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Institut des Sciences Moléculaires d'Orsay


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lundi 24 février


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Accueil > Équipes scientifiques > Systèmes Moléculaires, Astrophysique et Environnement (SYSTEMAE) > Offres de stages, thèses et post-docs > Time-resolved accumulative charge transfer in molecular systems, Investigation of the intramolecular dynamics toward photoreduction of CO2

Stage de M2

Time-resolved accumulative charge transfer in molecular systems, Investigation of the intramolecular dynamics toward photoreduction of CO2

Niveau M2 ou thèse

The conversion and storage of solar energy into a fuel by artificial photosynthesis is a very promising approach for future renewable energy production. By such approach, abundant and stable molecules such as H2O and CO2 could be turned into H2 or carbon-based fuel. To achieve this goal, new molecular photo-catalysts for the reduction of CO2 have been developed by chemists. However, we are far from having in hands solutions to deploy on a large scale. It is thus necessary to provide a deeper understanding on the processes in competition and stimulate further studies towards the design of more efficient photocatalysts for CO2 reduction. To date, the competition between the constructive and deleterious relaxation pathways within the molecular systems for the photo-activation of CO2 is still poorly understood.

One of the most challenging tasks is the design of molecular constructs that mimic the natural photosystem performing sequential accumulation of multiple charges at the catalytic sites by multiphoton excitation [1]. We have very recently developed a new nanosecond transient absorption technique with sequential excitation (Pump- Pump Probe experiment) to investigate light-induced charge accumulation in a molecular photosensitizer-electron acceptor assembly [2]. This fundamental work has provided us an exhaustive mapping of all the constructive and deleterious electronic relaxation pathways taking place upon the accumulation of two electrons at an embarked electron acceptor.
The objective of this internship is to use different photophysical methods in order to get more insights into the mechanistic events in the sequential light induced 2-electron activation of CO2 with photocatalysts. Different spectroscopic techniques including single/double optical transient absorption at multiple timescales from femtosecond to milliseconds will be employed. A time-resolved resonance Raman spectroscopy with sequential excitation will be developed to investigate the structural and electronic changes during the photocatalytic cycle. Understanding such fundamental processes in light induced processes stands as the stepping stones towards the development of efficient CO2 photoreduction into solar fuels.
A candidate in the field of physics/chemical-physics is required.

References :
[1] Hammarström, L., Accumulative Charge Separation for Solar Fuels Production : Coupling Light-Induced Single Electron Transfer to Multielectron Catalysis. Acc. Chem. Res. 2015, 48 (3), 840-850.

[2] Mendes Marinho, S. ; Ha-Thi, M.-H. ; Pham, V.-T. ; Quaranta, A. ; Pino, T. ; Lefumeux, C. ; Chamaille, T. ; Leibl, W. ; Aukauloo, A., Time-resolved interception of multiple charge accumulation in a sensitizer-acceptor dyad. Angew. Chem. Int. Ed. 2017, 56 (50), 15936-15940.

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