PNNL

Abstract

In this work a-Cr2O3/a-Fe2O3 core-shell polycrystalline nanostructures were synthesized using a-Cr2O3 nanoparticles as seed crystals during aqueous nucleation. The formation of a-Fe2O3 polycrystallites on a-Cr2O3 surfaces were confirmed by x-ray diffraction, transmission electron microscopy, and energy dispersive x-ray analysis. The excited state relaxation dynamics of as-grown core-shell structures and \pure" a-Fe2O3 particles of the same size were measured using femtosecond transient absorption spectroscopy. The results show the carrier lifetimes decay within a few picoseconds regardless of sample. This is likely due to fast recombination/trapping of carriers to defects and iron d-states.