This activity is oriented towards the functionalization of octahedral clusters of 4d and 5d metals and their introduction into organic or hybrid matrices. It relies on the dual skills of our team in synthesis by solid chemistry at high temperature and in multi-step organic synthesis at milder temperatures. The direct use of solid state compounds for applications is limited because of their ceramic nature (brittle, low plasticity). One solution to overcome this drawback is the use of hybrid organic-inorganic technologies that associate an organic matrix with photoactive inorganic moieties. The objective is thus to obtain new easy-shaping materials for applications in the field of light energy conversion, optics, optoelectronics or nanomedicine. Apart from the simple mixture of components, we have developed three integration methods leading to the genesis of homogeneous hybrid copolymers and clustomesogens (liquid crystals containing metal clusters).
Hybrid copolymers: from solid material to the production of films and waveguides
The team is developing new composite materials in which the clusters are integrated into a polymer matrix that is easy to shape (ink-jet printing, dropcasting, spin- or dip-coating) and capable of accommodating other
issues. The figure shows a copolymer integrating an organic emitter and a polymerizable cluster. This combination widens the emission band of the material, opening up interesting prospects for anti-counterfeiting, display and lighting applications. Inter-emitter interactions, modulated by the local oxygen concentration, allow to write or print data on the copolymer film by UV irradiation in a reversible and furtive manner. Within the framework of the ANR RENOIR project (Broadband integrated 1D sources based on a nanocomposite emitting in the deep red), in collaboration with FOTON, these polymers were used for the design of guiding structures. In collaboration with the University of Franca (Brazil), we have associated luminescent clusters with Ormocer®-type diureasil matrices emitting in the blue-green to design materials whose emission properties are flexible across the entire range of the visible window.
Nanotechnology, 2016, 27 (25), pp.255201
Materials Today, 2020, 35, 34-41 (cover)
UR1-CNRS patent Eur. Pat. Appl., 2020, EP 3730588 A1 20201028, PCT Int. Appl., 2020, WO 2020216717 A1 20201029
Materials today News, April 2020
CNRS : la lettre innovation, March 2020
Les Echos, 5 May 2020
Le télégramme, 13 May 2020
L’Actualité Chimique, en bref, June 2020
Full sciences, n°2, Aug-Oct 2020, p 134
Chemistry-a European Journal, 2019, 25(67), 15248-15251
Patent UR1-CNRS - U. Franca Eur. Pat. Appl., n: 17306490.8,30 / 10/2017; PCT Int. Appl. WO2019086477; SATT “Clustobrane” prematuration,
UR1-CNRS patent: Eur. Pat. Appl., N: 19395523.3.
Clustomesogens
The association of clusters with ligands, cations or macrocycles, containing mesogenic promoters leads to clustomesogens: mesomorphic compounds whose self-organization capacities, mainly linked to the
geometry of supermolecular hybrid bricks, can be modulated. Thus columnar, lamellar or nematic phases have been obtained. This theme was the subject of 2 ANR contracts, including an ANR PRCI with the University of Stuttgart (ANR Snapster 2018-2021, preceded by a PRC contract) and a collaboration with the University of Oxford. The dynamic control of the material nanostructuration by playing with temperature or by applying an electric field, allows the control of the clustomesogen emission (intensity, polarization).
ACS Applied Materials & Interfaces, 2020, 12 (12), 14400
Angew. Chem. Int. Ed., 2018, 57, 11692
J. Mater. Chem. C, 2018, 6, 2556
Acc. Chem. Res., 2016, 49, 8, 1514
Adv. Optical Mater., 2015, 3, 10, 1368
Adv. Func. Mater., 2015, 25, 4966 (cover)
Surfaces functionalized by monolayers of clusters
The team has been developing for several years within the frame of multidisciplinary collaborations (ISCR and IPR / Rennes, ITQ Valencia) an activity aimed at functionalizing different types of surfaces by clusters of transitional elements. Depending on their nature (Si, Au, amorphous carbon or graphene) and the method of grafting implemented, the immobilization of clusters makes it possible either to modify their electronic properties, or to promote new properties such as luminescence or photo-catalysis.
Red-NIR luminescence of Mo6 monolayered assembly directly anchored on Au(001)
Gold surfaces were functionalized by monolayers of Mo6 clusters using thiocyanate linkers (NCS). This bidentate ligand is covalently grafted onto the cluster and interacts strongly with the gold surface via sulfur. This is the first example of a luminescent pigment grafted directly onto a surface whose luminescence properties are not extinguished following grafting.
Mater. Horizons, 2019, 6, 1828-1833
Supramolecular anchoring of octahedral molybdenum clusters onto graphene and their synergies in photocatalytic water reduction
In collaboration with the ITQ in Valencia (Spain), several grafting strategies have been implemented to immobilize clusters on graphene or graphene oxide. The systems thus obtained exhibit photo-reduction properties of water. Dihydrogen (H2) production from sunlight should become one of the most important energy production means in the future. To reach this goal, low-cost and efficient photocatalysts still need to be discovered. We showed that red near-IR luminescent metal cluster anions, once combined with pyrene-containing cations, are able to photocatalytically produce molecular hydrogen from water. The pyrene moieties act
simultaneously as energy transmitters and as supramolecular linkers between the cluster anions and graphene. This association results in a hybrid material combining the emission abilities of pyrene and cluster moieties with the electronic conduction efficiency of graphene. Hydrogen evolution reaction (HER) studies show that this association induces a significant increase of H2 production compared to that produced separately by clusters or graphene. Considering the versatility of the strategy used to design this photocatalytic hybrid material, transition-metal clusters are promising candidates to develop new, environmentally friendly, and low-cost photocatalysts for HER.
Inorg. Chem., 2019, 58, 15443-15454
CHEMSUSCHEM, 2016, 9,1963-1971
Nanoparticles {Mo6}@PLGA as a new tool for Photodynamic Therapy (PDT) in Ovarian Cancer
Original concepts are developed in the group consisting in including the clusters in a biocompatible matrix allowing the controlled transport and release of clusters in cancer cells. The chosen matrix is PLGA (poly-D, L-lactide-co-glycolide acid) which has many advantages: i) PLGA is naturally assimilated and quickly destroyed by the human body, ii) PLGA nanoparticles are directly injectable. Under UV-vis irradiation, the clusters released by the nanoparticles generate reactive oxygen species (ROS) which destroy cancer cells (almost 100% mortality compared to conditions where the nanoparticles are not irradiated).
European Journal Pharmaceutics Biopharmaceutics, 2018, 125, 95-105
European Journal Pharmaceutics Biopharmaceutics, 2020, 576, 119025
European Journal Pharmaceutics Biopharmaceutics, 2021, 592, 120079
