Oxidation of copper nanoparticles in water: mechanistic insights revealed by oxygen uptake and spectroscopic methods.

Oxidation of aqueous ∼8 nm unprotected copper nanoparticles takes place under air in approximately 2 hours at 30 °C to give Cu(2+) as a final product through an intermediate Cu(+) species. At 5 °C the process is about 5 times slower; similarly, vitamin C, which plays a sacrificial role, also slows down the oxidation, while CuNP catalyses the oxidation. In this work, we present a detailed analysis of the oxidation mechanism of colloidal CuNP inferred through spectroscopic methods (UV-visible and EPR) combined with oxygen uptake measurements, with emphasis on factors affecting the oxidative process.