Photoswitching of electron transfer property of diarylethene–viologen linked molecular layer constructed on a hydrogen-terminated Si(111) Surface

Abstract

An organic monolayer with diarylethene and viologen moieties as a photochromic and an electroactive group, respectively, was constructed on a hydrogen-terminated Si (111) surface by sequential surface reactions. Photoswitching behaviour of electron transfer from the Si electrode to viologen moiety, larger and smaller current after UV and visible irradiation, respectively, was observed. This photoswitching behaviour can be explained by change in molecular conductivity of diarylethene moiety, which separates Si surface and viologen moiety, induced by ring closing and opening UV and visible irradiation, respectively.

Quantitative IR Readout of Fulgimide Monolayer Switching on Si(111) Surfaces

“…“Switching surfaces”, i.e., surfaces with reversible modulation of their wetting properties, were obtained by formation of self assembled monolayers (SAM) of PC species on a planar substrate,19, 20 which is particularly useful for micro fluidics 17. This concept is now applied to the switching of any properties of a surface such as conductance,11, 12, 21–23 contact potential or work function 24–26. Switching surfaces may also be used to transform light into mechanical work 27.…”

“…The vast majority of switching surfaces have been realized using SAM of thiolates on gold substrates 28. A few reports deal also with functionalized H‐terminated silicon surfaces21, 22, 29 using established protocols30, 31 to achieve a Si‐C linkage, which ensures superior thermal and chemical stability. Silane monolayers were sometimes used 19…”

“…and the most elegant one, combining both vertical and lateral control is mounting the azobenzene groups on molecular platforms 33, 34. A more simple and versatile method is however post‐anchoring the active molecules onto a functionalized surface, though it has not been frequently used on gold and was mostly used on silicon 21, 22, 29…”

Influence of Light Polarization on Photoswitching of Fulgimide Monolayers on Surfaces

“…Photochromic molecules can also be used in the context of biological systems [16], to structure soft matter with light [10], to control the function of biomaterials [17], or to promote catalytic activity [18]. Immobilization of photochromic molecules on surfaces [19] [27], very often on gold, or self-assembled as Langmuir-Blodgett (LB) layers [28] is a further approach to control wettability of surfaces with external light [29], which is crucial in microfluidics, or to tailor surface conductance [30] [31] [32] [33] [34] and surface work function. [35] [36] [37] [38] Photochromic molecules can be also adsorbed on nanoparticles to control their properties [39].…”

“…This may partly due to steric hindrance, chemical and/or electronic coupling with the substrate. This motivated studies aiming at increasing the free volume around photochromic compounds [56] [19] [57,58] and to reduce the electronic coupling with the substrate [59] [33] [31] using chemical spacers or a semimetal as substrate {Nickel, 2017 #1352}. In such constructs the photo kinetics of photo isomerization of photochromic molecules, characterized by its effective cross section ( ), may be as fast as in solution.…”