Driving soft molecular vehicles on a metallic surface

December 27, 2017, National Institute for Materials Science
Driving soft molecular vehicles on a metallic surface
Schematic diagram showing the interaction of tunneling current with molecules. Credit: National Institute for Materials Science

Soft molecules deposited on metallic surfaces were driven using a scanning tunneling microscope (STM) without mechanically pulling or pushing them, but by inducing inelastic excitations with the tunneling current.

In nanoscience, compared to rigid , it is challenging to control the movement of soft molecules due to their flexibility. Notably, only one part of soft molecules is suitable for absorbing current energy that should be used for inducing motion, and not conformational changes of the molecules.

A collaboration led by Waka Nakanishi and Katsuhiko Ariga at WPI-MANA and We-hyo Soe and Christian Joachim at GNS and WPI-MANA Satellite, CEMES-CNRS in Toulouse designed, synthesized and characterized a conformationally flexible molecule consisting of two binaphtyl paddles mounted on a simple phenyl chassis. The vibration modes of the lateral paddles can be exploited to induce the motion of the molecule on an Au(111) surface using STM inelastic tunneling effects. The molecule has two different nonplanar configurations in solution that it retains when absorbed on the surface. However, on the metallic surface it is possible to switch molecules, one at a time, to a flat configuration using a specific STM mechanical manipulation protocol. The flat configuration is the most interesting one for this work, because only flat molecules can be controllably moved on the surface by local STM excitations. Once they assume this configuration, the molecules are reasonably stable on the surface.

Molecules in the flat configuration were characterized to determine the spots where tunneling electrons should be injected to make them move on the surface without mechanically pushing them. Indeed, depending on the location at which the tunneling current enters the molecule, this can assume a nonplanar configuration (different from the original one) instead of moving. If the current is applied on the correct spot, the molecule can move in a controlled way. The experimental characterization of the molecules was complemented by and density functional theory calculations, which helped to uncover the energetics of the molecules. In April 2017, a 'nanocar race' took place, in which several molecular machines synthesized by groups from around the world competed with the goal of covering a set distance on a gold in the minimum possible amount of time, driven by STM tips. The molecule presented in this paper is one of the vehicles that took part to the race.

Explore further: Tracking a solvation process step by step

More information: We-Hyo Soe et al. Conformation Manipulation and Motion of a Double Paddle Molecule on an Au(111) Surface, ACS Nano (2017). DOI: 10.1021/acsnano.7b05314

Related Stories

Tracking a solvation process step by step

December 21, 2017

Chemists of Ruhr-Universität Bochum have tracked with unprecedented spatial resolution how individual water molecules attach to an organic molecule. They used low-temperature scanning tunneling microscopy to visualize the ...

Molecules move faster near sticky surfaces

September 1, 2017

Molecules move faster as they get closer to adhesive surfaces, but this effect is not permanent. Such is the puzzling conclusion of a study published in Physical Review Letters, carried out by Simone Napolitano and his colleagues ...

Better measurements of single molecule circuits

February 18, 2015

It's nearly 50 years since Gordon Moore predicted that the density of transistors on an integrated circuit would double every two years. "Moore's Law" has turned out to be a self-fulfilling prophecy that technologists pushed ...

Recommended for you

Solving mazes with single-molecule DNA navigators

November 16, 2018

The field of intelligent nanorobotics is based on the great promise of molecular devices with information processing capabilities. In a new study that supports the trend of DNA-based information carriers, scientists have ...

A way to make batteries almost any shape desired

November 16, 2018

A team of researchers from Korea Advanced Institute of Science and Technology, Harvard University and Korea Research Institute of Chemical Technology has developed a way to make batteries in almost any shape that can be imagined. ...

'Smart skin' simplifies spotting strain in structures

November 15, 2018

Thanks to one peculiar characteristic of carbon nanotubes, engineers will soon be able to measure the accumulated strain in an airplane, a bridge or a pipeline – or just about anything – over the entire surface or down ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.