Fe2O3/Cu2O heterostructured nanocrystals

We report the synthesis of colloidal gamma-Fe2O3/Cu2O hetero-nanocrystals (HNCs) using a solution-phase seeded-growth approach. gamma-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 gamma-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 gamma-Fe2O3/Cu2O dimers by removing the larger aggregates. Ultraviolet photoelectron spectroscopy was used to determine that gamma-Fe2O3 and Cu2O are n-doped and p-doped respectively and form a staggered, type II band alignment. As such, gamma-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.