Preparation and Oxygen Sensitivity of a Range of Noble-Metal Nanoparticles (Ir, Pt, and Au) Protected by a Series of Chalcogen-Dodecane Ligands (S, Se, and Te)

Iridium, platinum, and gold nanoparticles, protected with sulfur, selenium, or tellurium dodecane ligands, were synthesized under ambient laboratory conditions. These nine nanoparticles were characterized by thermogravimetric analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS). XPS was used to determine the degree of oxidation present at the metal-chalcogen interface at the time of synthesis and after 1 week of aging under ambient laboratory conditions. Upon synthesis, interfaces involving sulfur atoms were found to have no degree of oxidation and to retain this lack of oxidation over the course of 1 week. In contrast, all interfaces involving tellurium were found to have some degree of oxidation (28, 77, and 76% for Ir, Pt, and Au particles, respectively) at the time of synthesis, and this degree of oxidation increased over the course of 1 week to 38, 83, and 92% for Ir, Pt, and Au, respectively. For interfaces involving selenium, all interfaces initially lacked any oxidation and the iridium and platinum interface was found to be stable over 1 week. On the other hand, the gold interface oxidized over time, reaching 60% oxidation after 1 week under ambient laboratory conditions. Thus, our work shows that IrS, IrSe, PtS, PtSe, and AuS provide metal-ligand interfaces that are stable, with respect to oxidation under ambient conditions.