Search

Monodisperse ruthenium nanoparticles were prepared by reduction of RuCl3 in 1,2-propanediol. The mean particle size was controlled by appropriate choice of the reduction temperature and the acetate ion concentration. Colloidal solutions in toluene were obtained by coating the metal particles with dodecanethiol. High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XANES and EXAFS for the Ru K-absorption edge) were performed on particles of two different diameters, 2 and 4 nm, and in different environments, polyol/acetate or thiol. For particles stored in polyol/acetate XPS studies revealed superficial oxidation limited to one monolayer and a surface coating containing mostly acetate ions. Analysis of the EXAFS spectra showed both oxygen and ruthenium atoms around the ruthenium atoms with a Ru-Ru coordination number N smaller than the bulk value, as expected for fine particles. In the case of 2 nm acetate-capped particles N is consistent with particles made up of a metallic core and an oxidized monolayer. For 2 nm thiol-coated particles, a Ru-S bond was evidenced by XPS and XAS. For the 4 nm particles XANES and XPS studies showed that most of the ruthenium atoms are in the zerovalent state. Nevertheless, in both cases, when capped with thiol, the Ru-Ru coordination number inferred from EXAFS is much smaller than for particles of the same size stored in polyol. This is attributed to a structural disorganization of the particles by thiol chemisorption. HRTEM studies confirm the marked dependence of the structural properties of the ruthenium particles on their chemical environment; they show the acetate-coated particles to be single crystals, whereas the thiol-coated particles appear to be polycrystalline.

A butyltin oxo-cluster, {(BuSn)12O14(OH)6}2+, functionalized through electrostatic interactions with two 2-acrylamido-2-methyl-1-propanesulfonate anions (AMPS), has been synthesized and characterized by single crystal X-ray diffraction and multinuclear (1H, 13C and 119Sn) NMR. Its polymerization or co-polymerization with methyl acrylate yield hybrid materials where the nanobuilding blocks are fully preserved and act as nano-fillers and cross-linking agents. According to the electrostatic nature of the cross-linking, these materials can yield gels or solutions depending on the solvent used to swell them.

Hybrid copolymers have been prepared by free radical polymerization, in toluene, of methylacrylate (MA) and varying amounts of an organotin oxo-cluster functionalized with two acrylamido groups, {(BuSn)12O14(OH)6}(AMPS)2. The tin based nanobuilding block is fully preserved in the final materials. These copolymers formed networks where the cross-linking is based on the electrostatic interactions that take place between the macrocation {(BuSn)12O14(OH)6}2 + and its two functional anions (AMPS–). Accordingly, these copolymers can yield gels or solutions depending on the solvent used to swell them.

Solid state (47,49)Ti, (137)Ba, (87)Sr NMR spectra have been recorded on BaxSrl-xTiO3 (0/= x/=1) perovskite samples prepared by the powder sintering method. Multinuclear solid state NMR shows great potential for characterising such systems since the quadrupolar parameters are very sensitive to any geometric deformation around the studied nucleus. (47,49)Ti NMR powder lineshapes appear strongly influenced by the presence of even a small amount of barium (or strontium) in the coordination second sphere of the probed titanium site: substitution of strontium by barium induces the broadening of the peaks, due to quadrupolar effects, while the isotropic chemical shift increases. (137)Ba NMR spectra exhibit a distribution of the quadrupolar interaction, that could be tentatively quantified, CQ increasing with the amount of strontium. Preliminary results were also obtained on (87)Sr NMR showing behaviour comparable to (137)Ba NMR, i.e. a broadening of the peaks due to an increasing quadrupolar interaction with the amount of barium distorting the environment of the strontium sites.