Physikalische Chemie - Direktor: Prof. Dr. Martin Wolf
PC Online Talk
Chair: Takashi Kumagai

Thursday, April 29, 2021, 11:00 am
Seminar Link
Max Halbauer
FHI Department PC
Scanning Probe Microscopy Investigation of Nonahelicene on Ag(110)
Carbohelicenes are an important class of organic chiral molecules. They possess a conjugated aromatic backbone that is arranged in a helical shape. This results in strong chiroptical responses and makes them attractive targets for physical devices. Moreover, their shape resembles that of macroscopic springs, although their exact mechanical properties are unknown. Scanning probe microscopy [1-3] with the capability of single-molecule manipulation in combination with tip-enhanced Raman spectroscopy [4-5] can offer a unique insight to these properties. A STM and AFM study of nonahelicene ([9]H) on Ag(110) is presented and the experimental techniques are shortly introduced. The molecular self-assembly on the surface is presented and highlights the great control over the local environment. Results from high-resolution imaging with functionalized and unfunctionalized tips were then used to determine the conformation, chirality and orientation of adsorbed [9]H-molecules and to establish the interaction behavior with the underlying Ag(110)-substrate. Scanning tunneling spectroscopy (STS) allowed an insight to the electronic structure of the molecule. The first results of frequency-shift spectroscopy with the qPlus-AFM sensor are presented, as they offer one opportunity for investigation of the spring-like properties of helicenes. An overview of the experiments that are currently in progress and conclusions for future experiments is given at the end.
[1] J. Repp, G. Meyer, et. al., Phys. Rev. Lett. 2005, 94, 026803.
[2] L. Gross, N. Moll, et. al., Phys. Rev. Lett. 2011, 107, 086101.
[3] L. Gross, F. Mohn, et. al., Science 2009, 325, 1110-1114.

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