The growing concern over the toxicity of Gd-based contrast agents used in magnetic resonance imaging (MRI) motivates the search for less toxic and more effective alternatives. Among these alternatives, iron–iron oxide (Fe@FeOx) core-shell architectures have been long recognized as promising MRI contrast agents while limited information on their engineering is available. Here we report the synthesis of 10 nm large Fe@FeOx nanoparticles, their coating with a 11 nm thick layer of dense silica and functionalization by 5 kDa PEG chains to improve their biocompatibility. The nanomaterials obtained have been characterized by a set of complementary techniques such as infra-red and nuclear magnetic resonance spectroscopies, transmission electron microscopy, dynamic light scattering and zetametry, and magnetometry. They display hydrodynamic diameters in the 100 nm range, zetapotential values around −30 mV, and magnetization values higher than the reference contrast agent RESOVIST^®. They display no cytotoxicity against 1BR3G and HCT116 cell lines and no hemolytic activity against human red blood cells. Their nuclear magnetic relaxation dispersion (NMRD) profiles are typical for nanomaterials of this size and magnetization. They display high r₂ relaxivity values and low r₁ leading to enhanced r₂/r₁ ratios in comparison with RESOVIST^®. All these data make them promising contrast agents to detect early stage tumors.

Given that the properties of metal nanoparticles (NPs) depend on several parameters (namely, morphology, size, surface composition, crystalline structure, etc.), a computational model that brings a better understanding of a structure–property relationship at the nanoscale is a significant plus in order to explain the surface properties of metal NPs and also their catalytic viability, in particular, when envisaging a new stabilizing agent. In this study we combined experimental and theoretical tools to obtain a mapping of the surface of ruthenium NPs stabilized by ethanoic acid as a new capping ligand. For this purpose, the organometallic approach was applied as the synthesis method. The morphology and crystalline structure of the obtained particles was characterized by state-of-the art techniques (TEM, HRTEM, WAXS) and their surface composition was determined by various techniques (solution and solid-state NMR, IR, chemical titration, DFT calculations). DFT calculations of the vibrational features of model NPs and of the chemical shifts of model clusters allowed us to secure the spectroscopic experimental assignations. Spectroscopic data as well as DFT mechanistic studies showed that ethanoic acid lies on the metal surface as ethanoate, together with hydrogen atoms. The optimal surface composition determined by DFT calculations appeared to be ca. [0.4–0.6] H/Ru_surf and 0.4 ethanoate/Ru_Surf, which was corroborated by experimental results. Moreover, for such a composition, a hydrogen adsorption Gibbs free energy in the range −2.0 to −3.0 kcal mol⁻¹ was calculated, which makes these ruthenium NPs a promising nanocatalyst for the hydrogen evolution reaction in the electrolysis of water.

Colloidal synthesis of morphologically stable oxide-free cobalt nanodisks (diameter ≈ 21 nm, thickness ≈ 12 nm) has been achieved. The hcp c-axis is found to be perpendicular to the flat side of the disk which is explained by surface energy considerations. Magnetic measurements and comparisons with simulations show that the nanodisks are single magnetic domains with a magnetisation oriented perpendicular to the plane of the disks and reaching that of bulk cobalt, and high anisotropy field. These disks are thus potential candidates for magnetic data storage, magnetic sensor arrays, and cheap permanent magnets.

Phosphonic acid derivatives are suitable compounds for controlling the surface properties of materials and nanomaterials. Here, we present for the first time the use of alkyl phosphonic acid ligands to transfer into water zero-valent iron nanoparticles (FeNP) synthesized by an organometallic approach. The transfer takes place with the formation of an oxide layer at the surface of the iron nanoparticles, beneficial for the coordination of the alkyl phosphonic acid ligands. The nanoparticles are highly soluble in water and present a core–shell structure, with a monocrystalline body-centered cubic iron core of ca. 10 nm in size surrounded by a spinel oxide shell of ca. 2 nm thickness. These hydrophilic nanoparticles display excellent structural stability, magnetization still reaching 70% of that of bulk iron, and a transversal relaxivity r₂ of 335 mM⁻¹ s⁻¹ which give them high potential for biomedical applications.

A variety of imaging technologies are now routinely used in the medical field, their use being continuously enlarged through the development of contrast agents. Recently nanoparticles (NPs) proved efficient to improve imaging in vivo by increasing contrast and targeting capabilities. The current trend is now focused on the development of dual contrast agents combining two or more functionalities on the same NP. Motivated by this new challenge we developed FeBi NPs as new nanomaterials with potential application as a contrast agent for MRI and CT imaging. In addition to the well-known use of iron in the development MRI contrast agents, we chose Bi as a CT imaging agent rather than the more documented gold, because it possesses a larger X-ray attenuation coefficient and is much less expensive. Two sets of NPs, with sizes around 150 nm and 14 nm, were synthesized using organometallic approaches. In both cases, the NPs are spherical, and contain distinct domains of Fe and Bi, with the surface being enriched with Fe, and a hydrophobic coating. This coating differs from one sample to the other: the surfaces of the 150 nm large NPs are coated by amine ligands, while those of the 14 nm large NPs are coated by a mixture of an amine and its hydrochloride salt. Exchange of the surface ligands to afford water soluble NPs has been attempted. We show that only the larger NPs could be functionalized with water soluble ligands, which is in agreement with the lability of their initial surface coating. Colloidal aqueous solutions of FeBi NPs with glycoPEG ligands have been obtained.