Overview
We are investigating the fundamental properties of individual atoms and molecules on solid surfaces. We are specifically interested in the build-up of novel molecules and atomic-scale nanostructures using atom manipulation, that is, creating them with the tip of the microscope.
Our experiments exploit the extreme versatility and sensitivity of our home built low-temperature scanning tunneling microscope/atomic force microscope (STM/AFM). Such a machine is not only a nano-analytical instrument to perform imaging and spectroscopy on the atomic scale, but can also be used as a tool to assemble atomic structures, manipulate and switch molecules, attach and remove single charges at will, and induce chemical reactions including the synthesis of individual molecules.
Technique
Imaging the structure of molecules with atomic resolution was achieved by noncontact atomic force microscopy (NC-AFM). Our low-temperature STM/AFM is based on a qPlus sensor design [Ref] and is operated in an ultrahigh vacuum at a temperature of 5 K.
The key step to achieving atomic resolution on molecules is the functionalization of the microscope’s tip apex with a suitable, atomically well-defined termination, such as a CO molecule [Ref]. In this case, atomic manipulation techniques are essential for the controlled buildup of the tip used for AFM imaging [Ref].
We also perform density functional theory (DFT) calculations to elucidate the physical origins of the contrast observed. The calculations reveal that the Pauli repulsion is the source of the atomic resolution [Ref] and yield insights into the important role of the tip functionalization [Ref].
“Bond-order discrimination by atomic force microscopy”
L. Gross, F. Mohn, N. Moll, B. Schuler, A. Criado, E. Guitian, D. Peña, A. Gourdon, G. Meyer, Science 337, 1326, 2012. Cover image.
Molecule characterization
We strive to image and measure molecular properties with ever increasing resolution. Using AFM imaging with functionalized tips we demonstrated that several complementary properties of individual molecules can be resolved atomically with regard to their charge distribution [Ref], charge state [Ref], bond order [Ref], and adsorption geometry [Ref].
In addition, molecular orbital densities can be resolved by STM [Refs].
We employ molecule characterization by AFM and STM to identify molecules in our search for novel natural products [Refs] to verify synthesized molecules [Refs] and to study the properties of elusive molecules created by atom manipulation [Refs].
Molecular mixture characterization
The single molecule sensitivity of AFM gives us the unprecedented ability to investigate complex molecular mixtures on the basis of individual molecules, i.e., molecule by molecule. In close collaboration with external groups we apply our technique to investigate molecular mixtures related to
Individual molecules resolved in incipient soot formation [from Ref].
Molecule synthesis by atom manipulation
Using atomic manipulation, we can form and break individual bonds within molecules [Ref]. We create radicals on the surface and characterize them. Intramolecular bonds can also be created, as demonstrated in the reversible Bergman reaction, induced by atomic manipulation [Ref]. We also use atom manipulation to create and study elusive and novel molecules such as
- Arynes, highly reactive intermediates involved in many chemical transformations [Ref],
- Triangulene, a pi-diradical featuring a triplet ground state [Ref],
- Indenofluorene, an antiaromatic molecule [Ref],
- Polyynes, which are linear, single-atom-wide carbon wires [Ref],
- Cyclo[18]carbon, an elusive carbon allotrope that consists only of sp-hybridized carbon. Using AFM, we could reveal its polyynic structure [Ref].
Switches
We aim to employ single atoms and molecules as switches and logic elements for novel concepts in information technology, based on single electron transfer, with ultimate scaling and low power consumption. We discovered and characterized reversible switches based on bond formation between a metal atom and a molecule [Ref], cyclization in radicals (reversible Bergman reaction, switching of the spin multiplicity) [Ref] and switching atomic charge states [Ref] and adsorption geometries [Ref].
Au cation switch that can be used to toggle the local electrostatic field [Ref].
Charge control
One can attach and detach single electron charges to molecules and atoms using the microscope tip [Ref]. Using Kelvin probe force microscopy, we detect atomic charge states [Ref] and molecular charge distributions [Ref].
We are interested in controlling and measuring single electron charge transfer between molecules [Ref] and ultimately within molecule–metal networks on surfaces. Recently we measured the reorganization energy upon charging a single molecule on an insulator. For this we used the AFM as a single-electron current meter [Ref].
Moreover, we study the minute changes in the molecular structure, related to different charge states. The structural and functional changes of charged molecules are important in catalysis, electrochemistry, photoconversion and charge transfer [Ref].
Structure elucidation with Charge control [Ref].
Prophine, the parent compound of hemoglobin and chlorophyll, imaged in three different charge states: neutral (F0), negative (F-1) and doubly negative (F-2). [Ref].
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Florian Albrecht
Post-doctoral researcher
Projects & funding
This work received partial support from the ERC consolidator grant AMSEL (ongoing), the ERC advanced grant CEMAS (concluded) and the EU projects SPRING (ongoing) and PAMS (concluded). It is also part of the IBM Research Frontiers Institute.
