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  • 1.
    Niu, Kaifeng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Chen, Lin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    CO2 Hydrogenation with High Selectivity by Single Bi Atoms on MXenes Enabled by a Concerted Mechanism2024Ingår i: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 14, nr 3, s. 1824-1833Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Developing efficient catalysts for the capture and direct conversion of CO2 into various chemicals is essential to alleviate CO2 emissions and minimize the negative environmental effects of fossil fuels. Combining density functional theory calculations and microkinetic analysis, we propose that single Bi atoms supported on V2CO2 MXenes (Bi@V2CO2) are promising single-atom catalysts (SAC) for CO2 hydrogenation. The catalytic performance of Bi SACs is ensured by the stable single-atom dispersion of Bi atoms on V2CO2 and enhanced adsorption of CO2. Of importance, Bi@V2CO2 exhibits remarkable selectivity toward the synthesis of formic acid (HCOOH), in which the main competing reaction, namely, the reverse water gas shift (RWGS) and the formation of CO, is strictly prohibited. In contrast to conventional Cu or In2O3 catalysts, CO2 hydrogenation exhibits a unique mechanism on Bi@V2CO2, in which the formic acid is directly generated via a concerted pathway. As a result, the formation of both intermediate HCOO and COOH is prevented, leading to high selectivity (nearly 100%) toward HCOOH on Bi@V2CO2. Moreover, analysis of the kinetic behavior suggests that the stabilization of HCOOH adsorption would be an effective approach to promote catalyst performance toward methanol synthesis.

  • 2.
    Grossmann, Lukas
    et al.
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Hocke, Manuela
    Tech Univ Munich, Germany.
    Galeotti, Gianluca
    Deutsch Museum, Germany.
    Contini, Giorgio
    CNR, Italy; Univ Roma Tor Vergata, Italy.
    Floreano, Luca
    CNR, Italy.
    Cossaro, Albano
    CNR, Italy; Univ Trieste, Italy.
    Ghosh, Amit
    Univ Siegen, Germany.
    Schmittel, Michael
    Univ Siegen, Germany.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Heckl, Wolfgang M.
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Lackinger, Markus
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Mechanistic insights into on-surface reactions from isothermal temperature-programmed X-ray photoelectron spectroscopy2024Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    On-surface synthesis often proceeds under kinetic control due to the irreversibility of key reaction steps, rendering kinetic studies pivotal. The accurate quantification of reaction rates also bears potential for unveiling reaction mechanisms. Temperature-Programmed X-ray Photoelectron Spectroscopy (TP-XPS) has emerged as an analytical tool for kinetic studies with splendid chemical and sufficient temporal resolution. Here, we demonstrate that the common linear temperature ramps lead to fitting ambiguities. Moreover, pinpointing the reaction order remains intricate, although this key parameter entails information on atomistic mechanisms. Yet, TP-XPS experiments with a stepped temperature profile comprised of isothermal segments facilitate the direct quantification of rate constants from fitting time courses. Thereby, rate constants are obtained for a series of temperatures, which allows independent extraction of both activation energies and pre-exponentials from Arrhenius plots. By using two analogous doubly versus triply brominated aromatic model compounds, we found that their debromination on Ag(111) is best modeled by second-order kinetics and thus proceeds via the involvement of a second, non-obvious reactant. Accordingly, we propose that debromination is activated by surface supplied Ag adatoms. This hypothesis is supported by Density Functional Theory (DFT) calculations. We foresee auspicious prospects for this TP-XPS variant for further exploring the kinetics and mechanisms of on-surface reactions. The temporal evolution of the reactant concentrations as measured by XPS for different temperature profiles reveals that the debromination of organic molecules on Ag(111) is activated by Ag adatoms.

  • 3.
    Wang, Jiu
    et al.
    Univ Calgary, Canada.
    Zhao, Heng
    Univ Calgary, Canada; Eastern Inst Technol, Peoples R China.
    Chen, Lin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Kumar, Pawan
    Wuhan Univ Technol, Peoples R China.
    Jing, Liquan
    Univ Calgary, Canada.
    Chen, Jun
    Wuhan Univ Technol, Peoples R China.
    Kibria, Md Golam
    Univ Calgary, Canada.
    Hu, Jinguang
    Univ Calgary, Canada.
    Selective cellobiose photoreforming for simultaneous gluconic acid and syngas production in acidic conditions2024Ingår i: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 344, artikel-id 123665Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Here, we demonstrate the selective cellobiose (building block of cellulose) photoreforming for gluconic acid and syngas co-production in acidic conditions by rationally designing a bifunctional polymeric carbon nitride (CN) with potassium/sulfur co-dopant. This heteroatomic doped CN photocatalyst possesses enhanced visible light absorption, higher charge separation efficiency than pristine CN. Under acidic conditions, cellobiose is not only more efficiently hydrolyzed into glucose but also promotes the syngas and gluconic acid production. Density functional theory (DFT) calculations reveal the favorable generation of center dot O-2(-) during the photocatalytic reaction, which is essential for gluconic acid production. Consequently, the fine-designed photocatalyst presents excellent cellobiose conversion (>80%) and gluconic acid selectivity (>70%) together with the co-production of syngas (similar to 56 mu mol g(-1) h(-1)) under light illumination. The current work demonstrates the feasibility of biomass photoreforming with value-added chemicals and syngas co-production under mild condition.

  • 4.
    Malina, Tomas
    et al.
    Karolinska Inst, Sweden.
    Hamawandi, Bejan
    KTH Royal Inst Technol, Sweden.
    Toprak, Muhammet S.
    KTH Royal Inst Technol, Sweden.
    Chen, Lin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Zhou, Jie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Fadeel, Bengt
    Karolinska Inst, Sweden.
    Tuning the transformation and cellular signaling of 2D titanium carbide MXenes using a natural antioxidant2024Ingår i: Matter, ISSN 2590-2393, E-ISSN 2590-2385, Vol. 7, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    2D titanium carbide (Ti3C2) MXenes have emerged as promising candidates for biomedical applications. However, the biological properties of these materials are poorly understood. Moreover, MXenes are prone to oxidation under ambient conditions. Here, we show that glutathione (GSH), a natural antioxidant present in millimolar concentrations in the cytosol of most cells, protects MXenes from oxidation in aqueous suspensions while preserving the biocompatibility of the material. Reactive molecular dynamics (RMD) simulations confirm that GSH protects MXenes. Moreover, we provide evidence of the intracellular biotransformation of Ti3C2 MXenes to the rutile form of TiO2, and we show that GSH tunes the transformation process, resulting in the secretion of pro -inflammatory interleukin (IL) -1b through a non -canonical, elastase-dependent pathway. These results are important because they shed new light on the biotransformation of Ti3C2 MXenes and its ramifications for cellular signaling.

  • 5.
    Yusupov, Khabib
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    A systematic study of work function and electronic properties of MXenes from first principles2023Ingår i: Nanoscale Advances, E-ISSN 2516-0230, Vol. 5, nr 15, s. 3976-3984Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Functional 2D materials are interesting for a wide range of applications. The rapid growth of the MXene family is due to its compositional diversity, which, in turn, allows significant tuning of the properties, and hence their applicability. The properties are to a large extent dictated by surface terminations. In the present work, we demonstrate the influence of termination species (O, NH, N, S, F, Cl, Br, I) on the changes in electronic structure, work function, dynamical stability, and atomic charges and distances of MXenes (Ti2C, Nb2C, V2C, Mo2C, Ti3C2, and Nb4C3). Among these systems, the work function values were not previously reported for & SIM;60% of the systems, and most of the previously reported MXenes with semiconducting nature are here proven to be dynamically unstable. The results show that the work function generally decreases with a reduced electronegativity of the terminating species, which in turn is correlated to a reduced charge of both the metal and terminating species and an increased metal-termination distance. An exception to this trend is NH terminations, which display a significantly reduced work function due to an intrinsic dipole moment within the termination. Furthermore, the results suggest that halogen terminations improve the electrical conductivity of the materials.

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  • 6.
    Zhou, Jie
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Dahlqvist, Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Atomic Scale Design of MXenes and Their Parent Materials-From Theoretical and Experimental Perspectives2023Ingår i: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 123, nr 23, s. 13291-13322Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    More than a decade after the discovery of MXene, there has been a remarkable increase in research on synthesis, characterization, and applications of this growing family of two-dimensional (2D) carbides and nitrides. Today, these materials include one, two, or more transition metals arranged in chemically ordered or disordered structures of three, five, seven, or nine atomic layers, with a surface chemistry characterized by surface terminations. By combining M, X, and various surface terminations, it appears that a virtually endless number of MXenes is possible. However, for the design and discovery of structures and compositions beyond current MXenes, one needs suitable (stable) precursors, an assessment of viable pathways for 3D to 2D conversion, and utilization or development of corresponding synthesis techniques. Here, we present a critical and forward-looking review of the field of atomic scale design and synthesis of MXenes and their parent materials. We discuss theoretical methods for predicting MXene precursors and for assessing whether they are chemically exfoliable. We also summarize current experimental methods for realizing the predicted materials, listing all verified MXenes to date, and outline research directions that will improve the fundamental understanding of MXene processing, enabling atomic scale design of future 2D materials, for emerging technologies.

  • 7.
    Barragan, Ana
    et al.
    IMDEA Nanosci Inst, Spain.
    Nicolas-Garcia, Tomas
    IMDEA Nanosci Inst, Spain.
    Lauwaet, Koen
    IMDEA Nanosci Inst, Spain.
    Sanchez-Grande, Ana
    IMDEA Nanosci Inst, Spain; Czech Acad Sci, Czech Republic.
    Urgel, Jose I
    IMDEA Nanosci Inst, Spain.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Perez, Emilio M.
    IMDEA Nanosci Inst, Spain.
    Ecija, David
    IMDEA Nanosci Inst, Spain.
    Design and Manipulation of a Minimalistic Hydrocarbon Nanocar on Au(111)2023Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 62, nr 6, artikel-id e202212395Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanocars are carbon-based single-molecules with a precise design that facilitates their atomic-scale control on a surface. The rational design of these molecules is important in atomic and molecular-scale manipulation to advance the development of molecular machines, as well as for a better understanding of self-assembly, diffusion and desorption processes. Here, we introduce the molecular design and construction of a collection of minimalistic nanocars. They feature an anthracene chassis and four benzene derivatives as wheels. After sublimation and adsorption on an Au(111) surface, we show controlled and fast manipulation of the nanocars along the surface using the tip of a scanning tunneling microscope (STM). The mechanism behind the successful displacement is the induced dipole created over the nanocar by the STM tip. We utilized carbon monoxide functionalized tips both to avoid decomposition and accidentally picking the nanocars up during the manipulation. This strategy allowed thousands of maneuvers to successfully win the Nanocar Race II championship.

