Surfactant-assisted hollowing of cu nanoparticles involving halide-induced corrosion-oxidation processes

We have demonstrated a simple fabrication of hollow nanoparticles by halide-induced corrosion oxidation with the aid of surfactants. Cuprous oxide Cu₂O nanoshells can be generated by simply mixing Cu nanoparticles with alkyltrimethylammonium halides at 55°C for 16 min. The hollowing mechanism proposed is that absorption of surfactants onto the Cu surface facilitates the formation of the void interior through an oxidative etching process. Upon extending the reaction up to 4 h. fragmentation, oxidation, and self-assembly were observed and the CuO ellipsoidal structures were formed. The headgroup lengths of the surfactants influenced the degree of CuO ellipsoidal formation, whereby longer surfactants favored the generation of ellipsoids. Optical absorption measured by UV-visible spectroscopy was used to monitor both oxidation courses of Cu→Cu₂O and Cu₂O→CuO and to determine the band-gap energies as 2.4 eV for Cu₂O nanoshells and 1.89 eV for CuO ellipsoids. For the contact-angle measurements, the wettability changed from hydrophilicity (18°) to hydrophobicity (140°) as the Cu₂O nanoshells shifted to CuO ellipsoids.