| 1. |
- Wang, Junbo, et al.
(author)
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Influence of Molecular Configurations on the Desulfonylation Reactions on Metal Surfaces
- 2022
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In: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 144:47, s. 21596-21605
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Journal article (peer-reviewed)abstract
- On-surface synthesis is a powerful methodology for the fabrication of low-dimensional functional materials. The precursor molecules usually anchor on different metal surfaces via similar configurations. The activation energies are therefore solely determined by the chemical activity of the respective metal surfaces. Here, we studied the influence of the detailed adsorption configuration on the activation energy on different metal surfaces. We systematically studied the desulfonylation homocoupling for a molecular precursor on Au(111) and Ag(111) and found that the activation energy is lower on inert Au(111) than on Ag(111). Combining scanning tunneling microscopy observations, synchrotron radiation photoemission spectroscopy measurements, and density functional theory calculations, we elucidate that the phenomenon arises from different molecule-substrate interactions. The molecular precursors anchor on Au(111) via Au-S interactions, which lead to weakening of the phenyl-S bonds. On the other hand, the molecular precursors anchor on Ag(111) via Ag-O interactions, resulting in the lifting of the S atoms. As a consequence, the activation barrier of the desulfonylation reactions is higher on Ag(111), although silver is generally more chemically active than gold. Our study not only reports a new type of on-surface chemical reaction but also clarifies the influence of detailed adsorption configurations on specific on-surface chemical reactions.
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| 2. |
- Cai, Liangliang, et al.
(author)
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Direct Formation of C-C Double-Bonded Structural Motifs by On-Surface Dehalogenative Homocoupling of gem-Dibromomethyl Molecules
- 2018
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In: ACS Nano. - : AMER CHEMICAL SOC. - 1936-0851 .- 1936-086X. ; 12:8, s. 7959-7966
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Journal article (peer-reviewed)abstract
- Conductive polymers are of great importance in a variety of chemistry-related disciplines and applications. The recently developed bottom-up on-surface synthesis strategy provides us with opportunities for the fabrication of various nanostructures in a flexible and facile manner, which could be investigated by high-resolution microscopic techniques in real space. Herein, we designed and synthesized molecular precursors functionalized with benzal gem-dibromomethyl groups. A combination of scanning tunneling microscopy, noncontact atomic force microscopy, high-resolution synchrotron radiation photoemission spectroscopy, and density functional theory calculations demonstrated that it is feasible to achieve the direct formation of C-C double-bonded structural motifs via on-surface dehalogenative homocoupling reactions on the Au(111) surface. Correspondingly, we convert the sp(3)-hybridized state to an sp(2)-hybridized state of carbon atoms, i.e., from an alkyl group to an alkenyl one. Moreover, by such a bottom-up strategy, we have successfully fabricated poly(phenylenevinylene) chains on the surface, which is anticipated to inspire further studies toward understanding the nature of conductive polymers at the atomic scale.
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| 3. |
- Hao, Zhengming, et al.
(author)
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Converting n-Alkanol to Conjugated Polyenal on Cu(110) Surface at Mild Temperature
- 2022
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In: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 13:14, s. 3276-3282
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Journal article (peer-reviewed)abstract
- Achieving C(sp(3))-H activation at a mild temperature is of great importance from both scientific and technologic points of view. Herein, on the basis of the on-surface synthesis strategy, we report the significant reduction of the C(sp(3))-H activation barrier, which results in the full C(sp(3))-H to C(sp(2))-H transformation of n-alkanol (octacosan-1-ol) at a mild temperature as low as 350 K on the Cu(110) surface, yielding the conjugated polyenal (octacosa-tridecaenal) as the final product. The reaction mechanism is revealed by the combined scanning tunneling microscope, density functional theory, and synchrotron radiation photoemission spectroscopy.
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| 4. |
- Li, Qing, et al.
(author)
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Hierarchical Dehydrogenation Reactions on a Copper Surface
- 2018
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In: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 140:19, s. 6076-6082
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Journal article (peer-reviewed)abstract
- Hierarchical control of chemical reactions is being considered as one of the most ambitious and challenging topics in modern organic chemistry. In this study, we have realized the one-by-one scission of the X-H bonds (X = N and C) of aromatic amines in a controlled fashion on the Cu(lll) surface. Each dehydrogenation reaction leads to certain metal-organic supramolecular structures, which were monitored in single-bond resolution via scanning tunneling microscopy and noncontact atomic force microscopy. Moreover, the reaction pathways were elucidated from X-ray photoelectron spectroscopy measurements and density functional theory calculations. Our insights pave the way for connecting molecules into complex structures in a more reliable and predictable manner, utilizing carefully tuned stepwise on-surface synthesis protocols.
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| 5. |
- Zhang, Hui, et al.
(author)
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Comprehensive electronic structure characterization of pristine and nitrogen/phosphorus doped carbon nanocages
- 2016
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In: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 103, s. 480-487
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Journal article (peer-reviewed)abstract
- The electronic structures of carbon nanocages (CNCs) and nitrogen/phosphorus doped carbon nanocages (N-CNCs/P-CNCs) have been studied by X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant X-ray emission spectroscopy (RXES). The doping configurations for N/P dopants are identified from the experiments. The results have shown that there are three major doping configurations for nitrogen but only one doping configuration for phosphorus. The nitrogen doping reveals the complex coexistence of graphite-like, pyridine-like and pyrrole-like configurations that are proved by density functional theory (DFT) simulations, while the phosphorus doping presents only the "graphite-like" configuration. The different configuration profiles result in less atomic structure ordering of N-CNCs than that of P-CNCs. XAS spectra obtained from both surface and bulk sensitive detection suggest different chemical environments between the interior and shell for all types of nanocages. The electronic structure modifications show significant difference between nitrogen and phosphorus doping from the DOS calculations. (C) 2016 Elsevier Ltd. All rights reserved.
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| 6. |
- Zhang, Liang, et al.
(author)
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Probing substrate-induced perturbations on the band structure of graphene on Ni(111) by soft X-ray emission spectroscopy
- 2013
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In: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 580, s. 43-47
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Journal article (peer-reviewed)abstract
- The influence of substrate-induced perturbations on the band structure of graphene has been investigated by soft X-ray emission spectroscopy (XES) for graphene on Ni(111). The band-dispersion features of graphene on Ni(111) are different from those of HOPG and 'quasi-freestanding' graphene (graphene/Cu) because of the strong interfacial interaction. By comparing the XES spectra excited with energy at the pi* resonance of HOPG, graphene/Cu and graphene/Ni in detail, we find that the spectral shape change can be directly related to the different electronic states hybridization strength of graphene on metal substrates, supplying a feasible way for investigating the graphene-metal bonding strength. (C) 2013 Elsevier B.V. All rights reserved.
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