  • 8.
    Zhong, Qigang
    et al.
    Justus Liebig Univ Giessen, Germany.
    Barat, Viktor
    Nanyang Technol Univ, Singapore.
    Csokas, Daniel
    Res Ctr Nat Sci, Hungary.
    Niu, Kaifeng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten. Soochow Univ, Peoples R China.
    Gorecki, Marcin
    Polish Acad Sci, Poland.
    Ghosh, Animesh
    Nanyang Technol Univ, Singapore.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Ebeling, Daniel
    Justus Liebig Univ Giessen, Germany.
    Chi, Lifeng
    Soochow Univ, Peoples R China; Macau Univ Sci & Technol, Peoples R China.
    Schirmeisen, Andre
    Justus Liebig Univ Giessen, Germany.
    Stuparu, Mihaiela C.
    Nanyang Technol Univ, Singapore.
    On-Surface Stereochemical Characterization of a Highly Curved Chiral Nanographene by Noncontact Atomic Force Microscopy and Scanning Tunneling Microscopy2023Ingår i: CCS CHEMISTRY, ISSN 2096-5745Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A highly distorted chiral nanographene structure composed of triple corannulene-fused [5]helicenes is prepared with the help of the Heck reaction and oxidative photocyclization with an overall isolated yield of 28%. The complex three-dimensional (3D) structure of the bowl-helix hybrid nanostructure is studied by a combination of non contact atomic force microscopy (AFM) and scanning tunneling microscopy (STM) on the Cu(111) surface, density functional theory calculations, AFM/STM simulations, and high-performance liquid chromatography-electronic circular dichroism analysis. This examination reveals a molecular structure in which the three bowl-shaped corannulene bladesd position themselves in a C3-symmetric fashion around a highly twisted triphenylene core. The molecule appears to be shaped like a propeller in which the concave side of the bowls face away from the connected [5]helicene motif. The chirality of the nanostructure is confirmed by the direct visualization of both MMM and PPP enantiomers at the single-molecule level by scanning probe microscopies. These results underline that submolecular resolution imaging by AFM/STM is a powerful real-space tool for the stereochemical characterization of 3D curved chiral nanographene structures.

  • 9.
    Cao, Nan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Tech Univ Munich, Germany.
    Yang, Biao
    Tech Univ Munich, Germany.
    Riss, Alexander
    Tech Univ Munich, Germany.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Barth, Johannes V.
    Tech Univ Munich, Germany.
    On-surface synthesis of enetriynes2023Ingår i: Nature Communications, E-ISSN 2041-1723, Vol. 14, nr 1, artikel-id 1255Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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 O-2 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 pi-system compounds. Enetriynes, which belong to the enyne family, are characterized by a distinct electron-rich carbon-bonding scheme. Here, the authors report the formation of enetriynes with high selectivity by tetramerization of terminal alkynes on Ag(100).

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  • 10.
    Yang, Biao
    et al.
    Tech Univ Munich, Germany; Tech Univ Munich, Germany.
    Niu, Kaifeng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Cao, Nan
    Tech Univ Munich, Germany.
    Grover, Nitika
    Univ Dublin, Ireland.
    Zhao, Wenchao
    Tech Univ Munich, Germany.
    Riss, Alexander
    Tech Univ Munich, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Auwaerter, Willi
    Tech Univ Munich, Germany.
    Barth, Johannes V.
    Tech Univ Munich, Germany.
    Senge, Mathias O.
    Tech Univ Munich, Germany.
    On-Surface Synthesis of Polyphenylene Wires Comprising Rigid Aliphatic Bicyclo[1.1.1]Pentane Isolator Units2023Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 62, nr 19, artikel-id e202218211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bicyclo[1.1.1]pentane (BCP) motifs are of growing importance to the pharmaceutical industry as sp(3)-rich bioisosteres of benzene rings and as molecular building blocks in materials science. Herein we explore the behavior of 1,3-disubstituted BCP moieties on metal surfaces by combining low-temperature scanning tunneling microscopy / non-contact atomic force microscopy studies with density functional theory modeling. We examine the configuration of individual BCP-containing precursors on Au(111), their supramolecular assembly and thermally activated dehalogenative coupling reactions, affording polymeric chains with incorporated electronically isolating units. Our studies not only provide the first sub-molecular insights of the BCP scaffold behavior on surfaces, but also extend the potential application of BCP derivatives towards integration in custom-designed surface architectures.

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  • 11.
    Björk, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Halim, Joseph
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Zhou, Jie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Predicting chemical exfoliation: fundamental insights into the synthesis of MXenes2023Ingår i: NPJ 2D MATERIALS AND APPLICATIONS, ISSN 2397-7132, Vol. 7, nr 1, artikel-id 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The factors controlling the top-down synthesis of MXenes, by selectively removing the A elements from parent MAX phases, is still under debate. In particular, understanding why some MAX phases can be used for creating MXenes, while others cannot, is of immense interest and would greatly support computational screening and identification of new two-dimensional materials that could also be created by chemical exfoliation. Here we computationally study the etching of MAX phases in hydrofluoric acid, considering the complete exfoliation process and competing processes during the initial steps of the synthesis. The results are compared to experiments and MAX phases successfully converted to MXenes, as well as so far unsuccessful attempts, including previously unpublished experimental data, rationalizing why some MAX phases are exfoliable while others are not. Our results provide an improved understanding of the synthesis of MXenes under acid conditions, anticipated to be vital for our ability to discover novel two-dimensional materials.

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  • 12.
    Li, Xuechao
    et al.
    Soochow Univ, Peoples R China.
    Niu, Kaifeng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten. Soochow Univ, Peoples R China.
    Duan, Sai
    Fudan Univ, Peoples R China.
    Tang, Yanning
    Soochow Univ, Peoples R China.
    Hao, Zhengming
    Soochow Univ, Peoples R China.
    Xu, Zhichao
    Soochow Univ, Peoples R China.
    Ge, Haitao
    Soochow Univ, Peoples R China.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Zhang, Haiming
    Soochow Univ, Peoples R China.
    Xu, Xin
    Fudan Univ, Peoples R China.
    Chi, Lifeng
    Soochow Univ, Peoples R China.
    Pyridinic Nitrogen Modification for Selective Acetylenic Homocoupling on Au(111)2023Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 145, nr 8, s. 4545-4552Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    On-surface acetylenic homocoupling has been proposed to construct carbon nanostructures featuring sp hybrid-ization. However, the efficiency of linear acetylenic coupling is far from satisfactory, often resulting in undesired enyne products or cyclotrimerization products due to the lack of strategies to enhance chemical selectivity. Herein, we inspect the acetylenic homocou-pling reaction of polarized terminal alkynes (TAs) on Au(111) with bond-resolved scanning probe microscopy. The replacement of benzene with pyridine moieties significantly prohibits the cyclotrimerization pathway and facilitates the linear coupling to produce well-aligned N-doped graphdiyne nanowires. Combined with density functional theory calculations, we reveal that the pyridinic nitrogen modification substantially differentiates the coupling motifs at the initial C-C coupling stage (head-to-head vs head-to-tail), which is decisive for the preference of linear coupling over cyclotrimerization.

  • 13.
    Karlsson, Max
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Elektroniska och fotoniska material. Linköpings universitet, Tekniska fakulteten.
    Qin, Jiajun
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Elektroniska och fotoniska material. Linköpings universitet, Tekniska fakulteten.
    Niu, Kaifeng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Luo, Xiyu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Elektroniska och fotoniska material. Linköpings universitet, Tekniska fakulteten. Tsinghua Univ, Peoples R China.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Duan, Lian
    Tsinghua Univ, Peoples R China.
    Xu, Weidong
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Elektroniska och fotoniska material. Linköpings universitet, Tekniska fakulteten. Northwestern Polytech Univ, Peoples R China.
    Gao, Feng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Elektroniska och fotoniska material. Linköpings universitet, Tekniska fakulteten.
    Role of chloride on the instability of blue emitting mixed-halide perovskites2023Ingår i: FRONTIERS OF OPTOELECTRONICS, ISSN 2095-2759, Vol. 16, nr 1, artikel-id 37Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although perovskite light-emitting diodes (PeLEDs) have seen unprecedented development in device efficiency over the past decade, they suffer significantly from poor operational stability. This is especially true for blue PeLEDs, whose operational lifetime remains orders of magnitude behind their green and red counterparts. Here, we systematically investigate this efficiency-stability discrepancy in a series of green- to blue-emitting PeLEDs based on mixed Br/Cl-perovskites. We find that chloride incorporation, while having only a limited impact on efficiency, detrimentally affects device stability even in small amounts. Device lifetime drops exponentially with increasing Cl-content, accompanied by an increased rate of change in electrical properties during operation. We ascribe this phenomenon to an increased mobility of halogen ions in the mixed-halide lattice due to an increased chemically and structurally disordered landscape with reduced migration barriers. Our results indicate that the stability enhancement for PeLEDs might require different strategies from those used for improving efficiency.

  • 14.
    Hu, Yong-Jie
    et al.
    Drexel Univ, PA 19104 USA.
    Tandoc, Christopher
    Drexel Univ, PA 19104 USA.
    Barsoum, Michel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten. Drexel Univ, PA 19104 USA.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Structural and electronic properties of two-dimensional titanium carbo-oxides2023Ingår i: 2D Materials, E-ISSN 2053-1583, Vol. 10, nr 1, artikel-id 015019Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work was inspired by new experimental findings where we discovered a two-dimensional (2D) material comprised of titanium-oxide-based one-dimensional (1D) sub-nanometer filaments. Preliminary results suggest that the 2D material contains considerable amounts of carbon, C, in addition to titanium, Ti, and oxygen, O. The aim of this study is to investigate the low-energy, stable atomic forms of 2D titanium carbo-oxides as a function of C content. Via a combination of first-principles calculations and an effective structure sampling scheme, the stable configurations of C-substitutions are comprehensively searched by templating different 2D TiO2 polymorphs and considering a two O to one C replacement scheme. Among the searched stable configurations, a structure where the (101) planes of anatase bound the top and bottom surfaces with a chemical formula of TiC1/4O3/2 was of particularly low energy. Furthermore, the variations in the electronic band structure and chemical bonding environments caused by the high-content C substitution are investigated via additional calculations using a hybrid exchange-correlation functional.

