Direct monitoring of opto-mechanical switching of self-assembled monolayer films containing the azobenzene group

Einat Tirosh, Enrico Benassi, Silvio Pipolo, Marcel Mayor, Michal Valásek, Veronica Frydman, Stefano Corni, Sidney R. Cohen

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The potential for manipulation and control inherent in molecule-based motors holds great scientific and technological promise. Molecules containing the azobenzene group have been heavily studied in this context. While the effects of the cis-trans isomerization of the azo group in such molecules have been examined macroscopically by a number of techniques, modulations of the elastic modulus upon isomerization in self-assembled films were not yet measured directly. Here, we examine the mechanical response upon optical switching of bis[(1,1'-biphenyl)-4-yl]diazene organized in a self-assembled film on Au islands, using atomic force microscopy. Analysis of higher harmonics by means of a torsional harmonic cantilever allowed real-time extraction of mechanical data. Quantitative analysis of elastic modulus maps obtained simultaneously with topographic images show that the modulus of the cis-form is approximately twice that of the trans-isomer. Quantum mechanical and molecular dynamics studies show good agreement with this experimental result, and indicate that the stiffer response in the cis-form comprises contributions both from the individual molecular bonds and from intermolecular interactions in the film. These results demonstrate the power and insights gained from cutting-edge AFM technologies, and advanced computational methods.

Original languageEnglish
Pages (from-to)834-844
Number of pages11
JournalBeilstein Journal of Nanotechnology
Volume2
Issue number1
DOIs
Publication statusPublished - 1 Dec 2011
Externally publishedYes

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Keywords

  • AFM
  • Azobenzene
  • Elastic modulus
  • Molecular dynamics
  • Nanomechanics
  • Photoswitch
  • Quantum mechanics computation
  • Self-assembled monolayer

ASJC Scopus subject areas

  • Materials Science(all)
  • Physics and Astronomy(all)
  • Electrical and Electronic Engineering

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