Bruno Chaudret

The decomposition of Ru(cod)(cot) (1; cod = 1,5-cyclooctadiene, cot = 1,3,5-cyclooctatriene) under an H2 atmosphere (3 bars) in pure heptanol produces crystalline monodisperse nanoparticles of 3 nm mean size characterized by TEM and WAXS techniques. Solution NMR studies demonstrate the presence of surface hydrogens due to the synthesis process and suggest a fast exchange between free and coordinated heptanol molecules.

A robust silicon gas sensor chip (platinum heater, low deformation membrane) has been designed and successfully operated with various metal oxide nanoparticles synthesized by an organometallic route (SnO₂, ZnO) and deposited by a generic ink-jet method. High quality and micron thick layers are obtained and the CO gas sensitivity is presented.

Post-synthesis thermal treatments are often used to induce the crystallization of amorphous nanoparticles obtained by wet chemical synthesis in order for them to display the physical properties of the bulk. We have studied the structural and magnetic evolution of FeCo magnetic nanoparticles synthesized via an organometallic route during a soft controlled annealing treatment. Despite very mild conditions, the structural study, carried out using WAXS, EXAFS and Mössbauer spectroscopy, evidences the presence of carbon atoms in the as-synthesized structure and their continuous insertion in the structure upon heating, as they form a rather ordered structure including carbides, before being expelled from the particles as the crystallization of the bcc alloyed phase takes place at higher annealing temperatures. The magnetic properties, recorded along the process, accordingly show highly depleted values as the carbon atoms insert in the structure, and reach the Ms bulk value as the bcc phase is restored.

This work deals with the synthesis of a new magnetic liquid crystalline material: a side chain liquid crystal silicone, doped with magnetic cobalt nanorods. This new material presents very promising magnetic properties, discussed in terms of the influence of the lateral liquid crystal groups.

Conditions for the elaboration of nanostructured varistors by spark plasma sintering (SPS) are investigated, using 8‐nm zinc oxide nanoparticles synthesized following an organometallic approach. A binary system constituted of zinc oxide and bismuth oxide nanoparticles is used for this purpose. It is synthesized at room temperature in an organic solution through the hydrolysis of dicyclohexylzinc and bismuth acetate precursors. Sintering of this material is performed by SPS at various temperatures and dwell times. The determination of the microstructure and the chemical composition of the as‐prepared ceramics are based on scanning electron microscopy and X‐ray diffraction analysis. The nonlinear electrical characteristics are evidenced by current–voltage measurements. The breakdown voltage of these nanostructured varistors strongly depends on grain sizes. The results show that nanostructured varistors are obtained by SPS at sintering temperatures ranging from 550 to 600 °C.

The integration of inductors raises the need for highly magnetic monodomain and insulating materials. With this aim in mind, we investigate the synthesis of FeCo nanoparticles using an organometallic approach. The role of the nature of the ligands, of the organometallic precursors and of the experimental conditions are addressed, leading to the formation of nanoparticles displaying different compositions and structural and magnetic properties. After optimization of the reaction conditions, 20 nm monodisperse nanoparticles, self-organized into millimetre long super-crystals, are obtained. They display a structural atomic disorder, due to the kinetics of decomposition of the precursors leading to a loss in their magnetic properties. Organized arrays of these nanoparticles could also be generated onto silicon wafers with thicknesses from 100 nm to several microns. Such densely packed layers are suitable for inductor nanotechnology

Maghemite (γ‐Fe₂O₃) nanoparticles stabilized by long‐alkyl‐chain amines are synthesized by using an organometallic approach. This method consists of the hydrolysis and oxidation of an organometallic precursor, Fe[N(SiMe₃)₂]₂, in the presence of amine ligands as stabilizing agent in an organic solvent, namely tetrahydrofuran or toluene. Whatever the experimental conditions, particles with a diameter of 2.8 nm are obtained. The use of high‐resolution transmission electron microscopy and wide‐angle X‐ray scattering, together with Mössbauer spectroscopy and SQuId magnetometry, allows a complete characterization of these particles. Herein, we show that their structure is composed of a well‐ordered core surrounded by a more disordered shell. The size of the latter varies from 0.65 to 0.50 nm depending on the experimental conditions and is of prime importance for the understanding of the magnetic properties. We demonstrate that the shorter the alkyl chain length of the amine 1) the better the crystallinity of the particle’s core and 2) the stronger the interparticle interactions.