  • 15.
    Cao, Nan
    et al.
    Tech Univ Munich, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Corral-Rascon, Eduardo
    Tech Univ Munich, Germany.
    Chen, Zhi
    Karlsruhe Inst Technol, Germany; Shenzhen Univ, Peoples R China.
    Ruben, Mario
    Karlsruhe Inst Technol, Germany; Univ Strasbourg, France; Karlsruhe Inst Technol, Germany.
    Senge, Mathias O.
    Tech Univ Munich, Germany.
    Barth, Johannes V.
    Tech Univ Munich, Germany.
    Riss, Alexander
    Tech Univ Munich, Germany.
    The role of aromaticity in the cyclization and polymerization of alkyne-substituted porphyrins on Au(111)2023Ingår i: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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. While aromaticity is a useful concept for assessing the reactivity of organic compounds, the connection between aromaticity and on-surface chemistry remains largely unexplored. Now, scanning probe experiments on cyclization reactions of porphyrins on Au(111) show that the peripheral carbon atoms outside of the aromatic 18-& pi; electron pathway exhibit a higher reactivity.

  • 16.
    Niu, Kaifeng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten. Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou China.
    Fan, Qitang
    Department of Chemistry, Philipps-Universität Marburg, Germany.
    Chi, Lifeng
    Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, China; Department of Materials Science and Engineering, Macau University of Science and Technology, Macau, China.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Gottfried, J. Michael
    Department of Chemistry, Philipps-Universität Marburg, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Unveiling the formation mechanism of the biphenylene network2023Ingår i: Nanoscale Horizons, ISSN 2055-6764, E-ISSN 2055-6756, Vol. 8, nr 3, s. 368-376Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have computationally studied the formation mechanism of the biphenylene network via the intermolecular HF zipping, as well as identified key intermediates experimentally, on the Au(111) surface. We elucidate that the zipping process consists of a series of defluorinations, dehydrogenations, and C–C coupling reactions. The Au substrate not only serves as the active site for defluorination and dehydrogenation, but also forms C–Au bonds that stabilize the defluorinated and dehydrogenated phenylene radicals, leading to "standing" benzyne groups. Despite that the C–C coupling between the "standing" benzyne groups is identified as the rate-limiting step, the limiting barrier can be reduced by the adjacent chemisorbed benzyne groups. The theoretically proposed mechanism is further supported by scanning tunneling microscopy experiments, in which the key intermediate state containing chemisorbed benzyne groups can be observed. This study provides a comprehensive understanding towards the on-surface intermolecular HF zipping, anticipated to be instructive for its future applications.

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  • 17.
    Yang, Biao
    et al.
    Soochow Univ, Peoples R China; Tech Univ Munich, Germany.
    Niu, Kaifeng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Soochow Univ, Peoples R China.
    Haag, Felix
    Tech Univ Munich, Germany.
    Cao, Nan
    Soochow Univ, Peoples R China; Tech Univ Munich, Germany.
    Zhang, Junjie
    Soochow Univ, Peoples R China.
    Zhang, Haiming
    Soochow Univ, Peoples R China.
    Li, Qing
    Soochow Univ, Peoples R China.
    Allegretti, Francesco
    Tech Univ Munich, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign.
    Barth, Johannes V
    Tech Univ Munich, Germany.
    Chi, Lifeng
    Soochow Univ, Peoples R China; Tech Univ Munich, Germany.
    Abiotic Formation of an Amide Bond via Surface-Supported Direct Carboxyl-Amine Coupling2022Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 61, nr 5, artikel-id e202113590Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 18.
    Badr, Hussein O.
    et al.
    Drexel Univ, PA 19104 USA.
    El-Melegy, Tarek
    Drexel Univ, PA 19104 USA.
    Carey, Michael
    Drexel Univ, PA 19104 USA.
    Natu, Varun
    Drexel Univ, PA 19104 USA.
    Hassig, Mary Q.
    Drexel Univ, PA 19104 USA.
    Johnson, Craig
    Drexel Univ, PA 19104 USA.
    Qian, Qian
    Drexel Univ, PA 19104 USA.
    Li, Christopher Y.
    Drexel Univ, PA 19104 USA.
    Kushnir, Kateryna
    Worcester Polytech Inst, MA 01609 USA.
    Colin-Ulloa, Erika
    Worcester Polytech Inst, MA 01609 USA.
    Titova, Lyubov V
    Worcester Polytech Inst, MA 01609 USA.
    Martin, Julia L.
    Worcester Polytech Inst, MA 01609 USA.
    Grimm, Ronald L.
    Worcester Polytech Inst, MA 01609 USA.
    Pai, Rahul
    Drexel Univ, PA 19104 USA.
    Kalra, Vibha
    Drexel Univ, PA 19104 USA.
    Karmakar, Avishek
    Drexel Univ, PA 19104 USA.
    Ruffino, Anthony
    Drexel Univ, PA 19104 USA.
    Masiuk, Stefan
    Drexel Univ, PA 19104 USA.
    Liang, Kun
    Tulane Univ, LA 70118 USA.
    Naguib, Michael
    Tulane Univ, LA 70118 USA.
    Wilson, Olivia
    Drexel Univ, PA 19104 USA.
    Magenau, Andrew
    Drexel Univ, PA 19104 USA.
    Montazeri, Kiana
    Drexel Univ, PA 19104 USA.
    Zhu, Yucheng
    Drexel Univ, PA 19104 USA.
    Cheng, Hao
    Drexel Univ, PA 19104 USA.
    Torita, Takeshi
    Murata Mfg Co Ltd, Japan.
    Koyanagi, Masashi
    Murata Mfg Co Ltd, Japan.
    Yanagimachi, Akimaro
    Murata Mfg Co Ltd, Japan.
    Ouisse, Thierry
    Univ Grenoble Alpes, France.
    Barbier, Maxime
    Univ Grenoble Alpes, France; European Synchrotron Radiat Facil ESRF, France.
    Wilhelm, Fabrice
    European Synchrotron Radiat Facil ESRF, France.
    Rogalev, Andrei
    European Synchrotron Radiat Facil ESRF, France.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Persson, Per O A
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hu, Yong-Jie
    Drexel Univ, PA 19104 USA.
    Barsoum, Michel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Drexel Univ, PA 19104 USA.
    Bottom-up, scalable synthesis of anatase nanofilament-based two-dimensional titanium carbo-oxide flakes2022Ingår i: Materials Today, ISSN 1369-7021, E-ISSN 1873-4103, Vol. 54Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two-dimensional (2D) materials offer advantages that their 3D counterparts do not. The conventional method for the bulk synthesis of 2D materials has predominantly been through etching layered solids. Herein, we convert - through a bottom-up approach - 10 binary and ternary titanium carbides, nitrides, borides, phosphides, and silicides into 2D flakes by immersing them in a tetramethylammonium hydroxide solution at temperatures in the 25-85 degrees C range. Based on X-ray diffraction, density functional theory, X-ray photoelectron, electron energy loss, Raman, X-ray absorption near edge structure spectroscopies, transmission and scanning electron microscope images and selected area diffraction, we conclude that the resulting flakes are carbon containing anatase-based layers that are, in turn, comprised of approximate to 6 x 10 angstrom(2) nanofilaments in cross-section some of which are few microns long. Electrodes made from some of these films performed well in lithium-ion and lithium-sulphur systems. These materials also reduce the viability of cancer cells thus showing potential in biomedical applications. Synthesizing 2D materials, at near ambient conditions, with non-layered, inexpensive, green precursors (e.g., TiC) is paradigm shifting and will undoubtedly open new and exciting avenues of research and applications.

  • 19.
    Grossmann, Lukas
    et al.
    Deutsches Museum, Museumsinsel 1, 80538 München, Germany. markus@lackinger.org; Technische Universität München, Physics Department, James-Franck-Strasse 1, 85748 Garching, Germany.
    Duncan, David A.
    Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0QX, UK.
    Jarvis, Samuel P
    Lancaster University, Physics Department, Lancaster LA1 4YB, UK.
    Jones, Robert G
    University of Nottingham, Department of Physical Chemistry, School of Chemistry, Nottingham NG7 2RD, UK.
    De, Soumen
    Center of Micro and Nanochemistry and Engineering, Organische Chemie I, Universität Siegen, Adolf-Reichwein-Str. 2, 57068 Siegen, Germany.
    Rosén, Johanna
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign.
    Schmittel, Michael
    Center of Micro and Nanochemistry and Engineering, Organische Chemie I, Universität Siegen, Adolf-Reichwein-Str. 2, 57068 Siegen, Germany.
    Heckl, Wolfgang M
    Deutsches Museum, Museumsinsel 1, 80538 München, Germany. markus@lackinger.org; Technische Universität München, Physics Department, James-Franck-Strasse 1, 85748 Garching, Germany.
    Björk, Jonas
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign.
    Lackinger, Markus
    Deutsches Museum, Museumsinsel 1, 80538 München, Germany. markus@lackinger.org; Technische Universität München, Physics Department, James-Franck-Strasse 1, 85748 Garching, Germany.
    Evolution of adsorption heights in the on-surface synthesis and decoupling of covalent organic networks on Ag(111) by normal-incidence X-ray standing wave2022Ingår i: Nanoscale Horizons, ISSN 2055-6764, E-ISSN 2055-6756, Vol. 7, nr 1, s. 51-62Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Structural characterization in on-surface synthesis is primarily carried out by Scanning Probe Microscopy (SPM) which provides high lateral resolution. Yet, important fresh perspectives on surface interactions and molecular conformations are gained from adsorption heights that remain largely inaccessible to SPM, but can be precisely measured with both elemental and chemical sensitivity by Normal-Incidence X-ray Standing Wave (NIXSW) analysis. Here, we study the evolution of adsorption heights in the on-surface synthesis and post-synthetic decoupling of porous covalent triazine-phenylene networks obtained from 2,4,6-tris(4-bromophenyl)-1,3,5-triazine (TBPT) precursors on Ag(111). Room temperature deposition of TBPT and mild annealing to ~150 C result in full debromination and formation of organometallic intermediates, where the monomers are linked into reticulated networks by C-Ag-C bonds. Topologically identical covalent networks comprised of triazine vertices that are interconnected by biphenyl units are obtained by a thermally activated chemical transformation of the organometallic intermediates. Exposure to iodine vapor facilitates decoupling by intercalation of an iodine monolayer between the covalent networks and the Ag(111) surface. Accordingly, Scanning Tunneling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and NIXSW experiments are carried out for three successive sample stages: organometallic intermediates, covalent networks directly on Ag(111) and after decoupling. NIXSW analysis facilitates the determination of adsorption heights of chemically distinct carbon species, i.e. in the phenyl and triazine rings, and also for the organometallic carbon atoms. Thereby, molecular conformations are assessed for each sample stage. The interpretation of experimental results is informed by Density Functional Theory (DFT) calculations, providing a consistent picture of adsorption heights and molecular deformations in the networks that result from the interplay between steric hindrance and surface interactions. Quantitative adsorption heights, i.e. vertical distances between adsorbates and surface, provide detailed insight into surface interactions, but are underexplored in on-surface synthesis. In particular, the direct comparison with an in situ prepared decoupled state unveils the surface influence on the network structure, and shows that iodine intercalation is a powerful decoupling strategy.

