sophiecarenco

When thinking of nanoparticles, one typically imagines what transmission electron microscopy shows us: a nice assembly of a few thousands metal atoms, all clean and standing amidst the world without a care for the outside environment. This ideal view has little to do with the actual aspect of a nanoparticle in the beaker, on the bench or inside a composite material.

We show that phosphines with adequate steric hindrance (e.g., PnBu₃ and PiBu₃) lower the onset temperature for phenylacetylene hydrogenation by nickel NPs under 7 bar of H₂, by ca 10 to 20 °C depending on the NP diameter. This result is of conceptual value because the hydrogenation may have been driven by the frustrated Lewis pair (FLP) between the Lewis basic phosphine and the Lewis acid nickel surface, forming a so-called “NanoFLP”. Moreover, we demonstrated that less than 2 phosphines per Ni surface atom are enough for the effect to arise. We showed that other terminal alkynes, like 1-octyne, can be hydrogenated with this method.

K. Azouzi, A. Ropp, S. Carenco, ACS Catalysis 2024, DOI 10.1021/acscatal.4c00054.

We report the positive effect of phosphine additives on the activity of cobalt phosphide nano-urchins for the semi-hydrogenation of phenylacetylene. While the nanocatalyst's activity was low under mild conditions (7 bar of H₂, 100 °C), the addition of a catalytic amount of phosphine remarkably increased the conversion, e. g., from 13 % to 98 % in the case of PⁿBu₃. A stereo-electronic map was proposed: the strongest effect was observed for low to moderately hindered phosphines, associated with strong electron donor abilities.

A. Ropp, R. F. André, S. Carenco, ChemPlusChem 2023, DOI 10.1002/cplu.202300469.

We propose the concept of a NanoFLP in a colloidal solution where one partner is a phosphine Lewis base and the other is the Lewis acid surface of a NiCo nanoparticle. We attempt to apply this concept to the hydrosilylative reduction of benzaldehyde. We identify a correlation between the Tolman cone angle and the silane conversion, consistent with both mechanisms; however, we found no clear correlation between the Tolman electronic parameter and the reaction outcome. Structural analyses evidenced that the nanoparticles are not altered during the reaction, which led us to propose the formation of a NanoFLP as a transient species in solution.

A. Palazzolo, S. Carenco. Chem. Mater. 2021, acs.chemmater.1c03105.

Copper nanoparticle synthesis was studied by thorough characterization of the organic reactions happening during the synthesis. The reduction of copper(II) acetate by oleylamine resulted in a high amount of water and few by-products while the reduction of copper(II) acetylacetonate resulted in a low amount of water and many products. The nanoparticles showed different abilities to further dehydrogenate and transaminate oleylamine in the synthesis reaction pot. This was explained by the presence of a copper oxide phase in the nanoparticles prepared from copper acetate.

A. Pesesse, S. Carenco, Cat. Sci. Tech.., 2021, 10.1039/D1CY00639H.

N-Heterocyclic carbene-stabilized copper nanoparticles are synthesized using a NHC-borane and mesitylcopper(I) in thermal conditions (refluxing toluene for 2.5 h). Nanoparticles with a size distribution of 11.6 ± 1.8 nm were obtained. The interaction between Cu NPs and NHC ligands was probed by XPS, showing the covalent binding of the NHC to the surface of the nanoparticles.

Mechanistic studies suggest that the NHC-borane plays two roles: contributing to the reduction of [CuMes]₂ to release Cu⁰ species and providing NHC ligands to stabilize the copper nanoparticles.

X. Frogneux, L. Hippolyte, D. Mercier, D. Portehault, C. Chaneac, C. Sanchez, P. Marcus, F. Ribot, L. Fensterbank, S. Carenco, Chem. Eur. J. 2019, 25, 11481-85.

Functionalized copper nanoparticles are widely used as catalysts. In this study we investigate hydride-assisted reduction reactions with special focus on the structural evolution of copper nanoparticles in the presence of phosphine and nitrogen-based ligands. Ultrasmall nano-objects are formed as key intermediates to produce catalytically active species in the hydrosilylation of benzaldehyde. Moreover, we found that the strength of the hydride donor is essential for the formation of the active catalysts.

X. Frogneux, F. Borondics, S. Lefrançois, F. D’Accriscio, C. Sanchez, S. Carenco, Catal. Sci. Technol. 2018, 8, 5073-80.

We present a study of the structure and reactivity of Ru nanoparticles of different sizes for CO hydrogenation using gas phase NMR and mass spectroscopy. In addition the nanoparticles were characterized under reaction mixtures in situ by ambient-pressure X-ray photoelectron spectroscopy. We found that during reaction the Ru is in the metallic state and that the diphosphine ligands (dppb) on the surface of nanoparticles of 1.9 and 3.1 nm, act not only as capping and protecting agents, but stay on the surface during reaction and improve their activity and selectivity towards C2-C4 hydrocarbons.

L. M. Martínez-Prieto, S. Carenco, C. H. Wu, E. Bonnefille, S. Axnanda, Z. Liu, P. F. Fazzini, K. Philippot, M. Salmeron, B. Chaudret, ACS Catal. 2014, 4, 3160

CO₂ can be converted into hydrocarbon using cobalt-based catalysts. However and to our surprise, core-shell nickel-cobalt nanoparticles produced oxygenated molecules instead (CO, methanol, formaldehyde).

We showed that, as a result of the heating and the presence of reactive gas, nickel was able to migrate to the surface of the nanoparticle. Alongside, small amounts of phosphorus were also found to get exposed to the surface. This phosphorus actually comes from the ligands (TOP) that were required in the first step of the nanoparticles synthesis but partially decomposed upon heating.

The active catalyst should not be seen as a cobalt surface, but rather as a nickel-cobalt alloy containing significant level of phosphide species.

S. Carenco, C.-H. Wu, A. Shavorskiy, S. Alayoglu, G. A. Somorjai, H. Bluhm, M. Salmeron, Small 2015, 11, 3045

Surface and core of inorganic nanoparticles may undergo profound transformations in their environment of use. Accurate description is key to understand and control surface reactivity.

Through a selection of case studies, this feature article proposes a journey from surface science to nanoparticle design, while illustrating state-of-the-art spectroscopies that help provide a relevant description of inorganic nanoparticles in the context of surface reactivity.

S. Carenco, Chem. Commun. 2018, 54, 6719-6727