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 language | English |
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Pages (from-to) | 834-844 |
Number of pages | 11 |
Journal | Beilstein Journal of Nanotechnology |
Volume | 2 |
Issue number | 1 |
DOIs | |
Publication status | Published - 1 Dec 2011 |
Externally published | Yes |
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