Photoredox catalysts based on assembling quantum dots and metallic nanoparticles

Investigation of a new class of photocatalysts based on composites systems obtained by connexion between quantum dots and metallic nanoparticles in colloidal state.

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Scientific context and objective

During the last decade photoredox catalysis emerged has an efficient strategy to perform selective organic chemistry reactions in more environmentally friendly conditions. The majority of the reported reactions relies on molecular photocatalysts, but few groups demonstrated few years ago that colloidal semi-conductor nanoparticles (colloidal quantum dots, named hereafter “QD”) can act as efficient photocatalysts. In such photoredox catalysis reactions, the QD absorb the light and, from their excited state (1st exciton), transfer charges (electrons and holes) to the surrounding organic electron donors and acceptors, so enabling both reduction and oxidation steps necessary for the photocatalytic cycle. Unfortunately, most of the photogenerated electrons and holes recombine inside the photoexcited QD, instead of performing the desired reactions (typical quantum yields are < 1%) and the photocatalytic systems have to be illuminated for a quite long period of time (typically few hours) for completing the chemical reactions. So, it would be highly desirable to modify QD photocatalysts in a way that would prevent charges recombination.
During the last 3 years the Optima team of Institut Neel (F. Dubois and A. Barbara), in collaboration with CEA-CAMPE group (V. Maurel), started to explore together an original and modular strategy consisting of associating CdSe@ZnS QDs with gold nanoparticles by creating a covalent links between some ligands of the two types of nanoparticles. We expected that AuNP could act as electrons sinks and so avoid the charges recombination.

Trainee's work

The M1 trainee will investigate the optimization of the controlled covalent association between different type of QD (Cdse@ZnS, InP@ZnS and/or CuInS2) and different metallic colloids (silver, gold, spherical systems, prismatic systems…) by different approach: preparation in water phase by a click chemistry approach (Huisgen cycloaddition of azides and alkynes) or by organic chemistry coupling in organic media to open the way for organic chemistry transformation using photo-activation in different polar or non-polar media. The resulting composite colloids will be characterized by different technics such as DLS (dynamic light scattering), zeta-potential measurement (surface charge), spectroscopic measurements (absorption, fluorescence, fluorescence lifetime) and electronic microscopy…

Background expected:  master student in the Nanochemistry track
The candidate should have a strong background in chemistry and interest for nanoparticles synthesis, surface functionalization and spectroscopic characterizations.

 
Published on March 31, 2022
Updated on September 9, 2022