050-7488.
@article{nokey,
title = {Internal nanoscale architecture and charge carrier dynamics of wide bandgap non-fullerene bulk heterojunction active layers in organic solar cells},
author = {X Jiang and H Kim and P S Deimel and W Chen and W Cao and D Yang and S Yin and R Schaffrinna and F Allegretti and J V Barth and M Schwager and H Tang and K Wang and M Schwartzkopf and S V Roth and P M\"{u}ller-Buschbaum},
url = {http://dx.doi.org/10.1039/D0TA09671G},
doi = {10.1039/D0TA09671G},
issn = {2050-7488},
year = {2020},
date = {2020-10-19},
journal = {Journal of Materials Chemistry A},
volume = {8},
number = {44},
pages = {23628-23636},
abstract = {Bulk heterojunction (BHJ) organic solar cells have gained increasing attention in the past few years. In this work, active layers of a wide-bandgap polymer donor with benzodithiophene units PBDB-T-2F and a non-fullerene small molecule acceptor IT-M are assembled into photovoltaic devices with different amounts of solvent additive 1,8-diiodooctane (DIO). The influence of DIO on the nanoscale film morphology and crystalline structure as well as the charge carrier dynamics of the active layers are investigated by combining grazing-incidence small-angle X-ray scattering (GISAXS), grazing-incidence wide-angle X-ray scattering (GIWAXS), X-ray reflectivity (XRR), UV-visible (UV-vis) absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), time-resolved photoluminescence (TRPL) and space charge limited current measurements, which are correlated with the corresponding performance of the solar cells. At 0.5 vol% DIO addition, the wide-bandgap non-fullerene organic solar cells show the best performance due to high open-circuit voltage and short-circuit current resulting from an improved charge carrier management due to the optimal inner nanoscale morphology of the active layers in terms of surface enrichment, crystallinity and crystalline orientation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Bulk heterojunction (BHJ) organic solar cells have gained increasing attention in the past few years. In this work, active layers of a wide-bandgap polymer donor with benzodithiophene units PBDB-T-2F and a non-fullerene small molecule acceptor IT-M are assembled into photovoltaic devices with different amounts of solvent additive 1,8-diiodooctane (DIO). The influence of DIO on the nanoscale film morphology and crystalline structure as well as the charge carrier dynamics of the active layers are investigated by combining grazing-incidence small-angle X-ray scattering (GISAXS), grazing-incidence wide-angle X-ray scattering (GIWAXS), X-ray reflectivity (XRR), UV-visible (UV-vis) absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), time-resolved photoluminescence (TRPL) and space charge limited current measurements, which are correlated with the corresponding performance of the solar cells. At 0.5 vol% DIO addition, the wide-bandgap non-fullerene organic solar cells show the best performance due to high open-circuit voltage and short-circuit current resulting from an improved charge carrier management due to the optimal inner nanoscale morphology of the active layers in terms of surface enrichment, crystallinity and crystalline orientation.
3.
P T P Ryan, P L Lalaguna, F Haag, M M Braim, P Ding, D J Payne, J V Barth, T L Lee, D P Woodruff, F Allegretti, D A Duncan
Validation of the inverted adsorption structure for free-base tetraphenyl porphyrin on Cu(111) Journal Article
In: Chemical Communications, vol. 56, no. 25, pp. 3681-3684, 2020, ISSN: 1359-7345.
@article{,
title = {Validation of the inverted adsorption structure for free-base tetraphenyl porphyrin on Cu(111)},
author = {P T P Ryan and P L Lalaguna and F Haag and M M Braim and P Ding and D J Payne and J V Barth and T L Lee and D P Woodruff and F Allegretti and D A Duncan},
url = {\<Go to ISI\>://WOS:000526692700019},
doi = {10.1039/c9cc09638h},
issn = {1359-7345},
year = {2020},
date = {2020-03-28},
journal = {Chemical Communications},
volume = {56},
number = {25},
pages = {3681-3684},
abstract = {Utilising normal incidence X-ray standing waves we rigourously scrutinise the "inverted model" as the adsorption structure of free-base tetraphenyl porphyrin on Cu(111). We demonstrate that the iminic N atoms are anchored at near-bridge adsorption sites on the surface displaced laterally by 1.1 +/- 0.2 angstrom in excellent agreement with previously published calculations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Utilising normal incidence X-ray standing waves we rigourously scrutinise the "inverted model" as the adsorption structure of free-base tetraphenyl porphyrin on Cu(111). We demonstrate that the iminic N atoms are anchored at near-bridge adsorption sites on the surface displaced laterally by 1.1 +/- 0.2 angstrom in excellent agreement with previously published calculations.
