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LIGHT-INDUCED MASS MOTION: AN ATOMIC FORCE MICROSCOPY STUDY AND A RANDOM-WALK MODEL

Abstract : First evidenced in 1995, the light-induced mass motion in layers of azobenzene-containing molecules remains partly unexplained. Although it is agreed that the isomerization of the azobenzene function triggers the phenomenon, it has led to diverging interpretations: some view it as an individual process where each molecule is independently put in motion, others as a collective one.
In this memoir, as a contribution to the study of this mass motion, we discuss a light-driven random-walk model where each moving azobenzene function drags the molecule to which it is grafted.
The experimental part of this work lies on atomic force microscopy measurements of the light-induced deformations and on the study of the evolution of the absorption properties of the layers of azobenzene-containing molecules. These results allow us to draw the main characteristics of the phenomenon. We also evidence the bleaching of the azobenzene chromophores which is bound to limit the mass motion.
The theoretical section that follows starts with a presentation of the hypotheses of the model. It consists in a diffusion motion of the azobenzene functions where each random step follows an isomerising absorption
Applied to the environment of layers, as resorted to experimentally, this model provides a suitable description of the light-induced surface deformations experimentally observed.
In the frame of this model, we assess the distance over which an azobenzene-containing molecule can be dragged. We also estimate the energetic output of this dragging process.
Finally, we discuss the microscopic origin of these molecular motors and we compare it to the model of thermal ratchets which are extensively resorted to in Biology nowadays.
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https://tel.archives-ouvertes.fr/tel-00011978
Contributor : Boris Bellini <>
Submitted on : Sunday, March 19, 2006 - 10:59:41 AM
Last modification on : Thursday, January 18, 2018 - 1:38:20 AM
Long-term archiving on: : Saturday, April 3, 2010 - 9:56:31 PM

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  • HAL Id : tel-00011978, version 1

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Boris Bellini. LIGHT-INDUCED MASS MOTION: AN ATOMIC FORCE MICROSCOPY STUDY AND A RANDOM-WALK MODEL. Atomic Physics [physics.atom-ph]. Université de la Méditerranée - Aix-Marseille II, 2005. English. ⟨tel-00011978⟩

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