Surfactant-free syntheses and pair distribution function analysis of osmium nanoparticles

A surfactant-free synthesis of precious metal nanoparticles performed in low boiling point solvents and in alkaline conditions has been reported recently. This strategy presents several advantages over alternative colloidal syntheses. The resulting nanoparticles are readily relevant for applications like catalysis and the synthetic process is compatible with large scale production. Alkaline mono-alcohols are here investigated as solvent and reducing agents to obtain colloidal Os nanoparticles by this low temperature (< 100 °C) surfactant-free synthesis. The effect of precursor (OsCl3 or H2OsCl6), precursor concentration (up to 100 mM), solvent (methanol or ethanol), presence or absence of base (NaOH) and addition of water (0 to 100 v.%) on the resulting nanomaterials is discussed. It is fond that no base is required to obtain Os nanoparticles as opposed to the case of Pt NPs for instance. The robustness of the synthesis for concentration of precursor up to 100 mM allows to perform X-ray total scattering with pair distribution function (PDF) analysis that shows that the 1-2 nm hcp NPs forms from chain-like [OsOxCly]-complexes.