  • 20.
    Wang, Junbo
    et al.
    Shaanxi Normal Univ, Peoples R China; Soochow Univ, Peoples R China.
    Niu, Kaifeng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten. Soochow Univ, Peoples R China.
    Xu, Chaojie
    Soochow Univ, Peoples R China.
    Zhu, Huaming
    Shaanxi Normal Univ, Peoples R China.
    Ding, Honghe
    Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China.
    Han, Dong
    Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China.
    Zheng, Yuanjing
    Soochow Univ, Peoples R China.
    Xi, Jiahao
    Soochow Univ, Peoples R China.
    You, Sifan
    Soochow Univ, Peoples R China.
    Deng, Chuan
    Shaanxi Normal Univ, Peoples R China.
    Lin, Haiping
    Shaanxi Normal Univ, Peoples R China.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Zhu, Junfa
    Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Li, Qing
    Shaanxi Normal Univ, Peoples R China.
    Chi, Lifeng
    Soochow Univ, Peoples R China; Macau Univ Sci & Technol, Peoples R China.
    Influence of Molecular Configurations on the Desulfonylation Reactions on Metal Surfaces2022Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 144, nr 47, s. 21596-21605Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 21.
    Helmer, Pernilla
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Halim, Joseph
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Zhou, Jie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Mohan, Roopathy
    Chemical Physics, Department of Physics, Chalmers University of Technology, Gothenburg.
    Wickman, Björn
    Chemical Physics, Department of Physics, Chalmers University of Technology, Gothenburg.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Investigation of 2D Boridene from First Principles and Experiments2022Ingår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 32, nr 14, artikel-id 2109060Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recently, a 2D metal boride - boridene - has been experimentally realized in the form of single-layer molybdenum boride sheets with ordered metal vacancies, through selective etching of the nanolaminated 3D parent borides (Mo2/3Y1/3)2AlB2 and (Mo2/3Sc1/3)2AlB2. The chemical formula of the boridene was suggested to be Mo4/3B2-xTz, where Tz denotes surface terminations. Here, the termination composition and material properties of Mo4/3B2-xTz from both theoretical and experimental perspectives are investigated. Termination sites are considered theoretically for termination species T = O, OH, and F, and the energetically favored termination configuration is identified at z = 2 for both single species terminations and binary termination mixes of different stoichiometries in ordered and disordered configurations. Mo4/3B2-xTz is shown to be dynamically stable for multiple termination stoichiometries, displaying semiconducting, semimetallic, or metallic behavior depending on how different terminations are combined. The approximate chemical formula of a freestanding film of boridene is attained as Mo1.33B1.9O0.3(OH)1.5F0.7 from X-ray photoelectron spectroscopy (XPS) analysis which, within error margins, is consistent with the theoretical results. Finally, metallic and additive-free Mo4/3B2-xTz shows high catalytic performance for the hydrogen evolution reaction, with an onset potential of 0.15 V versus the reversible hydrogen electrode.

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  • 22.
    Grossmann, Lukas
    et al.
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    Ringel, Eva
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    Rastgoo-Lahrood, Atena
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    King, Benjamin T.
    Univ Nevada, NV 89557 USA.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Heckl, Wolfgang M.
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    Opris, Dorina
    Empa, Switzerland.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Lackinger, Markus
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    Steering Self-Assembly of Three-Dimensional Iptycenes on Au(111) by Tuning Molecule-Surface Interactions2022Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 61, nr 25, artikel-id e202201044Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Self-assembly of three-dimensional molecules is scarcely studied on surfaces. Their modes of adsorption can exhibit far greater variability compared to (nearly) planar molecules that adsorb mostly flat on surfaces. This additional degree of freedom can have decisive consequences for the expression of intermolecular binding motifs, hence the formation of supramolecular structures. The determining molecule-surface interactions can be widely tuned, thereby providing a new powerful lever for crystal engineering in two dimensions. Here, we study the self-assembly of triptycene derivatives with anthracene blades on Au(111) by Scanning Tunneling Microscopy, Near Edge X-ray Absorption Fine Structure and Density Functional Theory. The impact of molecule-surface interactions was experimentally tested by comparing pristine with iodine-passivated Au(111) surfaces. Thereby, we observed a fundamental change of the adsorption mode that triggered self-assembly of an entirely different structure.

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  • 23.
    Zhong, Qigang
    et al.
    Soochow Univ, Peoples R China; Justus Liebig Univ Giessen, Germany.
    Niu, Kaifeng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten. Soochow Univ, Peoples R China.
    Chen, Long
    Max Planck Inst Polymer Res, Germany; Jilin Univ, Peoples R China.
    Zhang, Haiming
    Soochow Univ, Peoples R China.
    Ebeling, Daniel
    Justus Liebig Univ Giessen, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Mullen, Klaus
    Max Planck Inst Polymer Res, Germany; Johannes Gutenberg Univ Mainz, Germany.
    Schirmeisen, Andre
    Justus Liebig Univ Giessen, Germany.
    Chi, Lifeng
    Soochow Univ, Peoples R China.
    Substrate-Modulated Synthesis of Metal-Organic Hybrids by Tunable Multiple Aryl-Metal Bonds2022Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 144, nr 18, s. 8214-8222Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Assembly of semiconducting organic molecules with multiple aryl-metal covalent bonds into stable one- and two- dimensional (1D and 2D) metal-organic frameworks represents a promising route to the integration of single-molecule electronics in terms of structural robustness and charge transport efficiency. Although various metastable organometallic frameworks have been constructed by the extensive use of single aryl-metal bonds, it remains a great challenge to embed multiple aryl-metal bonds into these structures due to inadequate knowledge of harnessing such complex bonding motifs. Here, we demonstrate the substrate-modulated synthesis of 1D and 2D metal-organic hybrids (MOHs) with the organic building blocks (perylene) interlinked solely with multiple aryl-metal bonds via the stepwise thermal dehalogenation of 3,4,9,10-tetrabromo-1,6,7,12-tetrachloroperylene and subsequent metal-organic connection on metal surfaces. More importantly, the conversion from 1D to 2D MOHs is completely impeded on Au(111) but dominant on Ag(111). We comprehensively study the distinct reaction pathways on the two surfaces by visually tracking the structural evolution of the MOHs with high-resolution scanning tunneling and noncontact atomic force microscopy, supported by first-principles density functional theory calculations. The substrate-dependent structural control of the MOHs is attributed to the variation of the M-X (M = Au, Ag; X = C, Cl) bond strength regulated by the nature of the metal species.

  • 24.
    Sanchez-Grande, Ana
    et al.
    IMDEA Nanosci, Spain.
    Urgel, Jose I.
    IMDEA Nanosci, Spain.
    Garcia-Benito, Ines
    IMDEA Nanosci, Spain; Univ Complutense, Spain.
    Santos, Jose
    Univ Complutense, Spain.
    Biswas, Kalyan
    IMDEA Nanosci, Spain.
    Lauwaet, Koen
    IMDEA Nanosci, Spain.
    Gallego, Jose M.
    CSIC, Spain.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Miranda, Rodolfo
    IMDEA Nanosci, Spain; Univ Autonoma Madrid, Spain.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Martin, Nazario
    IMDEA Nanosci, Spain; Univ Complutense, Spain.
    Ecija, David
    IMDEA Nanosci, Spain.
    Surface-Assisted Synthesis of N-Containing pi-Conjugated Polymers2022Ingår i: Advanced Science, E-ISSN 2198-3844, Vol. 9, nr 19, artikel-id 2200407Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    On-surface synthesis has recently emerged as a powerful strategy to design conjugated polymers previously precluded in conventional solution chemistry. Here, an N-containing pentacene-based precursor (tetraazapentacene) is ex-professo synthesized endowed with terminal dibromomethylene (:CBr2) groups to steer homocoupling via dehalogenation on metallic supports. Combined scanning probe microscopy investigations complemented by theoretical calculations reveal how the substrate selection drives different reaction mechanisms. On Ag(111) the dissociation of bromine atoms at room temperature triggers the homocoupling of tetraazapentacene units together with the binding of silver adatoms to the nitrogen atoms of the monomers giving rise to a N-containing conjugated coordination polymer (P1). Subsequently, P1 undergoes ladderization at 200 degrees C, affording a pyrrolopyrrole-bridged conjugated polymer (P2). On Au(111) the formation of the intermediate polymer P1 is not observed and, instead, after annealing at 100 degrees C, the conjugated ladder polymer P2 is obtained, revealing the crucial role of metal adatoms on Ag(111) as compared to Au(111). Finally, on Ag(100) the loss of :CBr2 groups affords the formation of tetraazapentacene monomers, which coexist with polymer P1. Our results contribute to introduce protocols for the synthesis of N-containing conjugated polymers, illustrating the selective role of the metallic support in the underlying reaction mechanisms.

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  • 25.
    Niu, Kaifeng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten. Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Chi, Lifeng
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Termination-Accelerated Electrochemical Nitrogen Fixation on Single-Atom Catalysts Supported by MXenes2022Ingår i: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 13, nr 12, s. 2800-2807Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The synthesis of ammonia (NH3) from nitrogen (N2) under ambientconditions is of great significance but hindered by the lack of highly efficient catalysts. Byperformingfirst-principles calculations, we have investigated the feasibility for employing atransition metal (TM) atom, supported on Ti3C2T2MXene with O/OH terminations, as asingle-atom catalyst (SAC) for electrochemical nitrogen reduction. The potential catalyticperformance of TM single atoms is evaluated by their adsorption behavior on the MXene,together with their ability to bind N2and to desorb NH3molecules. Of importance, the OHterminations on Ti3C2T2MXene can effectively enhance the N2adsorption and decrease theNH3adsorption for single atoms. Based on proposed criteria for promising SACs, ourcalculations further demonstrate that the Ni/Ti3C2O0.19(OH)1.81exhibits reasonablethermodynamics and kinetics toward electrochemical nitrogen reduction.

