Measurement of the conformational switching of azobenzenes from the macro- to attomolar scale in self-assembled 2D and 3D nanostructures
Journal article, 2021

It is important, but challenging, to measure the (photo)induced switching of molecules in different chemical environments, from solution through thin layers to solid bulk crystals. We compare the cis-trans conformational switching of commercial azobenzene molecules in different liquid and solid environments: polar solutions, liquid polymers, 2D nanostructures and 3D crystals. We achieve this goal by using complementary techniques: optical absorption spectroscopy, femtosecond transient absorption spectroscopy, Kelvin probe force microscopy and reflectance spectroscopy, supported by density functional theory calculations. We could observe the same molecule showing fast switching in a few picoseconds, when studied as an isolated molecule in water, or slow switching in tens of minutes, when assembled in 3D crystals. It is worth noting that we could also observe switching for small ensembles of molecules (a few attomoles), representing an intermediate case between single molecules and bulk structures. This was achieved using Kelvin probe force microscopy to monitor the change of surface potential of nanometric thin 2D islands containing ca. 10(6) molecules each, self-assembled on a substrate. This approach is not limited to azobenzenes, but can be used to observe molecular switching in isolated ensembles of molecules or other nano-objects and to study synergistic molecular processes at the nanoscale.


Vanesa Quintano

Institute for organic syntheses and photoreactivity (ISOF-CNR)

Valentin Diez-Cabanes

Universite de Mons

Simone Dell'Elce


Lorenzo Di Mario

Institute of structure of matter (ISM)

Stefano Pelli Cresi

Institute of structure of matter (ISM)

Alessandra Paladini

Institute of structure of matter (ISM)

David Beljonne

Universite de Mons

Andrea Liscio

National Research Council of Italy (CNR)

Vincenzo Palermo

Institute for organic syntheses and photoreactivity (ISOF-CNR)

Chalmers, Industrial and Materials Science, Materials and manufacture

Physical Chemistry Chemical Physics

1463-9076 (ISSN) 1463-9084 (eISSN)

Vol. In Press

Subject Categories

Physical Chemistry

Theoretical Chemistry

Condensed Matter Physics





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6/1/2021 1