Characterization of Au and Pd nanoparticles by high-temperature TGA–MS

Abstract

Noble metal nanoparticles (NPs) prepared by a surfactant-free single-phase solution method have been proposed to contain fewer ionic contaminants than similar NPs prepared by a two-phase method. Reported herein is the possible contamination of Au and Pd NPs, prepared by a surfactant-free single-phase method, with Li2CO3 and other Li salts. High-temperature thermal gravimetric analysis measurements coupled with mass spectrometry (TGA–MS) up to 1100 °C were employed to determine the relative amounts of ionic contaminants since protecting thiolate groups and inorganic contaminants were removed in separate weight loss events. Assignment of the different weight loss events was supported by MS analysis of the evolved gases. TGA–MS also revealed the presence of larger amounts of oxidized sulfur species in the Pd NPs. High-resolution transmission electron microscopy (HRTEM), UV–vis, IR, elemental analysis (EA), and X-ray photoelectron spectroscopy (XPS) measurements complemented the characterization of the NPs. The amount of ionic contaminants crucially depended on the workup conditions, and quenching of the reaction mixture with ethanol was found to be essential for the formation of Li2CO3. Workup procedures that avoid the formation of TGA–MS detectable ionic contaminants are proposed along with purification steps for contaminated NPs.Key words: gold, palladium, nanoparticles, TGA, mass spectrometry, ionic contamination.