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  • 26.
    Björk, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Sanchez-Sanchez, Carlos
    Swiss Fed Labs Mat Sci & Technol, Switzerland; Inst Mat Sci Madrid ICMM CSIC, Spain.
    Chen, Qiang
    Max Planck Inst Polymer Res, Germany; Univ Oxford, England.
    Pignedoli, Carlo A.
    Swiss Fed Labs Mat Sci & Technol, Switzerland.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Ruffieux, Pascal
    Swiss Fed Labs Mat Sci & Technol, Switzerland.
    Feng, Xinliang
    Tech Univ Dresden, Germany; Tech Univ Dresden, Germany.
    Narita, Akimitsu
    Max Planck Inst Polymer Res, Germany; Okinawa Inst Sci & Technol Grad Univ, Japan.
    Mullen, Klaus
    Max Planck Inst Polymer Res, Germany.
    Fasel, Roman
    Swiss Fed Labs Mat Sci & Technol, Switzerland; Univ Bern, Switzerland.
    The Role of Metal Adatoms in a Surface-Assisted Cyclodehydrogenation Reaction on a Gold Surface2022Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 61, nr 49, artikel-id e202212354Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dehydrogenation reactions are key steps in many metal-catalyzed chemical processes and in the on-surface synthesis of atomically precise nanomaterials. The principal role of the metal substrate in these reactions is undisputed, but the role of metal adatoms remains, to a large extent, unanswered, particularly on gold substrates. Here, we discuss their importance by studying the surface-assisted cyclodehydrogenation on Au(111) as an ideal model case. We choose a polymer theoretically predicted to give one of two cyclization products depending on the presence or absence of gold adatoms. Scanning probe microscopy experiments observe only the product associated with adatoms. We challenge the prevalent understanding of surface-assisted cyclodehydrogenation, unveiling the catalytic role of adatoms and their effect on regioselectivity. The study adds new perspectives to the understanding of metal catalysis and the design of on-surface synthesis protocols for novel carbon nanomaterials.

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  • 27.
    Björk, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materialdesign. Linköpings universitet, Tekniska fakulteten.
    Functionalizing MXenes by Tailoring Surface Terminations in Different Chemical Environments2021Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 33, nr 23, s. 9108-9118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two-dimensional metal carbides and nitrides-MXenes-represent a group of materials which have attained growing attention over the last decade due to their chemical versatility, making them highly promising in areas such as energy storage, superconductivity, and heterogenous catalysis. Surface terminations are a natural consequence of the MXene synthesis, conventionally consisting of O, OH, and F. However, recent studies have extended the chemical domain of the surface terminations to other elements, and they should be considered as an additional parameter governing the MXene properties. There is a shortfall in the understanding of how various chemical species could act as terminations on different MXenes. In particular, there is limited comprehension in which chemical environments different terminations are stable. Here, we present an extensive theoretical study of the surface terminations of MXenes in different atmospheres by considering in total six experimentally achieved MXenes (Ti2C, Nb2C, V2C, Mo2C, Ti3C2, and Nb4C3) and twelve surface terminations (O, OH, N, NH, NH2, S, SH, H, F, Cl, Br, and I). We consider fully terminated (single termination) MXenes and also the impact of substituting individual terminations. Our study provides insights into what terminations are stable on which MXenes in different chemical environments, with predictions of how to obtain single-termination MXenes and which MXenes are resilient under ambient conditions. In addition, we propose synthesis protocols of MXenes which have not yet been realized in experiments. It is anticipated that alongside the development of new synthesis routes, our study will provide design rules for how to tailor the surface terminations of MXenes.

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  • 28.
    Grossmann, Lukas
    et al.
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    King, Benjamin T.
    Univ Nevada, NV 89557 USA.
    Reichlmaier, Stefan
    Phys Elect GmbH, Germany.
    Hartmann, Nicolai
    Neaspec GmbH, Germany.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Heckl, Wolfgang M.
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Lackinger, Markus
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    On-surface photopolymerization of two-dimensional polymers ordered on the mesoscale2021Ingår i: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 13, nr 8, s. 730-736Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of solid supports and ultra-high vacuum conditions for the synthesis of two-dimensional polymers is attractive, as it can enable thorough characterization, often with submolecular resolution, and prevent contamination. However, most on-surface polymerizations are thermally activated, which often leads to high defect densities and relatively small domain sizes. Here, we have obtained a porous two-dimensional polymer that is ordered on the mesoscale by the two-staged topochemical photopolymerization of fluorinated anthracene triptycene (fantrip) monomers on alkane-passivated graphite surfaces under ultra-high vacuum. First, the fantrip monomers self-assemble into highly ordered monolayer structures, where all anthracene moieties adopt a suitable arrangement for photopolymerization. Irradiation with violet light then induces complete covalent cross-linking by [4+4] photocycloaddition to form a two-dimensional polymer, while fully preserving the long-range order of the self-assembled structure. The extent of the polymerization is confirmed by local infrared spectroscopy and scanning tunnelling microscopy characterization, in agreement with density functional theory calculations, which also gives mechanistic insights.

  • 29.
    Niu, Kaifeng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Chi, Lifeng
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Structure-activity correlation of Ti2CT2 MXenes for C-H activation2021Ingår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 33, nr 23, artikel-id 235201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As a bourgeoning class of 2D materials, MXenes have recently attracted significant attention within heterogeneous catalysis for promoting reactions such as hydrogen evolution and C-H activation. However, the catalytic activity of MXenes is highly dependent on the structural configuration including termination groups and their distribution. Therefore, understanding the relation between the structure and the activity is desired for the rational design of MXenes as high-efficient catalysts. Here, we present that the correlation between the structure and activity of Ti2CT2 (T is a combination of O, OH and/or F) MXenes for C-H activation can be linked by a quantitative descriptor: the hydrogen affinity (E (H)). A linear correlation is observed between the mean hydrogen affinity and the overall ratio of O terminations (x (O)) in Ti2CT2 MXenes, in which hydrogen affinity increases as the x (O) decreases, regardless to the species of termination groups. In addition, the hydrogen affinity is more sensitive to the presence of OH termination than F terminations. Moreover, the linear correlation between the hydrogen affinity and the activity of Ti2CT2 MXenes for C-H activation of both -CH3 and -CH2- groups can be extended to be valid for all three possible termination groups. Such a correlation provides fast prediction of the activity of general Ti2CT2 MXenes, avoiding tedious activation energy calculations. We anticipate that the findings have the potential to accelerate the development of MXenes for heterogeneous catalysis applications.

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  • 30.
    Niu, Kaifeng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Soochow Univ, Peoples R China.
    Chi, Lifeng
    Soochow Univ, Peoples R China.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    C-H activation of light alkanes on MXenes predicted by hydrogen affinity2020Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, nr 33, s. 18622-18630Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    C-H activation of light alkanes is one of the most important reactions for a plethora of applications but requires catalysts to operate at feasible conditions. MXenes, a new group of two-dimensional materials, have shown great promise as heterogeneous catalysts for several applications. However, the catalytic activity of MXenes depends on the type and distribution of termination groups. Theoretically, it is desired to search for a relation between the catalytic activity and the termination configuration by employing a simple descriptor in order to avoid tedious activation energy calculations. Here, we show that MXenes are promising for splitting C-H bonds of light alkanes. Furthermore, we present how a quantitative descriptor - the hydrogen affinity - can be used to characterize the termination configuration of Ti2CTz(T = O, OH) MXenes, as well as the catalytic activity towards dehydrogenation reactions, using propane as model system. First-principles calculations reveal that the hydrogen affinity can be considered as an intrinsic property of O and OH terminated Ti2C MXenes, in which the mean hydrogen affinity for the terminated Ti2C MXenes is linearly correlated to the statistical average of their OH fraction. In addition, the C-H activation energies exhibit a strong scaling relationship to the hydrogen affinity. This quantity can therefore yield quick predictions of catalytic activity of terminated Ti2C MXenes towards C-H activations, and even predict their chemical selectivity toward scissoring different C-H bonds. We believe that the hydrogen affinity will accelerate the discovery of further applications of the broad family of MXenes in heterogeneous catalysis.

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  • 31.
    Esau, Derek
    et al.
    Queens Univ, Canada.
    Schuett, Fabian M.
    Ulm Univ, Germany.
    Varvaris, K. Liam
    Queens Univ, Canada.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Jacob, Timo
    Ulm Univ, Germany; Helmholtz Inst Ulm HIU Electrochem Energy Storage, Germany; KIT, Germany.
    Jerkiewicz, Gregory
    Queens Univ, Canada.
    Controlled-Atmosphere Flame Fusion Growth of Nickel Poly-oriented Spherical Single Crystals-Unraveling Decades of Impossibility2020Ingår i: Electrocatalysis, ISSN 1868-2529, E-ISSN 1868-5994, Vol. 11, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experimental research using monocrystalline electrodes has been a hallmark of interfacial electrochemistry and electrocatalysis since 1980. However, it has been limited to mainly noble metals because of the challenges encountered when using non-noble metals. We report on the development of controlled-atmosphere flame fusion that enables the growth of spherical single crystals of non-noble metals in controlled gaseous atmosphere and without the formation of surface or bulk oxides. The set-up is used to grow nickel single crystals the structure of which is verified using Laue X-ray back-scattering and scanning electron microscopy (SEM). The equilibrium shape of the nickel single crystals calculated using Wulff construction agrees with the actual shape determined using SEM. Electrochemical measurements in aqueous NaOH solution using the monocrystalline Ni electrodes reveal cyclic voltammetry features unique to their surface structure. The methodology, transferrable to other metals, creates enormous research opportunities in interfacial electrochemistry, electrocatalysis, surface science, gas-phase catalysis, and corrosion science.

  • 32.
    Schuett, Fabian M.
    et al.
    Ulm Univ, Germany.
    Esau, Derek
    Queens Univ, Canada.
    Varvaris, K. Liam
    Queens Univ, Canada.
    Gelman, Shelly
    Queens Univ, Canada.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Jerkiewicz, Gregory
    Queens Univ, Canada.
    Jacob, Timo
    Ulm Univ, Germany; Helmholtz Inst Ulm HIU, Germany; Karlsruhe Inst Technol KIT, Germany.
    Controlled-Atmosphere Flame Fusion Single-Crystal Growth of Non-Noble fcc, hcp, and bcc Metals Using Copper, Cobalt, and Iron2020Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 59, nr 32, s. 13246-13252Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The growth of noble-metal single crystals via the flame fusion method was developed in the 1980s. Since then, there have been no major advancements to the technique until the recent development of the controlled-atmosphere flame fusion (CAFF) method to grow non-noble Ni single crystals. Herein, we demonstrate the generality of this method with the first preparation of fcc Cu as well as the first hcp and bcc single crystals of Co and Fe, respectively. The high quality of the single crystals was verified using scanning electron microscopy and Laue X-ray backscattering. Based on Wulff constructions, the equilibrium shapes of the single-crystal particles were studied, confirming the symmetry of the fcc, hcp, and bcc single-crystal lattices. The low cost of the CAFF method makes all kinds of high-quality non-noble single crystals independent of their lattice accessible for use in electrocatalysis, electrochemistry, surface science, and materials science.

