Fe2O3/Cu2O heterostructured nanocrystals

Abstract

We report the synthesis of colloidal γ-Fe₂O₃/Cu₂O hetero-nanocrystals (HNCs) using a solution-phase seeded-growth approach. γ-Fe₂O₃ nanocrystals were used as seeds for the nucleation of metallic Cu followed by oxidation of the Cu domain to Cu₂O upon exposure to air. The resulting dimer, trimer, and oligomer HNCs were characterized by high resolution electron microscopy, energy dispersive X-ray spectroscopy, and powder X-ray diffraction. The iron oxide component was found to be mainly γ-Fe₂O₃ using a combination of Raman and X-ray photoelectron spectroscopy. A maximal HNC yield of 72% was achieved by reducing particle growth time to a lower growth temperature with respect to the individual component particles. Size-selective precipitation was used to enrich the nanoparticle mixture in γ-Fe₂O₃/Cu₂O dimers by removing the larger aggregates. Ultraviolet photoelectron spectroscopy was used to determine that γ-Fe₂O₃ and Cu₂O are n-doped and p-doped respectively and form a staggered, type II band alignment. As such, γ-Fe₂O₃/Cu₂O HNCs may be attractive candidates for applications in solar energy conversion and represent a valuable addition to the growing library of oxide–oxide hetero-nanocrystals.