Description of the thesis topic

The transfer of electronic excitation energy (EEE) – hereafter referred to as exciton - between identical, nearby chromophores on the nanometer scale is the mechanism responsible for exciton transport and diffusion over meso- to macro- scopic scales in condensed matter. The efficiency of natural and synthetic photochemical or photovoltaic energy conversion largely rests on the efficient exciton transport to the reaction center or to a donor-acceptor interface, respectively. Characterizing, modeling and improving exciton transport properties in molecular materials remain essential tasks in order to enhance the performance of functional, molecular materials targeting photocatalytic, photovoltaic or biosensing applications.
Natural, light-harvesting (LH) pigment-protein complexes absorb light and transport EEE to the photosynthetic reaction center, where conversion into chemical energy takes place with near-unity efficiency. No artificial system has been able to approach this performance to date. We contribute a multidisciplinary research effort aiming at developing biomimetic LH materials - i.e. efficient at transporting EEE within thousands of dyes - for applications to light energy conversion and biosensing. Novel synthetic strategies are being explored to (i) develop LH materials from polymer nanoparticles, wires and films, or from DNA-templated materials, and (ii) tune the dye nature, organization and structural order, as well as the EE transport dimensionality (2D versus 3D) to push beyond state-of-the-art energy transport lengths in synthetic LH systems.
In this context we propose a PhD thesis focusing on the experimental, photophysical investigations of these synthetic materials obtained via collaborations. A collection of time-resolved spectroscopy techniques will be employed for ensemble measurements as well as single nano-object investigations to uncover the underlying light-harvesting physics. The goal will be to measure the EEE diffusion length via the monitoring of exciton-exciton annihilation kinetics, ultrafast fluorescence anisotropy decay, or the kinetics of energy transfer to EEE acceptors. Tight interaction with theoreticians (collaborations) will allow us to rationalize our observations. The ambition of our experimental work within this multidisciplinary consortium is to address a very fundamental question about synthetic and natural, multi-chromophoric LH systems: what are the conditions for the onset of EE 'delocalization' (i.e. quantum coherence) in the proposed materials, and what is its putative effect on the EE transport efficiency? A second objective is about material sciences: how far can we exploit the knowledge gained by these fundamental investigations towards designing efficient, general-purpose LH materials, applicable to functional light energy conversion?
The candidate (M/F) must have solid training in fundamental physics (in particular optics and quantum physics), experimental physics (in particular optics, spectroscopy), and if possible in physical chemistry. The required level of English is B2 (European Framework of Reference for Languages - CEFR)

Work Context

The fellow will be registered at the Ecole Doctorale for Physics and Physical chemistry (ED182) of the Université de Strasbourg. He or she will work in the BIODYN team (“Biophysics and Dynamics of Organic Nanostructures”: a research team led by J. Léonard and S. Haacke; https://www.ipcms.fr/en/equipe/biophysics-and-dynamics-of-organic- nanostructures-biodyn/) at the Institut de Physique et Chimie des Matériaux de Strasbourg, on the CNRS campus in Cronenbourg (university restaurant on site). The BIODYN team studies the time-resolved spectroscopy of natural and synthetic molecular devices and materials for various applications and fundamental investigations.
In the context of LH materials, we conduct time-resolved spectroscopy experiments - UV/VIS absorption and fluorescence. We will carry out these experiments in the frame of the DEVILISH ANR project (2024-2027) together with three partners in charge of (i) synthesizing novel DNA-templated LH materials and (ii) building a theoretical description of the EE transport in these materials (https://anr.fr/Projet-ANR-24-CE50-4784). In parallel, we will maintain our long-standing collaboration with our local partner (A. Klymchenko, Pharmacy Faculty, Strasbourg), expert at synthesizing LH polymer materials from nanoparticles to films.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.

Constraints and risks

Laser safety
Minor chemical hazards (solvent handling)

Additional Information

Funding assured by ANR project DEVILISH