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  • 33.
    Sanchez-Grande, Ana
    et al.
    IMDEA Nanociencia, Spain.
    de la Torre, Bruno
    Palacky Univ Olomouc, Czech Republic; Czech Acad Sci, Czech Republic.
    Santos, Jose
    IMDEA Nanociencia, Spain.
    Cirera, Borja
    IMDEA Nanociencia, Spain.
    Lauwaet, Koen
    IMDEA Nanociencia, Spain.
    Chutora, Taras
    Palacky Univ Olomouc, Czech Republic.
    Edalatmanesh, Shayan
    Czech Acad Sci, Czech Republic.
    Mutombo, Pingo
    Czech Acad Sci, Czech Republic.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Zboril, Radek
    Palacky Univ Olomouc, Czech Republic.
    Miranda, Rodolfo
    IMDEA Nanociencia, Spain; Univ Autonoma Madrid, Spain.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Jelinek, Pavel
    Palacky Univ Olomouc, Czech Republic; Czech Acad Sci, Czech Republic.
    Martin, Nazario
    IMDEA Nanociencia, Spain; Univ Complutense, Spain.
    Ecija, David
    IMDEA Nanociencia, Spain.
    On-Surface Synthesis of Ethynylene-Bridged Anthracene Polymers2019Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 58, nr 20, s. 6559-6563Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Engineering low-band-gap -conjugated polymers is a growing area in basic and applied research. The main synthetic challenge lies in the solubility of the starting materials, which precludes advancements in the field. Here, we report an on-surface synthesis protocol to overcome such difficulties and produce poly(p-anthracene ethynylene) molecular wires on Au(111). To this aim, a quinoid anthracene precursor with =CBr2 moieties is deposited and annealed to 400K, resulting in anthracene-based polymers. High-resolution nc-AFM measurements confirm the nature of the ethynylene-bridge bond between the anthracene moieties. Theoretical simulations illustrate the mechanism of the chemical reaction, highlighting three major steps: dehalogenation, diffusion of surface-stabilized carbenes, and homocoupling, which enables the formation of an ethynylene bridge. Our results introduce a novel chemical protocol to design -conjugated polymers based on oligoacene precursors and pave new avenues for advancing the emerging field of on-surface synthesis.

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  • 34.
    Ahsan, Aisha
    et al.
    Univ Basel, Switzerland.
    Mousavi, S. Fatemeh
    Univ Basel, Switzerland.
    Nijs, Thomas
    Univ Basel, Switzerland.
    Nowakowska, Sylwia
    Univ Basel, Switzerland.
    Popova, Olha
    Univ Basel, Switzerland.
    Wackerlin, Aneliia
    Univ Basel, Switzerland.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Gade, Lutz H.
    Heidelberg Univ, Germany.
    Jung, Thomas A.
    Paul Scherrer Inst, Switzerland.
    Phase Transitions in Confinements: Controlling Solid to Fluid Transitions of Xenon Atoms in an On-Surface Network2019Ingår i: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 15, nr 3, artikel-id 1803169Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study reports on "phase" transitions of Xe condensates in on-surface confinements induced by temperature changes and local probe excitation. The pores of a metal-organic network occupied with 1 up to 9 Xe atoms are investigated in their propensity to undergo "condensed solid" to "confined fluid" transitions. Different transition temperatures are identified, which depend on the number of Xe atoms in the condensate and relate to the stability of the Xe clustering in the condensed "phase." This work reveals the feature-rich behavior of transitions of confined planar condensates, which provide a showcase toward future "phase-transition" storage media patterned by self-assembly. This work is also of fundamental interest as it paves the way to real space investigations of reversible solid to fluid transitions of magic cluster condensates in an array of extremely well-defined quantum confinements.

  • 35.
    Paintner, Tobias
    et al.
    Tech Univ Munich, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Du, Ping
    Karlsruhe Inst Technol, Germany.
    Klyatskaya, Svetlana
    Karlsruhe Inst Technol, Germany.
    Paszkiewicz, Mateusz
    Tech Univ Munich, Germany.
    Hellwig, Raphael
    Tech Univ Munich, Germany.
    Uphoff, Martin
    Tech Univ Munich, Germany.
    Oener, Murat A.
    Tech Univ Munich, Germany.
    Cuniberto, Edoardo
    Tech Univ Munich, Germany.
    Deimel, Peter S.
    Tech Univ Munich, Germany.
    Zhang, Yi-Qi
    Tech Univ Munich, Germany.
    Palma, Carlos-Andres
    Tech Univ Munich, Germany; Chinese Acad Sci, Peoples R China.
    Allegretti, Francesco
    Tech Univ Munich, Germany.
    Ruben, Mario
    Karlsruhe Inst Technol, Germany; Univ Strasbourg, France.
    Barth, Johannes V
    Tech Univ Munich, Germany.
    Klappenberger, Florian
    Tech Univ Munich, Germany.
    Quantum Tunneling Mediated Interfacial Synthesis of a Benzofuran Derivative2019Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 58, nr 33, s. 11285-11290Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reaction pathways involving quantum tunneling of protons are fundamental to chemistry and biology. They are responsible for essential aspects of interstellar synthesis, the degradation and isomerization of compounds, enzymatic activity, and protein dynamics. On-surface conditions have been demonstrated to open alternative routes for organic synthesis, often with intricate transformations not accessible in solution. Here, we investigate a hydroalkoxylation reaction of a molecular species adsorbed on a Ag(111) surface by scanning tunneling microscopy complemented by X-ray electron spectroscopy and density functional theory. The closure of the furan ring proceeds at low temperature (down to 150 K) and without detectable side reactions. We unravel a proton-tunneling-mediated pathway theoretically and confirm experimentally its dominant contribution through the kinetic isotope effect with the deuterated derivative.

  • 36.
    Fritton, Massimo
    et al.
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Duncan, David A.
    Tech Univ Munich, Germany; Diamond Light Source, England.
    Deimel, Peter S.
    Tech Univ Munich, Germany.
    Rastgoo-Lahrood, Atena
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Allegretti, Francesco
    Tech Univ Munich, Germany.
    Barth, Johannes V.
    Tech Univ Munich, Germany.
    Heckl, Wolfgang M.
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Lackinger, Markus
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    The Role of Kinetics versus Thermodynamics in Surface-Assisted Ullmann Coupling on Gold and Silver Surfaces2019Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 141, nr 12, s. 4824-4832Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface-assisted Ullmann coupling is the workhorse of on-surface synthesis. Despite its obvious relevance, many fundamental and mechanistic aspects remain elusive. To shed light on individual reaction steps and their progression with temperature, temperature-programmed X-ray photoelectron spectroscopy (TP-XPS) experiments are performed for a prototypical model system. The activation of the coupling by initial dehalogenation is tracked by monitoring Br 3d core levels, whereas the C 1s signature is used to follow the emergence of metastable organometallic intermediates and their conversion to the final covalent products upon heating in real time. The employed 1,3,5-tris(4-bromophenyl)benzene precursor is comparatively studied on Ag(111) versus Au(111), whereby intermolecular bonds and network topologies are additionally characterized by scanning tunneling microscopy (STM). Besides the well-comprehended differences in activation temperatures for debromination, the thermal progression shows marked differences between the two surfaces. Debromination proceeds rapidly on Ag(111), but is relatively gradual on Au(111). While on Ag(111) debromination is well explained by first-order reaction kinetics, thermodynamics prevail on Au(111), underpinned by a close agreement between experimentally deduced and density functional theory (DFT) calculated reaction enthalpies. Thermodynamically controlled debromination on Au(111) over a large temperature range implies an unexpectedly long lifetime of surface-stabilized radicals prior to covalent coupling, as corroborated by TP-XPS of C is core levels. These insights are anticipated to play an important role regarding our ability to rationally synthesize atomically precise low-dimensional covalent nanostructures on surfaces.

  • 37.
    Ahsan, Aisha
    et al.
    Univ Basel, Switzerland.
    Mousavi, S. Fatemeh
    Univ Basel, Switzerland.
    Nijs, Thomas
    Univ Basel, Switzerland.
    Nowakowska, Sylwia
    Univ Basel, Switzerland.
    Popova, Olha
    Univ Basel, Switzerland.
    Wackerlin, Aneliia
    Univ Basel, Switzerland.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Gade, Lutz H.
    Heidelberg Univ, Germany.
    Jung, Thomas A.
    Univ Basel, Switzerland; Paul Scherrer Inst, Switzerland.
    Watching nanostructure growth: kinetically controlled diffusion and condensation of Xe in a surface metal organic network2019Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, nr 11, s. 4895-4903Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Diffusion, nucleation and growth provide the fundamental access to control nanostructure growth. In this study, the temperature activated diffusion of Xe at and between different compartments of an on-surface metal organic coordination network on Cu(111) has been visualized in real space. Xe atoms adsorbed at lower energy sites become mobile with increased temperature and gradually populate energetically more favourable binding sites or remain in a delocalized fluid form confined to diffusion along a topological subset of the on-surface network. These diffusion pathways can be studied individually under kinetic control via the chosen thermal energy kT of the sample and are determined by the network and sample architecture. The spatial distribution of Xe in its different modes of mobility and the time scales of the motion is revealed by Scanning Tunneling Microscopy (STM) at variable temperatures up to 40 K and subsequent cooling to 4 K. The system provides insight into the diffusion of a van der Waals gas on a complex structured surface and its nucleation and coarsening/growth into larger condensates at elevated temperature under thermodynamic conditions.

