Atomically Resolved Chemical Reactivity of Small Fe Clusters

Berwanger, Julian; Polesya, S.; Mankovsky, S.; Ebert, H.; Giessibl, Franz J.

doi:10.1103/physrevlett.124.096001

Cited by 50 publications

(59 citation statements)

References 53 publications

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“…A major breakthrough in nc-AFM was the ability to resolve the internal structure of simple organic molecules in real space 2 , which was enabled by functionalizing a metallic AFM tip apex with a carbon-monoxide (CO) molecule. Since then, CO-terminated tips (CO tips) have been widely applied in AFM experiments to study molecular adsorbates [3][4][5][6][7][8][9] and various types of surfaces and adsorbates with atomic resolution [10][11][12][13][14][15] . The interaction of a CO tip with a sample surface is composed of different physical mechanisms, including van der Waals attraction and Pauli repulsion, which can be described by a Lennard-Jones potential 12,16,17 , and electrostatic interaction between the complex electric field of the CO tip and the sample electron density 12,13,18 .…”

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confidence: 99%

Quantifying the evolution of atomic interaction of a complex surface with a functionalized atomic force microscopy tip

Liebig

Hapala

Weymouth

et al. 2020

Sci Rep

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terminating the tip of an atomic force microscope with a co molecule allows data to be acquired with a well-known and inert apex. Previous studies have shown conflicting results regarding the electrostatic interaction, indicating in some cases that the negative charge at the apex of the co dominates, whereas in other cases the positive charge at the end of the metal tip dominates. to clarify this, we investigated CaF 2 (111). CaF 2 is an ionic crystal and the (111) surface does not possess charge inversion symmetry. far from the surface, the interaction is dominated by electrostatics via the negative charge at the apex. closer to the surface, pauli repulsion and co bending dominate, which leads to an unexpected appearance of the complex 3-atom unit cell. We compare simulated data in which the electrostatics are modeled by point particles versus a charge density calculated by Dft. We also compare modeling pauli repulsion via individual Lennard-Jones potentials versus a total charge density overlap. In doing so, we determine forcefield parameters useful for future investigations of biochemical processes.

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confidence: 99%

Quantifying the evolution of atomic interaction of a complex surface with a functionalized atomic force microscopy tip

Liebig

Hapala

Weymouth

et al. 2020

Sci Rep

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“…1, top row). The atomic surface geometries in terms of CN are related to chemical bond formation and catalytic activity confined to the surface [41][42][43][44] .…”

Section: Resultsmentioning

confidence: 99%

“…The lower CN of surface atoms is directly related to a tendency to form bonds with external species, explaining their catalytic reactivity [41][42][43][44] . However, it is not straightforward to predict catalytic performance based on CN, since surface atoms with the same CN are often surrounded by different surface geometries and show dissimilar adsorption properties 42,43 .…”

Section: Resultsmentioning

confidence: 99%

Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals

et al. 2021

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Active sites and catalytic activity of heterogeneous catalysts is determined by their surface atomic structures. However, probing surface structure at atomic resolution is difficult especially for solution ensembles of catalytic nanocrystals which consist of heterogeneous particles with irregular shapes and surfaces. Here, we constructed 3D maps of coordination number (CN) and generalized CN ( CN ) for individual surface atoms of sub-3 nm Pt nanocrystals. Our results reveal that the synthesized Pt nanocrystals are enclosed by islands of atoms with non-uniform shapes that lead to complex surface structures, including a high ratio of low-coordination surface atoms, reduced domain size of low-index facets, and various types of exposed high-index facets. 3D maps of CN are directly correlated to catalytic activities assigned to individual surface atoms with distinct local coordination structures, which explains the origin of high catalytic performance of small Pt nanocrystals in important reactions such as oxygen reduction reaction and CO electro-oxidation.

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“…CO terminated tips also enable atomic resolution of metal clusters [ 61 ]. In spite of their lateral flexibility [ 59 ], these tips have the capability to atomically manipulate metal atoms on surfaces [ 62 ] and to study the chemical reactivity of small metal clusters as a function of the atomic site [ 63 ]. Surprisingly, the reactivity of CO terminated tips scatters somewhat even if the CO tip termination sits at the foremost single front atom of the tip, apparently depending on the tip cluster behind the metal front atom that holds the CO tip molecule (see Figure 1 in [ 63 ]).…”

Section: Resultsmentioning

confidence: 99%

Probing the Nature of Chemical Bonds by Atomic Force Microscopy

Giessibl¹

2021

Molecules

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The nature of the chemical bond is important in all natural sciences, ranging from biology to chemistry, physics and materials science. The atomic force microscope (AFM) allows to put a single chemical bond on the test bench, probing its strength and angular dependence. We review experimental AFM data, covering precise studies of van-der-Waals-, covalent-, ionic-, metallic- and hydrogen bonds as well as bonds between artificial and natural atoms. Further, we discuss some of the density functional theory calculations that are related to the experimental studies of the chemical bonds. A description of frequency modulation AFM, the most precise AFM method, discusses some of the experimental challenges in measuring bonding forces. In frequency modulation AFM, forces between the tip of an oscillating cantilever change its frequency. Initially, cantilevers were made mainly from silicon. Most of the high precision measurements of bonding strengths by AFM became possible with a technology transfer from the quartz watch technology to AFM by using quartz-based cantilevers (“qPlus force sensors”), briefly described here.

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Atomically Resolved Chemical Reactivity of Small Fe Clusters

Cited by 50 publications

References 53 publications

Quantifying the evolution of atomic interaction of a complex surface with a functionalized atomic force microscopy tip

Quantifying the evolution of atomic interaction of a complex surface with a functionalized atomic force microscopy tip

Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals

Probing the Nature of Chemical Bonds by Atomic Force Microscopy

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