Work Group Prof. Dr. F. Temps

Azobenzene-functionalized gold nanoparticles

The photoswitching properties of molecules on surfaces are subject to several mechanisms affecting or hindering the outcome. First, dense packing of the surface-bound molecules may leave too little free space for the transformation to proceed, especially when a photo-induced reaction is associated with a large-amplitude structural change. Second, energy transfer either between the attached switches or between the switch and the nanoparticle substrate may lead to a rapid electronic deactivation of the photoexcited molecules and even prevent the reaction altogether. A third major issue arises when a change in properties of NPs upon isomerization of the switches in the ligand shell leads to aggregation of the NPs, which may impede further switching after only a few cycles.

Azobenzene-Functionalized AuNP
 
Functionalized AuNP with a mixed self-assembled monolayer (mSAM) of azothiolate and alkylthiolate ligands.

 

Surface-functionalized gold nanoparticles (AuNPs) carrying a self-assembled monolayer (SAMs) of azobenzene (AB) photoswitches constitute ideal model systems for investigating the photophysical and photochemical dynamics of molecules on surfaces because they can be studied using our entire arsenal of femtosecond spectroscopy methods. Our work thus aims to resolve differences in the photoswitching dynamics of ABs on AuNPs compared to the same ABs in solution.

Important papers:

  • A. Köhntopp, M. Dittner, F. Temps, "Femtosecond Time-Resolved Dynamics of trans-Azobenzene on Gold Nanoparticles", J. Phys. Chem. Lett., 7, 1088 - 1095 (2016). DOI: 10.1021/acs.jpclett.6b00102
  • A. Köhntopp, A. Dabrowski, M. Malicki, F. Temps, "Photoisomerisation and Ligand-Controlled Reversible Aggregation of Azobenzene-Functionalised Gold Nanoparticles", Chem. Commun. 50, 10105 - 10107 (2014).  DOI: 10.1039/c4cc02250e