  • 38.
    Cai, Liangliang
    et al.
    Tongji Univ, Peoples R China.
    Yu, Xin
    Tongji Univ, Peoples R China.
    Liu, Mengxi
    Natl Ctr Nanosci and Technol, Peoples R China.
    Sun, Qiang
    Tongji Univ, Peoples R China.
    Bao, Meiling
    Tongji Univ, Peoples R China.
    Zha, Zeqi
    Natl Ctr Nanosci and Technol, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Pan, Jinliang
    Natl Ctr Nanosci and Technol, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Ma, Honghong
    Tongji Univ, Peoples R China.
    Ju, Huanxin
    Univ Sci and Technol China, Peoples R China.
    Hu, Shanwei
    Univ Sci and Technol China, Peoples R China.
    Xu, Liang
    Tongji Univ, Peoples R China.
    Zou, Jiacheng
    Tongji Univ, Peoples R China.
    Yuan, Chunxue
    Tongji Univ, Peoples R China.
    Jacob, Timo
    Ulm Univ, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Zhu, Junfa
    Univ Sci and Technol China, Peoples R China.
    Qu, Xiaohui
    Natl Ctr Nanosci and Technol, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Xu, Wei
    Tongji Univ, Peoples R China.
    Direct Formation of C-C Double-Bonded Structural Motifs by On-Surface Dehalogenative Homocoupling of gem-Dibromomethyl Molecules2018Ingår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, nr 8, s. 7959-7966Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 39.
    Li, Qing
    et al.
    Soochow Univ, Peoples R China.
    Yang, Biao
    Soochow Univ, Peoples R China.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Zhong, Qigang
    Soochow Univ, Peoples R China; Justus Liebig Univ Giessen, Germany.
    Ju, Huanxin
    Univ Sci and Technol China, Peoples R China.
    Zhang, Junjie
    Soochow Univ, Peoples R China.
    Cao, Nan
    Soochow Univ, Peoples R China.
    Shi, Ziliang
    Soochow Univ, Peoples R China.
    Zhang, Haiming
    Soochow Univ, Peoples R China.
    Ebeling, Daniel
    Justus Liebig Univ Giessen, Germany.
    Schirmeisen, Andre
    Justus Liebig Univ Giessen, Germany.
    Zhu, Junfa
    Univ Sci and Technol China, Peoples R China.
    Chi, Lifeng
    Soochow Univ, Peoples R China.
    Hierarchical Dehydrogenation Reactions on a Copper Surface2018Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 140, nr 19, s. 6076-6082Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 40.
    Hellwig, Raphael
    et al.
    Tech Univ Munich, Germany.
    Uphoff, Martin
    Tech Univ Munich, Germany.
    Paintner, Tobias
    Tech Univ Munich, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Ruben, Mario
    KIT, Sweden; Univ Strasbourg, France.
    Klappenberger, Florian
    Tech Univ Munich, Germany.
    Barth, Johannes V.
    Tech Univ Munich, Germany.
    Ho-Mediated Alkyne Reactions at Low Temperatures on Ag(111)2018Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, nr 60, s. 16126-16135Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low-temperature approaches to catalytic conversions promise efficiency, selectivity, and sustainable processes. Control over certain coupling reactions can be obtained via the pre-positioning of reactive moieties by self-assembly. However, in the striving field of on-surface synthesis atomistic precision and control remains largely elusive, because the employed coupling reactions proceed at temperatures beyond the thermal stability of the supramolecular templates. Here, utilizing scanning tunneling microscopy, we demonstrate terminal alkyne on-surface reactions mediated by Ho atoms at a weakly reactive Ag(111) substrate at lowtemperatures. Density functional theory calculations confirm the catalytic activity of the involved adatoms. Pre-deposited Ho induces alkyne dehydrogenation starting at substrate temperatures as low as 100 K. Ho arriving at molecularly pre-covered surfaces held at 130 and 200 K produces covalent enyne-linked dimers and initiates cyclotrimerization, respectively. Statistical product analysis indicates a two-step pathway for the latter, whereby the enyne intermediates influence the distribution of the products. High chemoselectivity results from the absence of cyclotetramerization and diyne-forming homocoupling. Our analysis indicates that mainly the arriving Ho adatoms enable the coupling. These findings support the concept of dynamic heterogeneity by single-atom catalysts and pave the way for alternative means to control on-surface reactions.

  • 41.
    Lischka, Matthias
    et al.
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Fritton, Massimo
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Eichhorn, Johanna
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Vyas, Vijay S.
    Max Planck Inst Solid State Res, Germany; Marquette Univ, WI 53233 USA.
    Strunskus, Thomas
    Christian Albrechts Univ Kiel, Germany.
    Lotsch, Bettina V.
    Max Planck Inst Solid State Res, Germany; Nanosyst Initiat Munich, Germany; Ctr NanoSci, Germany; Univ Munich LMU, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Heckl, Wolfgang M.
    Tech Univ Munich, Germany; Deutsch Museum, Germany; Nanosyst Initiat Munich, Germany; Ctr NanoSci, Germany.
    Lackinger, Markus
    Tech Univ Munich, Germany; Deutsch Museum, Germany; Nanosyst Initiat Munich, Germany; Ctr NanoSci, Germany.
    On-Surface Polymerization of 1,6-Dibromo-3,8-diiodpyrene-A Comparative Study on Au(111) Versus Ag(111) by STM, XPS, and NEXAFS2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 11, s. 5967-5977Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The surface chemistry of 1,6-dibromo-3,8-diiodopyrene (Br2I2Py) is comparatively studied on Au(111) versus Ag(111) surfaces under ultrahigh vacuum conditions by a combination of high-resolution scanning tunneling microscopy (STM) and X-ray spectroscopy. The chemical state of the molecular networks, that is, the dehalogenation and the possible formation of organometallic intermediates, is assessed by X-ray photoelectron spectroscopy. In addition, pyrene tilt angles are quantified by carbon K-edge near edge X-ray absorption fine structure experiments. Upon room-temperature (RT) deposition of Br2I2Py onto Au(111), only partial deiodination was found, and STM revealed the coexistence of ordered arrangements of both intact Br2I2Py molecules and organometallic dimers as well as few larger aggregates. Further annealing to 100 C triggered full deiodination followed by the formation of organometallic chains of otherwise still brominated molecules. By contrast, on Ag(111), iodine is fully and bromine is partly dissociated upon RT deposition of Br2I2Py. The initially disordered organometallic aggregates can be reorganized into more ordered structures by mild annealing at 125 degrees C. Yet, the conversion of the organometallic intermediates into well-defined cross-linked quasi 2D covalent networks was neither possible on Au(111) nor on Ag(111). This is attributed to the large steric hindrance in the covalently linked adsorbed state.

  • 42.
    Fritton, Massimo
    et al.
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    Otte, Katrin
    Bavarian Acad Sci and Humanities, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Biswas, Pronay Kumar
    Univ Siegen, Germany.
    Heckl, Wolfgang M.
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    Schmittel, Michael
    Univ Siegen, Germany.
    Lackinger, Markus
    Deutsch Museum, Germany; Tech Univ Munich, Germany.
    The influence of ortho-methyl substitution in organometallic self-assembly - a comparative study on Cu(111) vs. Ag(111)2018Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 54, nr 70, s. 9745-9748Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Metal surface-induced dehalogenation of precursors is known to initiate self-assembly of organometallic networks, where tectons are connected via carbon-metal-carbon (C-M-C) bonds. Even though reversibility of the C-M-C bonds facilitates structural equilibration, defects associated with highly bent organometallic linkages are still commonly observed. By introducing a steric hindrance to reduce the C-M-C bond angle flexibility, we find well ordered organometallic networks of an ortho-methyl substituted 1,3,5-tris(p-bromophenyl)-benzene analogue on Cu(111) after room-temperature (RT) deposition and on Ag(111) after annealing.

  • 43.
    Cirera, B.
    et al.
    IMDEA Nanosci, Spain.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Otero, R.
    IMDEA Nanosci, Spain; University of Autonoma Madrid, Spain.
    Gallego, J. M.
    CSIC, Spain.
    Miranda, R.
    IMDEA Nanosci, Spain; University of Autonoma Madrid, Spain.
    Ecija, D.
    IMDEA Nanosci, Spain.
    Efficient Lanthanide Catalyzed Debromination and Oligomeric Length-Controlled Ullmann Coupling of Aryl Halides2017Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 14, s. 8033-8041Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lanthanide elements play a vital role in a broad range of high-tech applications, and there is an increasing interest in their catalytic activity, particularly in organo-metallics. However, their catalytic role on surfaces remains unexplored. Here, we present a scanning tunneling microscopy and density functional theory study of the debromination, contacting, and coupling of dibromine terphenyl species with Dy (f-block element) and Ag (d-block element) adatoms, respectively. We show that Dy debrominates the targeted species more efficiently than Ag adatoms at room temperature, promoting the formation of unprecedented C-Dy-C organo-metallic supramolecules versus C-Ag-C parallel chains for the Ag case. DFT calculations corroborate our results showing an almost spontaneous debromination process with Dy compared to Ag. Upon annealing, for samples containing Dy, the formation of C-Ag-C organometallic bonds and concomitant C-C coupling is inhibited, giving rise to a self-assembly of debrominated monomers, showing only a minority number of covalent dimes species. For samples without Dy covalent chains of irregular length are promoted. Our studies open new avenues for using lanthanide elements as efficient dehalogenation catalysts. Furthermore, we illustrate their potential as inhibitors of uncontrolled C-C coupling reactions, of great relevance for fine-tuning the length of polymeric compounds.

  • 44.
    Wang, Xiao-Ye
    et al.
    Max Planck Institute Polymer Research, Germany.
    Richter, Marcus
    Technical University of Dresden, Germany.
    He, Yuanqin
    Technical University of Munich, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Riss, Alexander
    Technical University of Munich, Germany.
    Rajesh, Raju
    Max Planck Institute Polymer Research, Germany.
    Garnica, Manuela
    Technical University of Munich, Germany.
    Hennersdorf, Felix
    Technical University of Dresden, Germany.
    Weigand, Jan J.
    Technical University of Dresden, Germany.
    Narita, Akimitsu
    Max Planck Institute Polymer Research, Germany.
    Berger, Reinhard
    Technical University of Dresden, Germany.
    Feng, Xinliang
    Technical University of Dresden, Germany.
    Auwaerter, Willi
    Technical University of Munich, Germany.
    Barth, Johannes V.
    Technical University of Munich, Germany.
    Palma, Carlos-Andres
    Technical University of Munich, Germany.
    Muellen, Klaus
    Max Planck Institute Polymer Research, Germany.
    Exploration of pyrazine-embedded antiaromatic polycyclic hydrocarbons generated by solution and on-surface azomethine ylide homocoupling2017Ingår i: Nature Communications, E-ISSN 2041-1723, Vol. 8, artikel-id 1948Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanographenes, namely polycyclic aromatic hydrocarbons (PAHs) with nanoscale dimensions (amp;gt;1 nm), are atomically precise cutouts from graphene. They represent prime models to enhance the scope of chemical and physical properties of graphene through structural modulation and functionalization. Defined nitrogen doping in nanographenes is particularly attractive due to its potential for increasing the number of p-electrons, with the possibility of introducing localized antiaromatic ring elements. Herein we present azomethine ylide homocoupling as a strategy to afford internally nitrogen-doped, non-planar PAH in solution and planar nanographene on surfaces, with central pyrazine rings. Localized antiaromaticity of the central ring is indicated by optical absorption spectroscopy in conjunction with theoretical calculations. Our strategy opens up methods for chemically tailoring graphene and nanographenes, modified by antiaromatic dopants.

