Layered hydroxide metal acetates (metal ) zinc, cobalt, and nickel) have been prepared by a new route belonging to the chimie douce method. This novel method involves the hydrolysis, in polyol medium, of in situ-formed complexes supposed to be alkoxyacetates. These layered hydroxide metal acetates present poorly ordered character, and their X-ray patterns have features typical of lamellar compounds with turbostratic disorder. Their chemical formula was established to be M(OH) 2-x (CH 3 COO) x ‚nH 2 O with (x, n) ) (0.42, 0.31), (0.38, 0.53), and (0.40, 0.63) for Zn, Co, and Ni, respectively. The layered hydroxide nickel acetate has a classical brucite structure with a random substitution of some hydroxyl groups by acetate groups. The layered hydroxide zinc and cobalt acetates are isomorphous with the hydrozincite structure, in which cations are located in both octahedral and tetrahedral sites. The acetate anion behaves as a unidentate ligand in LHS-Ni and LHS-Co, where LHS indicates layered hydroxide salt, and is intercalated as a free anion in the zinc compound. The dehydration is a reversible topotactic process for LHS-Ni and Co, whereas it is a destructive process in the case of LHS-Zn.

Ruthenium nanoparticles were prepared by reduction of RuCl 3 in a liquid polyol. The mean particle size was restricted to the 1-6 nm range by appropriate choice of the reduction temperature and the acetate ion concentration in the solution. Very narrow particle diameter distributions were obtained. In some samples, among nearly isotropic particles, platelets with aspect ratios as low as 1/4 were detected. Colloidal solutions in toluene were obtained by coating the metal particles with dodecane thiol. Self-assemblies of 4-nm-sized coated particles were studied on a transmission electron microscope grid. The dodecane thiol concentration in the colloidal solution was found to determine, within the particle monolayer, the formation of either columnar units made up of edgewise stacked platelets, or a hexagonal network with a mean distance between the particles of 2 nm. The stacking of hexagonal arrays of particles was also studied, and both closed-packed and noncompact stackings were found. In the noncompact stacking, moire ´images resulted from the twisting of the two hexagonal layers with respect to each other. Reconstructions of moire ´patterns were observed to favor the 6-fold and 2-fold sites.

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.