Selected publications
- “Atomically resolved single-molecule triplet quenching”
J. Peng et al.,
Science 373, 452, 2021. - “Imaging Titan’s Organic Haze at Atomic Scale”
F. Schulz et al.,
Astrophys. J. 908, L13, 2021. - “Probing molecular excited states by atomic force microscopy”
S. Fatayer et al.,
Phys. Rev. Lett. 126, 176801, 2021. - “Intramolecular coupling of terminal alkynes by atom manipulation”
F. Albrecht et al.,
Angew. Chem. Int. Ed. 59, 22989, 2020. - “Synthesis of Cyclo[18]carbon via Debromination of C18Br6”
L.M. Scriven et al.,
J. Am. Chem. Soc. 142, 12921, 2020. - “Molecular structure elucidation with charge-state control”
S. Fatayer et al.,
Science 365, 6449, 2019. - “An sp-hybridized molecular carbon allotrope, cyclo [18] carbon”
K. Kaiser et al.,
Science 365, 1299, 2019. - “Reorganization energy upon charging a single molecule on an insulator measured by atomic force microscopy”
S. Fatayer et al.,
Nat. Nano. 13, 376–380, 2018. - “Studying an antiaromatic polycyclic hydrocarbon adsorbed on different surfaces”
Z. Majzik et al.,
Nat. Comm. 9, 1198, 2018. - “Insights into incipient soot formation by atomic force microscopy”
F. Schulz et al.,
Proc. Comb. Inst., 2018. - “Atomic force microscopy identifying fuel pyrolysis products and directing the synthesis of analytical standards”
S. Fatayer et al.,
J. Am. Chem. Soc. 140, 8156–8161, 2018. - “Direct visualization of individual aromatic compound structures in low molecular weight marine dissolved organic carbon”
S. Fatayer et al.,
Geophys. Res. Lett., 2018. - “Polyyne formation via skeletal rearrangement induced by atomic manipulation”
N. Pavliček et al.,
Nat. Chem. 10, 2018. - “Heavy oil based mixtures of different origins and treatments studied by AFM”
B. Schuler et al.,
Energy & Fuels 31, 6856–6861, 2017. - “Generation and Characterization of a Meta-Aryne on Cu and NaCl Surfaces”
N. Pavliček et al.,
ACS nano 11, 10768–10773, 2017. - “Synthesis and characterization of triangulene”
N. Pavliček et al.,
Nat. Nano. 12, 308–311, 2017. - “Synthesis of a Naphthodiazaborinine and Its Verification by Planarization with Atomic Force Microscopy”
Z. Majzik et al.,
ACS Nano 10, 5340, 2016.
- “Reversible Bergman cyclization by atomic manipulation”
B. Schuler et al.,
Nat. Chem. 8, 220, 2016. - “Probe-based measurement of lateral single-electron transfer between individual molecules”
W. Steurer et al.,
Nat. Commun. 6, 8353, 2015. - “Unraveling the Molecular Structures of Asphaltenes by Atomic Force Microscopy”
B. Schuler et al.,
J. Am. Chem. Soc. 137, 9870, 2015. - “Manipulation of the Charge State of Single Au Atoms on Insulating Multilayer Films”
W. Steurer et al.,
Phys. Rev. Lett. 114, 03680, 2015. - “Toggling the Local Electric Field with an Embedded Adatom Switch”
W. Steurer et al.,
Nano Lett. 15, 5564, 2015. - “On-surface generation and imaging of arynes by atomic force microscopy”
N. Pavliček et al.,
Nat. Chem. 7, 62, 2015. - “From Perylene to a 22‐Ring Aromatic Hydrocarbon in One‐Pot”
B. Schuler et al.,
Angew. Chem. Int. Ed. 126, 9150, 2014. - “Different tips for high-resolution atomic force microscopy and scanning tunneling microscopy of single molecules”
F. Mohn et al.,
Appl. Phys. Lett. 102, 073109, 2013. - “Adsorption Geometry Determination of Single Molecules by Atomic Force Microscopy”
B. Schuler et al.,
Phys. Rev. Lett. 111, 106103, 2013. - [20] “Bond-order discrimination by atomic force microscopy”
L. Gross et al.,
Science 337, 1326, 2012. Cover image. - “Imaging the charge distribution within a single molecule”
F. Mohn et al.,
Nat. Nanotech. 7, 227, 2012. - “A combined atomic force microscopy and computational approach for the structural elucidation of breitfussin A and B: Highly modified halogenated dipeptides from Thuiaria breitfussi”
K.O. Hanssen et al.,
Angew. Chem. Int. Ed. 51, 12238, 2012. - “High-Resolution Molecular Orbital Imaging Using a p-Wave STM Tip”
L. Gross et al.,
Phys. Rev. Lett. 107, 086101, 2011. - “Reversible Bond Formation in a Gold-Atom–Organic-Molecule Complex as a Molecular Switch”
F. Mohn et al.,
Phys. Rev. Lett. 105, 266102, 2010. - “Organic structure determination using atomic-resolution scanning probe microscopy”
L. Gross et al.,
Nat. Chem. 2, 821, 2010. - “The chemical structure of a molecule resolved by atomic force microscopy”
L. Gross et al.,
Science 325, 1110, 2009. - “Measuring the Charge State of an Adatom with Noncontact Atomic Force Microscopy”
L. Gross et al.,
Science 324, 1428–1431, 2009.