Self‐assembled Azobenzenethiol Monolayer on Electrode Surfaces: Effect of Photo‐switching on the Surface and Electrical Property

Abstract

Azobenzenethiol molecules carrying different para-substituents were used to form mixed monolayers with n-alkanethiol molecules on Au and Ag surfaces. UV-and visible light irradiation of the surfaces resulted in reversible alternation of contact angle and characteristic infrared absorption peak intensities, as well as the work function of the metal surfaces. The alternations can be correlated with the cis-trans isomerization of the azobenzene moieties at the surface. Electron transport from the metal electrode to a redox center in a contacting solution was measured and analyzed based on the change in the work function of the electrode as well as the monolayer film structure upon isomerization. Wang et al. monolayer differ from that in KBr as a result of oriented azobenzene chromophore and the alkyl chain at the sur-face. 15 Furthermore, the positions of CH 2 asymmetric and symmetric stretching bands at 2919 and 2850 cm -1 imply Wang et al. Fig. 5. Water contact angles on (a) mixed ratio 1:1 on Au (b) mixed ratio 1:1 on Ag as a function of irradiation cycles.

Synthesis and Surface‐Spectroscopic Characterization of Photoisomerizable glyco‐SAMs on Au(111)

“…Based on the SSR and supporting data from the literature, [27] we assume that the intensity reduction of the 1250 cm À1 band indicates an E!Z conversion of the azobenzene moiety of 7 (see above). This hypothesis can be checked by the Z!E back isomerization experiment using irradiation with 440 nm light (Figure 8).…”

“…[30] Sulfur 2p spectra were fitted with two lines of equal width with a fixed splitting of 1.2 eV and a fixed intensity ratio of 1:2 for the doublet. [27] Synthesis E-4-(4'-Hydroxyphenylazo)phenyl 2,3,4,6-tetra-O-acetyl-a-d-mannopyranoside (3): To a solution of the azobenzene derivative 1 (653 mg, 3.05 mmol) and the mannosyl donor 2 (1.00 g, 2.03 mmol) in dry CH 3 CN (15 mL), BF 3 -etherate (260 mL, 2.03 mmol) was added at 0 8C under nitrogen atmosphere. It was stirred at this temperature for 15 min and then at room temperature overnight.…”

Molecular Motions in Functional Self-Assembled Nanostructures

“…They all aim to laterally space photo-sensitive units from each other to enable a complete and reversible isomerization. Examples of these strategies include co-adsorption of photo-sensitive and inert building blocks [154,155], the use of bulky tripods as anchoring headgroups [156,157], adsorption on porous network [158,159], and addition of lateral group within building blocks to increase the occupied area per molecule [160,161]. …”