Oxidation Behavior of Copper Nanocrystals

Nanoparticles of noble metals such as gold, silver, and copper interact with visible light in unique ways, giving rise to collective electron oscillations called the localized surface plasmon resonance (LSPR). The LSPR activity of copper has not been widely studied because of copper’s propensity to oxidize. We have characterized the optical response of copper nanocrystals in oxygenated solvents to monitor in-situ and in real time the formation of a monolayer of copper oxide.  Further, we obtained data on oxygen diffusivities throughout the nanoparticles based on thermogravimetric analysis.  The electronic interactions between the solvent electrons and the copper nanoparticles can significantly quench the LSPR until a monolayer of copper oxide forms, and differing diffusion rates for copper and oxygen over time leads to hollow copper oxide nanoparticles.