Reversible light induced conductance switching of asymmetric diarylethenes on gold

In this publication of Nanoscale, scientists explain the fabrication, surface and electronic structures of reversible photoswitches based on diarylethene embedded in a matrix of dodecanethiol on gold. The characterization was made with scanning tunneling microscopy for the analysis of the effect when the “on” state appears higher than the “off” state by several Ångstroms.

This is the abstract of the interesting experiment:

We report on the light-induced switching of conductance of a new generation of diarylethene switches embedded in an insulating matrix of dodecanethiol on Au(111), by using scanning tunneling microscopy (STM). The diarylethene switches we synthesize and study are modified diarylethenes where the thiophene unit at one side of the molecular backbone introduces an intrinsic asymmetry into the switch, which is expected to influence its photo-conductance properties. We show that reversible conversion between two distinguishable conductance states can be controlled via photoisomerisation of the switches by using alternative irradiation with UV (λ = 313 nm) or visible (λ > 420 nm) light. We addressed this phenomenon by using STM in ambient conditions, based on switching of the apparent height of the molecules which convert from 4–6 Å in their closed form to 0–1 Å in their open form. Furthermore, the levels of the frontier molecular orbital levels (HOMO and LUMO) were evaluated for these asymmetric switches by using Scanning Tunneling Spectroscopy at 77 K, which allowed us to determine a HOMO–LUMO energy gap of 2.24 eV.

Arramel, Thomas C. Pijper, Tibor Kudernac, Nathalie Katsonis, Minko van der Maas, Ben L. Feringa and Bart J. van Wees. (2013) Reversible light induced conductance switching of asymmetric diarylethenes on gold: surface and electronic studies. Nanoscale. DOI: 10.1039/C3NR00832K