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  • How Precisely Can Individual Molecules Be Analyzed? A Case Study on Locally Quantifying Forces and Energies Using Scanning Probe Microscopy
Title: How Precisely Can Individual Molecules Be Analyzed? A Case Study on Locally Quantifying Forces and Energies Using Scanning Probe Microscopy
Recent advances in scanning probe microscopy methodology have enabled the measurement of tip−sample interactions with picometer accuracy in all three spatial dimensions, thereby providing a detailed site-specific and distance-dependent picture of the related properties. This paper explores the degree of detail and accuracy that can be achieved in locally quantifying probe−molecule interaction forces and energies for adsorbed molecules. Toward this end, cobalt phthalocyanine (CoPc), a promising CO2 reduction catalyst, was studied on Ag(111) as a model system using low-temperature, ultrahigh vacuum noncontact atomic force microscopy. Data were recorded as a function of distance from the surface, from which detailed three-dimensional maps of the molecule’s interaction with the tip for normal and lateral forces as well as the tip−molecule interaction potential were constructed. The data were collected with a CO molecule at the tip apex, which enabled a detailed visualization of the atomic structure. Determination of the tip−substrate interaction as a function of distance allowed isolation of the molecule−tip interactions; when analyzing these in terms of a Lennard−Jones-type potential, the atomically resolved equilibrium interaction energies between the CO tethered to the tip and the CoPc molecule could be recovered. Interaction energies peaked at less than 160 meV, indicating a physisorption interaction. As expected, the interaction was weakest at the aromatic hydrogens around the periphery of the molecule and strongest surrounding the metal center. The interaction, however, did not peak directly above the Co atom but rather in pockets surrounding it.  more » « less
Award ID(s):
2203589
PAR ID:
10543782
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
American Chemical Society
Date Published:
Journal Name:
ACS Nano
Volume:
18
ISSN:
1936-0851
Page Range / eLocation ID:
4495-4506
Subject(s) / Keyword(s):
cobalt phthalocyanines, noncontact atomic force microscopy, scanning tunneling force microscopy, three-dimensional atomic force microscopy, site-specific quantification of forces, surface catalysis, molecular catalysts
Format(s):
Medium: X Size: 1.8MB Other: pdf
Size(s):
1.8MB
Sponsoring Org:
National Science Foundation
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