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  • 45.
    Cirera, Borja
    et al.
    IMDEA Nanosci, Spain.
    Trukhina, Olga
    University of Autonoma Madrid, Spain.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Bottari, Giovanni
    IMDEA Nanosci, Spain; University of Autonoma Madrid, Spain; University of Autonoma Madrid, Spain.
    Rodriguez-Fernandez, Jonathan
    University of Autonoma Madrid, Spain.
    Martin-Jimenez, Alberto
    IMDEA Nanosci, Spain.
    Islyaikin, Mikhail K.
    Ivanovo State University of Chemistry and Technology, Russia.
    Otero, Roberto
    IMDEA Nanosci, Spain; University of Autonoma Madrid, Spain.
    Gallego, Jose M.
    CSIC, Spain.
    Miranda, Rodolfo
    IMDEA Nanosci, Spain; University of Autonoma Madrid, Spain.
    Torres, Tomas
    IMDEA Nanosci, Spain; University of Autonoma Madrid, Spain; University of Autonoma Madrid, Spain.
    Ecija, David
    IMDEA Nanosci, Spain.
    Long-Range Orientational Self-Assembly, Spatially Controlled Deprotonation, and Off-Centered Metalation of an Expanded Porphyrin2017Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, nr 40, s. 14129-14136Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Expanded porphyrins are large-cavity macro cycles with enormous potential in coordination chemistry, anion sensing, photodynamic therapy, and optoelectronics. In the last two decades, the surface science community has assessed the physicochemical properties of tetrapyrrolic-like macrocydes. However, to date, the sublimation, self-assembly and atomistic insights of expanded porphyrins on surfaces have remained elusive. Here, we show the self-assembly on Au(111) of an expanded aza-porphyrin, namely, an "expanded hemi-spatially-controlled porphyrazine", through a unique growth mechanism based on deprotonation long-range orientational self-assembly. Furthermore, a spatially controlled "writing" protocol on such self-assembled architecture is presented based on the STM tip-induced deprotonation of the inner protons of individual macrocydes. Finally, the capability of these surface-confined macrocydes to host lanthanide elements is assessed, introducing a novel off-centered coordination motif. The presented findings represent a milestone in the fields of porphyrinoid chemistry and surface science, revealing a great potential for novel surface patterning, opening new avenues for molecular level information storage, and boosting the emerging field of surface-confined coordination chemistry involving f-block elements.

  • 46.
    Lin, Tao
    et al.
    Technical University of Munich, Germany.
    Zhang, Liding
    Technical University of Munich, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Chen, Zhi
    Karlsruhe Institute Technology, Germany.
    Ruben, Mario
    Karlsruhe Institute Technology, Germany; University of Strasbourg, France.
    Barth, Johannes V.
    Technical University of Munich, Germany.
    Klappenberger, Florian
    Technical University of Munich, Germany.
    Terminal Alkyne Coupling on a Corrugated Noble Metal Surface: From Controlled Precursor Alignment to Selective Reactions2017Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, nr 62, s. 15588-15593Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface-templated covalent coupling of organic precursors currently emerges as a promising route to the atom-precise fabrication of low-dimensional carbon materials. Here, we investigate the adsorption and the coupling reactions of 4,4-diethynyl-1,1:4,1-terphenyl on Au(110) under ultra-high vacuum conditions by using scanning tunneling microscopy combined with density functional theory and kinetic Monte Carlo calculations. Temperature treatment induces both 1,2,4-asymmetric cyclotrimerization and homocoupling, resulting in various reaction products, including a previously unreported, surface-templated H-shaped pentamer. Our analysis of the temperature-dependent relative product abundances unravels that 1,2,4-trimerization and homocoupling proceed via identical intermediate species with the final products depending on the competition of coupling to a third monomer versus dehydrogenation. Our study sheds light on the control of coupling reactions by corrugated surfaces and annealing protocols.

  • 47.
    Nowakowska, Sylwia
    et al.
    Department of Physics, University of Basel, Basel, Switzerland.
    Wäckerlin, Aneliia
    Department of Physics, University of Basel, Basel, Switzerland.
    Piquero-Zulaica, Ignacio
    Centro de Física de Materiales (CSIC/UPV-EHU)—Materials Physics Center, San Sebastián, Spain.
    Nowakowski, Jan
    Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, Villigen, PSI, Switzerland.
    Kawai, Shigeki
    Department of Physics, University of Basel, Basel, Switzerland; PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama, Japan.
    Wäckerlin, Christian
    Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, Villigen, PSI, Switzerland.
    Matena, Manfred
    Department of Physics, University of Basel, Basel, Switzerland; Donostia International Physics Center (DIPC), San Sebastián, Spain.
    Nijs, Thomas
    Department of Physics, University of Basel, Basel, Switzerland.
    Fatayer, Shadi
    Department of Physics, University of Basel, Basel, Switzerland; Departamento de Física Aplicada, Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, Campinas, Brazil.
    Popova, Olha
    Department of Physics, University of Basel, Basel, Switzerland.
    Ahsan, Aisha
    Department of Physics, University of Basel, Basel, Switzerland.
    Mousavi, S. Fatemeh
    Department of Physics, University of Basel, Basel, Switzerland.
    Ivas, Toni
    Department of Physics, University of Basel, Basel, Switzerland.
    Meyer, Ernst
    Department of Physics, University of Basel, Basel, Switzerland.
    Stöhr, Meike
    Zernike Institute for Advanced Materials, University of Groningen, AG, Groningen, The Netherlands.
    Ortega, J. Enrique
    Centro de Física de Materiales (CSIC/UPV-EHU)—Materials Physics Center, San Sebastián, Spain; Donostia International Physics Center (DIPC), San Sebastián, Spain; Departamento Física Aplicada I, Universidad del País Vasco, San Sebastián, Spain.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk kemi. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Gade, Lutz H.
    Anorganisch-Chemisches Institut, Universität Heidelberg, Heidelberg, Germany.
    Lobo-Checa, Jorge
    Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Zaragoza, Spain; Departamento de Física de la Materia Condensada, Universidad de Zaragoza, Zaragoza, Spain.
    Jung, Thomas A.
    Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, Villigen, PSI, Switzerland.
    Configuring Electronic States in an Atomically Precise Array of Quantum Boxes2016Ingår i: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 12, nr 28, s. 3757-3763Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A 2D array of electronically coupled quantum boxes is fabricated by means of on-surface self-assembly assuring ultimate precision of each box. The quantum states embedded in the boxes are configured by adsorbates, whose occupancy is controlled with atomic precision. The electronic interbox coupling can be maintained or significantly reduced by proper arrangement of empty and filled boxes.

  • 48.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk kemi. Linköpings universitet, Tekniska fakulteten.
    Formation mechanisms of covalent nanostructures from density functional theory2016Ingår i: Proceedings of International Workshop on On-Surface Synthesis, Cham: Springer, 2016, s. 269-287Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this chapter, it is demonstrated how electronic structure calculations, with focus on density functional theory, can be used to gain insight about on-surface reactions. I first give a brief introduction to how density functional theory can be used to study reactions. The focus is then shifted to two different types of on-surface reactions, highlighting the theoretical work that has been performed to gain detailed atomistic insight into them. First, the state of the art of the theory behind on-surface Ullmann coupling is described. In this reaction, molecular building blocks dehalogenate, which enables them to covalently couple. The most crucial reaction parameters are identified—the diffusion and coupling barriers of surface-supported radicals—and the potential for theory to optimize these is discussed. We then concentrate on the homo-coupling between terminal alkynes, a rudimentarily different process where molecules initially couple before undergoing a dehydrogenation step. The theory of the mechanism behind this coupling strategy is less developed than that of the on-surface Ullmann coupling, where fundamental questions remain to be unraveled. For example, by the subtle change of substrate from Ag to Au, the on-surface alkyne chemistry is completely altered from the homo-coupling to a cyclodehydrogenation reaction for the same molecular building block, of which origin remains unknown. The main objective of the chapter is to give an impression of what kind of information theory can obtain about reaction on surface, as well as to motivate and inspire for future theoretical studies, which will be needed to turn on-surface synthesis into a more predictive discipline.

  • 49.
    Zhang, Yi-Qi
    et al.
    Technical University of Munich, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk kemi. Linköpings universitet, Tekniska fakulteten.
    Barth, Johannes V.
    Technical University of Munich, Germany.
    Klappenberger, Florian
    Technical University of Munich, Germany.
    Intermolecular Hybridization Creating Nanopore Orbital in a Supramolecular Hydrocarbon Sheet2016Ingår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 16, nr 7, s. 4274-4281Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molecular orbital engineering is a key ingredient for the design of organic devices. Intermolecular hybridization promises efficient charge carrier transport but usually requires dense packing for significant wave function overlap. Here we use scanning tunneling spectroscopy to spatially resolve the electronic structure of a surface-confined nanoporous supramolecular sheet of a prototypical hydrocarbon compound featuring terminal alkyne (CCH) groups. Surprisingly, localized nanopore orbitals are observed, with their electron density centered in the cavities surrounded by the functional moieties. Density functional theory calculations reveal that these new electronic states originate from the intermolecular hybridization of six in-plane x-orbitals of the carbon carbon triple bonds, exhibiting significant electronic splitting and an energy downshift of approximately 1 eV. Importantly, these nanopore states are distinct from previously reported interfacial states. We unravel the underlying connection between the formation of nanopore orbital and geometric arrangements of functional groups, thus demonstrating the generality of applying related orbital engineering concepts in various types of porous organic structures.

  • 50.
    Morchutt, Claudius
    et al.
    Max Planck Institute Solid State Research, Germany; Ecole Polytech Federal Lausanne, Switzerland.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Strasser, Carola
    Max Planck Institute Solid State Research, Germany.
    Starke, Ulrich
    Max Planck Institute Solid State Research, Germany.
    Gutzler, Rico
    Max Planck Institute Solid State Research, Germany.
    Kern, Klaus
    Max Planck Institute Solid State Research, Germany; Ecole Polytech Federal Lausanne, Switzerland.
    Interplay of Chemical and Electronic Structure on the Single-Molecule Level in 2D Polymerization2016Ingår i: ACS NANO, ISSN 1936-0851, Vol. 10, nr 12, s. 11511-11518Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Single layers of covalently linked organic materials in the form of two-dimensional (2D) polymers constitute structures complementary to inorganic 2D materials. The electronic properties of 2D polymers may be manipulated through a deliberate choice of the organic precursors. Here we address the changes in electronic CO structure-from precursor molecule to oligomer by scanning tunneling spectroscopy and ultraviolet photoelectron spectroscopy. For this purpose, we introduce the polymerization reaction of 1,3,5-tris(4-carboxyphenyl)benzene via decarboxylation on Cu(111), which is thoroughly characterized by scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory calculations. We present a comprehensive study of a contamination-free on-surface coupling scheme and study how dehydrogenation, decarboxylation, and polymerization affect the electronic structure on the molecular level.

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