2.
H Bi, C A Palma, Y X Gong, K Stallhofer, M Nuber, C Jing, F Meggendorfer, S Z Wen, C Y Yam, R Kienberger, M Elbing, M Mayor, H Iglev, J V Barth, J Reichert
Electron-Phonon Coupling in Current-Driven Single-Molecule Junctions Journal Article
In: Journal of the American Chemical Society, vol. 142, no. 7, pp. 3384-3391, 2020, ISSN: 0002-7863.
@article{,
title = {Electron-Phonon Coupling in Current-Driven Single-Molecule Junctions},
author = {H Bi and C A Palma and Y X Gong and K Stallhofer and M Nuber and C Jing and F Meggendorfer and S Z Wen and C Y Yam and R Kienberger and M Elbing and M Mayor and H Iglev and J V Barth and J Reichert},
url = {\<Go to ISI\>://WOS:000515214000020},
doi = {10.1021/jacs.9b07757},
issn = {0002-7863},
year = {2020},
date = {2020-02-19},
journal = {Journal of the American Chemical Society},
volume = {142},
number = {7},
pages = {3384-3391},
abstract = {Vibrational excitations provoked by coupling effects during charge transport through single molecules are intrinsic energy dissipation phenomena, in close analogy to electron-phonon coupling in solids. One fundamental challenge in molecular electronics is the quantitative determination of charge-vibrational (electron-phonon) coupling for single-molecule junctions. The ability to record electron-phonon coupling phenomena at the single-molecule level is a key prerequisite to fully rationalize and optimize charge-transport efficiencies for specific molecular configurations and currents. Here we exemplarily determine the pertaining coupling characteristics for a current-carrying chemically well-defined molecule by synchronous vibrational and current- voltage spectroscopy. These metal-molecule-metal junction insights are complemented by time-resolved infrared spectroscopy to assess the intramolecular vibrational relaxation dynamics. By measuring and analyzing the steady-state vibrational distribution during transient charge transport in a bis-phenylethynyl-anthracene derivative using anti-Stokes Raman scattering, we find similar to 0.5 vibrational excitations per elementary charge passing through the metal-moleculemetal junction, by means of a rate model ansatz and quantum-chemical calculations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Vibrational excitations provoked by coupling effects during charge transport through single molecules are intrinsic energy dissipation phenomena, in close analogy to electron-phonon coupling in solids. One fundamental challenge in molecular electronics is the quantitative determination of charge-vibrational (electron-phonon) coupling for single-molecule junctions. The ability to record electron-phonon coupling phenomena at the single-molecule level is a key prerequisite to fully rationalize and optimize charge-transport efficiencies for specific molecular configurations and currents. Here we exemplarily determine the pertaining coupling characteristics for a current-carrying chemically well-defined molecule by synchronous vibrational and current- voltage spectroscopy. These metal-molecule-metal junction insights are complemented by time-resolved infrared spectroscopy to assess the intramolecular vibrational relaxation dynamics. By measuring and analyzing the steady-state vibrational distribution during transient charge transport in a bis-phenylethynyl-anthracene derivative using anti-Stokes Raman scattering, we find similar to 0.5 vibrational excitations per elementary charge passing through the metal-moleculemetal junction, by means of a rate model ansatz and quantum-chemical calculations.
1.
D A Duncan, P S Deimel, A Wiengarten, M Paszkiewicz, P C Aguilar, R G Acres, F Klappenberger, W Auwarter, A P Seitsonen, J V Barth, F Allegretti
Bottom-Up Fabrication of a Metal-Supported Oxo-Metal Porphyrin Journal Article
In: Journal of Physical Chemistry C, vol. 123, no. 51, pp. 31011-31025, 2019, ISSN: 1932-7447.
@article{,
title = {Bottom-Up Fabrication of a Metal-Supported Oxo-Metal Porphyrin},
author = {D A Duncan and P S Deimel and A Wiengarten and M Paszkiewicz and P C Aguilar and R G Acres and F Klappenberger and W Auwarter and A P Seitsonen and J V Barth and F Allegretti},
url = {\<Go to ISI\>://WOS:000505632900028},
doi = {10.1021/acs.jpcc.9b08661},
issn = {1932-7447},
year = {2019},
date = {2019-11-25},
journal = {Journal of Physical Chemistry C},
volume = {123},
number = {51},
pages = {31011-31025},
keywords = {},
pubstate = {published},
tppubtype = {article}
}