Photoswitching Behavior of Azobenzene-Containing Alkanethiol Self-Assembled Monolayers on Au Surfaces

Abstract

The photoisomerization of self-assembled monolayers of azobenzene-containing alkanethiols, as well as of mixed monolayers of these substances with n-alkanethiol spacer molecules on Au surfaces, was studied by photoelectrochemical measurements and surface plasmon resonance spectroscopy. A strong dependence on the molecular structure of the adsorbates was found, specifically on the linker between the azobenzene moiety and the alkanethiol: while molecules with an amide group were photoinactive, those with an ether group exhibited pronounced, reversible photoisomerization in pure and mixed adlayers. Both trans-cis and cis-trans isomerization followed first-order kinetics with time constants that suggest high quantum efficiencies for these processes.

Optical properties of azobenzene-functionalized self-assembled monolayers: Intermolecular coupling and many-body interactions

“…[7][8][9][10][11][12] Unfortunately, such systems come with a substantial drawback: The photo-isomerization rate is drastically suppressed due to steric hindrance or excitonic coupling. 13,14 A number of experimental strategies have been suggested to overcome this problem, such as replacing the aliphatic linker by an aromatic one 15 or even bulkier groups, [16][17][18] or diluting the azobenzene moieties in densely-packed alkanethiolate SAMs. 14,[19][20][21][22] From a theoretical viewpoint the issue of hindered photo-isomerization in densely-packed azobenzenefunctionalized SAMs has been addressed by a few works, mainly focused on the excitonic coupling between the chromophores, 23,24 as well as on the effects of a metal substrate.…”

UV/Vis Spectroscopy Studies of the Photoisomerization Kinetics in Self-Assembled Azobenzene-Containing Adlayers

“…Most previous studies employed rather indirect methods for investigating the photoisomerization in these photochromic SAMs, such as surface plasmon resonance spectroscopy (SPR) 11,[30][31][32] or electrochemical techniques 31,33 . Here, a signal is measured, which is coupled in a complex way to the different optical or chemical properties of the trans and cis state.…”

Two-photon photoemission from ex-situ prepared butanethiol SAMs on Au (111)

“…Recent STM data have shown that mixed SAMs of C4 and the molecular switch 3-(4-(4-hexyl-phenylazo)-phenoxy)-propane-1-thiolate exhibit a similar superstructure [15]. Our experimental results are in qualitative agreement with 2PPE spectra of in situ prepared hexanethiolate [CH 3 -(CH 2 ) nÀ1 -S-, n = 6] SAMs on Au (111)-in the following referred to as C6/Au (111) [11].…”