Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 39: Symposium Molecular Switches and Motors at Surfaces (O jointly with BP, CPP)

O 39.5: Hauptvortrag

Mittwoch, 2. April 2014, 11:45–12:15, HSZ 02

Unidirectional motion by inelastic electron tunneling — •Karl-Heinz Ernst — Empa, Swiss Federal Laboratories for Materials Science and Technology — Department of Chemistry, University of Zurich

Propelling single molecules in a controlled manner along an unmodified surface remains extremely challenging because it requires molecules that can use light, chemical or electrical energy to modulate their interaction with the surface in a way that generates motion. Biomolecular motors, such as the protein kinesin or the F1-ATPase, function as linear walkers or rotary motors. Chemists strive for synthesis of molecules that can perform unidirectional motion on surfaces. One successful approach was the use of ratchet-style unidirectional rotors based on overcrowded helical systems.

We show that excitation with inelastically tunneling electrons emanating from the tip of a scanning tunneling microscope (STM) very efficiently excites the rotors and leads to linear movement of the molecule on the surface for the right isomer. This requires a transient electron attachment into the LUMO, while vibronic excitation of the motor axles lead to reversible rearrangement without movement. We will discuss possible mechanisms and implication for further research and design of nanotechnological devices.