Femto-SWITCH:
Ultrafast spectroscopy of bio-mimetic photoswitches
– Towards rational design
PhD in Physics or Physical Chemistry
For candidates with interest in ultrafast optics, molecular spectroscopy
and functional materials
Starting date: October 2026
Contact:
Stefan Haacke, PR University of Strasbourg
Tel +33 3 88 10 71 71 : stefan.haacke@ipcms.unistra.fr
Team’s web site: https://www.ipcms.fr/en/equipe/biodyn/
Submit your application here
Applications must include: your CV, including short summaries of your master internships, a letter of motivation, and a letter of recommendation, preferably from your master supervisor
Photoswitches are molecules, which, after absorption of light, change their chemical structure and hence their “color”/absorption spectrum. Many examples exist for organic photoswitches, also in Nature, where photo-switching is very useful for biological processes like in rhodopsin, the light-sensing protein for vision (figure 1), or for many other light-dependent processes, like protein expression (plant growth). Inspired by the high photo-isomerization reaction yield of these proteins, the French-German FEMTO-Switch project aims to establish rational bases between the chemical structure of synthetic organic photo-switches and their ultrafast reaction dynamics including the reaction quantum yield. These new switches are based on oxindole [1] and oxopyrrole [2] frameworks. According to many quantum mechanical simulations, conical intersections, i.e. the crossing points between molecular potential energy surfaces, (cf. figure 1) ultimately determine the
Figure 1: Left : Photo-isomerisation of 11-cis retinal in rhodopsin, with a schematic of the reaction coordinates spanning the excited and ground state potential energy surfaces around the Conical Intersection, leading to the all-trans isomer (from Schnedermann et al., JACS 2015). Right : Basic structures of the oxindole (OxI) and oxopyrrole (OxP) photo-switches. Chemical modifications will be introduced by our chemistry partners, with the aim of tuning the excited state potentials and the reaction QY.
quantum yields of photoswitch reactions, the probability of reaching the all-trans isomer in the case of rhodopsin. Finding rational principles to enhance these quantum yields by chemical design would have large impacts for important applications in photoswitching of nanomaterials, in molecular motors and photo-pharmacology [3].
FEMTO-Switch is a new French-German project, which started in January 2025. Five research teams in Berlin, Strasbourg, Marseille, Padua (Italy) and Uppsala (Sweden) combine their experimental and theoretical know-how for the investigation of organic photoswitches mimicking the ultrafast photoisomerization of retinal pigments of vision (rhodopsins).
In the BIODYN team at IPCMS (University of Strasbourg-CNRS), we study the details of the photo-isomerization reaction in small rhodopsin-mimicking photo-switches and motors [1-2,4-5], which are presently being used for photo-regulating the expression of DNA. We use femtosecond transient absorption, and fluorescence spectroscopy (300 – 1050 nm), in order to detect the effect of chemical substitutions on the speed and efficiency of the photo-reactions.
Candidates must hold a master degree in Physics or Physical Chemistry. A good background in molecular spectroscopy and nonlinear optics is a plus, but not mandatory. Additional qualifications such as proficiency in Python and/or Matlab are valuable assets.
[1] M. Mgbukwu et al., J. Phys. Chem. B, (2025), https://doi.org/10.1021/acs.jpcb.4c06856
[2] M. Paolino et al., J. Am. Chem. Soc. 2016, 138, 9807−9825, https://doi.org/10.1021/jacs.5b10812
[3] « Molecular Photoswitches : Chemistry, Properties, and Applications », Ed. Z L. Pianowski, Wiley-VCH (2022)
[4] M. Gueye et al. Nature Comm. 9, 313 (2018) ; http://www.nature.com/articles/s41467-017-02668-w
[5] M. Filatov et al., Nature Comm. 13, 6433 (2022) ; https://www.nature.com/articles/s41467-022-33695-x
