Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Demonstration of macroscopic movement of an object across a surface through mechanical motion at the molecular level

A single layer of light-driven molecular shuttles attached to a self-assembled monolayer of thiols on gold is able to transport microlitre droplets of diiodomethane along the surface - a mechanical macroscopic response from a mechanical molecular event.

In order to demonstrate macroscopic movement of an object across a surface through mechanical motion at the molecular level, we created a photo-responsive surface based on switchable fluorinated molecular shuttles. For this we developed a protocol for grafting light-switchable rotaxanes with the fluoroalkane region exposed (E-1) onto a SAM of 11-MUA on Au(111) deposited onto either glass or mica to create a polarophobic surface, 111 which could be switched by light to polarophilic.

Photoemission spectroscopy and scanning tunnelling microscopy data showed that the grafting was successful and were consistent with the molecular shuttles lying parallel to the Au surface. Both measurements gave evidence for a functionalisation yield of 2-3% of the alkanethiols, which, given the dimensions of the rotaxane, corresponds to a rather dense packing of the molecules.

The mechanism is that the macrocycle movement of the shuttle is used to either conceal or reveal a fluoroalkane (“Teflon-like”) residue, which dramatically alters the surface tension of the droplet. Not only can this transport a droplet across a flat surface but it can also be used to the transport of a droplet against gravity, elevating it 1 mm up a 12° slope.

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THE UNIVERSITY OF EDINBURGH
The King's Buildings
EH9 3JJ EDINBURGH
United Kingdom
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