Measuring reversible photomechanical switching rates for a molecule at a surface

Abstract

We have used single-molecule-resolved scanning tunneling microscopy to measure the photomechanical switching rates of azobenzene-derived molecules at a gold surface during exposure to UV and visible light. This enables the direct determination of both the forward and reverse photoswitching cross sections for surface-mounted molecules at different wavelengths. In a dramatic departure from molecular behavior in solution-based environments, visible light does not efficiently reverse the reaction for azobenzene-derived molecules at a gold surface.

Light driven reactions of single physisorbed azobenzenes

“…This is an order of magnitude higher than for surface mediated isomerization of TBA adsorbed on Au(111). 18 In conclusion, electron-induced and direct photoisomerization of a dye molecule are feasible even on a noninert surface such as Cu(111). Decoupling is achieved via physisorption.…”

Photoswitching of azobenzene multilayers on a layered semiconductor

“…If the coupling is too strong, the switching efficiency will be strongly suppressed as compared to the one achieved in nonsolid environments. [9][10][11][12][13] To solve this problem, elaborate strategies have been introduced in which the switching units are spatially separated from the substrate and from each other.…”

Sensitivity of photoelectron diffraction to conformational changes of adsorbed molecules: Tetra-tert-butyl-azobenzene/Au(111)

“…The effective total isomerization cross-section σ eff derived here is higher by several orders of magnitude than cross-sections of 10 −23 cm 2 at a photon energy of about 3 eV and 30 K (Ref. 27) or 10 −22 cm 2 for visible light and a temperature of 90 K 28 . This can be explained by the higher photoionization cross-section of the Au 5d states 37 and the possible direct photo-ionization of the TBA molecule.…”