sophiecarenco

There are only so many elements that the chemist may use for building new forms of matter: oxygen, carbon, some metals... One could think that all simple combinations were explored already. But certain forms of matter still resist! Here, we explore combination of oxygen, sulfur and one or two metals. We also do our best to limit the size of the grains to a few nanometer... taking to our advantages the many exciting properties that the chemists expect at this scale!

This review summarizes the syntheses and applications of metal oxysulfides. Bulk compounds of rare earth and transition metals are discussed in the section Introduction. After a presentation of their main properties and applications, their structures are presented and their syntheses are discussed. The section Bulk Materials and Their Main Applications is dedicated to the growing field of nanoscaled metal oxysulfides. Lanthanide-based nanoparticles are discussed first, followed by transition-metal based nanoparticles.

C. Larquet, S. Carenco, Frontiers in Chem. 2020, doi:10.3389/fchem.2020.00179

We developed here thin films of lanthanide oxysulfide, of optical quality by dip coating. As a model compound in the family of oxysulfides, (Gd,Ce)₂O₂S anisotropic nanoplates were used. The band gap of the materials was preserved through the deposition process. The thickness of the films was tuned in a broad range, from a few nanometers to 150 nm, using different concentrations of the colloidal suspensions and single-layer and multilayer deposition. Lastly, thermal treatment of the thin films was optimized to remove the stabilizing organic ligands of the nanoparticles while preserving their integrity.

L. Meyniel, C. Boissière, N. Krins, S. Carenco, Langmuir 2023, 39, 728-738, doi 10.1021/acs.langmuir.2c02026

Acceptability and relevance of nanoparticles in the society is greatly improved using a safer-by-design strategy. However, this is difficult to implement when nanoparticles are already on the market We employ this strategy for emerging nanoparticles of lanthanide oxysulfide, relevant for photocatalysis as well as for multimodal imaging. We investigated the production of reactive oxygen species (ROS) as a function of cerium content, in abiotic conditions and in vitro using murine macrophage RAW 264.7 cell line. We propose a risk analysis for lanthanide oxysulfide nanoparticles, leading to a technology assessment that fulfills the safer-by-design strategy.

A.-M. Nguyen, A. E. Pradas del Real, O. Durupthy, S. Lanone, C. Chanéac, S. Carenco, Nanomaterials 2022, 12, 422.

Alkali cations are required for the colloidal synthesis of Ln₂O₂S nanoplates in organic solvent. We challenge the commonly accepted scenario of partial lanthanide substitution by the alkali. We demonstrate the formation of an alkali-stabilized oleate mesophase acting as a template for nanoparticle nucleation and growth.

C. Larquet, D. Carriere, A.-M. Nguyen, T. K.-C. Le, X. Frogneux-Plé, I. Génois, P. Le Griel, A. Gauzzi, C. Sanchez, S. Carenco, Chem. Mater. 2020, doi:10.1021/acs.chemmater.9b04059

(Gd,Ce)₂O₂S anisotropic nanoparticles with hexagonal structure exhibit colors varying from white to brown with increasing Ce concentration. Bandgap engineering is thus possible, from 4.7 eV to 2.1 eV. Surprisingly, due to the limited thickness of the lamellar nanoparticles, the bandgap of the nanoparticles is direct as validated by density functional theory on slabs. The fine control of the bandgap over a wide range, solely triggered by the cation ratio, is rarely described in the literature and highly promising for further development of this class of compounds.

C. Larquet, A.-M. Nguyen, E. Glais, L. Paulatto, C. Sassoye, M. Selmane, P. Lecante, C. Maheu, C. Geantet, L. Cardenas, C. Chanéac, A.Gauzzi, C. Sanchez, S. Carenco, Chem. Mater. 2019, 31, 5014-23.

Capping ligands play an important role in the chemistry of nanoparticles. Ultrathin monodisperse Ln₂O₂S_x oxysulfide nanoparticles (Ln = lanthanide) show promising luminescence and light absorption properties. Here, we show that the thermal stability of Gd₂O₂S_x nanocrystals is limited because of their non‐stoichiometric composition and strongly depends on the annealing atmosphere. Annealing the nanoparticles in air enables removing the ligands without altering the nanocrystals structure.

C. Larquet, D. Hourlier, A.-M. Nguyen, A. Torres-Pardo, A. Gauzzi, C. Sanchez, S. Carenco, ChemNanoMat 2019, 5, 539-46.

Gadolinium oxysulfide nanoparticles are suitable candidates for bimodal imaging Here, we synthesized and characterized bimetallic (Gd,Ce)₂O₂S nanoparticles and demonstrated that they are paramagnetic over a wide temperature range including the body one. The mixture of Gd and Ce magnetic centers enables a fine control of the magnetic properties up to high Ce concentrations (80%) and over a large range of magnetic moments, while photoemission properties are guaranteed up to 20% of Ce owing to a regular dispersion of the Ce centers.

C. Larquet, Y. Klein, D. Hrabovsky, A. Gauzzi, C. Sanchez, S. Carenco, EurJIc. 2019, 6, 762-765 | EurJIc Cover.

This article describes the synthesis of bimetallic oxysulftide nanoplatelets. They could be obtained over the whole (Gd,Ce) composition range with good control of size and cristallinity.

We observed that cerium-rich nanoparticles are less stable in air than Gd-rich nanoparticles. With in situ X-ray absorption and X-ray photoelectron spectroscopy, we could demonstrate that (i) all these nanoparticles actually exhibit surface sulfate, (ii) sulfate form as a consequence of exposure to water and/or oxygen, (iii) there is a threshold of 50% Ce above which the structure is not stable anymore in air, due to the formation of Ce(IV) species.

C. Larquet, A.-M. Nguyen, M. Ávila-Gutiérrez, L. Tinat, B. Lassalle-Kaiser, J.-J. Gallet, F. Bournel, A. Gauzzi, C. Sanchez, S. Carenco, Inorg. Chem. 2017, 22, 14227-14236

Les oxysulfures de métaux contiennent du soufre à un état d’oxydation négatif. Les oxysulfures de lanthanides cristallins sont utilisés depuis plus de cinquante ans mais les premières synthèses de nanoparticules datent du début du siècle. Cet article discute de la stratégie à adopter pour préparer de telles nanoparticules avec l’exemple de l’oxysulfure de gadolinium. Ces nanoparticules présentent une surface réactive, comme le montre la formation spontanée de sulfates à l’air libre.

C. Larquet, A.-M. Nguyen, T. K.-C. Le, M. Avila-Gutierrez, S. Carenco, L'Actualité Chimique. 2019, 436, 28-31.