A research team with participants from Konstanz presents a molecular switch so far unmatched in its reproducibility
The theoretical physicists Junior Professor Fabian Pauly and his postdoc Dr. Safa G. Bahoosh now succeeded in a team of experimental physicists and chemists in demonstrating a reliable and reproducible single molecule switch.
Schematic of a tripodal single molecule switch. The height of the molecular head, containing a dipolar group, can be changed through applied electric fields. In this way an electric current can flow between the gold electrodes through the molecule or not, the switch is "on" or "off."
Credit: Prof. Fabian Pauly, University of Konstanz
The basis for this switch is a specifically synthesized molecule with special properties. This is an important step towards realising fundamental ideas of molecular electronics. The results were published in the online journal Nature Communications on 9 March 2017.
Fabian Pauly compares the molecule, which was synthesised by Professor Marcel Mayor who is affiliated to the University of Basel in Switzerland and to the Karlsruhe Institute of Technology (KIT) in Germany, with a three-legged lunar landing spacecraft that has some sort of head on top and is standing on the moon's surface.
Its three "legs" have anchor groups that form robust links to the surface - in this case a gold substrate. A nitrile group, positioned at its "head", points away from the gold surface and is thus well separated from it. A second electrode, the gold tip of a scanning tunnelling microscope, can connect and establish contact.
In this way electric current can flow through the molecule. Using the highly precise technique of the scanning tunnelling microscope, it has now become possible for the first time for such a complex three-legged molecule to measure the conductance value at every position above the nitrile group. Length control in the range of picometres, the trillionth part of a metre, is required for this process.
The nitrile group's dipole moment, i.e. an electric plus-minus charge, makes not only mechanical control possible, but also control through electric fields. The voltage between the electrodes can be used to adjust the height of the head, as was demonstrated by Safa G. Bahoosh in theoretical calculations. If a positive field is applied, the molecule's head is pressed down. If the field becomes negative through polarity reversal, the head moves up.
This means that the contact can be electrically established or broken, and thus the current can be switched on and off. "What's really great about this result is that we have a well-defined on and off state", says Fabian Pauly. Previous concepts often failed because it was too difficult to control the electronic contact to single molecules and therefore only statistical interpretations of the behaviour of molecular contacts could be made.
Now, for the first time, contact between a molecule and the gold tip of the scanning tunnelling microscope could be opened and closed reproducibly many thousand times both mechanically and electrically, without causing any plastic deformations. Fabian Pauly's team member Safa G. Bahoosh, who has just succeeded in acquiring funding from the German Research Foundation (DFG) for her position for the next three years, used density functional theory to calculate geometric structures, electric conductance values and the images that would be produced by the scanning tunnelling microscope.
With her simulations she was able to predict the shape of the individual molecule on the surface. Her results agree with the experiments conducted at the KIT. There, headed by Dr. Lukas Gerhard and Professor Wulf Wulfhekel, the electron transport was measured with the scanning tunnelling microscope. In addition to the switching functionality, the theoretical simulations combined with the systematic experiments reveal new insights into minute energies and forces that occur during reconfigurations in molecular contacts.
Original publication: Lukas Gerhard, Kevin Edelmann, Jan Homberg, Michael Valášek, Safa G. Bahoosh, Maya Lukas, Fabian Pauly, Marcel Mayor & Wulf Wulfhekel: An electrically actuated molecular toggle switch. Nature Communications 9 March 2017 DOI: 10.1038/NCOMMS14672; Link: https:/
Note to editors:
You can download a photo here: https:/
Caption: Schematic of a tripodal single molecule switch. The height of the molecular head, containing a dipolar group, can be changed through applied electric fields. In this way an electric current can flow between the gold electrodes through the molecule or not, the switch is "on" or "off".
University of Konstanz
Communications and Marketing
Phone: + 49 7531 88-3603
Julia Wandt | EurekAlert!
Magnetic nano-imaging on a table top
20.04.2018 | Georg-August-Universität Göttingen
New record on squeezing light to one atom: Atomic Lego guides light below one nanometer
20.04.2018 | ICFO-The Institute of Photonic Sciences
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
20.04.2018 | Physics and Astronomy
20.04.2018 | Interdisciplinary Research
20.04.2018 | Physics and Astronomy