Abstract
A surfactant-free synthesis of precious metal nanoparticles (NPs) performed in alkaline low-boiling-point solvents has been recently reported. Monoalcohols are here investigated as solvents and reducing agents to obtain colloidal Os nanoparticles by using low-temperature (<100 °C) surfactant-free syntheses. The effect of the precursor (OsCl3 or H2OsCl6), precursor concentration (up to 100 mM), solvent (methanol or ethanol), presence or absence of a base (NaOH), and addition of water (0 to 100 vol %) on the resulting nanomaterials is discussed. It is found that no base is required to obtain Os nanoparticles as opposed to the case of Pt or Ir NPs. The robustness of the synthesis for a precursor concentration up to 100 mM allows for the performance of X-ray total scattering with pair distribution function (PDF) analysis, which shows that 1–2 nm hexagonal close packed (hcp) NPs are formed from chain-like [OsOxCly] complexes.
Highlights
Our experiment showed that either methanol or ethanol is needed for the reaction to proceed playing the role of reducing agents, as no product is formed when the synthesis is performed in 100% water
To develop a simple and relatively inexpensive synthesis of Os NPs requiring only few chemicals, it was concluded that OsCl3, no base, and a relatively high-water content using methanol as the reducing agent were favourable conditions to obtain Os NPs for further studies
Os NPs with a hcp crystal structure and a size of approx. 1–2 nm are synthesized in methanol, ethanol, and water mixtures of OsCl3 or H2OsCl6 precursors, without the need for surfactants
Summary
We screened the influence of several experimental parameters across a large parametric space by investigating the influence of the precursors: OsCl3 and H2OsCl6, the nature of the solvent/reducing agent: methanol and ethanol, the absence or presence of a base (NaOH), and the effect of adding water at: 0, 10, 25, 50, 66, 75 or 100 vol %. When further comparing the results from the large parameter space (Figures S2–S21, Supporting Information File 1), it is clear that the synthesis conditions, have little influence on the resulting size of the Os NPs, which in all cases is 1–2 nm.
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